Patent Publication Number: US-2023158882-A1

Title: Corner module apparatus for vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application Nos. 10-2021-0162194 and 10-2021-0188610, filed on Nov. 23, 2021 and Dec. 27, 2021, respectively, the entire disclosures of which are hereby incorporated by reference for all purposes as if set forth herein. 
     BACKGROUND 
     1. Field 
     The present disclosure relates to a corner module apparatus for a vehicle, and more particularly, to a corner module apparatus for a vehicle in which driving, braking, steering, and suspension systems are integrated. 
     2. Description of Related Art 
     In general, an electric vehicle refers to an eco-friendly vehicle devoid of the discharge of exhaust gas. A high-voltage battery for supplying energy for driving, a motor for driving for generating rotatory power from power outputted by the high-voltage battery, etc. are mounted on the electric vehicle. The electric vehicle is driven by the rotation power of the motor being delivered to wheels through a driving shaft. 
     Recently, an in-wheel motor vehicle in which a motor is directly installed inside a wheel so that power of the motor is directly delivered to the wheel by taking into consideration advantages in which weight of the vehicle can be reduced and an energy loss in a power transfer process can be reduced has been in the spotlight because a power transfer unit of an intermediate stage, such as a decelerator or a differential gear, has been can be omitted. Furthermore, a wheel in which braking, steering, and suspension systems are integrated in addition to a driving system is also being actively developed. 
     The background technology of the present disclosure is disclosed in Korean Patent Application Publication No. 10-2019-0041855 published on Apr. 23, 2019 and entitled “STEERING SYSTEM FOR IN-WHEEL MOTOR VEHICLE.” 
     SUMMARY 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
     In one general aspect, a corner module apparatus, includes a corner module including a driving unit configured to provide driving power to a wheel of a vehicle, a suspension unit coupled with the driving unit and configured to absorb an impact to the wheel from a road surface, and a steering unit coupled with the suspension unit and configured to adjust a steering angle of the wheel; a main platform installed under a vehicle body of the vehicle and configured to have a battery mounted thereon; a first corner module platform detachably coupled with one side of the main platform and configured to have the corner module coupled therewith; and a second corner module platform detachably coupled with another side of the main platform and configured to have the corner module coupled therewith. 
     The first corner module platform may include first corner module platforms that neighbor each other and are serially connected in a length direction of the vehicle body. The second corner module platform may include second corner module platforms that neighbor each other and are serially connected in the length direction of the vehicle body. 
     A number of the first corner module platforms and a number of the second corner module platforms may be identical with each other. 
     A number of the first corner module platforms and a number of the second corner module platforms may be different from each other. 
     The main platform may include a main plate configured to seat the battery, a main wheel housing extended from the main plate and configured to have the corner module accommodated therein, and a main fastening part provided in the main plate and the main wheel housing. 
     The main wheel housing may include main wheel housings disposed on corner sides of the main plate, respectively. 
     The first corner module platform may include a first corner module plate configured to seat an inverter; a first corner module wheel housing, extended from the first corner module plate, configured to accommodate the corner module and comprise a first mounting plate supporting the corner module; and a first corner module fastening part, provided in the first corner module plate and the first corner module wheel housing, detachably coupled with the main fastening part. 
     The main platform and the first corner module platform may be configured to contact when the main fastening part and the first corner module fastening part are coupled. 
     The first corner module platform may further include a first corner module extension fastening part provided in the first corner module plate and the first corner module wheel housing, and disposed on a side opposite to the first corner module fastening part. 
     The first corner module platform may include first corner module platforms, and the first corner module extension fastening part provided in any one of the first corner module platforms is detachably coupled with the first corner module fastening part provided in another one of the first corner module platforms neighboring the any one of the first corner module platforms. 
     Neighboring ones of the first corner module platforms may be configured to contact when the first corner module extension fastening part and the first corner module fastening part are coupled. 
     The second corner module platform may include a second corner module plate configured to seat an inverter; a second corner module wheel housing extended from the second corner module plate, configured to accommodate the corner module, and comprising a second mounting plate configured to support the corner module; and a second corner module fastening part, provided in the second corner module plate and the second corner module wheel housing, detachably coupled with the main fastening part. 
     The second corner module platform may further include a second corner module extension fastening part provided in the second corner module plate and the second corner module wheel housing, and disposed on a side opposite to the second corner module fastening part. 
     In another general aspect, a corner module apparatus includes: a corner module comprising a driving unit configured to provide driving power to a wheel of a vehicle, a suspension unit coupled with the driving unit and configured to absorb an impact to the wheel from a road surface, and a steering unit coupled with the suspension unit and configured to adjust a steering angle of the wheel; a main platform assembly, comprising main platforms installed under a vehicle body of the vehicle, configured to have a battery mounted thereon, and a middle module platform disposed between the main platforms; a first corner module platform, detachably coupled with one side of the main platform assembly, configured to have the corner module coupled therewith; and a second corner module platform, detachably coupled with another side of the main platform assembly, configured to have the corner module coupled therewith. 
     The middle module platform may include one or more third corner module platforms configured to have the corner module coupled therewith. 
     In another general aspect, a vehicle includes: a corner module apparatus including a corner module including a driving unit configured to provide driving power to a wheel, a suspension unit coupled with the driving unit and configured to absorb an impact to the wheel from a road surface, and a steering unit coupled with the suspension unit and configured to adjust a steering angle of the wheel, a main platform disposed under a vehicle body and configured to have a battery mounted thereon, a first corner module platform detachably coupled with one side of the main platform and configured to have the corner module coupled therewith and have an inverter mounted thereon, and a second corner module platform detachably coupled with another side of the main platform and configured to have the corner module coupled therewith and have the inverter mounted thereon; a top hat, mounted on a top of the corner module apparatus, configured to have a boarding space provided therein; and a door part, installed in the top hat, configured to be opened and closed. 
     The door part may include a first door disposed over the main platform. 
     A height of the battery may be lower than a height of the main platform. 
     The door part may further include a second door disposed on either one or both of the first corner module platform and the second corner module platform. 
     A height of the inverter may be lower than heights of the first corner module platform and the second corner module platform. 
     Other features and aspects will be apparent from the following detailed description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a front view schematically illustrating a configuration of a vehicle including a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
         FIG.  2    is a perspective view schematically illustrating a configuration of a vehicle including a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
         FIG.  3    is a perspective view schematically illustrating a configuration of a main platform according to an embodiment of the present disclosure. 
         FIGS.  4  and  5    are enlarged views schematically illustrating configurations of a main fastening part according to an embodiment of the present disclosure. 
         FIG.  6    is a perspective view schematically illustrating a configuration of a first corner module platform and a second corner module platform according to an embodiment of the present disclosure. 
         FIGS.  7  and  8    are enlarged views schematically illustrating configurations of a first corner module fastening part and a second corner module fastening part according to an embodiment of the present disclosure. 
         FIG.  9    is a perspective view schematically illustrating a configuration of a corner module according to a first embodiment of the present disclosure. 
         FIG.  10    is a perspective view illustrating a configuration of the corner module according to the first embodiment of the present disclosure at a view different from that of the configuration of  FIG.  9   . 
         FIG.  11    is a front view schematically illustrating a configuration of the corner module according to the first embodiment of the present disclosure. 
         FIG.  12    is a side view schematically illustrating a configuration of the corner module according to the first embodiment of the present disclosure. 
         FIG.  13    is an exploded perspective view schematically illustrating a configuration of the corner module according to the first embodiment of the present disclosure. 
         FIG.  14    is a cross-sectional view schematically illustrating a configuration of a steering driving unit according to the first embodiment of the present disclosure. 
         FIGS.  15 ,  16 A and  16 B  are operation diagrams schematically illustrating an operating process of the corner module according to the first embodiment of the present disclosure. 
         FIG.  17    is a diagram schematically illustrating a configuration of a vehicle including a corner module apparatus for a vehicle according to another embodiment of the present disclosure. 
         FIG.  18    is a diagram schematically illustrating a configuration of a first corner module platform and a second corner module platform according to another embodiment of the present disclosure. 
         FIGS.  19  and  20    are enlarged views schematically illustrating a configuration of a first corner module extension fastening part and a second corner module extension fastening part according to an embodiment of the present disclosure. 
         FIG.  21    is a diagram schematically illustrating a configuration of a vehicle including a corner module apparatus for a vehicle according to still another embodiment of the present disclosure. 
         FIG.  22    is a block diagram for describing a function of a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
         FIG.  23    is a diagram schematically illustrating a series of processes of calculating first to fourth target angles in a first application (individual steering architecture) of a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
         FIG.  24    is a diagram illustrating first to fourth target angles in a front-wheel steering mode in the first application (individual steering architecture) of a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
         FIGS.  25  and  26    are diagrams illustrating first to fourth target angles in a four-wheel inphase steering mode in the first application (individual steering architecture) of a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
         FIGS.  27  and  28    are diagrams illustrating first to fourth target angles in a four-wheel reversed-phase steering mode in the first application (individual steering architecture) of a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
         FIG.  29    is a flowchart for describing an operating method in the first application (individual steering architecture) of a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
         FIGS.  30  to  33    are diagrams illustrating a relation between a slope and a location of a vehicle in a second application (a braking mechanism through individual steering) of a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
         FIGS.  34  to  36    are diagrams illustrating the state in which wheels have been aligned according to a direction angle in the second application (the braking mechanism through individual steering) a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
         FIG.  37    is a flowchart for describing an operating method in the second application (the braking mechanism through individual steering) of a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
         FIG.  38    is a diagram illustrating a method of determining a variable gain in a third application (a posture control mechanism for improving straight driving performance) of a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
         FIG.  39    is a flowchart for describing an operating method in the third application (the posture control mechanism for improving straight driving performance) of a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
         FIG.  40    is a flowchart for describing an operating method in a fourth application (a posture control mechanism for solving a slip) of a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
         FIG.  41    is a diagram illustrating a process of calculating distance information and center target curvature in a fifth application (a target trajectory generation and tracking control mechanism) of a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
         FIG.  42    is a diagram illustrating a process of calculating left target curvature and right target curvature in the fifth application (the target trajectory generation and tracking control mechanism) of a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
         FIG.  43    is a diagram illustrating a process of calculating a target steering angle in the fifth application (the target trajectory generation and tracking control mechanism) of a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
         FIG.  44    is a block diagram illustrating a method of independently controlling the steering of each wheel in the fifth application (the target trajectory generation and tracking control mechanism) of a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
         FIG.  45    is a flowchart for describing an operating method in the fifth application (the target trajectory generation and tracking control mechanism) of a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
     
    
    
     Throughout the drawings and the detailed description, the same reference numerals refer to the same or like elements. The drawings may not be to scale, and the relative size, proportions, and depiction of elements in the drawings may be exaggerated for clarity, illustration, and convenience. 
     DETAILED DESCRIPTION 
     The following detailed description is provided to assist the reader in gaining a comprehensive understanding of the methods, apparatuses, and/or systems described herein. However, various changes, modifications, and equivalents of the methods, apparatuses, and/or systems described herein will be apparent after an understanding of the disclosure of this application. For example, the sequences of operations described herein are merely examples, and are not limited to those set forth herein, but may be changed as will be apparent after an understanding of the disclosure of this application, with the exception of operations necessarily occurring in a certain order. Also, descriptions of features that are known after understanding of the disclosure of this application may be omitted for increased clarity and conciseness. 
     The features described herein may be embodied in different forms, and are not to be construed as being limited to the examples described herein. Rather, the examples described herein have been provided merely to illustrate some of the many possible ways of implementing the methods, apparatuses, and/or systems described herein that will be apparent after an understanding of the disclosure of this application. 
     Throughout the specification, when an element, such as a layer, region, or substrate, is described as being “on,” “connected to,” or “coupled to” another element, it may be directly “on,” “connected to,” or “coupled to” the other element, or there may be one or more other elements intervening therebetween. In contrast, when an element is described as being “directly on,” “directly connected to,” or “directly coupled to” another element, there can be no other elements intervening therebetween. 
     As used herein, the term “and/or” includes any one and any combination of any two or more of the associated listed items. 
     Although terms such as “first,” “second,” and “third” may be used herein to describe various members, components, regions, layers, or sections, these members, components, regions, layers, or sections are not to be limited by these terms. Rather, these terms are only used to distinguish one member, component, region, layer, or section from another member, component, region, layer, or section. Thus, a first member, component, region, layer, or section referred to in examples described herein may also be referred to as a second member, component, region, layer, or section without departing from the teachings of the examples. 
     Spatially relative terms such as “above,” “upper,” “below,” and “lower” may be used herein for ease of description to describe one element&#39;s relationship to another element as shown in the figures. Such spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, an element described as being “above” or “upper” relative to another element will then be “below” or “lower” relative to the other element. Thus, the term “above” encompasses both the above and below orientations depending on the spatial orientation of the device. The device may also be oriented in other ways (for example, rotated 90 degrees or at other orientations), and the spatially relative terms used herein are to be interpreted accordingly. 
     The terminology used herein is for describing various examples only, and is not to be used to limit the disclosure. The articles “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “includes,” and “has” specify the presence of stated features, numbers, operations, members, elements, and/or combinations thereof, but do not preclude the presence or addition of one or more other features, numbers, operations, members, elements, and/or combinations thereof. 
     Due to manufacturing techniques and/or tolerances, variations of the shapes shown in the drawings may occur. Thus, the examples described herein are not limited to the specific shapes shown in the drawings, but include changes in shape that occur during manufacturing. 
     The features of the examples described herein may be combined in various ways as will be apparent after an understanding of the disclosure of this application. Further, although the examples described herein have a variety of configurations, other configurations are possible as will be apparent after an understanding of the disclosure of this application. 
     Hereinafter, embodiments of a vehicle including a corner module apparatus for a vehicle and an operating method of the corner module apparatus for a vehicle according to the present disclosure will be described with reference to the accompanying drawings. 
     Various embodiments are directed to providing a corner module apparatus for a vehicle, which can freely adjust the number and alignment of wheels to suit a purpose of a vehicle. 
     Furthermore, various embodiments are directed to providing a corner module apparatus for a vehicle, which can independently control operations of each wheel. 
     1. Structure of Vehicle Including Corner Module Apparatus for Vehicle 
       FIG.  1    is a front view schematically illustrating a configuration of a vehicle including a corner module apparatus for a vehicle according to an embodiment of the present disclosure.  FIG.  2    is a perspective view schematically illustrating a configuration of a vehicle including a corner module apparatus for a vehicle according to an embodiment of the present disclosure. 
     Referring to  FIGS.  1  and  2   , the vehicle including a corner module apparatus for a vehicle according to an embodiment of the present disclosure includes a corner module apparatus  1  for a vehicle, a top hat  2 , and a door part  3 . 
     The corner module apparatus  1  for a vehicle according to an embodiment of the present disclosure includes a frame module  100  and a corner module  200 . 
     The frame module  100  is installed on the lower side of a vehicle body, and generally supports the corner module  200 , a battery  400 , and an inverter  500 . 
     Referring to  FIG.  2   , the frame module  100  according to the present embodiment includes a main platform  1100 , a first corner module platform  1200 A, and a second corner module platform  1200 B. 
     The main platform  1100  is installed on the lower side of the vehicle body. The battery  400  for supplying a power source to the corner module  200  described later is mounted within the main platform  1100 . The main platform  1100  may have a highly rigid material, such as metal, so that main platform can sufficiently withstand weight applied from the battery  400 . The battery  400  is formed to have a lower height than the main platform  1100 . 
       FIG.  3    is a perspective view schematically illustrating a configuration of the main platform  1100  according to an embodiment of the present disclosure. 
     Referring to  FIG.  3   , the main platform  1100  according to the present embodiment includes a main plate  1110 , a main wheel housing  1120 , and a main fastening part  1130 . 
     The main plate  1110  forms an external appearance of a central part of the main platform  1100 , and generally supports the main wheel housing  1120  described later. The main plate  1110  according to an embodiment of the present disclosure may be formed to have a form of a flat plate that is disposed in parallel the ground. The battery  400  is seated on the top of the main plate  1110 , and the inverter  500  may be seated thereon, if necessary. The design of the area of the main plate  1110  may be variously changed depending on the size of the vehicle body, the size of the battery  400 , etc. 
     The main wheel housing  1120  extends from the main plate  1110 , and provides a space in which the corner module  200  is accommodated. The main wheel housing  1120  according to the present embodiment may be formed to have a form of a pillar that is perpendicularly upward extended from the top of the main plate  1110 . More specifically, the main wheel housing  1120  is disposed on the corner side of the main plate  1110 , and is formed to have an outside surface thereof opened. For example, the main wheel housing  1120  may be extended to the top of the corner of the main plate  1110  with a cross-sectional form of an approximately “−7” form as illustrated in  FIG.  3   . Accordingly, the main wheel housing  1120  may provide a space in which the corner module  200  is accommodated. 
     The top of the main wheel housing  1120  is formed to have a form of a flat plate that is disposed in parallel to the main plate  1110 . Accordingly, the main wheel housing  1120  may provide a space in which the main fastening part  1130  described later may be formed on the top of the main wheel housing  1120 . 
     The main wheel housing  1120  may be provided in plural. The plurality of main wheel housings  1120  may be disposed on the plurality of corner sides of the main plate  1110 , respectively. 
     The main fastening part  1130  is provided in the main plate  1110  and the main wheel housing  1120 , and is fastened to the first corner module platform  1200 A and the second corner module platform  1200 B described later. 
       FIGS.  4  and  5    are enlarged views schematically illustrating configurations of the main fastening part according to an embodiment of the present disclosure. 
     Referring to  FIGS.  3  to  5   , the main fastening part  1130  according to the present embodiment includes an upper main fastening part  1131  and a lower main fastening part  1132 . 
     The upper main fastening part  1131  according to the present embodiment may be formed to have a form of a groove that is concavely recessed and formed from an outside surface of the main wheel housing  1120 . The upper main fastening part  1131  is perpendicularly downward extended from the top of the main wheel housing  1120 . The upper main fastening part  1131  may have a cross-sectional form having a step form so that the upper main fastening part  1131  is locked and coupled with a first corner module upper-fastening part  1231 A and a second corner module upper-fastening part  1231 B described later. The upper main fastening part  1131  is disposed at the end of the main wheel housing  1120  disposed to face the first corner module platform  1200 A and the second corner module platform  1200 B described later. The upper main fastening part  1131  may be provided in plural, and may be individually provided in the main wheel housings  1120 , respectively. 
     The lower main fastening part  1132  according to the present embodiment may be formed to have a form of a groove that is concavely recessed and formed from the outside surface of the main plate  1110 . The lower main fastening part  1132  may have a cross-sectional form having a step form so that lower main fastening part  1132  is locked and coupled with a first corner module lower-fastening part  1232 A and a second corner module lower-fastening part  1232 B described later. 
     The lower main fastening part  1132  is extended in a direction opposite to a direction of the upper main fastening part  1131 . More specifically, the lower main fastening part  1132  is perpendicularly upward extended from the lower side of the main plate  1110 . Accordingly, when being fastened to a first corner module fastening part  1230 A and a second corner module fastening part  1230 B described later, the upper main fastening part  1131  and the lower main fastening part  1132  can prevent the first corner module fastening part  1230 A and the second corner module fastening part  1230 B from deviating in any one direction. 
     The lower main fastening part  1132  is provided in pair, and is disposed at the ends of the main plate  1110  disposed to face the first corner module platform  1200 A and the second corner module platform  1200 B described later, respectively. 
     The first corner module platform  1200 A and the second corner module platform  1200 B are detachably coupled to both sides of the main platform  1100 , respectively. The first corner module platform  1200 A and the second corner module platform  1200 B have the corner modules  200  described later coupled to lower sides thereof, respectively, and support the corner modules  200 . The corner module  200  and the inverter  500  that converts DC power supplied from the battery  400  into AC power and transmits the AC power to the corner module  200  are mounted within each of the first corner module platform  1200 A and the second corner module platform  1200 B. The inverter  500  is formed to have a lower height than the first corner module platform  1200 A and the second corner module platform  1200 B. The first corner module platform  1200 A and the second corner module platform  1200 B may have a highly rigid material, such as metal, so that the first corner module platform  1200 A and the second corner module platform  1200 B can sufficiently withstand weight applied from the corner module  200  and the battery  400 . 
       FIG.  6    is a perspective view schematically illustrating a configuration of the first corner module platform and the second corner module platform according to an embodiment of the present disclosure. 
     Referring to  FIG.  6   , the first corner module platform  1200 A according to the present embodiment includes a first corner module plate  1210 A, a first corner module wheel housing  1220 A, and the first corner module fastening part  1230 A. 
     The first corner module plate  1210 A forms an external appearance of a central part of the first corner module platform  1200 A, and generally supports the first corner module wheel housing  1220 A described later. The first corner module plate  1210 A according to the present embodiment may be formed to have a form of a flat plate that is disposed in parallel to the ground. The inverter  500  is seated on the top of the first corner module plate  1210 A, and the battery  400  may be seated thereon, if necessary. The design of the area of the first corner module plate  1210 A may be variously changed the size of the main plate  1110 , the size of the inverter  500 , etc. 
     The first corner module wheel housing  1220 A extends from the first corner module plate  1210 A and provides a space in which the corner module  200  is accommodated. The first corner module wheel housing  1220 A according to the present embodiment may be formed to have a form of a plate that extends upward from the top of the main plate  1110 . The first corner module wheel housing  1220 A may be provided in pair, and may be disposed at the ends of the first corner module plate  1210 A in a width direction thereof, respectively. 
     The first corner module wheel housing  1220 A is provided with a first mounting plate  1221 A that supports the corner module  200 . The first mounting plate  1221 A may be formed to have a form of a flat plate that extends in the width direction of the first corner module plate  1210 A from the top of the first corner module wheel housing  1220 A. The first mounting plate  1221 A is disposed in parallel to the first corner module plate  1210 A. The lower side of the first mounting plate  1221 A is detachably coupled to the corner module  200  by bolting coupling, etc. 
     In this case, the first corner module wheel housing  1220 A may be extended to the outside of the first corner module plate  1210 A in the width direction thereof with a cross-sectional form having an approximately “¬” form as illustrated in  FIG.  6   . Accordingly, the first corner module wheel housing  1220 A may provide a space in which the corner module  200  is accommodated. 
     The first corner module fastening part  1230 A is provided in the first corner module plate  1210 A and the first corner module wheel housing  1220 A, and is fastened to the main fastening part  1130  disposed on one side of the main platform  1100 . When the main platform  1100  and the first corner module platform  1200 A are assembled, the first corner module fastening part  1230 A is disposed at a location that faces the main fastening part  1130  disposed on the one side of the main platform  1100 . The first corner module fastening part  1230 A is locked and coupled with the main fastening part  1130  disposed on the one side of the main platform  1100  as the first corner module platform  1200 A mutually comes into contact with the main platform  1100  in a direction parallel to the length direction of a vehicle. Accordingly, the main fastening part  1130  and the first corner module fastening part  1230 A can improve assembly performance of the main platform  1100  and the first corner module platform  1200 A. 
       FIGS.  7  and  8    are enlarged views schematically illustrating configurations of the first corner module fastening part and the second corner module fastening part according to an embodiment of the present disclosure. 
     Referring to  FIGS.  6  to  8   , the first corner module fastening part  1230 A according to an embodiment of the present disclosure includes the first corner module upper-fastening part  1231 A and the first corner module lower-fastening part  1232 A. 
     The first corner module upper-fastening part  1231 A according to the present embodiment may be formed to have a form of a protrusion that protrudes from the outside surface of the first corner module wheel housing  1220 A. More specifically, the first corner module upper-fastening part  1231 A is transversely extended from the end of the front or rear of the first mounting plate  1221 A, more specifically, an end disposed to face the end of the main platform  1100  on one side thereof. The first corner module upper-fastening part  1231 A is inserted into the upper main fastening part  1131  disposed on the one side of the main platform  1100  as the first corner module platform  1200 A comes into contact with the main platform  1100  in the direction parallel to the length direction of the vehicle. In this case, the first corner module upper-fastening part  1231 A may have a shape having an end bent in a hook form so that the first corner module upper-fastening part  1231 A is locked and coupled with the upper main fastening part  1131  disposed on the one side of the main platform  1100 . The first corner module upper-fastening part  1231 A may be provided in plural, and may be individually provided in the first corner module wheel housings  1220 A, respectively. 
     The first corner module lower-fastening part  1232 A according to the present embodiment may be formed to have a form of a protrusion that protrudes from the outside surface of the first corner module plate  1210 A. More specifically, the first corner module lower-fastening part  1232 A is transversely extended from any one end of the front or rear of the first corner module plate  1210 A, more specifically, an end disposed to face the end of the main platform  1100  on the one side thereof. The first corner module lower-fastening part  1232 A is inserted into the lower main fastening part  1132  disposed on the one side of the main platform  1100  as the first corner module platform  1200 A comes into contact with the main platform  1100  in the direction parallel to the length direction of the vehicle. 
     The first corner module lower-fastening part  1232 A may have a shape having an end bent in a hook form so that the first corner module lower-fastening part  1232 A is locked and coupled with the lower main fastening part  1132 . In this case, the end of the first corner module lower-fastening part  1232 A is bent in a direction opposite to a direction of the end of the first corner module upper-fastening part  1231 A. For example, the end of the first corner module upper-fastening part  1231 A may be downward bent, and the end of the first corner module lower-fastening part  1232 A may be upward bent. Accordingly, when being fastened to the main fastening part  1130 , the first corner module upper-fastening part  1231 A and the first corner module lower-fastening part  1232 A can prevent the upper main fastening part  1131  and the lower main fastening part  1132  from deviating in any direction thereof. 
     The second corner module platform  1200 B includes a second corner module plate  1210 B, a second corner module wheel housing  1220 B, and the second corner module fastening part  1230 B. 
     Detailed shapes of the second corner module plate  1210 B and the second corner module wheel housing  1220 B may be formed to have the same forms as the above-mentioned first corner module plate  1210 A and the first corner module wheel housing  1220 A, respectively. 
     The second corner module fastening part  1230 B is provided in the second corner module plate  1210 B and the second corner module wheel housing  1220 B, and is fastened to the main fastening part  1130  disposed on the other side of the main platform  1100 . When the main platform  1100  and the second corner module platform  1200 B are assembled, the second corner module fastening part  1230 B is disposed at a location that faces the main fastening part  1130  disposed on the other side of the main platform  1100 . The second corner module fastening part  1230 B is locked and coupled with the main fastening part  1130  disposed on the other side of the main platform  1100  as the second corner module platform  1200 B comes into contact with the main platform  1100  in the direction parallel to the length direction of the vehicle. 
     The second corner module fastening part  1230 B according to the present embodiment includes the second corner module upper-fastening part  1231 B and the second corner module lower-fastening part  1232 B. 
     The second corner module upper-fastening part  1231 B according to the present embodiment may be formed to have a form of a protrusion that protrudes from an outside surface of the second corner module wheel housing  1220 B. More specifically, the second corner module upper-fastening part  1231 B is transversely extended from the end of the front or rear of a second mounting plate  1221 B, more specifically, an end disposed to face the end of the main platform  1100  on the other side thereof. The second corner module upper-fastening part  1231 B is inserted into the upper main fastening part  1131  disposed on the one side of the main platform  1100  as the second corner module platform  1200 B comes into contact with the main platform  1100  in the direction parallel to the length direction of the vehicle. In this case, the second corner module upper-fastening part  1231 B may have a shape having an end bent in a hook form so that the second corner module upper-fastening part  1231 B is locked and coupled with the upper main fastening part  1131  disposed on the one side of the main platform  1100 . The second corner module upper-fastening part  1231 B may be provided in plural, and may be individually provided in the second corner module wheel housings  1220 B, respectively. 
     The second corner module lower-fastening part  1232 B according to the present embodiment may be formed to have a form of a protrusion that protrudes from an outside surface of the second corner module plate  1210 B. More specifically, the second corner module lower-fastening part  1232 B is transversely extended from any one end of the front and rear of the second corner module plate  1210 B, more specifically, an end disposed to face the end of the main platform  1100  on the other side thereof. The second corner module lower-fastening part  1232 B is inserted into the lower main fastening part  1132  disposed on the other side of the main platform  1100  as the first corner module platform  1200 B comes into contact with the main platform  1100  in the direction parallel to the length direction of the vehicle. 
     The second corner module lower-fastening part  1232 B may have a shape having an end bent in a hook form so that the second corner module lower-fastening part  1232 B is locked and coupled with the lower main fastening part  1132 . In this case, the end of the second corner module lower-fastening part  1232 B is bent in a direction opposite to that of the end of the second corner module upper-fastening part  1231 B. For example, the end of the second corner module upper-fastening part  1231 B may be downward bent, and the end of the second corner module lower-fastening part  1232 B may be upward bent. Accordingly, when being fastened to the main fastening part  1130 , the second corner module upper-fastening part  1231 B and the second corner module lower-fastening part  1232 B can prevent the upper main fastening part  1131  and the lower main fastening part  1132  from deviating in any one direction. 
     The corner module  200  is supported by the frame module  100  and connected to a wheel of the vehicle  300 , and generally performs an operation, such as driving, braking, steering, or suspension. The corner module  200  may be provided in plural, and may be individually connected to each of the wheels  300 . Each of the plurality of corner modules  200  may independently perform an operation, such as driving, braking, steering, or suspension, on each of the wheels  300 . A detailed embodiment of the corner module  200  is described later. 
     The top hat  2  is mounted on the top of the corner module apparatus  1  for the vehicle. A boarding space for a passenger is provided within the top hat  2 . 
     Referring to  FIGS.  1  and  2   , the top hat  2  according to the present embodiment may be formed to have a form of a box whose interior is empted and bottom is opened. Various articles and devices suitable for a purpose of a passenger, such as a seat, a manipulation panel, and a table, may be installed within the top hat  2 . The opened bottom of the top hat  2  is disposed to face the top of the frame module  100 , that is, the top of the main platform  1100 , the first corner module platform  1200 A, and the second corner module platform  1200 B. The bottom of the top hat  2  may be coupled to the top of the main wheel housing  1120 , the first corner module wheel housing  1220 A, and the second corner module wheel housing  1220 B through bolting, and may be detachably fixed to the frame module  100 . The design of the area and length of the top hat  2  may be variously changed depending on the area, length, etc. of the frame module  100 . 
     The door part  3  is installed in the top hat  2  in a way to be opened and closed, and enables a passenger to get in the top hat  2  when opened. 
     The door part  3  according to the present embodiment includes a first door  3   a  and a second door  3   b.    
     The first door  3   a  is installed on one side of the top hat  2  in a way to be opened and closed, and is disposed on the top of the main platform  1100 . Referring to  FIGS.  1  and  2   , the first door  3   a  according to the present embodiment is installed on the side of the top hat  2  in a width direction thereof in a way to be opened and closed. The first door  3   a  may be installed on the top hat  2  in a way to be opened and closed by using various methods, such as an open and close method and a sliding method. The first door  3   a  may be provided in pair, and may be installed on both sides of the top hat  2 , respectively, in the width direction thereof in a way to be opened and closed. Both ends of the first door  3   a  are disposed between the pair of main wheel housings  1120  spaced apart from each other in the length direction of the main plate  1110 . The bottom of the first door  3   a  is disposed to face the top of the battery  400  seated on the top of the main plate  1110 . As the battery  400  is formed to have a lower height than the main platform  1100 , the bottom of the first door  3   a  may be disposed close to the ground, thereby inducing smooth boarding of a passenger. 
     The second door  3   b  is installed on the other side of the top hat  2  in a way to be opened and closed, and is disposed on the top of at least one of the first corner module platform  1200 A and the second corner module platform  1200 B. Hereinafter, an example in which the second door  3   b  is disposed on both the tops of the first corner module platform  1200 A and the second corner module platform  1200 B will be described, but the second door  3   b  is not limited to the example. It is also possible for the second door  3   b  to be disposed on the top of any one of the first corner module platform  1200 A and the second corner module platform  1200 B. 
     Referring to  FIGS.  1  and  2   , the second door  3   b  according to the present embodiment is provided in pair, and is installed on the sides of the top hat  2  in forward and backward directions in a way to be opened and closed. Accordingly, the second door  3   b  may be disposed in a direction perpendicular to the first door  3   a . The second door  3   b  may be installed in the top hat  2  in a way to be opened and closed by using various methods, such as an open and close method and a sliding method. Both ends of each of the pair of second doors  3   b  is disposed between the pair of first corner module wheel housing  1220 A and second corner module wheel housing  1220 B. The bottom of each of the pair of second doors  3   b  is disposed to face the top of the inverter  500  seated on the top of each of the first corner module plate  1210 A and the second corner module plate  1210 B. As the inverter  500  is formed to have a lower height than the first corner module platform  1200 A and the second corner module platform  1200 B, the bottom of the second door  3   b  may be disposed close to the ground, thereby inducing smooth boarding of a passenger. 
     Hereinafter, a configuration of a corner module  200  according to a first embodiment of the present disclosure is described. 
       FIG.  9    is a perspective view schematically illustrating a configuration of the corner module according to the first embodiment of the present disclosure.  FIG.  10    is a perspective view illustrating a configuration of the corner module according to the first embodiment of the present disclosure at a view different from that of the configuration of  FIG.  9   .  FIG.  11    is a front view schematically illustrating a configuration of the corner module according to the first embodiment of the present disclosure.  FIG.  12    is a side view schematically illustrating a configuration of the corner module according to the first embodiment of the present disclosure.  FIG.  13    is an exploded perspective view schematically illustrating a configuration of the corner module according to the first embodiment of the present disclosure. 
     Referring to  FIGS.  9  to  13   , the corner module  200  according to the first embodiment of the present disclosure includes a driving unit  2100 , a braking unit  2200 , a suspension unit  2300 , and a steering unit  2400 . 
     The driving unit  2100  rotates the wheel  300  by providing driving power to the wheel  300 . 
     The driving unit  2100  according to the present embodiment includes an in-wheel motor  2110  and a knuckle  2120 . 
     The in-wheel motor  2110  is installed in the inner side of the wheel  300 , and generates the driving power. The in-wheel motor  2110  according to the present embodiment may be configured to include a stator that is fixed in the inner side of the wheel  300  and that forms a magnetic field by receiving a power source from the battery  400  and a rotor that is rotatably installed in the inner side of the wheel  300  and that rotates the wheel  300  by an electromagnetic interaction with the stator. The stator and the rotor may have their central axis disposed on the same line as the central axis of the wheel  300 , and may be disposed in a concentric form from the inner side of the wheel  300  in a way to be stacked with each other. 
     The knuckle  2120  is coupled with the in-wheel motor  2110 , and provides a mechanical connection to the driving unit  2100  between the braking unit  2200  and the suspension unit  2300  described later. The knuckle  2120  according to the present embodiment may be coupled and supported by the stator of the in-wheel motor  2110  by bolting, etc. The knuckle  2120  may rotatably support the rotor of the in-wheel motor  2110  through the medium of a wheel bearing etc. The knuckle  2120  may be fabricated by molding a metal-series material through casting, etc. in order to secure sufficient stiffness. A detailed shape of the knuckle  2120  is not limited to a shape illustrated in  FIG.  13   . The design of the knuckle  2120  may be changed in various shapes capable of supporting the in-wheel motor  2110 . 
     The braking unit  2200  applies or releases braking power by being interrupted by the rotation of the wheel  300 . 
     The braking unit  2200  according to the present embodiment includes a brake disk  2210  and a brake caliper  2220 . 
     The brake disk  2210  is connected to the wheel  300  or the in-wheel motor  2110  and is rotated while being interlocked with the rotation of the wheel  300 . The brake disk  2210  according to the present embodiment is formed to have a disc shape and installed in the inner side of the wheel  300 . The brake disk  2210  is disposed to have its central axis placed on the same line as the central axis of the wheel  300 . The brake disk  2210  may be integratedly connected with the wheel  300  or the rotor of the in-wheel motor  2110  by bolting, etc. Accordingly, when the wheel  300  is rotated, the brake disk  2210  may be rotated by using the central axis as an axis along with the wheel  300 . The design of the diameter of the brake disk  2210  may be variously changed depending on the diameter of the wheel  300 , the size of the in-wheel motor  2110 , etc. 
     Upon braking of the vehicle, the brake caliper  2220  applies braking power by pressurizing the brake disk  2210 . The brake caliper  2220  according to the present embodiment may be configured to include a brake pad disposed to face the brake disk  2210 , a caliper housing coupled with the knuckle  2120  and movably supporting the brake pad, and a piston that is movably installed in the caliper housing in a way to advance and retreat and that pressurizes the brake pad toward the brake disk  2210  or releases the pressing of the brake pad in a moving direction thereof. 
     The suspension unit  2300  is connected to the driving unit  2100 , and absorbs an impact delivered from a road surface while the vehicle drives. 
     The suspension unit  2300  according to the present embodiment includes a suspension arm  2310  and a shock absorber module  2320 . 
     The suspension arm  2310  is provided between the driving unit  2100  and the steering unit  2400  described later, and supports the wheel  300 . More specifically, the suspension arm  2310  absorbs weight applied from the wheel  300  while the vehicle drives by its own stiffness simultaneously with connecting the wheel  300  with the vehicle body, and plays a role in adjusting a movement of the wheel  300 . 
     The suspension arm  2310  according to the present embodiment may include a first arm  2311  and a second arm  2312 . 
     The first arm  2311  and the second arm  2312  have one ends rotatably connected to a steering body  2410  of the steering unit  2400  and the other ends rotatably connected to the knuckle  2120  of the driving unit  2100 . In this case, the first arm  2311  and the second arm  2312  may be rotatably coupled to the steering body  2410  and the knuckle  2120  through the medium of a bush, a ball joint, a pin etc. The first arm  2311  and the second arm  2312  are spaced apart from each other in up and down directions and are disposed to face each other. The first arm  2311  and the second arm  2312  may be formed to have a double wishbone form. Accordingly, the first arm  2311  and the second arm  2312  are able to set negative camber of the wheel  300  to improve the cornering performance of the vehicle, and to set a low floor configuration that lowers the height of the vehicle. The first arm  2311  and the second arm  2312  may be slantly disposed to form a predetermined angle. Accordingly, the first arm  2311  and the second arm  2312  may set the length and center of a side view swing arm (SVSA) corresponding to the type of vehicle, a driving condition etc. through a relative angle formed by the first arm  2311  and the second arm  2312 . 
     The shock absorber module  2320  is provided in a way to be retractile in a length direction thereof, and absorbs an impact or vibration delivered from a road surface to the vehicle body through the wheel  300 . The shock absorber module  2320  according to the present embodiment includes a cylinder  2321 , a rod  2322 , and an elastic body  2323 . 
     The cylinder  2321  is extended in up and down directions and is filled with a fluid. The bottom of the cylinder  2321  may penetrate the first arm  2311 , and the cylinder  2321  may be rotatably connected to the top of the second arm  2312 . 
     The rod  2322  is extended in the length direction of the cylinder  2321 . The rod  2322  has a lower side inserted into the upper end of the cylinder  2321 , and is installed in a way to slidingly move in the length direction of the cylinder  2321 . The rod  2322  has an upper side coupled to the steering body  2410  by bolting, etc. The rod  2322  slidingly moves in the length direction of the cylinder  2321  by being interlocked by pressure of a fluid filled into the cylinder  2321 . 
     The elastic body  2323  is disposed to surround outside surfaces of the cylinder  2321  and the rod  2322 . The length of the elastic body  2323  is changed by being interlocked with a slide movement of the rod  2322 . The elastic body  2323  according to the present embodiment may be formed to have a form of a coil spring capable of being retractile in the length direction thereof. The elastic body  2323  may have both ends coupled and supported by a lower sheet fixed to the cylinder  2321  and an upper sheet fixed to the rod  2322 . The elastic body  2323  may be compressed or extended when the rod  2322  slidingly moves, may accumulate an elastic restoring force, and may offset an impact applied from a road surface by the accumulated elastic restoring force. 
     The steering unit  2400  is connected to the suspension unit  2300  and is rotatably installed on the lower side of the frame module  100 . The steering unit  2400  is rotated clockwise or counterclockwise by using the frame module  100  as an axis, and adjusts a steering angle of the wheel  300 . The steering unit  2400  is installed on the lower side of the frame module  100 , and can prevent a part of the structure of the corner module  200  from protruding upward from the frame module  100 . Accordingly, a spatial or shape problem upon vehicle body mounting design, package, and vehicle design can be solved. 
     The steering unit  2400  according to the present embodiment includes the steering body  2410  and a steering driving unit  2420 . 
     The steering body  2410  is disposed to face the bottom of the frame module  100 , and supports the suspension unit  2300 . The steering body  2410  according to the present embodiment has a length direction extended in a direction parallel to the height direction of the vehicle, and is disposed between the frame module  100  and the suspension unit  2300 . An area of the top of the steering body  2410  is formed to be greater than an area of the bottom thereof. Accordingly, the steering body  2410  is formed to have an approximately “¬” cross-sectional form. The bottom of the steering body  2410  is coupled with one ends of the first arm  2311  and the second arm  2312  through the medium of a bush, a ball joint, a pin, etc., and rotatably supports the first arm  2311  and the second arm  2312 . The lower side of the top of the steering body  2410  is coupled with the top of the rod  2322  by bolting, etc., and supports the shock absorber module  2320 . 
     An accommodation part  2411  in which the steering driving unit  2420  described later is accommodated is provided in the steering body  2410 . The accommodation part  2411  according to the present embodiment may be formed to have a form of a groove that is concavely recessed and formed downward from the upper side of the top of the steering body  2410 . The design of a detailed cross-sectional form of the accommodation part  2411  may be variously changed depending on a shape of the steering driving unit  2420 . 
     The steering driving unit  2420  is installed in the steering body  2410 , and rotatably supports the steering body  2410  with respect to the frame module  100 . The steering driving unit  2420  is rotated by using the frame module  100  as an axis upon steering of the vehicle, and rotates the steering body  2410  clockwise or counterclockwise. Accordingly, a steering angle of the wheel  300  connected to the steering body  2410  through the medium of the suspension unit  2300  can be adjusted. 
     The steering driving unit  2420  according to the present embodiment includes a power generation module  2421 , a rotation module  2422 , and a power transfer module  2423 . 
       FIG.  14    is a cross-sectional view schematically illustrating a configuration of the steering driving unit according to the first embodiment of the present disclosure. 
     Referring to  FIG.  14   , the steering driving unit  2420  according to the present embodiment includes a power generation module  2421 , a rotation module  2422 , and a power transfer module  2423 . 
     The power generation module  2421  generates rotatory power by receiving a power source. The power generation module  2421  according to the first embodiment of the present disclosure may be exemplified as various types of electric motors which convert, into rotatory power, a power source applied from the outside and output the rotatory power through a driving shaft  2421   a . The power generation module  2421  may be connected to the battery  400  installed in the frame module  100 , and may be supplied with the power source from the battery  400 . 
     The power generation module  2421  may be seated on one side of the accommodation part  2411 , and may be detachably fixed to the steering body  2410  by bolting, etc. The driving shaft  2421   a  of the power generation module  2421  is disposed to be placed on the same axis as the central axis A of the power generation module  2421 . The central axis A of the power generation module  2421  may be disposed in parallel to the central axis B of the rotation module  2422  described later. However, the power generation module  2421  is not limited to such an example. The power generation module  2421  may be disposed perpendicularly to the central axis B of the rotation module  2422  depending on a detailed structure of the power transfer module  2423  described later. 
     The rotation module  2422  is rotated by using the frame module  100  as an axis by being interlocked with rotatory power generated by the power generation module  2421 . As the rotation module  2422  is rotated by using the frame module  100  as an axis, the rotation module  2422  adjusts a steering angle of the wheel  300  by performing an orbital motion on the power generation module  2421  around the rotation module  2422 . Such a detailed operation process of the power generation module  2421  is described later. 
     The rotation module  2422  is seated on the other side of the accommodation part  2411 , and is disposed in a way to be spaced apart from the power generation module  2421 . The rotation module  2422  may be detachably fixed to the steering body  2410  by bolting, etc. The rotation module  2422  is connected to the power generation module  2421  through the medium of the power transfer module  2423  described later. The rotation module  2422  may be installed in the steering body  2410  in the state in which the rotation module  2422  has been integratedly accommodated in the same case, etc. along with the power generation module  2421  and the power transfer module  2423  as illustrated in  FIG.  14   , and may be installed in the steering body  2410  separately from the power generation module  2421  and the power transfer module  2423 . 
     The central axis B of the rotation module  2422  may be disposed on the same plane as a central surface of the wheel  300 . In this case, the central surface of the wheel  300  may be exemplified as a plane that belongs to a plane through which the central axis of the wheel  300  perpendicularly penetrates and that symmetrically divides the wheel  300  in the width direction of the vehicle. Accordingly, the central axis of rotation of the rotation module  2422  may coincide with an actual steering axis of the wheel  300 , thereby inducing stable steering of the wheel  300 . 
     The rotation module  2422  according to the present embodiment includes a mounting part  2422   a , a rotation module body  2422   b , an input shaft  2422   c , an output shaft  2422   d , a deceleration module  2422   e , and a steering guide  2422   f.    
     The mounting part  2422   a  forms an upper external appearance of the rotation module  2422 , and is fixed to the lower side of the frame module  100 . The mounting part  2422   a  according to the present embodiment may be formed to have a form of a plate facing parallel to the frame module  100 , more specifically, the first mounting plate  1221 A or the second mounting plate  1221 B. The top of the mounting part  2422   a  is detachably coupled to the bottom of the first mounting plate  1221 A or the second mounting plate  1221 B by bolting, etc. The mounting part  2422   a  is fixed to the bottom of the frame module  100 , and generally supports the corner module  200  with respect to the frame module  100 . 
     The rotation module main body  2422   b  forms a lower external appearance of the rotation module  2422 , and is relatively rotatably installed along with the mounting part  2422   a . The rotation module main body  2422   b  according to the present embodiment is formed to have a cylindrical shape having the inside empted, and is installed on the lower side of the mounting part  2422   a . The top of the rotation module main body  2422   b  is rotatably connected to the bottom of the mounting part  2422   a  through the medium of a bearing, etc. The bottom of the rotation module main body  2422   b  is seated on the other side of the accommodation part  2411  and supported by the accommodation part  2411 . The rotation module main body  2422   b  may be assembled in a case in which the rotation module main body  2422   b  is integratedly accommodated along with the power generation module  2421  and the power transfer module  2423 , and may be fixed to the steering body  2410 . The rotation module main body  2422   b  may be directly assembled and fixed to the steering body  2410 . 
     The input shaft  2422   c  is rotatably installed within the rotation module main body  2422   b , and is rotated by rotatory power delivered from the power transfer module  2423 . The input shaft  2422   c  according to the present embodiment may be formed to have a form of a shaft in which the central axis thereof is disposed on the same axis as the central axis B of the rotation module  2422 . The bottom of the input shaft  2422   c  protrudes downward from the rotation module main body  2422   b , and is connected to the power transfer module  2423 . 
     The output shaft  2422   d  is rotatably supported by the mounting part  2422   a . The output shaft  2422   d  is rotated by being interlocked with the rotation of the input shaft  2422   c , and rotates the steering body  2410  by using the mounting part  2422   a  as an axis. The output shaft  2422   d  according to the present embodiment may be formed to have a form of a shaft in which the central axis thereof is disposed on the same axis as the central axis B of the rotation module  2422 . The bottom of the output shaft  2422   d  is relatively rotatably connected to the top of the input shaft  2422   c  through the medium of a bearing. The top of the output shaft  2422   d  is rotatably inserted into the bottom of the mounting part  2422   a  by using the mounting part  2422   a  as an axis. The output shaft  2422   d  is connected to the deceleration module  2422   e  described later, and is rotated by rotatory power delivered from the deceleration module  2422   e  when the input shaft  2422   c  is rotated. 
     The deceleration module  2422   e  is provided between the input shaft  2422   c  and the output shaft  2422   d , and delivers rotatory power of the input shaft  2422   c  to the output shaft  2422   d . More specifically, the deceleration module  2422   e  amplifies the size of rotatory power delivered to the output shaft  2422   d  by decelerating a rotation speed of the input shaft  2422   c  at a set deceleration ratio, and rotates the output shaft  2422   d  by outputted rotatory power. The deceleration module  2422   e  according to the present embodiment may be exemplified as strain wave gearing including a wave generator, a flex spline, or a circular spline. 
     The steering guide  2422   f  is extended from the rotation module main body  2422   b  and is connected to a measurement module  2424  described later. The steering guide  2422   f  according to the present embodiment may be formed to have a disc shape having a hollow form in which an end of an inner circumference thereof is bent upward, and may be disposed between the rotation module main body  2422   b  and the output shaft  2422   d . The steering guide  2422   f  has an outer circumferential surface fixed to the inner circumferential surface of the rotation module main body  2422   b , and is rotated by using the central axis thereof as an axis along with the rotation module main body  2422   b  when the rotation module main body  2422   b  is rotated. An end of the inner circumference of the steering guide  2422   f  is coupled to an inner diameter part  2424   a  of the measurement module  2424  described later. The steering guide  2422   f  rotates the inner diameter part  2424   a  by being interlocked with the rotation of the rotation module main body  2422   b.    
     The power transfer module  2423  is provided between the power generation module  2421  and the rotation module  2422 , and delivers, to the rotation module  2422 , rotatory power generated by the power generation module  2421 . The power transfer module  2423  according to the present embodiment may be formed to have a form of a belt or chain formed to form a closed curve. The power transfer module  2423  has both ends connected to the ends of the driving shaft  2421   a  of the power generation module  2421  and the input shaft  2422   c  of the rotation module  2422 , respectively. In this case, the power transfer module  2423  can be prevented from twisting, etc. as the central axis A of the power generation module  2421  is disposed in parallel to the central axis B of the rotation module  2422 . When the driving shaft  2421   a  is rotated, the power transfer module  2423  is moved in a caterpillar way and delivers rotatory power to the input shaft  2422   c . However, the power transfer module  2423  is not limited to such a structure. The design of the power transfer module  2423  may be changed in various types of power transfer means which can deliver, to the rotation module  2422 , rotatory power generated by the power generation module  2421 , such a worm or a worm wheel. 
     The measurement module  2424  measures a rotation angle of the rotation module  2422  according to the steering of the wheel  300 . The measurement module  2424  according to the present embodiment is disposed within the rotation module main body  2422   b  and fixed to the bottom of the mounting part  2422   a . The inner diameter part  2424   a  capable of being rotated by using the central axis of the measurement module  2424  as an axis is provided in the inner circumferential surface of the measurement module  2424 . The inner diameter part  2424   a  is connected to the steering guide  2422   f  and rotated along with the steering guide  2422   f  when the output shaft  2422   d  is rotated. Upon steering of the vehicle, the measurement module  2424  measures a rotation angle of the rotation module  2422  by measuring an angle at which the inner diameter part  2424   a  has been rotated on the basis of an initial location of the output shaft  2422   d . A detailed form of the measurement module  2424  is not limited to any one, and may be exemplified as various types of steering angle sensors capable of detecting a rotation angle of the output shaft  2422   d . The measurement module  2424  transmits data about a measured rotation angle of the rotation module  2422  to a control unit, such as the ECU of the vehicle, that is, a control unit  20  described later, so that the control unit performs rolling control, rotation control, etc. of the vehicle. 
     Hereinafter, an operating process of the corner module  200  according to the first embodiment of the present disclosure is described in detail. 
       FIGS.  15 ,  16 A and  16 B  are operation diagrams schematically illustrating an operating process of the corner module according to the first embodiment of the present disclosure. 
     When a vehicle requires rotation driving while driving, the driving shaft  2421   a  is rotated by the power generation module  2421 , and rotatory power is generated. 
     The power transfer module  2423  is moved in a caterpillar way by the rotation of the driving shaft  2421   a , and delivers the rotatory power of the power generation module  2421  to the rotation module  2422 . 
     The rotatory power delivered to the rotation module  2422  is delivered to the output shaft  2422   d  sequentially through the input shaft  2422   c  and the deceleration module  2422   e.    
     More specifically, the elliptical cam of a wave generator of the deceleration module  2422   e  is rotated by the rotatory power of the input shaft  2422   c.    
     Thereafter, the flex spline is rotated while generating elastic deformation. Accordingly, locations of the teeth of a gear on the outer circumferential surface of the flex spline partially engaged with the teeth of a gear on the inner circumferential surface of the circular spline are sequentially moved. 
     When the elliptical cam is rotated once, the flex spline is moved in a direction opposite to the rotation direction of the elliptical cam by a difference between the number of teeth of the gear on the outer circumferential surface of the flex spline and the number of teeth of the gear on the inner circumferential surface of the flex spline. 
     Accordingly, the output shaft  2422   d  coupled with the flex spline is rotated in a direction opposite to the rotation direction of the input shaft  2422   c  at a reduced rotation speed than a rotation speed of the input shaft  2422   c.    
     The output shaft  2422   d  is rotated by using the mounting part  2422   a  fixed to the first mounting plate  1221 A or the second mounting plate  1221 B, more specifically, the central axis B of the rotation module  2422  as an axis. 
     As the output shaft  2422   d  is rotated by using the central axis B of the rotation module  2422  as an axis, the rotation module main body  2422   b  integrated with the output shaft  2422   d  and the steering body  2410  are also rotated by using the central axis B of the rotation module  2422  as an axis. 
     Accordingly, the power generation module  2421  spaced apart from the central axis B of the rotation module  2422  at a predetermined interval performs an orbital motion around the central axis B of the rotation module  2422 . 
     Rotatory power generated as the steering body  2410  is rotated is delivered to the wheel  300  sequentially through the suspension unit  2300  and the driving unit  2100 . 
     As the central axis B of the rotation module  2422  is disposed on the same plane as the central surface of the wheel  300 , the wheel  300  is rotated by the delivered rotatory power by using the central axis B of the rotation module  2422  as an axis. The wheel  300  has its steering angle adjusted and rotates and drives the vehicle. 
     Hereinafter, a configuration of a vehicle including a corner module apparatus according to another embodiment of the present disclosure is described. 
     In this process, a description redundant with that of the vehicle including the corner module apparatus according to the aforementioned embodiment of the present disclosure is omitted for convenience of description. 
       FIG.  17    is a front view schematically illustrating a configuration of a vehicle including a corner module apparatus according to another embodiment of the present disclosure. 
     Referring to  FIG.  17   , a frame module  100  according to another embodiment of the present disclosure includes a plurality of first corner module platforms  1200 A and a plurality of second corner modules platforms  1200 B. 
     The plurality of first corner module platforms  1200 A and the plurality of second corner module platforms  1200 B are extended in the length direction of a vehicle body from one side and the other side of a main platform  1100 . 
     More specifically, the neighboring first corner module platforms  1200 A are connected in series in the length direction of the vehicle body from one side of the main platform  1100 . The neighboring second corner module platforms  1200 B are connected in series in the length direction of the vehicle body from the other side of the main platform  1100 . In this case, the numbers of plurality of first corner module platforms  1200 A and plurality of second corner module platforms  1200 B may be identical and may be different. Accordingly, the number of corner modules  200  installed in the frame module  100  according to another embodiment of the present disclosure may be freely expanded to both sides of the main platform  1100  based on a purpose of a vehicle. 
       FIG.  18    is a diagram schematically illustrating a configuration of a first corner module platform and a second corner module platform according to another embodiment of the present disclosure. 
     Referring to  FIG.  18   , the first corner module platform  1200 A and the second corner module platform  1200 B according to the present embodiment further include a first corner module extension fastening part  1240 A and a second corner module extension fastening part  1240 B, respectively. 
     The first corner module extension fastening part  1240 A includes a first corner module plate  1210 A and a first corner module wheel housing  1220 A. The first corner module extension fastening part  1240 A is disposed on the opposite side of a first corner module fastening part  1230 A in the first corner module platform  1200 A. That is, the first corner module fastening part  1230 A and the first corner module extension fastening part  1240 A are disposed at both ends of the first corner module platform  1200 A. 
     The first corner module extension fastening part  1240 A provided in any one first corner module platform  1200 A is detachably coupled to the first corner module fastening part  1230 A provided in a neighbor first corner module platform  1200 A. More specifically, the first corner module extension fastening part  1240 A is locked and coupled with the first corner module fastening part  1230 A as neighbor first corner module platforms  1200 A come into contact with each other in a direction parallel to the length direction of a vehicle. Accordingly, the plurality of first corner module platforms  1200 A that are extended in series may be sequentially connected in the length direction of the vehicle. 
       FIGS.  19  and  20    are enlarged views schematically illustrating a configuration of the first corner module extension fastening part and the second corner module extension fastening part according to another embodiment of the present disclosure. 
     Referring to  FIGS.  19  and  20   , the first corner module extension fastening part  1240 A according to the present embodiment includes a first corner module upper-extension fastening part  1241 A and a first corner module lower-extension fastening part  1242 A. 
     The first corner module upper-extension fastening part  1241 A according to the present embodiment may be formed to have a form of a groove that is concavely recessed and formed from the first corner module wheel housing  1220 A, more specifically, an outside surface of a first mounting plate  1221 A. The first corner module upper-extension fastening part  1241 A is perpendicularly downward extended from the top of the first corner module wheel housing  1220 A. The first corner module upper-extension fastening part  1241 A is disposed at the end of the other of the front or rear of the first corner module wheel housing  1220 A, that is, on a side opposite to the first corner module upper-fastening part  1231 A. The first corner module upper-extension fastening part  1241 A may have a cross-sectional form having a step form so that the first corner module upper-extension fastening part  1241 A is locked and coupled with a first corner module upper-fastening part  1231 A provided in a neighbor first corner module platform  1200 A. The first corner module upper-extension fastening part  1241 A may be provided in plural, and may be individually provided in the first corner module wheel housings  1220 A. 
     The first corner module lower-extension fastening part  1242 A according to the present embodiment may be formed to have a form of a groove that is concavely recessed and formed from an outside surface of the first corner module plate  1210 A. 
     The first corner module lower-extension fastening part  1242 A is extended in a direction opposite to a direction of the first corner module upper-extension fastening part  1241 A. More specifically, the first corner module lower-extension fastening part  1242 A is perpendicularly upward extended from the bottom of the first corner module plate  1210 A. Accordingly, when being fastened to the first corner module fastening parts  1230 A, the first corner module upper-extension fastening part  1241 A and the first corner module lower-extension fastening part  1242 A can prevent the first corner module fastening part  1230 A from deviating to any one direction. 
     The first corner module lower-extension fastening part  1242 A is disposed at the end of the other of the front or rear of the first corner module plate  1210 A, that is, on a side opposite to the first corner module lower-fastening part  1232 A. The first corner module lower-extension fastening part  1242 A may have a cross-sectional form having a step form so that the first corner module lower-extension fastening part  1242 A is locked and coupled with a first corner module lower-fastening part  1232 A provided in a neighbor first corner module platform  1200 A. 
     The second corner module extension fastening part  1240 B is provided in the second corner module plate  1210 B and the second corner module wheel housing  1220 B. The second corner module extension fastening part  1240 B is disposed on the opposite side of a second corner module fastening part  1230 B in the second corner module platform  1200 B. That is, the second corner module fastening part  1230 B and the second corner module extension fastening part  1240 B are disposed at both ends of the second corner module platform  1200 B, respectively. 
     The second corner module extension fastening part  1240 B provided in any one second corner module platform  1200 B is detachably coupled the second corner module fastening part  1230 B provided in a neighbor second corner module platform  1200 B. More specifically, when neighbor second corner module platforms  1200 B are brought into contact with each other in a direction parallel to the length direction of the vehicle, the second corner module extension fastening part  1240 B is locked and coupled with the second corner module fastening part  1230 B. Accordingly, a plurality of second corner module platforms  1200 B that are extended in series may be sequentially connected in the length direction of the vehicle. 
     The second corner module extension fastening part  1240 B according to the present embodiment includes a second corner module upper-extension fastening part  1241 B and a second corner module lower-extension fastening part  1242 B. 
     The second corner module upper-extension fastening part  1241 B according to the present embodiment may be formed to have a form of a groove that is concavely recessed and formed from the second corner module wheel housing  1220 B, more specifically, an outside surface of a second mounting plate  1221 B. The second corner module upper-extension fastening part  1241 B is perpendicularly downward extended from the top of the second corner module wheel housing  1220 B. The second corner module upper-extension fastening part  1241 B is disposed at the end of the other of the front or rear of the second corner module wheel housing  1220 B, that is, on the opposite side of a second corner module upper-fastening part  1231 B. The second corner module upper-extension fastening part  1241 B may have a cross-sectional form having a step form so that the second corner module upper-extension fastening part  1241 B can be locked and coupled with the second corner module upper-fastening part  1231 B provided in a neighbor second corner module platform  1200 B. The second corner module upper-extension fastening part  1241 B may be provided in plural and individually provided in the second corner module wheel housing  1220 B. 
     The second corner module lower-extension fastening part  1242 B according to the present embodiment may be formed to have a form of a groove that is concavely recessed and formed from the outside surface of the second corner module plate  1210 B. 
     The second corner module lower-extension fastening part  1242 B is extended in a direction opposite to the direction of the second corner module upper-extension fastening part  1241 B. More specifically, the second corner module lower-extension fastening part  1242 B is perpendicularly upward extended from the bottom of the second corner module plate  1210 B. Accordingly, when being fastened to the second corner module fastening part  1230 B, the second corner module upper-extension fastening part  1241 B and the second corner module lower-extension fastening part  1242 B can prevent the second corner module fastening part  1230 B from deviating in any direction thereof. 
     The second corner module lower-extension fastening part  1242 B is disposed at the end of the other of the front or rear of the second corner module plate  1210 B, that is, on the opposite side of the second corner module lower-fastening part  1232 B. The second corner module lower-extension fastening part  1242 B may have a cross-sectional form having a step form so that the second corner module lower-extension fastening part  1242 B can be locked and coupled with the second corner module lower-fastening part  1232 B provided in a neighbor second corner module platform  1200 B. 
     A second door  3   b  according to the present embodiment is provided in pair. The pair of second doors  32   b  is installed on sides of the top hat  2  in forward and backward directions in a way to be opened and closed. The pair of second doors  3   b  may be disposed on the first corner module platform  1200 A and the second corner module platform  1200 B disposed on the outermost side thereof in the length direction of a vehicle body, respectively, among a plurality of first corner module platforms  1200 A and second corner module platforms  1200 B. 
     Hereinafter, a configuration of a vehicle including a corner module apparatus for a vehicle according to still another embodiment of the present disclosure is described in detail. 
     In this process, a description redundant with that of a vehicle including a corner module apparatus for a vehicle according to the embodiment or another embodiment of the present disclosure is omitted for convenience of description. 
       FIG.  21    is a front view schematically illustrating a configuration of a vehicle including a corner module apparatus for a vehicle according to still another embodiment of the present disclosure. 
     Referring to  FIG.  21   , the vehicle including the corner module apparatus for a vehicle according to still another embodiment of the present disclosure includes a main platform assembly  1000 , a first corner module platform  1200 A, and a second corner module platform  1200 B. 
     The main platform assembly  1000  includes a middle module platform  1300  disposed between at least two main platforms  1100  and a main platform. 
     Neighbor main platforms  1100  are disposed to be spaced apart from each other at a given interval in a length direction of the vehicle. In this case, the first corner module platform  1200 A is detachably coupled to one side (a left side of  FIG.  21   ) of the main platform  1100  disposed on the outermost side of one side (the left side of  FIG.  21   ) among the plurality of main platforms  1100 . The second corner module platform  1200 A is detachably coupled to the other side (a right side of  FIG.  21   ) of the main platform  1100  disposed on the outermost side of the other side (the right side of  FIG.  21   ) among the plurality of main platforms  1100 . Accordingly, the frame module  100  according to still another embodiment of the present disclosure may also be applied to a vehicle having a vehicle body whose length is relatively long, such as a tram, a bus, or a trailer, because weight of a battery  400  can be distributed through the plurality of main platforms  1100 . 
     The middle module platform  1300  includes a third corner module platform  1200 C disposed between neighbor main platforms  1100  and supporting a corner module  200 . 
     One or more third corner module platforms  1200 C may be provided between neighbor main platforms  1100 . If the third corner module platform  1200 C is provided in plural, the plurality of third corner module platforms  1200 C may be connected in series in the length direction of the vehicle body. The third corner module platform  1200 C disposed on the outermost side of the plurality of third corner module platforms  1200 C is detachably coupled to an end that belongs to the end of a neighbor main platform  1100  and with which the first corner module platform  1200 A and the second corner module platform  1200 B are not coupled. 
     The third corner module platform  1200 C has a bottom coupled with the corner module  200  described later and supports the corner module  200 . The corner module  200  and an inverter  500  for converting, into AC power, DC power supplied from the battery  400  and delivering the AC power to the corner module  200  are mounted within the third corner module platform  1200 C. 
     The third corner module platform  1200 C according to the present embodiment includes a third corner module plate, a third corner module wheel housing, and a third corner module fastening part. 
     Detailed shapes of the third corner module plate, the third corner module wheel housing, the third corner module fastening part, and the third corner module extension fastening part may be identical with the shapes of the first corner module plate  1210 A, the first corner module wheel housing  1220 A, the first corner module fastening part  1230 A, and the first corner module extension fastening part  1240 A illustrated in  FIG.  10   . 
     For the smooth coupling of the main platform  1100 , the third corner module extension fastening part provided in the third corner module platform  1200 C disposed at any one end among the plurality of third corner module platforms  1200 C disposed between neighbor main platforms  1100  may be formed to have a form of a hook that protrudes from the third corner module plate and the third corner module wheel housing. 
     The top of a mounting part  2422   a  provided in the plurality of corner modules  200  according to the present embodiment may be detachably coupled with the bottom of the first mounting plate  1221 A, the second mounting plate  1221 B, or the third mounting plate by bolting, etc. depending on a location. 
     An opened bottom of a top hat  2  according to the present embodiment is disposed to face the top of the frame module  100 , that is, the tops of the main platform assembly  1000 , the first corner module platform  1200 A, and the second corner module platform  1200 B. The top hat  2  may have the bottom coupled with the tops of the main wheel housing  1120 , the first corner module wheel housing  1220 A, the second corner module wheel housing  1220 B, and the third corner module wheel housing by bolting, and may be detachably fixed to the frame module  100 . 
     A first door  3   a  according to the present embodiment may be provided in plural. The first doors  3   a  may be spaced apart from each other at a given interval in the length direction of the top hat  2 , and may be individually disposed on the main platform  1100  provided in the main platform assembly  1000 . 
     II. Application of Corner Module Apparatus for Vehicle 
       FIG.  22    is a block diagram for describing a function of a corner module apparatus for a vehicle according to an embodiment of the present disclosure. Referring to  FIG.  22   , the corner module apparatus for a vehicle according to an embodiment of the present disclosure includes an acquisition module  10 , a controller  20 , and an output unit  30 . 
     The acquisition module  10  functions as a module for obtaining overall information that is necessary for the controller  20  to implement first to fifth applications described later, and includes a steering wheel angle acquisition part  11 , a lever ratio acquisition part  12 , a braking initiation manipulation acquisition unit  13 , a wheel velocity acquisition part  14 , and a vehicle information acquisition unit  15  as illustrated in  FIG.  22   . The steering wheel angle acquisition part  11  and the lever ratio acquisition part  12  are related to the first application. The braking initiation manipulation acquisition unit  13  is related to the second application. The wheel velocity acquisition part  14  is related to the third and fourth applications. The vehicle information acquisition unit  15  is related to the fifth application. 
     The steering wheel angle acquisition part  11  may obtain a steering wheel angle. The steering wheel angle may correspond to a steering angle formed through the steering of a driver for a steering wheel or a steering angle command from an ADAS system. Accordingly, the steering wheel angle acquisition part  11  may be implemented as a separate input module for obtaining a steering angle command outputted by a steering angle sensor or the ADAS system mounted on a vehicle. 
     The lever ratio acquisition part  12  may obtain the lever ratio. In the first application described later, the lever ratio is defined as a parameter indicating whether the front wheel and rear wheel of a bicycle model are inphase or reversed-phased and a steering angle ratio between the front wheel and rear wheel, which are defined with respect to a vehicle, and may have a value of −1 to 1. A sign of the lever ratio indicates whether the front wheel and rear wheel of the bicycle model are inphase or reverse-phased (e.g., an inphase when the sign is a positive value, and a reverse phase when the sign has a negative value). The size of the lever ratio indicates a steering angle ratio between the front wheel and rear wheel of the bicycle model (e.g., when the lever ratio is 0.5, a front wheel steering angle:a rear wheel steering angle=2:1). The lever ratio may be configured to be changed based on a manipulation of a driver. To this end, the lever ratio acquisition part  12  may be implemented as a lever structure (an example of  FIG.  23   ) provided in the interior of a vehicle or a touch screen structure provided in the instrument panel of a vehicle. Accordingly, the lever ratio may be changed by a lever manipulation of a driver or a touch manipulation of a driver on the touch screen. 
     The braking initiation manipulation acquisition unit  13  may obtain a braking initiation manipulation of a vehicle from a driver. In the second application described later, braking may correspond to a concept including a braking operation (e.g., sudden braking) in the state in which a vehicle drives on a slope S and a braking operation (i.e., parking braking) for maintaining a parked or stopped in a slope S. However, as described later, in the second application, an operation of the present embodiment may be applied when a vehicle moves in a preset low-speed area for the posture stability of the vehicle if a braking operation in the state in which the vehicle drives on the slope S is performed, in that braking is performed through a method of independently controlling the steering of each of the four wheels of the vehicle. The braking initiation manipulation acquisition unit  13  may be implemented in the form of a switch separately provided within a vehicle, and may obtain, as the braking initiation manipulation, a manipulation of a driver for the switch. 
     The wheel velocity acquisition part  14  may obtain a wheel velocity of the four wheels of a vehicle. The wheel velocity acquisition part  14  may be implemented as a motor sensor for sensing the number of revolutions of an in-wheel motor mounted on each wheel. The wheel velocity acquisition part  14  may obtain wheel velocities of a left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. 
     The vehicle information acquisition unit  15  may obtain driving state information and driving environment information of a vehicle. The driving state information may include a vehicle speed and heading angle of a vehicle. The driving environment information may include surrounding image information (e.g., a front image) of a vehicle. In order to obtain such driving state information and driving environment information, the vehicle information acquisition unit  15  may use various sensors (e.g., a vehicle sensor, a gyro sensor, and a camera sensor) mounted on a vehicle. Driving state information and driving environment information of a vehicle obtained by the vehicle information acquisition unit  15  may be used in a process of calculating information on a distance up to a target point, target curvature, and a target steering angle in the fifth application described later. 
     The controller  20  is a main agent that independently controls the driving and steering of the four wheels of a vehicle through individual driving torque for each of the four wheels, and may be implemented as an electronic control unit (ECU), a central processing unit (CPU), a processor, or a system on chip (SoC). The controller  20  may control a plurality of hardware or software components connected to the controller  20  by driving an operating system or an application, and may perform various data processing and operations. The controller  20  may be configured to execute at least one instruction stored in a memory and store data, that is, a result of the execution, in the memory. 
     The output unit  30  may correspond to a display, a speaker, etc. which is installed in a cluster of a vehicle or at a specific location within a vehicle. 
     Hereinafter, the first to fifth applications of the corner module apparatus for a vehicle and detailed operating methods thereof are described chiefly based on an operation of the controller  20 . 
     1. First Application: Individual Steering Architecture 
     In the first application, the controller  20  may calculate first to fourth target angles of a left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively, based on a steering wheel angle obtained by the steering wheel angle acquisition part  11  and a lever ratio obtained by the lever ratio acquisition part  12 , and may independently control the steering of each of the four wheels of the vehicle based on the calculated first to fourth target angles. 
       FIG.  23    illustrates, as a general example, a series of processes of calculating, by the controller  20 , the first to fourth target angles. Referring to  FIG.  23   , (process {circle around (1)}), first, the controller  20  may receive a steering wheel angle obtained by the steering wheel angle acquisition part  11  and a lever ratio obtained by the lever ratio acquisition part  12 . (Process {circle around (2)}) Next, the controller  20  may calculate a front wheel heading angle of the bicycle model from the steering wheel angle. In this case, the controller  20  may calculate the front wheel heading angle by multiplying the steering wheel angle by a preset steering sensitivity. The steering sensitivity may correspond to a total gear ratio (TGR) of a steering gear ratio variable device applied to the vehicle. (Process {circle around (3)}) When the front wheel heading angle is calculated, the controller  20  may calculate a rear wheel heading angle of the bicycle model based on the front wheel heading angle and a lever ratio obtained by the lever ratio acquisition part  12 . (Process {circle around (4)}), next, the controller  20  may expand the bicycle model to a four-wheel vehicle model and calculate first to fourth target angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel of the vehicle. 
     Among the aforementioned processes, the process {circle around (4)} corresponding to a direct process of calculating the first to fourth target angles may be performed in a differentiated way based on a value of the lever ratio obtained by the lever ratio acquisition part  12 . Specifically, in the present embodiment, a steering control mode of the controller  20  for the steering of the four wheels may be divided into a front-wheel steering mode, a four-wheel inphase steering mode, and a four-wheel reversed-phase steering mode based on a value of the lever ratio. The controller  20  may calculate the first to fourth target angles in differentiated ways based on a value of the lever ratio and for each steering control mode determined based on a value of the lever ratio. Hereinafter, a process of calculating the first to fourth target angles based on a value of the lever ratio and a steering control mode is described in detail. 
     First, the front-wheel steering mode corresponds to a steering control mode when the lever ratio is 0. That is, since the lever ratio is 0, rear-wheel steering control is not performed, and only common front-wheel steering control is performed. In this case, the controller  20  may calculate first and second target angles by applying the Ackerman geometry model to a front wheel heading angle, and may calculate third and fourth target angles as a neutral angle (i.e., 0°) indicative of the longitudinal direction of the vehicle because the lever ratio is 0.  FIG.  24    illustrates an example in which when a front wheel heading angle is 45°, first and second target angles are calculated as given values based on the center of rotation according to the Ackerman geometry model. 
     Next, the four-wheel inphase steering mode corresponds to a steering control mode when the lever ratio is greater than 0 and equal to or smaller than 1. That is, since the lever ratio is a positive value, the front wheel and the rear wheel are independently controlled in the state in which the lever ratio is inphase. In the four-wheel inphase steering mode, first to fourth target angles are calculated in differentiated ways “when the lever ratio is greater than 0 and smaller than 1” and “when the lever ratio is 1.” 
     When the lever ratio is greater than 0 and less than 1, the controller  20  may calculate first and second target angles by applying the Ackerman geometry model to a front wheel heading angle. Furthermore, the controller  20  may calculate a rear wheel heading angle of the bicycle model by applying (or multiplying) the lever ratio to the front wheel heading angle, and may calculate third and fourth target angles by applying the Ackerman geometry model to the calculated rear wheel heading angle.  FIG.  25    illustrates an example in which when the lever ratio is 0.5, that is, when a front wheel heading angle is 45°, first to fourth target angles are calculated as given values based on the center of rotation according to the Ackerman geometry model. 
     When the lever ratio is 1, the controller  20  may calculate first to fourth target angles as front wheel heading angles. That is, when the lever ratio is 1, this means a state in which the center of rotation according to the Ackerman geometry model is not present, the front wheels and the rear wheels have an inphase state, and steering angles are identically formed. The controller  20  may calculate the first to fourth target angles as front wheel heading angles.  FIG.  26    illustrates an example in which when the lever ratio is 1, that is, when a front wheel heading angle is 45°, first to fourth target angles are calculated as front wheel heading angles. 
     The four-wheel reversed-phase steering mode corresponds to a steering control mode when the lever ratio is equal to greater than −1 and less than 0. That is, since the lever ratio is a negative value, the front wheels and the rear wheels are independently controlled in the state in which the front wheels and the rear wheels have reversed phases. In the four-wheel reversed-phase steering mode, the center of rotation according to the Ackerman geometry model is always present. Accordingly, the controller  20  may calculate first and second target angles by applying the Ackerman geometry model to a front wheel heading angle, and may calculate third and fourth target angles by applying the Ackerman geometry model to a rear wheel heading angle of the bicycle model which is calculated by applying the lever ratio to the front wheel heading angle.  FIG.  27    illustrates an example in which when the lever ratio is −0.8, that is, when a front wheel heading angle is 45°, first to fourth target angles are calculated as predetermined values based on the center of rotation according to the Ackerman geometry model.  FIG.  28    illustrates an example in which when the lever ratio is −1, that is, when a front wheel heading angle is 45°, first to fourth target angles are calculated as predetermined values based on the center of rotation according to the Ackerman geometry model. 
     Table 1 below illustrates a method of calculating the first to fourth target angles based on a value of the lever ratio and a steering control mode. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Steering control 
                 Lever ratio 
                   
               
               
                 mode 
                 (R) 
                 Method of calculating target angle 
               
               
                   
               
             
            
               
                 Front-wheel 
                 0 
                 First and second target angles: 
               
               
                 steering mode 
                   
                 Ackerman geometry model 
               
               
                   
                   
                 Third and fourth target angles: neutral 
               
               
                   
                   
                 angle 
               
               
                 Four-wheel 
                 0 &lt; R &lt; 1 
                 First to fourth target angles: Ackerman 
               
               
                 inphase steering 
                   
                 geometry model 
               
               
                 mode 
               
               
                   
                 R = 1 
                 First to fourth target angles: front 
               
               
                   
                   
                 wheel heading angle 
               
               
                 Four-wheel 
                 −1 ≤ R &lt; 0 
                 First to fourth target angles: Ackerman 
               
               
                 reversed-phase 
                   
                 geometry model 
               
               
                 steering mode 
               
               
                   
               
            
           
         
       
     
     As described above, the lever ratio may be configured to be changed and set based on a manipulation of a driver. Accordingly, if sudden transition of a steering control mode is caused because the lever ratio is changed in a process of a vehicle driving, there occurs a problem in that the driving stability of a vehicle, such as a slip of a vehicle tire to the rollover of a vehicle, is reduced. In order to prevent such a problem, in the present embodiment, when the transition of a steering control mode is caused due to a change in the lever ratio, the controller  20  may perform the transition of the steering control mode during a preset excess time by controlling change speeds of the steering angles of the four wheels at a preset control speed. The control speed may be preset in the controller  20  based on experimental results of a designer so that the control speed has a sufficiently low value within a range in which the driving stability of a vehicle is secured without causing sudden transition of a steering control mode. The excess time may also be preset in the controller  20  as a value corresponding to a control speed. As a detailed example, if transition to the four-wheel reversed-phase steering mode is caused because a driver changes the lever ratio to −0.5 in the state in which a vehicle drives in the four-wheel inphase steering mode, the controller  20  changes a current steering angle of a rear wheel to a target angle (i.e., third and fourth target angles in the four-wheel reversed-phase steering mode), but may slowly change the steering angle of the rear wheel to the third and fourth target angles based on a control speed so that the driving stability of the vehicle can be secured. 
       FIG.  29    is a flowchart for describing an operating method in the first application of the corner module apparatus for a vehicle according to an embodiment of the present disclosure. An operating method of the corner module apparatus for a vehicle according to the present embodiment is described with reference to  FIG.  29   . A detailed description of a portion redundant with the aforementioned contents is omitted, and a time-series configuration thereof is chiefly described. 
     First, the steering wheel angle acquisition part  11  obtains a steering wheel angle (S 10   a ). The lever ratio acquisition part  12  obtains a lever ratio indicating whether the front wheels and rear wheels of the bicycle model are inphase and reversed-phased and a steering angle ratio between the front wheels and the rear wheels, which have been defined with respect to a vehicle (S 20   a ). The lever ratio has a value of −1 to 1. A sign of the lever ratio indicates whether the front wheels and rear wheels of the bicycle model are inphase and reversed-phased. The size of the lever ratio indicates a steering angle ratio between the front wheels and rear wheels of the bicycle model. 
     Next, the controller  20  calculates a front wheel heading angle of the bicycle model based on the steering wheel angle obtained in step S 10   a , and calculates a rear wheel heading angle of the bicycle model based on the calculated front wheel heading angle and the lever ratio obtained in step S 20   a  (S 30   a ). In step S 30   a , the controller  20  calculates the front wheel heading angle by multiplying the steering wheel angle by a preset steering sensitivity. 
     Next, the controller  20  expands the bicycle model to a four-wheel vehicle model, and calculates first to fourth target angles of a left front wheel, right front wheel, left rear wheel, and right rear wheel of the vehicle, respectively (S 40   a ). A method of calculating the first to fourth target angles in step S 40   a  is differentially determined based on the lever ratio obtained in step S 20   a . Specifically, the first to fourth target angles are calculated in differentiated ways based on a value of the lever ratio and for each steering control mode determined based on a value of the lever ratio. The steering control mode includes the front-wheel steering mode corresponding to a case where the lever ratio is 0, the four-wheel inphase steering mode corresponding to a case where the lever ratio is greater than 0 and equal to or smaller than 1, and the four-wheel reversed-phase steering mode corresponding to a case where the lever ratio is equal to greater than −1 and less than 0. 
     When a steering control mode of the vehicle is the front-wheel steering mode, in step S 40   a , the controller  20  calculates the first and second target angles by applying the Ackerman geometry model to the front wheel heading angle, and calculates the third and fourth target angles as a neutral angle indicative of the longitudinal direction of the vehicle. 
     When a steering control mode of the vehicle is the four-wheel inphase steering mode or the four-wheel reversed-phase steering mode in the state in which the lever ratio is greater than 0 and less than 1, in step S 40   a , the controller  20  (i) calculates the first and second target angles by applying the Ackerman geometry model to the front wheel heading angle and (ii) calculates a rear wheel heading angle of the bicycle model by applying the lever ratio to the front wheel heading angle and calculates the third and fourth target angles by applying the Ackerman geometry model to the calculated rear wheel heading angle. 
     When a steering control mode of the vehicle is the four-wheel inphase steering mode in the state in which the lever ratio is 1, in step S 40   a , the controller  20  calculates the first to fourth target angles as front wheel heading angles. 
     When the first to fourth target angles are calculated in step S 40   a , the controller  20  independently controls the steering of each of the four wheels of the vehicle based on the first to fourth target angles (S 50   a ). If the transition of a steering control mode is caused due to a change in the lever ratio, in step S 50   a , the controller  20  performs the transition of the steering control mode during a preset excess time by controlling change speeds of the steering angles of the four wheels at a preset control speed. 
     According to the first application, there are advantages in terms of expandability and a degree of freedom because independent control is applied to the steering of each of the four wheels compared to the existing front wheel steering method or rear wheel steering method (RWS). Independent control of the four wheels can be safely performed even in a driving state in addition to a case where a vehicle is parked and stopped because the transition of a steering control mode is implemented to have continuity. 
     2. Second Application: Braking Mechanism Through Individual Steering 
     In the second application, when a braking initiation manipulation is obtained by the braking initiation manipulation acquisition unit  13 , the controller  20  may perform the braking of a vehicle by independently controlling the steering of four wheels of the vehicle. 
     In the case of a structure in which the four wheels are independently controlled, the brake of each corner module may be removed depending on a design method, and a method of performing braking through an in-wheel motor may be applied. In this case, since control of the in-wheel motor is impossible in the state in which a power source of the vehicle has been off, a new braking logic is required because braking control is impossible. The present embodiment proposes a method of performing the braking of a vehicle in a way to control the state in which the four wheels of the vehicle have been aligned by independently controlling the steering of each of the four wheels with consideration taken of the design expandability of devices for independently driving the four wheels and the need for corresponding braking logic. The method is described in detail below. In order to help understanding of an embodiment, an example in which a braking operation (i.e., parking braking) for maintaining a parked or stopped state in a slope S is described. 
     In the present embodiment, when a braking initiation manipulation is obtained by the braking initiation manipulation acquisition unit  13  in the state in which a vehicle has been placed in the slope S, the controller  20  may perform the braking of the vehicle by independently controlling the steering of four wheels of the vehicle based on an angle (acute angle) (defined as a direction angle in the present embodiment) between an inclined direction of the slope S and a longitudinal direction of the vehicle.  FIG.  30    illustrates an example in which the vehicle is placed in the slope S.  FIGS.  31  to  33    illustrate postures of the vehicle when the vehicle and the slope S are viewed from a direction “A” in  FIG.  30    ( FIG.  31   : the direction angle is 0°,  FIG.  32   : the direction angle is 40°,  FIG.  33   : the direction angle is 80°). 
     In this case, the controller  20  may align the four wheels of the vehicle according to different rules with respect to down wheels DW disposed on the lower side of the slope S and up wheels UW disposed on the upper side of the slope S among the four wheels. The state in which the direction angle is 0° in  FIG.  31    is described as an example. A relatively great load is applied to the down wheels DW disposed on the lower side of the slope S and a relatively small load is applied to the up wheels UW disposed on the upper side of the slope S, on the basis of the inclined direction of the slope S. Accordingly, aligning the down wheels DW to which the relatively great load is applied in a way to limit a movement of the vehicle to the inclined direction of the slope S and aligning the up wheels UW to which the relatively small load is applied in a way to limit a movement of the vehicle to a direction perpendicular to the slope direction are effective in prohibiting a movement of the vehicle from the slope S to the longitudinal direction and transverse direction of the vehicle and maintaining the parking and stopping state of the vehicle. 
     Accordingly, if steering control rules for a down wheel DW and an up wheel UW are indicated as a first rule and a second rule, respectively, the first rule may be predefined in the controller  20  as a rule for limiting a movement of the vehicle to an inclined direction of the slope S. Furthermore, the second rule may be predefined in the controller  20  as a rule for limiting a movement of the vehicle to a direction perpendicular to a slope direction of the slope S on the inclined plane of the slope. 
     A process of aligning down wheels DW and up wheels UW according to the first rule and the second rule is described in detail with reference to  FIG.  34    illustrating an example in which the direction angle is 0°. When the direction angle is 0°, down wheels DW are defined as two wheels disposed on the lower side of the slope S among the four wheels. Up wheels UW are defined as the remaining two wheels disposed on the upper side of the slope S among the four wheels (the down wheels DW and the up wheels UW are differently defined depending on the direction angle, and is described in detail later). 
     As a criterion for aligning down wheels DW and up wheels UW, the present embodiment adopts a reference point that is defined as a point separated from the center of gravity (GC) of a vehicle by a set distance in a direction opposite to a slope direction. If a circle having the reference point as a center thereof and passing through the center of gravity (GC) of the vehicle is defined as a parking circle, the reference point may be named the center of parking circle (CPC). Wheels may be aligned on the basis of the reference point CPC, and the vehicle may converge on a stable state with respect to the slope S. The set distance may be represented as N*WB. In this case, WB is a distance between a front wheel axle and a rear wheel axle, and N corresponds to a value that is set based on a gradient of the vehicle (e.g., the controller  20  may set a value of N so that N has a higher value as the gradient becomes greater. In  FIGS.  34  to  36   , N=1.5). An algorithm that defines the reference point CPC may be preset in the controller  20 . 
     If the reference point CPC is defined as described above, the first rule may be defined as a rule for aligning down wheels DW so that a straight line that connects the reference point CPC and a center point of the down wheels DW and long axes of the down wheels DW become perpendicular to each other. The second rule may be defined as a rule for aligning up wheels UW so that a straight line that connects the reference point CPC and a center point of the up wheels UW and long axes of the up wheels UW are placed on the same line. 
     Accordingly, as illustrated in  FIG.  34   , the controller  20  may align down wheels DW so that a straight line that connects the reference point CPC and a center point of the down wheels DW and long axes of the down wheels DW become perpendicular to each other according to the first rule, and may align up wheels UW so that a straight line that connects the reference point CPC and a center point of the up wheels UW and long axes of the up wheels UW are placed on the same line according to the second rule. 
     A case where down wheels DW correspond to two wheels disposed on the lower side of the slope S among the four wheels and up wheels UW correspond to the remaining two wheels disposed on the upper side of the slope S among the four wheels has been described. However, as described above, in the present embodiment, down wheels DW and up wheels UW may be differently defined depending on a direction angle. As described above, a first area to a third area are defined.
         The first area: an area in which the direction angle is equal to or greater than 0° and less than a first reference angle   The second area: an area in which the direction angle is equal to or greater than the first reference angle and less than a second reference angle   The third area: an area in which the direction angle is equal to or greater than the second reference angle or equal to or smaller than 90°       

     The first reference angle and the second reference angle may be preset in the controller  20  based on specifications of a vehicle and experimental results of a designer. For example, the first reference angle may be set to 20°, and the second reference angle may be set to 70°. 
     Accordingly, if the direction angle is present in the first area or the third area, down wheels DW may be defined as two wheels disposed on the lower side of the slope S among the four wheels, and up wheels UW may be defined as the remaining two wheels disposed on the upper side of the slope S among the four wheels. Furthermore, if the direction angle is present in the second area, down wheels DW may be defined as three wheels disposed on the lower side of the slope S among the four wheels, and up wheel UW may be defined as the remaining one wheel disposed on the upper side of the slope S. A case where the direction angle is present in the first area has been described with reference to  FIG.  34   . Accordingly, cases where the direction angle is present in the second area and the third area are described. 
       FIGS.  32  and  35    illustrate examples of a case where the direction angle is 40° and present in the second area. The controller  20  may align down wheels DW so that a straight line that connects the reference point CPC and a center point of down wheels DW (i.e., three down wheels DW) and long axes of the down wheels DW become perpendicular to each other according to the first rule. Furthermore, the controller  20  may align up wheels UW so that a straight line that connects the reference point CPC and a center point of an up wheel UW (i.e., the remaining one up wheel UW) and long axes of the up wheels UW are placed on the same line according to the second rule. 
       FIGS.  33  and  36    illustrate examples of a case where the direction angle is 80° and present in the third area. The controller  20  may align down wheels DW so that a straight line that connects the reference point CPC and a center point of down wheels DW (i.e., two down wheels DW) and the long axes of the down wheels DW become perpendicular to each other according to the first rule. Furthermore, the controller  20  may align up wheels UW so that a straight line that connects the reference point CPC and a center point of up wheels UW (i.e., the remaining two up wheels UW) and long axes of the up wheels UW are placed on the same line according to the second rule. 
     Through such control of the steering of each wheel and braking through alignment, a movement of a vehicle to a longitudinal direction and transverse direction of the vehicle in the slope S can be prohibited, and a parking and stopping state can be effectively maintained. 
       FIG.  37    is a flowchart for describing an operating method in the second application of the corner module apparatus for a vehicle according to an embodiment of the present disclosure. An operating method of the corner module apparatus for a vehicle according to the present embodiment is described with reference  FIG.  37   . A detailed description of a portion redundant with the aforementioned contents is omitted, and a time-series configuration thereof is chiefly described. 
     First, the controller  20  determines whether a braking initiation manipulation of a vehicle by a driver has been obtained through the braking initiation manipulation acquisition unit  13  (S 10   b ). 
     Next, when the braking initiation manipulation is obtained in the state in which the vehicle has been placed in the slope S, the controller  20  performs the braking of the vehicle by independently controlling the steering of four wheels of the vehicle based on a direction angle that is defined as an angle between an inclined direction of the slope S and a longitudinal direction of the vehicle (S 20   b ). 
     In step S 20   b , the controller  20  aligns the four wheels of the vehicle according to the first rule and the second rule with respect to down wheels DW disposed on the lower side of the slope S and up wheels UW disposed on the upper side of the slope S among the four wheels of the vehicle. In this case, the down wheel DW and the up wheel UW may be defined based on the direction angle. Specifically, when the direction angle is present in the first area or the third area, the down wheels DW may be defined as two wheels disposed on the lower side of the slope S among the four wheels of the vehicle, and the up wheels UW may be defined as the remaining two wheels disposed on the upper side of the slope S among the four wheels of the vehicle. Furthermore, when the direction angle is present in the second area, the down wheels DW may be defined as three wheels disposed on the lower side of the slope S among the four wheels of the vehicle, and the up wheel UW may be defined as the remaining one wheel disposed on the upper side of the slope S among the four wheels of the vehicle. 
     The aforementioned first rule is a rule for limiting a movement of a vehicle to a slope direction. Furthermore, the second rule is a rule for limiting a movement of a vehicle to a direction perpendicular to a slope direction on an inclined plane of the slope S. The first rule and the second rule may be predefined in the controller  20 . Specifically, if a point isolated from the center of gravity (GC) of the vehicle by a set distance in a direction opposite to the slope direction is defined as the reference point CPC, the first rule is defined as a rule for aligning down wheels DW so that a straight line that connects the reference point CPC and a center point of down wheels DW, and long axes of the down wheels DW become perpendicular to each other. The second rule is defined as a rule for aligning up wheels UW so that a straight line that connects the reference point CPC and a center point of up wheels UW and long axes of the up wheels UW are placed on the same line. Accordingly, in step S 20 , the controller  20  aligns down wheels DW so that a straight line that connects the reference point CPC and a center point of down wheels DW and long axes of the down wheels DW become perpendicular to each other according to the first rule, and aligns up wheels UW so that a straight line that connects the reference point CPC and a center point of up wheels UW and long axes of the up wheels UW are placed on the same line according to the second rule. 
     According to the second application, the braking of a vehicle can be safely performed regardless of the on and off state of a power source of the vehicle because the braking of the vehicle is performed in a way to control the state in which the four wheels of the vehicle have been aligned by independently controlling the steering of each of the four wheels. 
     3. Third Application: Posture Control Mechanism for Improving Straight Driving Performance 
     In the case of the existing vehicle having an internal combustion engine structure, driving power is delivered through an engine—drive shaft—differential—axial shaft. In contrast, in the case of a four-wheel independent-driving method premised by the present embodiment, a speed difference may occur between the four wheels because the four wheels are individually and independently driven and an axial shaft is not present. Such a speed difference between the four wheels becomes a danger element that causes the spin or rollover of a vehicle when the vehicle drives straight ahead. Accordingly, the third application proposes a method of improving straight driving performance of a vehicle through an approach in terms of driving control, not in terms of mechanical or additional steering control of a vehicle. 
     To this end, the controller  20  may detect an abnormal wheel that causes the deterioration of straight driving performance of a vehicle based on the four wheel velocities obtained by the wheel velocity acquisition part  14 , may calculate a compensation parameter for compensating for a deviation between the wheel velocities based on a wheel velocity of the detected abnormal wheel, may determine target driving torque for driving the abnormal wheel based on the calculated compensation parameter, and may control the driving of the abnormal wheel based on the determined target driving torque. Hereinafter, a configuration of the present embodiment is described in detail for each operation of the controller  20 . 
     First, in relation to the method of detecting an abnormal wheel, the controller  20  may detect an abnormal wheel in a way to calculate a first average value of the four wheel velocities and determining whether an error between the calculated first average value and each of the four wheel velocities is equal to or greater than a preset threshold value. If wheel velocities of a left front wheel, right front wheel, left rear wheel, and right rear wheel are V fl , V fr , V rl , and V rr , a first average value V avg  may be represented as (V fl +V fr +V rl +V rr )/4. A method of detecting an abnormal wheel may be represented as a conditional expression “V avg −V i ≥threshold value, i=fl, fr, rl, rr.” For example, if a wheel that satisfies the conditional expression corresponds to the left front wheel (fl), an abnormal wheel may be specified as the left front wheel. If a wheel that satisfies the conditional expression corresponds is plural, an abnormal wheel may be specified as a wheel having a lower wheel velocity among the plurality of wheels. Accordingly, an abnormal wheel is specified as a wheel that deteriorates straight driving performance of a vehicle because the abnormal wheel has a lower wheel velocity by a predetermined value or more than other wheels when a vehicle drives straight ahead. In the conditional expression, the threshold value may be defined as another value based on the first average value. For example, by defining that the threshold value has a higher value as the first average value has a higher value, an abnormal wheel may be determined based on a more reinforced criterion for the driving stability of a vehicle in a high-speed area. 
     When detecting an abnormal wheel, the controller  20  may calculate a compensation parameter for compensating for a deviation between the wheel velocities based on a wheel velocity of the detected abnormal wheel. Compensating for a deviation between the wheel velocities means that a deviation between the wheel velocities of the abnormal wheel and another wheel is reduced by increasing and compensating for driving torque of the abnormal wheel (i.e., by increasing the wheel velocity of the abnormal wheel). 
     In this case, the controller  20  may calculate a second average value of wheel velocities of three wheels except the abnormal wheel, and may calculate a compensation parameter by using, as factors, a difference value between the calculated second average value and the wheel velocity of the abnormal wheel and a variable gain according to the second average value. In the example in which an abnormal wheel is detected as the left front wheel, the second average value V target  may be represented as (V fr +V rl +V rr )/3, and the compensation parameter may be represented as α*V target *(V target −V fl ). In the equation of the compensation parameter, the second term V target  functions as a term for taking into consideration a target wheel velocity that is the subject of tracking in the process of calculating the compensation parameter, and the third term V target −V fl  functions as a term for taking into consideration a deviation between the wheel velocity of the abnormal wheel and a target wheel velocity in the process of calculating the compensation parameter. The first term α is a variable gain, and functions as a scaling factor for scaling the size of the compensation parameter. 
     As illustrated in  FIG.  38   , the variable gain may be determined as a value that is decreased as the second average value is increased when the second average value (V target ) is placed in a predefined middle and low-speed area (e.g., an area having a predefined threshold velocity (V th ) or less), and may be determined as a predefined fixed when the second average value (V target ) is placed in a predefined high-speed area (e.g., an area having more than the predefined threshold velocity (V th )). That is, as the second average value V target  functioning as a target wheel velocity has a higher value, the compensation parameter functioning as compensation for driving torque of an abnormal wheel is calculated as a lower value. In this case, it is suitable to secure the driving stability of a vehicle without a sudden change in a current driving control state of the vehicle. If the second average value V target  is greater than the threshold velocity, it is suitable to maintain the driving stability of the vehicle in calculating the compensation parameter as a lower limit value (i.e., the fixed value). Accordingly, the controller  20  may calculate the compensation parameter so that the compensation parameter has a different value based on the second average value as illustrated in  FIG.  38   . 
     When calculating the compensation parameter, the controller  20  may determine target driving torque for driving the abnormal wheel based on the calculated compensation parameter. In this case, the controller  20  may determine the target driving torque by applying current driving torque (i.e., the existing driving torque) for driving the abnormal wheel to the compensation parameter (i.e., target driving torque=current driving torque*compensation parameter). Thereafter, the controller  20  may control the driving of the abnormal wheel based on the target driving torque determined as described above. Since the driving torque for driving the abnormal wheel is compensated for compared to a conventional technology, straight driving performance of the vehicle can be improved. 
     The controller  20  may recalculate a first average value of the four wheel velocities in the state in which the driving of the abnormal wheel is controlled based on the target driving torque, and may output alarm through the output unit  30  when an error between the recalculated first average value and a wheel velocity of the abnormal wheel is equal to or greater than the threshold value. That is, the controller  20  may determine whether straight driving performance of the vehicle has been improved in a way to determine whether an error between the recalculated first average value and the wheel velocity of the abnormal wheel is less than the threshold value, and may calculate target driving torque through the aforementioned process. Even though the driving of the abnormal wheel has been controlled, if it is determined that the error between the recalculated first average value and the wheel velocity of the abnormal wheel is equal to or greater than the threshold value, such a situation is a situation in which a danger element, such as the spin or rollover of the vehicle, is present because a deviation between the wheel velocities of the four wheels is equal to or greater than a predetermined value. Accordingly, the controller  20  may output alarm through the output unit  30  so that a driver can recognize the corresponding situation. 
       FIG.  39    is a flowchart for describing an operating method in the third application of the corner module apparatus for a vehicle according to an embodiment of the present disclosure. The operating method of the corner module apparatus for a vehicle according to the present embodiment is described with reference to  FIG.  39   . A detailed description of a portion redundant with the aforementioned contents is omitted, and a time-series configuration thereof is chiefly described. 
     First, the controller  20  obtains four wheel velocities of a vehicle through the wheel velocity acquisition part  14  (S 10   c ). 
     Next, the controller  20  detects an abnormal wheel that causes the deterioration of straight driving performance of the vehicle based on the four wheel velocities obtained in step S 10   c  (S 20   c ). In step S 20   c , the controller  20  calculates a first average value of the four wheel velocities, and detects an abnormal wheel in a way to determine whether an error between the calculated first average value and each of the four wheel velocities is equal to or greater than a preset threshold value. 
     Next, the controller  20  calculates a compensation parameter for compensating for a deviation between the four wheel velocities based on a wheel velocity of the abnormal wheel detected in step S 20   c  (S 30   c ). In step S 30   c , the controller  20  calculates a second average value of wheel velocities of three wheels except the abnormal wheel, and calculates the compensation parameter by using, as factors, a difference value between the calculated second average value and the wheel velocity of the abnormal wheel, a variable gain according to the second average value, and the second average value. The variable gain is determined as a value that is decreased as the second average value is increased when the second average value is placed in a predefined middle and low-speed area, and is determined as a predefined fixed value when the second average value is placed in a predefined high-speed area. 
     Next, the controller  20  determines target driving torque for driving the abnormal wheel based on the compensation parameter calculated in step S 30   c  (S 40   c ). Specifically, the controller  20  determines the target driving torque by applying the compensation parameter to current driving torque for driving the abnormal wheel. 
     Next, the controller  20  controls the driving of the abnormal wheel based on the target driving torque determined in step in S 40   c  (S 50   c ), and controls other wheels except the abnormal wheel based on the existing driving torque. 
     Next, the controller  20  recalculates a first average value of the four wheel velocities, and compares an error between the recalculated first average value and a wheel velocity of the abnormal wheel with the threshold value (S 60   c ). When determining that the error between the recalculated first average value and the wheel velocity of the abnormal wheel is equal to or greater than the threshold value in step S 60   c , the controller  20  outputs alarm through the output unit  30  (S 70   c ). 
     According to the third application, straight driving performance of the vehicle can be improved by compensating for a deviation between wheel velocities through only control of driving torque for four wheels without additional instrument to additional steering control for a vehicle. 
     4. Fourth Application: Posture Control Mechanism for Solving Slip 
     In the case of the existing front wheel driving vehicle, there is a limit in that battery consumption of a vehicle is increased because posture control over the vehicle is performed through electronic control systems, such as an anti-lock brake system (ABS), an electronic stability program (ESP), and electronic controlled suspension (ECS). In the present embodiment, posture control over a vehicle is possible in a way to control the driving and steering of each wheel compared to a conventional posture control over system of a vehicle because the driving of each wheel is independently controlled by applying the four wheel-independent driving method. Hereinafter, a detailed configuration for performing posture control over a vehicle in a way to control the driving and steering of each wheel is described on the basis of an operation of the controller  20 . 
     In the fourth application, the controller  20  may determine whether a predefined slip condition has been satisfied based on a wheel velocity of each wheel obtained by the wheel velocity acquisition part  14 , and may perform posture control over a vehicle through driving torque control for controlling driving torque of each wheel when determining that the slip condition has been satisfied. 
     The slip condition is a case where a slip has occurred in a wheel, and corresponds to a condition for determining whether posture control for the driving stability of a vehicle is required. In this case, the controller  20  may calculate a slip rate of each wheel based on a wheel velocity of each wheel (as noted, the slip rate of each wheel may be calculated as a ratio of “a difference between a vehicle speed and each wheel velocity” and “a vehicle speed”), may determine a maximum slip rate having a maximum value among the calculated slip rates of the wheels, and may determine that the slip condition has been satisfied when the determined maximum slip rate is equal to or greater than a preset threshold value. 
     If it is determined that the slip condition has been satisfied, the controller  20  may perform posture control over the vehicle through the aforementioned driving torque control. In this case, the controller  20  may control the driving of each wheel based on target driving torque having a lower value compared to current driving torque of each wheel (the target driving torque may be determined as a value lower than a minimum value among values of current driving torque of the four wheels now applied for the driving of the wheels). That is, the controller  20  may perform control for reducing driving torque of the wheels in order to solve the slip state of a current wheel, and may control the driving of each wheel based on the same target driving torque. In this case, in order to solve the corresponding slip state, it is necessary to decrease the driving torque of each wheel to a lower value as a maximum slip rate is greater. Accordingly, the target driving torque may be determined to have a lower value as the maximum slip rate has a higher value. For example, the target driving torque and the maximum slip rate may be defined to have a negative linear relation in the controller  20 . 
     After performing the driving torque control, the controller  20  may determine whether the slip state has been solved through driving torque control by re-determining whether the slip condition has been satisfied. If it is determined that the state in which the slip condition has been satisfied is maintained (i.e., if the slip state has not been solved), the controller  20  may perform posture control over the vehicle by subsequently performing steering control for controlling the steering of each wheel. 
     When performing the steering control, the controller  20  may perform the steering control in a way to displace the steering of two wheels on the opposite side of the transverse direction of a wheel having a maximum slip rate by a target steering angle. For example, if a wheel having a maximum slip rate corresponds to a right front wheel, the controller  20  may perform steering control in a way to displace the steering of a left front wheel and a left rear wheel by a target steering angle. In the above example, the steering control over the left front wheel and the left rear wheel is for solving the slip state of the right front wheel by deriving the braking effect of the vehicle, and a corresponding steering direction may be any one the left or the right. In this case, in order to solve the corresponding slip state, it is necessary to form greater steering angles of the two wheels on the opposite side of the transverse direction of the wheel as the maximum slip rate becomes greater. Accordingly, the target steering angle may be determined to have a higher value as the maximum slip rate has a higher value. For example, the target steering angle and the maximum slip rate may be defined to have a positive linear relation in the controller  20 . In order to prevent a phenomenon in which a behavior of the vehicle becomes unstable due to sudden steering control over the two wheels on the opposite side of the transverse direction of the wheel, a control time until the steering angles of the two wheels on the opposite side of the transverse direction reach the target steering angle may be set as a sufficiently set time based on experimental results of a designer, and may be set in the controller  20 . 
       FIG.  40    is a flowchart for describing an operating method in the fourth application of the corner module apparatus for a vehicle according to an embodiment of the present disclosure. The operating method of the corner module apparatus for a vehicle according to the present embodiment is described with reference to  FIG.  40   . A detailed description of a portion redundant with the aforementioned contents is omitted, and a time-series configuration thereof is chiefly described. 
     First, the controller  20  obtains a wheel velocity of each of four wheels of a vehicle through the wheel velocity acquisition part  14  (S 10   d ). 
     Next, the controller  20  determines whether a predefined slip condition has been satisfied based on the wheel velocity of each wheel obtained in step S 10   d  (S 20   d ). In step S 20   d , the controller  20  calculates a slip rate of each wheel based on the wheel velocity of each wheel, determines a maximum slip rate having a maximum value among the calculated slip rates of the four wheels, and determines that the slip condition has been satisfied when the determined maximum slip rate is equal to or greater than the preset threshold value. 
     If it is determined that the slip condition has been satisfied in step S 20   d , the controller  20  performs posture control over the vehicle through driving torque control for controlling driving torque of each wheel (S 30   d ). In step S 30   d , the controller  20  controls the driving of each wheel based on target driving torque having a lower value compared to current driving torque of each wheel. In this case, the target driving torque may be determined to have a lower value as the maximum slip rate has a higher value. 
     After step S 30   d , the controller  20  re-determines whether the slip condition has been satisfied (S 40   d ). 
     If it is determined that the state in which the slip condition has been satisfied is maintained in step S 40   d , the controller  20  performs posture control over the vehicle through steering control for controlling the steering of each wheel (S 50   d ). In step S 50   d , the controller  20  displaces the steering of two wheels on the opposite side of the transverse direction of a wheel having the maximum slip rate by a target steering angle. In this case, the target steering angle may be determined to have a higher value as the maximum slip rate has a higher value. 
     Steps S 40   d  and S 50   d  may be repeatedly performed within a predefined repetition number until it is determined that the slip condition has not been satisfied in step S 40   d  (i.e., until the slip state is solved). 
     According to the fourth application, dependency on a conventional posture control system of a vehicle can be removed, and posture control over a vehicle is possible by using only a method of controlling the driving and steering of each wheel. Accordingly, there is an effect in that an available battery capacity can be increased by reducing battery consumption required for posture control over a vehicle. 
     5. Fifth Application: Target Trajectory Generation and Tracking Control Mechanism 
     In the case of the four wheel-independent driving method, the steering of each wheel needs to be independently controlled because the four wheels are not mechanically connected. In particular, in order to secure the driving stability of a vehicle upon rotation driving, a quantitative control mechanism for steering control over each wheel needs to be provided. Accordingly, the fifth application proposes a method of independently controlling the steering of each of four wheels of a vehicle by differentially calculating a target steering angle of each wheel, if the vehicle to which the four wheel-independent driving method has been applied rotates and drives on a crossroad having a predetermined curvature (specifically, when the slip of each wheel does not occur, which corresponds to a case where the vehicle rotates at a low speed at a vehicle speed less than a set speed). 
     In the fifth application, the controller  20  may calculate information on a distance up to a target point, that is, a target of a movement of a vehicle, based on driving state information and driving environment information obtained by the vehicle information acquisition unit  15 , may calculate, based on the calculated information on the distance, target curvature defined as curvature of a target trajectory up to the target point, may calculate a target steering angle of each of four wheels of a vehicle based on the calculated target curvature, and may independently control the steering of each of the four wheels based on the target steering angles. Hereinafter, a configuration of the present embodiment is described in detail for each operation of the controller  20 . 
     First, in relation to a method of calculating the information on the distance up to the target point, the controller  20  may calculate the information on the distance up to the target point by using a vehicle speed of the vehicle, an offset distance of the vehicle from the middle ({circle around (4)} in  FIG.  41   ) of a carriageway calculated from surrounding image information, and a curvature radius of the carriageway based on the middle of the carriageway (the offset distance and the curvature radius of the carriageway may be calculated by analyzing a lane and the carriageway included in the surrounding image information). The information on the distance may include a straight-line distance, a longitudinal distance, and a transverse distance from a current location (C in  FIG.  41   ) of the vehicle to the target point (A in  FIG.  41   ). 
     Specifically, the controller  20  may calculate the straight-line distance up to the target point in a way to apply the vehicle speed of the vehicle to a predefined distance calculation algorithm. In this case, the distance calculation algorithm may be predefined in the controller  20  as an algorithm for calculating a greater straight-line distance as a vehicle speed becomes higher. For example, the distance calculation algorithm may be defined in a linear expression form of L=A*V x +B (L is the straight-line distance, V x  is the vehicle speed, and A and B are constant values designed based on experimental results of a designer). 
     When calculating the straight-line distance up to the target point, the controller  20  may calculate a longitudinal distance and transverse distance up to the target point by using the offset distance, a heading angle of the vehicle, the curvature radius of the carriageway, and the straight-line distance up to the target point. Referring to  FIG.  41   , Equation 1 below may be derived. 
     
       
         
           
             
               
                 
                   
                     R 
                     2 
                   
                   = 
                   
                     
                       
                         
                           
                             ( 
                             
                               R 
                               - 
                               y 
                               - 
                               c 
                             
                             ) 
                           
                           2 
                         
                         + 
                         
                           
                             x 
                             2 
                           
                           ⁢ 
                                
                           
                             ( 
                             
                               
                                 x 
                                 2 
                               
                               = 
                               
                                 
                                   L 
                                   2 
                                 
                                 - 
                                 
                                   y 
                                   2 
                                 
                               
                             
                             ) 
                           
                         
                       
                        
                       
                         R 
                         2 
                       
                     
                     = 
                     
                       
                         
                           
                             R 
                             2 
                           
                           + 
                           
                             y 
                             2 
                           
                           + 
                           
                             ε 
                             2 
                           
                           - 
                           
                             2 
                             ⁢ 
                             Ry 
                           
                           + 
                           
                             2 
                             ⁢ 
                             y 
                             ⁢ 
                             ε 
                           
                           - 
                           
                             2 
                             ⁢ 
                             ε 
                             ⁢ 
                             R 
                           
                           + 
                           
                             L 
                             2 
                           
                           - 
                           
                             y 
                             2 
                           
                         
                          
                         
                           2 
                           ⁢ 
                           
                             y 
                             ⁡ 
                             ( 
                             
                               R 
                               - 
                               ε 
                             
                             ) 
                           
                         
                       
                       = 
                       
                         
                           
                             
                               ε 
                               2 
                             
                             - 
                             
                               2 
                               ⁢ 
                               ε 
                               ⁢ 
                               R 
                             
                             + 
                             
                               L 
                               2 
                             
                           
                            
                           y 
                         
                         = 
                         
                           
                             
                               
                                 L 
                                 2 
                               
                               + 
                               
                                 ε 
                                 2 
                               
                               - 
                               
                                 2 
                                 ⁢ 
                                 ε 
                                 ⁢ 
                                 R 
                               
                             
                             
                               2 
                               ⁢ 
                               
                                 ( 
                                 
                                   R 
                                   - 
                                   ε 
                                 
                                 ) 
                               
                             
                           
                           = 
                           
                             
                               
                                 
                                   
                                     
                                       ρ 
                                       k 
                                     
                                     ( 
                                     
                                       
                                         L 
                                         2 
                                       
                                       + 
                                       
                                         ε 
                                         2 
                                       
                                     
                                     ) 
                                   
                                   - 
                                   
                                     2 
                                     ⁢ 
                                     ε 
                                   
                                 
                                 
                                   2 
                                   ⁢ 
                                   
                                     ( 
                                     
                                       1 
                                       - 
                                       
                                         
                                           ρ 
                                           k 
                                         
                                         ⁢ 
                                         ε 
                                       
                                     
                                     ) 
                                   
                                 
                               
                                
                               y 
                             
                             = 
                             
                               
                                 
                                   
                                     L 
                                     2 
                                   
                                   - 
                                   
                                     ε 
                                     2 
                                   
                                   - 
                                   
                                     2 
                                     ⁢ 
                                     
                                       ε 
                                       ⁡ 
                                       ( 
                                       
                                         R 
                                         - 
                                         ε 
                                       
                                       ) 
                                     
                                   
                                 
                                 
                                   2 
                                   ⁢ 
                                   
                                     ( 
                                     
                                       R 
                                       - 
                                       ε 
                                     
                                     ) 
                                   
                                 
                               
                               = 
                               
                                 
                                   
                                     
                                       ρ 
                                       k 
                                     
                                     ( 
                                     
                                       
                                         L 
                                         2 
                                       
                                       - 
                                       
                                         ε 
                                         2 
                                       
                                     
                                     ) 
                                   
                                   
                                     2 
                                     ⁢ 
                                     
                                       ( 
                                       
                                         1 
                                         - 
                                         
                                           
                                             ρ 
                                             k 
                                           
                                           ⁢ 
                                           ε 
                                         
                                       
                                       ) 
                                     
                                   
                                 
                                 - 
                                 ε 
                               
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     1 
                   
                   ] 
                 
               
             
           
         
       
     
     Equation 2 below is obtained by arranging Equation 1 with respect to x and y. 
     
       
         
           
             
               
                 
                   x 
                   = 
                   
                     
                       
                         L 
                         2 
                       
                       - 
                       
                         y 
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     2 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               : 
               y 
             
             = 
             
               
                 
                   
                     
                       ρ 
                       k 
                     
                     ( 
                     
                       
                         L 
                         2 
                       
                       + 
                       
                         ε 
                         2 
                       
                     
                     ) 
                   
                   - 
                   
                     2 
                     ⁢ 
                     ε 
                   
                 
                 
                   2 
                   ⁢ 
                   
                     ( 
                     
                       1 
                       - 
                       
                         
                           ρ 
                           k 
                         
                         ⁢ 
                         ε 
                       
                     
                     ) 
                   
                 
               
               = 
               
                 
                   
                     
                       ρ 
                       k 
                     
                     ( 
                     
                       
                         L 
                         2 
                       
                       - 
                       
                         ε 
                         2 
                       
                     
                     ) 
                   
                   
                     2 
                     ⁢ 
                     
                       ( 
                       
                         1 
                         - 
                         
                           
                             ρ 
                             k 
                           
                           ⁢ 
                           ε 
                         
                       
                       ) 
                     
                   
                 
                 - 
                 ε 
               
             
           
         
       
     
     In Equations 1 and 2, L, x, and y are the straight-line distance, the longitudinal distance, and the transverse distance up to the target point, respectively. R is the curvature radius of the carriageway. ρ k  is curvature (1/R) of the carriageway. ε is the offset distance. 
     When calculating the information on the distance up to the target point as described above, the controller  20  may calculate target curvature defined as curvature of a target trajectory up to the target point, based on the calculated information on the distance. In the present embodiment, the target curvature may be divided into center target curvature defined as curvature of a target trajectory based on the center of the vehicle (i.e., a moving target trajectory of the center of the vehicle, {circle around (1)} in  FIGS.  41  and  42   ), left target curvature defined as curvature of a target trajectory based on a left wheel of the vehicle (i.e., a moving target trajectory of the left wheel of the vehicle, {circle around (2)} in  FIG.  42   ), and right target curvature defined as curvature of a target trajectory based on a right wheel of the vehicle (i.e., a moving target trajectory of the right wheel of the vehicle, {circle around (3)} in  FIG.  42   ). After preferentially calculating the center target curvature, the controller  20  may expand the center target curvature to the left target curvature and the right target curvature by using wheel track information of the vehicle. 
     Referring to  FIGS.  41  and  42   , the center target curvature may be calculated according to Equation 3 below. 
     
       
         
           
             
               
                 
                   
                     
                       R 
                       c 
                     
                     ⁢ 
                     
                       cos 
                       ⁡ 
                       ( 
                       
                         φ 
                         + 
                         α 
                       
                       ) 
                     
                   
                   = 
                   
                     
                       
                         
                           R 
                           c 
                         
                         L 
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             y 
                             ⁢ 
                             cos 
                             ⁢ 
                             φ 
                           
                           - 
                           
                             x 
                             ⁢ 
                             sin 
                             ⁢ 
                             φ 
                           
                         
                         ) 
                       
                     
                     = 
                     
                       L 
                       2 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     3 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               ρ 
               c 
             
             = 
             
               
                 1 
                 
                   R 
                   c 
                 
               
               = 
               
                 
                   2 
                   
                     L 
                     2 
                   
                 
                 ⁢ 
                 
                   ( 
                   
                     
                       y 
                       ⁢ 
                       cos 
                       ⁢ 
                       φ 
                     
                     - 
                     
                       x 
                       ⁢ 
                       sin 
                       ⁢ 
                       φ 
                     
                   
                   ) 
                 
               
             
           
         
       
     
     In Equation 3, R C  is the curvature radius of the moving target trajectory of the center of the vehicle, φ is the heading angle of the vehicle, α is an angle formed by the vehicle and the target point, L is the straight-line distance up to the target point, and ρ C  is the center target curvature (1/R C ). 
     After calculating the center target curvature, the controller  20  may calculate the left target curvature and the right target curvature based on the center target curvature by using the wheel track information of the vehicle. Referring to  FIG.  42    illustrating an example in which the vehicle rotates and drives to the left, the left target curvature and the right target curvature may be calculated according to Equations 4 and 5 below, respectively. 
     
       
         
           
             
               
                 
                   
                     R 
                     L 
                   
                   = 
                   
                     
                       R 
                       C 
                     
                     - 
                     
                       w 
                       L 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     4 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               ρ 
               L 
             
             = 
             
               
                 1 
                 
                   R 
                   L 
                 
               
               = 
               
                 
                   1 
                   
                     
                       R 
                       C 
                     
                     - 
                     
                       w 
                       L 
                     
                   
                 
                 = 
                 
                   
                     ρ 
                     c 
                   
                   
                     1 
                     - 
                     
                       
                         ρ 
                         c 
                       
                       ⁢ 
                       
                         w 
                         L 
                       
                     
                   
                 
               
             
           
         
       
       
         
           
             
               
                 
                   
                     R 
                     R 
                   
                   = 
                   
                     
                       R 
                       C 
                     
                     + 
                     
                       w 
                       R 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     5 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               ρ 
               R 
             
             = 
             
               
                 1 
                 
                   R 
                   R 
                 
               
               = 
               
                 
                   1 
                   
                     
                       R 
                       C 
                     
                     + 
                     
                       w 
                       R 
                     
                   
                 
                 = 
                 
                   
                     ρ 
                     c 
                   
                   
                     1 
                     + 
                     
                       
                         ρ 
                         c 
                       
                       ⁢ 
                       
                         w 
                         R 
                       
                     
                   
                 
               
             
           
         
       
     
     In Equation 4, R L  is a curvature radius of a moving target trajectory of a left wheel of the vehicle, R C  is a curvature radius of a moving target trajectory of the center of the vehicle, w L  is a half value of a wheel track of the vehicle (w/2, w is the wheel track), and ρ L  is the left target curvature. In Equation 5, R R  is a curvature radius of a moving target trajectory of a right wheel of the vehicle, R C  is the curvature radius of the moving target trajectory of the center of the vehicle, w R  is a half value of a wheel track of the vehicle (w/2, w is the wheel track), and ρ R  is the right target curvature. 
       FIG.  42    and Equations 4 and 5 describe the left rotation driving of the vehicle as an example. In the case of the right rotation driving of the vehicle, since a rotation-inner wheel and a rotation-outer wheel are reversed, the left target curvature and the right target curvature are calculated according to Equation 6 below. 
     
       
         
           
             
               
                 
                   
                     ρ 
                     L 
                   
                   = 
                   
                     
                       ρ 
                       c 
                     
                     
                       1 
                       + 
                       
                         
                           ρ 
                           c 
                         
                         ⁢ 
                         
                           w 
                           L 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     6 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               ρ 
               R 
             
             = 
             
               
                 ρ 
                 c 
               
               
                 1 
                 - 
                 
                   
                     ρ 
                     c 
                   
                   ⁢ 
                   
                     w 
                     R 
                   
                 
               
             
           
         
       
     
     When calculating the left target curvature and the right target curvature as described above, the controller  20  may calculate a target steering angle of each of the four wheels of the vehicle based on each calculated target curvature. 
     Specifically, target yaw rates of a left wheel and a right wheel may be represented like Equation 7 based on the calculated left target curvature and right target curvature. 
       YR des,L =ρ L   v   x  
 
       YR des,R =ρ R   v   x   [Equation 7]
 
     In Equation 7, YR des,L  is the target yaw rate of the left wheel, ρ L  is the left target curvature, YR des,R  is the target yaw rate of the right wheel, ρ R  is the right target curvature, and v x  is the vehicle speed. 
       FIG.  43    illustrates an example of a vehicle kinetics model having a degree of 2 freedoms (only front and rear left wheels are illustrated in  FIG.  43   , for convenience sake). According to the vehicle kinetics model of  FIG.  43   , the slip angle of each wheel may be represented based on Equation 8 below. 
     
       
         
           
             
               
                 
                   
                     α 
                     fl 
                   
                   = 
                   
                     
                       δ 
                       fl 
                     
                     - 
                     
                       
                         
                           
                             β 
                             cg 
                           
                           ⁢ 
                           
                             v 
                             x 
                           
                         
                         + 
                         
                           
                             l 
                             f 
                           
                           ⁢ 
                           
                             YR 
                             
                               des 
                               , 
                               L 
                             
                           
                         
                       
                       
                         v 
                         x 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     8 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               α 
               fr 
             
             = 
             
               
                 δ 
                 fr 
               
               - 
               
                 
                   
                     
                       β 
                       cg 
                     
                     ⁢ 
                     
                       v 
                       x 
                     
                   
                   + 
                   
                     
                       l 
                       f 
                     
                     ⁢ 
                     
                       YR 
                       
                         des 
                         , 
                         R 
                       
                     
                   
                 
                 
                   v 
                   x 
                 
               
             
           
         
       
       
         
           
             
               α 
               rl 
             
             = 
             
               
                 δ 
                 rl 
               
               - 
               
                 
                   
                     
                       β 
                       cg 
                     
                     ⁢ 
                     
                       v 
                       x 
                     
                   
                   - 
                   
                     
                       l 
                       r 
                     
                     ⁢ 
                     
                       YR 
                       
                         des 
                         , 
                         L 
                       
                     
                   
                 
                 
                   v 
                   x 
                 
               
             
           
         
       
       
         
           
             
               α 
               rr 
             
             = 
             
               
                 δ 
                 rr 
               
               - 
               
                 
                   
                     
                       β 
                       cg 
                     
                     ⁢ 
                     
                       v 
                       x 
                     
                   
                   - 
                   
                     
                       l 
                       f 
                     
                     ⁢ 
                     
                       YR 
                       
                         des 
                         , 
                         R 
                       
                     
                   
                 
                 
                   v 
                   x 
                 
               
             
           
         
       
     
     In Equation 8, α fl , α fr , α rl , and α rr  are a slip angle of a left front wheel, a slip angle of a right front wheel, a slip angle of a left rear wheel, and a slip angle of a right rear wheel, respectively. β cg  is a slip angle of the center of the vehicle. v x  is the vehicle speed. I f  is a distance between the axle of the front wheel of the vehicle and the center (cg) of the vehicle. I r  is the axle of the rear wheel of the vehicle and the center (cg) of the vehicle. YR des,L  and YR des,R  are the target yaw rates of the left wheel and the right wheel. δ fl , δ fr , δ rl , and δ rr  are a target steering angle of the left front wheel, a target steering angle of the right front wheel, a target steering angle of the left rear wheel, and a target steering angle of the right rear wheel, respectively, which are subjects of calculation. 
     As described above, the present embodiment is a case where a vehicle rotates at a low speed and is subject to a case where the slip of each wheel does not occur. Accordingly, in Equation 8, α fl , α fr , α rl , α rr , and β cg  may be approximated as a value of 0. Furthermore, the target steering angle of the left front wheel, the target steering angle of the right front wheel, the target steering angle of the left rear wheel, and the target steering angle of the right rear wheel may be calculated according to Equation 9 below. 
     
       
         
           
             
               
                 
                   
                     δ 
                     fl 
                   
                   = 
                   
                     
                       
                         
                           l 
                           f 
                         
                         ⁢ 
                         
                           YR 
                           
                             des 
                             , 
                             L 
                           
                         
                       
                       
                         v 
                         x 
                       
                     
                     = 
                     
                       
                         l 
                         f 
                       
                       ⁢ 
                       
                         ρ 
                         L 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     9 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               δ 
               fr 
             
             = 
             
               
                 
                   
                     l 
                     f 
                   
                   ⁢ 
                   
                     YR 
                     
                       des 
                       , 
                       R 
                     
                   
                 
                 
                   v 
                   x 
                 
               
               = 
               
                 
                   l 
                   f 
                 
                 ⁢ 
                 
                   ρ 
                   R 
                 
               
             
           
         
       
       
         
           
             
               δ 
               rl 
             
             = 
             
               
                 - 
                 
                   
                     
                       l 
                       r 
                     
                     ⁢ 
                     
                       YR 
                       
                         des 
                         , 
                         L 
                       
                     
                   
                   
                     v 
                     x 
                   
                 
               
               = 
               
                 
                   - 
                   
                     l 
                     r 
                   
                 
                 ⁢ 
                 
                   ρ 
                   L 
                 
               
             
           
         
       
       
         
           
             
               δ 
               rr 
             
             = 
             
               
                 - 
                 
                   
                     
                       l 
                       r 
                     
                     ⁢ 
                     
                       YR 
                       
                         des 
                         , 
                         R 
                       
                     
                   
                   
                     v 
                     x 
                   
                 
               
               = 
               
                 
                   - 
                   
                     l 
                     r 
                   
                 
                 ⁢ 
                 
                   ρ 
                   R 
                 
               
             
           
         
       
     
     The above case is a process of calculating the target steering angles the front wheel and the rear wheel in the reverse-phased state. The target steering angles of the front wheel and the rear wheel in the inphase state may be calculated through the following process. 
     First, the vehicle kinetics model in the inphase state may be represented according to Equation 10 below. 
     
       
         
           
             
               
                 
                   
                     
                       d 
                       dt 
                     
                     [ 
                     
                       
                         
                           β 
                         
                       
                       
                         
                           Ψ 
                         
                       
                     
                     ] 
                   
                   = 
                   
                     
                       
                         [ 
                         
                           
                             
                               
                                 a 
                                 11 
                               
                             
                             
                               
                                 a 
                                 12 
                               
                             
                           
                           
                             
                               
                                 a 
                                 21 
                               
                             
                             
                               
                                 a 
                                 22 
                               
                             
                           
                         
                         ] 
                       
                       [ 
                       
                         
                           
                             β 
                           
                         
                         
                           
                             Ψ 
                           
                         
                       
                       ] 
                     
                     + 
                     
                       
                         [ 
                         
                           
                             
                               
                                 b 
                                 11 
                               
                             
                             
                               
                                 b 
                                 12 
                               
                             
                           
                           
                             
                               
                                 b 
                                 21 
                               
                             
                             
                               
                                 b 
                                 22 
                               
                             
                           
                         
                         ] 
                       
                       [ 
                       
                         
                           
                             
                               δ 
                               f 
                             
                           
                         
                         
                           
                             
                               δ 
                               r 
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     10 
                   
                   ] 
                 
               
             
           
         
       
       
         
           where 
         
       
       
         
           
             
               a 
               11 
             
             = 
             
               
                 
                   - 
                   
                     
                       
                         C 
                         f 
                       
                       + 
                       
                         C 
                         r 
                       
                     
                     
                       mv 
                       x 
                     
                   
                 
                 ⁢ 
                     
                 
                   a 
                   12 
                 
               
               = 
               
                 
                   - 
                   1 
                 
                 - 
                 
                   
                     
                       
                         C 
                         f 
                       
                       ⁢ 
                       
                         l 
                         f 
                       
                     
                     - 
                     
                       
                         C 
                         r 
                       
                       ⁢ 
                       
                         l 
                         r 
                       
                     
                   
                   
                     mv 
                     x 
                     2 
                   
                 
               
             
           
         
       
       
         
           
             
               a 
               21 
             
             = 
             
               
                 
                   - 
                   
                     
                       
                         
                           C 
                           f 
                         
                         ⁢ 
                         
                           l 
                           f 
                         
                       
                       - 
                       
                         
                           C 
                           r 
                         
                         ⁢ 
                         
                           l 
                           r 
                         
                       
                     
                     l 
                   
                 
                 ⁢ 
                     
                 
                   a 
                   22 
                 
               
               = 
               
                 - 
                 
                   
                     
                       
                         C 
                         f 
                       
                       ⁢ 
                       
                         l 
                         f 
                         2 
                       
                     
                     - 
                     
                       
                         C 
                         r 
                       
                       ⁢ 
                       
                         l 
                         r 
                         2 
                       
                     
                   
                   l 
                 
               
             
           
         
       
       
         
           
             
               b 
               11 
             
             = 
             
               
                 
                   
                     C 
                     f 
                   
                   
                     mv 
                     x 
                   
                 
                 ⁢ 
                     
                 
                   b 
                   12 
                 
               
               = 
               
                 
                   C 
                   r 
                 
                 
                   mv 
                   x 
                 
               
             
           
         
       
       
         
           
             
               b 
               21 
             
             = 
             
               
                 
                   
                     
                       C 
                       f 
                     
                     ⁢ 
                     
                       l 
                       f 
                     
                   
                   l 
                 
                 ⁢ 
                     
                 
                   b 
                   22 
                 
               
               = 
               
                 
                   
                     C 
                     r 
                   
                   ⁢ 
                   
                     l 
                     r 
                   
                 
                 l 
               
             
           
         
       
     
     In Equation 10, β and ψ are the slip angle and direction angle of the center of the vehicle. For each of factors that define a matrix parameter, reference is made to Table 2 below. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
             
            
               
                   
                 v x   
                 Vehicle Speed 
               
               
                   
                 m 
                 Vehicle Mass 
               
               
                   
                 I 
                 Yaw moment of Inertia 
               
               
                   
                 If 
                 Distance from the axle of the front wheel to C.G 
               
               
                   
                 Ir 
                 Distance from the axle of the rear wheel to C.G 
               
               
                   
                 Cf 
                 Front cornering coefficient 
               
               
                   
                 Cr 
                 Rear cornering coefficient 
               
               
                   
                   
               
            
           
         
       
     
     Since a case where the slip angle of the vehicle is 0 is presupposed, Equation 11 is derived because the left side and β in Equation 10 become 0. 
     
       
         
           
             
               
                 
                   
                     [ 
                     
                       
                         
                           β 
                         
                       
                       
                         
                           ψ 
                         
                       
                     
                     ] 
                   
                   = 
                   
                     
                       
                         
                           
                             [ 
                             
                               
                                 
                                   
                                     a 
                                     11 
                                   
                                 
                                 
                                   
                                     a 
                                     12 
                                   
                                 
                               
                               
                                 
                                   
                                     a 
                                     21 
                                   
                                 
                                 
                                   
                                     a 
                                     22 
                                   
                                 
                               
                             
                             ] 
                           
                           
                             - 
                             1 
                           
                         
                         [ 
                         
                           
                             
                               
                                 b 
                                 11 
                               
                             
                             
                               
                                 b 
                                 12 
                               
                             
                           
                           
                             
                               
                                 b 
                                 21 
                               
                             
                             
                               
                                 b 
                                 22 
                               
                             
                           
                         
                         ] 
                       
                       [ 
                       
                         
                           
                             
                               δ 
                               f 
                             
                           
                         
                         
                           
                             
                               δ 
                               r 
                             
                           
                         
                       
                       ] 
                     
                     = 
                       
                     
                       
                         [ 
                         
                           
                             
                               
                                 
                                   
                                     
                                       - 
                                       
                                         a 
                                         22 
                                       
                                     
                                     ⁢ 
                                     
                                       b 
                                       11 
                                     
                                   
                                   + 
                                   
                                     
                                       a 
                                       12 
                                     
                                     ⁢ 
                                     
                                       b 
                                       21 
                                     
                                   
                                 
                                 
                                   
                                     
                                       a 
                                       11 
                                     
                                     ⁢ 
                                     
                                       a 
                                       22 
                                     
                                   
                                   - 
                                   
                                     
                                       a 
                                       12 
                                     
                                     ⁢ 
                                     
                                       a 
                                       21 
                                     
                                   
                                 
                               
                             
                             
                               
                                 
                                   
                                     
                                       - 
                                       
                                         a 
                                         22 
                                       
                                     
                                     ⁢ 
                                     
                                       b 
                                       12 
                                     
                                   
                                   + 
                                   
                                     
                                       a 
                                       12 
                                     
                                     ⁢ 
                                     
                                       b 
                                       22 
                                     
                                   
                                 
                                 
                                   
                                     
                                       a 
                                       11 
                                     
                                     ⁢ 
                                     
                                       a 
                                       22 
                                     
                                   
                                   - 
                                   
                                     
                                       a 
                                       12 
                                     
                                     ⁢ 
                                     
                                       a 
                                       21 
                                     
                                   
                                 
                               
                             
                           
                           
                             
                               
                                 
                                   
                                     
                                       a 
                                       21 
                                     
                                     ⁢ 
                                     
                                       b 
                                       11 
                                     
                                   
                                   - 
                                   
                                     
                                       a 
                                       11 
                                     
                                     ⁢ 
                                     
                                       b 
                                       21 
                                     
                                   
                                 
                                 
                                   
                                     
                                       a 
                                       11 
                                     
                                     ⁢ 
                                     
                                       a 
                                       22 
                                     
                                   
                                   - 
                                   
                                     
                                       a 
                                       12 
                                     
                                     ⁢ 
                                     
                                       a 
                                       21 
                                     
                                   
                                 
                               
                             
                             
                               
                                 
                                   
                                     
                                       a 
                                       21 
                                     
                                     ⁢ 
                                     
                                       b 
                                       12 
                                     
                                   
                                   - 
                                   
                                     
                                       a 
                                       11 
                                     
                                     ⁢ 
                                     
                                       b 
                                       22 
                                     
                                   
                                 
                                 
                                   
                                     
                                       a 
                                       11 
                                     
                                     ⁢ 
                                     
                                       a 
                                       22 
                                     
                                   
                                   - 
                                   
                                     
                                       a 
                                       12 
                                     
                                     ⁢ 
                                     
                                       a 
                                       21 
                                     
                                   
                                 
                               
                             
                           
                         
                         ] 
                       
                       [ 
                       
                         
                           
                             
                               δ 
                               f 
                             
                           
                         
                         
                           
                             
                               δ 
                               r 
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     10 
                   
                   ] 
                 
               
             
           
         
       
     
     In the condition in which β=0, a relation between δ f  and δ r  is derived like Equation 12 below. 
     
       
         
           
             
               
                 
                   
                     δ 
                     r 
                   
                   = 
                   
                     
                       
                         
                           - 
                           
                             l 
                             r 
                           
                         
                         + 
                         
                           
                             [ 
                             
                               
                                 ml 
                                 f 
                               
                               / 
                               
                                 
                                   C 
                                   r 
                                 
                                 ( 
                                 
                                   
                                     l 
                                     f 
                                   
                                   + 
                                   
                                     l 
                                     r 
                                   
                                 
                                 ) 
                               
                             
                             ] 
                           
                           ⁢ 
                           
                             v 
                             x 
                             2 
                           
                         
                       
                       
                         
                           
                             l 
                             f 
                           
                           [ 
                           
                             
                               ml 
                               r 
                             
                             / 
                             
                               
                                 C 
                                 f 
                               
                               ( 
                               
                                 
                                   l 
                                   f 
                                 
                                 + 
                                 
                                   l 
                                   r 
                                 
                               
                               ) 
                             
                           
                           ] 
                         
                         ⁢ 
                         
                           v 
                           x 
                           2 
                         
                       
                     
                     ⁢ 
                     
                       δ 
                       f 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     12 
                   
                   ] 
                 
               
             
           
         
       
     
     The target steering angle of the left front wheel and the target steering angle of the right front wheel are calculated according to Equation 9. The target steering angle of the left rear wheel and the target steering angle of the right rear wheel are calculated according to a relation with Equation 12. Accordingly, in the inphase state, the target steering angle of the left front wheel, the target steering angle of the right front wheel, the target steering angle of the left rear wheel, and the target steering angle of the right rear wheel may be calculated according to Equation 13 below. 
     
       
         
           
             
               
                 
                   
                     δ 
                     fl 
                   
                   = 
                   
                     
                       
                         
                           l 
                           f 
                         
                         ⁢ 
                         
                           YR 
                           
                             des 
                             , 
                             L 
                           
                         
                       
                       
                         v 
                         x 
                       
                     
                     = 
                     
                       
                         l 
                         f 
                       
                       ⁢ 
                       
                         ρ 
                         L 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                       
                     13 
                   
                   ] 
                 
               
             
           
         
       
       
         
           
             
               δ 
               fr 
             
             = 
             
               
                 
                   
                     l 
                     f 
                   
                   ⁢ 
                   
                     YR 
                     
                       des 
                       , 
                       R 
                     
                   
                 
                 
                   v 
                   x 
                 
               
               = 
               
                 
                   l 
                   f 
                 
                 ⁢ 
                 
                   ρ 
                   R 
                 
               
             
           
         
       
       
         
           
             
               δ 
               rl 
             
             = 
             
               
                 
                   
                     - 
                     
                       l 
                       r 
                     
                   
                   + 
                   
                     
                       [ 
                       
                         
                           ml 
                           f 
                         
                         / 
                         
                           
                             C 
                             r 
                           
                           ( 
                           
                             
                               l 
                               f 
                             
                             + 
                             
                               l 
                               r 
                             
                           
                           ) 
                         
                       
                       ] 
                     
                     ⁢ 
                     
                       v 
                       x 
                       2 
                     
                   
                 
                 
                   
                     l 
                     f 
                   
                   + 
                   
                     
                       [ 
                       
                         
                           ml 
                           r 
                         
                         / 
                         
                           
                             C 
                             f 
                           
                           ( 
                           
                             
                               l 
                               f 
                             
                             + 
                             
                               l 
                               r 
                             
                           
                           ) 
                         
                       
                       ] 
                     
                     ⁢ 
                     
                       v 
                       x 
                       2 
                     
                   
                 
               
               · 
               
                 ( 
                 
                   
                     l 
                     f 
                   
                   ⁢ 
                   
                     ρ 
                     L 
                   
                 
                 ) 
               
             
           
         
       
       
         
           
             
               δ 
               rr 
             
             = 
             
               
                 
                   
                     - 
                     
                       l 
                       r 
                     
                   
                   + 
                   
                     
                       [ 
                       
                         
                           ml 
                           f 
                         
                         / 
                         
                           
                             C 
                             r 
                           
                           ( 
                           
                             
                               l 
                               f 
                             
                             + 
                             
                               l 
                               r 
                             
                           
                           ) 
                         
                       
                       ] 
                     
                     ⁢ 
                     
                       v 
                       x 
                       2 
                     
                   
                 
                 
                   
                     l 
                     f 
                   
                   + 
                   
                     
                       [ 
                       
                         
                           ml 
                           r 
                         
                         / 
                         
                           
                             C 
                             f 
                           
                           ( 
                           
                             
                               l 
                               f 
                             
                             + 
                             
                               l 
                               r 
                             
                           
                           ) 
                         
                       
                       ] 
                     
                     ⁢ 
                     
                       v 
                       x 
                       2 
                     
                   
                 
               
               · 
               
                 ( 
                 
                   
                     l 
                     f 
                   
                   ⁢ 
                   
                     ρ 
                     R 
                   
                 
                 ) 
               
             
           
         
       
     
     As a result, based on the predefined vehicle kinetics model, the controller  20  may calculate the target steering angle of the left front wheel by using a distance between the axle of the front wheel and center of the vehicle and the left target curvature, may calculate the target steering angle of the right front wheel by using a distance between the axle of the front wheel and center of the vehicle and the right target curvature, may calculate the target steering angle of the left rear wheel by using a distance between the axle of the rear wheel and center of the vehicle and the left target curvature, and may calculate the target steering angle of the right rear wheel by using a distance between the axle of the rear wheel and center of the vehicle and the right target curvature. 
     When calculating the target steering angle of each wheel, the controller  20  may independently control the steering of each of the four wheels based on each of the calculated target steering angles. In this case, as illustrated in  FIG.  44   , the controller  20  may calculate driving torque for driving the four wheels through feedforward control (understeer gradient) and feedback control (PID control) for each of the target steering angles and a current steering angle of the vehicle, and may independently control the steering of each of the four wheels in a way to control the driving of the four wheels. 
       FIG.  45    is a flowchart for describing an operating method in the fifth application of the corner module apparatus for a vehicle according to an embodiment of the present disclosure. The operating method of the corner module apparatus for a vehicle according to the present embodiment is described with reference to  FIG.  45   . A detailed description of a portion redundant with the aforementioned contents is omitted, and a time-series configuration thereof is chiefly described. 
     First, the controller  20  obtains driving state information and driving environment information of a vehicle through the vehicle information acquisition unit  15  (S 10   e ). The driving state information may include a vehicle speed and heading angle of the vehicle. The driving environment information may include surrounding image information (e.g., a front image) of the vehicle. 
     Next, the controller  20  calculates information on a distance up to a target point, that is, a target of a movement of the vehicle, based on the driving state information and driving environment information of the vehicle (S 20   e ). In step S 20   e , the controller  20  calculates a straight-line distance, a longitudinal distance, and a transverse distance from the vehicle to the target point as the information on the distance up to the target point, by using the vehicle speed of the vehicle, an offset distance of the vehicle from the middle of a carriageway calculated based on the surrounding image information, and curvature radius of the carriageway based on the middle of the carriageway. 
     Next, the controller  20  calculates target curvature, defined as curvature of a target trajectory up to the target point, based on the information on the distance calculated in step S 20   e  (S 30   e ). The target curvature may be divided into center target curvature defined as curvature of a target trajectory based on the center of the vehicle, left target curvature defined as curvature of a target trajectory based on a left wheel of the vehicle, and right target curvature defined as curvature of a target trajectory based on a right wheel of the vehicle. Accordingly, in step S 30   e , after calculating the center target curvature by using the straight-line distance, the longitudinal distance, and the transverse distance from the vehicle to the target point, and the heading angle of the vehicle, the controller  20  calculates the left target curvature and the right target curvature based on the center target curvature by using wheel track information of the vehicle. 
     Next, the controller  20  calculates a target steering angle of each of the four wheels of the vehicle based on the target curvature calculated in step S 30   e  (S 40   e ). In step S 40   e , based on the predefined vehicle kinetics model, the controller  20  calculates a target steering angle of the left front wheel based on a distance between the axle of the front wheel and center of the vehicle and the left target curvature, calculates a target steering angle of the right front wheel based on a distance between the axle of the front wheel and center of the vehicle and the right target curvature, calculates a target steering angle of the left rear wheel based on a distance between the axle of the rear wheel and center of the vehicle and the left target curvature, and calculates a target steering angle of the right rear wheel based on a distance between the axle of the rear wheel and center of the vehicle and the right target curvature. In this case, the controller  20  calculates the target steering angle of each of the four wheels in a condition in which a slip angle of each wheel of the vehicle is 0. 
     Next, the controller  20  independently controls the steering of each of the four wheels based on each of the target steering angles calculated in step S 40   e  (S 50   e ). In step S 50   e , the controller  20  calculates driving torque for driving each of the four wheels through feedforward and feedback control over each of the target steering angles and the current steering angle of the vehicle, and independently controls the steering of each of the four wheels in a way to control the driving of the four wheels. 
     According to the fifth application, there is proposed a quantitative control mechanism for independently controlling the steering of each of the four wheels by differentially calculating a target steering angle of each wheel upon rotation driving of a vehicle to which the four wheel-independent driving method has been applied. Accordingly, rotation driving performance and rotation driving stability of the vehicle can be improved. 
     A degree of freedom in design can be improved and various types of purpose built vehicles (PBVs) can be mass-produced because the number and arrangement of the first platforms and the second platforms can be adjusted suitably for the type or purpose of a vehicle. 
     A stable driving suitable for a driving state is possible and a range of a steering angle, such as rotation at its own position and side driving, can be more widely secured because the corner module can independently adjust operations of each wheel. 
     The term “part” used in this specification may include a unit implemented as hardware, software or firmware, and may be interchangeably used with a term, such as logic, a logical block, a unit, or a circuit. The “part” may be an integrated part, or a minimum unit of the part or a part thereof, which performs one or more functions. For example, according to an embodiment, the “part” may be implemented in the form of an application-specific integrated circuit (ASIC). Furthermore, an implementation described in this specification may be realized as a method or process, an apparatus, a software program, a data stream or a signal, for example. Although the present disclosure has been discussed only in the context of a single form of an implementation (e.g., discussed as only a method), an implementation having a discussed characteristic may also be realized in another form (e.g., apparatus or program). The apparatus may be implemented as proper hardware, software or firmware. The method may be implemented in an apparatus, such as a processor commonly referring to a processing device, including a computer, a microprocessor, an integrated circuit or a programmable logic device, for example. The processor includes a communication device, such as a computer, a cell phone, a mobile phone/personal digital assistant (“PDA”) and another device which facilitates the communication of information between end-users. 
     While this disclosure includes specific examples, it will be apparent after an understanding of the disclosure of this application that various changes in form and details may be made in these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein are to be considered in a descriptive sense only, and not for purposes of limitation. Descriptions of features or aspects in each example are to be considered as being applicable to similar features or aspects in other examples. Suitable results may be achieved if the described techniques are performed in a different order, and/or if components in a described system, architecture, device, or circuit are combined in a different manner, and/or replaced or supplemented by other components or their equivalents. Therefore, the scope of the disclosure is defined not by the detailed description, but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents are to be construed as being included in the disclosure.