Patent Publication Number: US-2019185015-A1

Title: Apparatus for limiting vehicle speed and method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims the benefit of priority to Korean Patent Application No. 10-2017-0173570, filed on Dec. 15, 2017, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to an apparatus for limiting vehicle speed, and a method thereof and, more particularly, to a technique for improving fuel economy of a vehicle by limiting the speed of the vehicle on the basis of an economical speed according to the driving environment of the vehicle. 
     BACKGROUND 
     In recent years, as vehicle performance and road environment have improved, traffic accidents due to overspeeding are increasing. 
     In Europe, drivers are allowed to set a speed limit of a vehicle, and an incentive is given to a vehicle equipped with a speed limiter that controls the speed of the vehicle to prevent the speed from increasing even though the driver presses an accelerator pedal when exceeding the speed limit. 
     In a conventional technique for limiting the speed of the vehicle, since the speed of the vehicle is limited on the basis of the speed limit set by the driver, the safety of the vehicle may be secured. However, such a speed limit is set without taking the driving environment of the vehicle into consideration. Thus, it would be difficult to improve fuel economy of the vehicle. 
     For example, the speed limit set by the driver may be a general road speed limit (for example, 80 km/h). Even if it is appropriate to drive at a speed of 60 km/h according to the driving environment of the vehicle, it may unnecessarily accelerate to 80 km/h and then decelerate to 60 km/h, thereby deteriorating the fuel economy of the vehicle. 
     SUMMARY 
     The present disclosure has been made to solve the above-mentioned problems occurring in the related art while advantages achieved by the related art are maintained intact. 
     An aspect of the present disclosure provides an apparatus of a vehicle for limiting vehicle speed and a method thereof that can prevent a vehicle from exceeding a speed limit to secure safety and improve fuel economy by calculating an economical speed corresponding to the driving environment of the vehicle and limiting the driving speed of the vehicle on the basis of the calculated economical speed. 
     According to an aspect of the present disclosure, an apparatus of a vehicle for limiting vehicle speed may include: a mode setting device for allowing a driver to set any one of a safety mode, a fuel economy mode, and a hybrid mode; a safety speed input device for allowing the driver to input a safety speed; one or more processors configured to determine an economical speed on the basis of a driving environment of the vehicle; and a controller communicatively connected to the one or more processors and configured to limit a speed of the vehicle on the basis of the safety speed or the economical speed according to a mode set by the driver. 
     The one or more processors may be further configured to determine, as a final economical speed, a minimum speed among an economical speed on the basis of a speed of a subject vehicle and a speed of a preceding vehicle, an economical speed on the basis of a fuel economy graph according to the speed of the subject vehicle, an economical speed on the basis of a speed profile according to a distance between the subject vehicle and a front obstacle, and a maximum speed of a driving road. 
     The controller may limit the speed of the vehicle on the basis of a torque corresponding to the input safety speed in the safety mode. 
     The controller may limit the speed of the vehicle on the basis of a torque corresponding to the determined economical speed in the fuel economy mode. 
     The controller may limit the speed of the vehicle on the basis of a torque corresponding to a lower speed of the input safety speed and the determined economical speed in the hybrid mode. 
     The one or more processors may be further configured to calculate a required torque of the driver on the basis of a voltage value transmitted from an accelerator position sensor (APS). 
     The controller may limit the speed of the vehicle on the basis of a lower torque of a torque corresponding to the input safety speed and the required torque of the driver in the safety mode. 
     The controller may limit the speed of the vehicle on the basis of a lower torque of a torque corresponding to the determined economical speed and the required torque of the driver in the fuel economy mode. 
     The controller may limit the speed of the vehicle on the basis of a lower torque of a torque corresponding to the input safety speed, a torque corresponding to the determined economical speed, and the required torque of the driver in the hybrid mode. 
     According to another aspect of the present disclosure, a method for limiting a speed of a vehicle may include: receiving, by a mode setting device, any one of a safety mode, a fuel economy mode, and a hybrid mode which is set by a driver; receiving, by a safety speed input device, a safety speed which is input by the driver in the safety mode or the hybrid mode; determining, by one or more processor, an economical speed on the basis of a driving environment of a vehicle in the fuel economy mode; and limiting, by a controller, a speed of the vehicle on the basis of the safety speed or the economical speed according to a mode set by the driver. 
     The determining of the economical speed may include: calculating a first economical speed on the basis of a speed of a subject vehicle and a speed of a preceding vehicle; calculating a second economical speed on the basis of a fuel economy graph according to the speed of the subject vehicle; calculating a third economical speed on the basis of a speed profile according to a distance between the subject vehicle and a front obstacle; acquiring a maximum speed of a driving road; and determining, as a final economical speed, a minimum speed among the first to third economical speeds and the maximum speed. 
     The limiting of the speed may include limiting the speed of the vehicle on the basis of a torque corresponding to the input safety speed in the safety mode. 
     The limiting of the speed may include limiting the speed of the vehicle on the basis of a torque corresponding to the determined economical speed in the fuel economy mode. 
     The limiting of the speed may include limiting the speed of the vehicle on the basis of a torque corresponding to a lower speed of the input safety speed and the determined economical speed in the hybrid mode. 
     The method may further include calculating a required torque of the driver on the basis of a voltage value transmitted from an accelerator position sensor (APS). 
     The limiting of the speed may include limiting the speed of the vehicle on the basis of a lower torque of a torque corresponding to the input safety speed and the required torque of the driver in the safety mode. 
     The limiting of the speed may include limiting the speed of the vehicle on the basis of a lower torque of a torque corresponding to the determined economical speed and the required torque of the driver in the fuel economy mode. 
     The limiting of the speed may include limiting the speed of the vehicle on the basis of a lower torque of a torque corresponding to the input safety speed, a torque corresponding to the determined economical speed, and the required torque of the driver in the hybrid mode. 
     According to another aspect of the present disclosure, an apparatus of a vehicle for limiting vehicle speed may include: an economical speed determination processor configured to determine an economical speed on the basis of a driving environment of a vehicle; a torque calculation processor configured to calculate a required torque of a driver; and a controller communicatively connected to the economical speed determination processor and the torque calculation processor, and configured to limit a speed of the vehicle on the basis of a lower torque of a torque corresponding to the determined economical speed and the required torque of the driver. 
     According to another aspect of the present disclosure, a method for limiting a speed of a vehicle may include: determining, by an economical speed determination processor, an economical speed on the basis of a driving environment of a vehicle; calculating, by a torque calculation processor, a required torque of a driver; and limiting, by a controller, a speed of the vehicle on the basis of a lower torque of a torque corresponding to the determined economical speed and the required torque of the driver. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present disclosure will be more apparent from the following detailed description taken in conjunction with the accompanying drawings: 
         FIG. 1  schematically illustrates the appearance of a vehicle to which the present inventive concept is applied; 
         FIG. 2  illustrates the internal structure of a vehicle to which the present inventive concept is applied; 
         FIG. 3  illustrates the configuration of an apparatus for limiting vehicle speed, according to an exemplary embodiment of the present disclosure; 
         FIG. 4  illustrates the configuration of an economical speed determination module in an apparatus for limiting vehicle speed, according to an exemplary embodiment of the present disclosure; 
         FIG. 5  illustrates a flowchart of a method for limiting a speed of a vehicle, according to an exemplary embodiment of the present disclosure; 
         FIG. 6  illustrates the configuration of an apparatus for limiting vehicle speed, according to another exemplary embodiment of the present disclosure; 
         FIG. 7  illustrates a flowchart of a method for limiting a speed of a vehicle, according to another exemplary embodiment of the present disclosure; 
         FIG. 8  illustrates a graph of fuel economy according to a speed of a subject vehicle, according to an exemplary embodiment of the present disclosure; 
         FIG. 9  illustrates an economical speed profile according to a distance to a preceding vehicle, according to an exemplary embodiment of the present disclosure; and 
         FIG. 10  illustrates a block diagram of a computing system by which a method for limiting a speed of a vehicle according to an exemplary embodiment of the present disclosure is executed. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals will be used throughout to designate the same or equivalent elements. In addition, a detailed description of well-known techniques associated with the present disclosure will be ruled out in order not to unnecessarily obscure the gist of the present disclosure. 
     Terms such as first, second, A, B, (a), and (b) may be used to describe the elements in exemplary embodiments of the present disclosure. These terms are only used to distinguish one element from another element, and the intrinsic features, sequence or order, and the like of the corresponding elements are not limited by the terms. Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meanings as those generally understood by those with ordinary knowledge in the field of art to which the present disclosure belongs. Such terms as those defined in a generally used dictionary are to be interpreted as having meanings equal to the contextual meanings in the relevant field of art, and are not to be interpreted as having ideal or excessively formal meanings unless clearly defined as having such in the present application. 
       FIG. 1  schematically illustrates the appearance of a vehicle to which the present inventive concept is applied. 
     Referring to  FIG. 1 , a vehicle  1  includes a vehicle body  10  forming the appearance thereof, and wheels  12  and  13  moving the vehicle  1 . 
     The vehicle body  10  includes a hood  11   a  protecting a variety of devices, such as an engine, a motor, a battery, and a transmission, required to drive the vehicle  1 , a roof panel  11   b  for the formation of an interior space, a trunk lid  11   c  providing a storage space, and front fenders  11   d  and quarter panels  11   e  provided on the sides of the vehicle  1 . In addition, a plurality of doors  15  may be provided on the sides of the vehicle body  10  to be hinge-coupled to the vehicle body  10 . 
     A front window (windshield)  19   a  may be disposed between the hood  11   a  and the roof panel  11   b  to provide visibility in front of the vehicle  1 , and a rear window  19   b  may be disposed between the roof panel  11   b  and the trunk lid  11   c  to provide visibility behind the vehicle  1 . In addition, side windows  19   c  may be disposed in upper portions of the doors  15  to provide visibility to the side. 
     In addition, headlamps  15  may be placed on the front of the vehicle  1  for illuminating in a travelling direction of the vehicle  1 . 
     In addition, turn signal lamps  16  may be placed on the front and rear of the vehicle  1  for signaling a change of the direction of the vehicle  1 . 
     The vehicle  1  may indicate the traveling/turning direction thereof by allowing the turn signal lamp  16  to flicker. In addition, tail lamps  17  may be placed on the rear of the vehicle  1 . The tail lamps  17  may display a gear shift state, a brake operating state, and the like of the vehicle  1 . 
     The exterior of the vehicle body may include side-view mirrors  18   a  and  18   b  providing the driver&#39;s rearward visibility behind the vehicle  1 . 
     The vehicle  1  may be an electric vehicle. Here, the electric vehicle includes an engine, a motor, a battery, and a transmission, and a controller thereof may control the conditions of the engine, the motor, the battery, and the transmission by performing controller area network (CAN) communications with a battery controller (not shown) to deliver power to the vehicle. 
       FIG. 2  illustrates the internal structure of a vehicle to which the present inventive concept is applied. 
     As illustrated in  FIG. 2 , the interior  120  of a vehicle includes seats  121  in which occupants sit, a dashboard  122 , an instrument panel (cluster)  123  disposed on the dashboard and including a tachometer, a speedometer, a coolant temperature indicator, a turn signal indicator, high beam indicator light, warning lights, seat-belt warning light, a trip odometer, an odometer, a gearshift position indicator, door open warning light, oil warning light, and low fuel warning light, a steering wheel  124  controlling the direction of the vehicle  1 , and a center fascia  125  including vents of an air conditioner, a control pad, and an audio system. 
     The seats  121  include a driver seat  121   a  in which a driver sits, a front passenger seat  121   b  in which a passenger sits, and rear seats located in the rear of the interior of the vehicle  1 . 
     The cluster  123  may be implemented in a digital manner. In other words, the cluster (digital instrument panel)  123  may display images related to vehicle state information and vehicle driving information, and display a driving range (travelable distance) of the vehicle  1  which is calculated on the basis of the charge amount (state of charge) of the battery. 
     The center fascia  125  may be located on the dashboard  122  between the driver seat  121   a  and the passenger seat  121   b.    
     The center fascia  125  may be provided with a head unit  126  for controlling the air conditioner and a heater. 
     The head unit  126  may include a variety of buttons for controlling the air conditioner and the heater. 
     A controller for controlling the air conditioner and the heater may be disposed inside the head unit  126 . 
     The head unit  126  may include an audio system  130  which performs a radio function, an input unit  130   a  which receives the input of an operation command of the audio system  130 , and a display unit  130   b  which displays operation information. Here, the audio system  130  provided in the vehicle  1  may be a head unit having a radio function, or an audio video navigation (AVN) terminal for a vehicle having a radio function. 
     The audio system  130  may receive a broadcast signal to output a broadcast. For example, as illustrated in  FIG. 2 , the audio system  130  may be disposed in the center fascia  125 , and speakers  134  receiving the broadcast signal from the audio system  130  to output the broadcast may be installed on the front doors of the vehicle. However,  FIG. 2  merely shows an example of the installation position of the speaker  134 , and the speaker may be installed in any place of the interior of the vehicle. 
     Here, the display unit  130   b  may also display the operation information of the air conditioner and the heater. In addition, an interface in relation to the operation of the vehicle may be displayed on the display unit  130   b , and an interface with respect to the travelable distance of the vehicle  1  may also be displayed on the display unit  130   b.    
     The center fascia  125  may be provided with vents, a cigar jack, and the like. In addition, the center fascia  125  may be provided with multiple terminals  127  to which external devices including a user terminal (not shown) are wired connected. In other words, the multiple terminals  127  may enable wired communications between the head unit  126  or a vehicle terminal  140  and the user terminal (not shown). 
     Here, the multiple terminals  127  may include a USB port and an AUX terminal, and further include a SD slot, and may be disposed adjacent to the head unit  126 . In addition, the multiple terminals  127  may be disposed adjacent to the vehicle terminal  140 , and may be electrically connected to the vehicle terminal  140  and the external devices through a connector or a cable. 
     Examples of the external devices may include a storage device, a user terminal, an MP3 player, and the like. The storage device may include a card-type memory and an external hard disk. 
     In addition, the user terminal included in the external device may be a mobile communication terminal, and examples thereof may include a smartphone, a notebook, a tablet, and the like. The vehicle  1  may further include an operation unit  128  receiving the input of operation commands for various functions. 
     The operation unit  128  may be provided on the head unit  126  and the center fascia  125 , and may include at least one physical button such as an operation on/off button for various functions, and a button for changing setting values of various functions. The operation unit  128  may transmit an operation signal of the button to the controller in the head unit  126  or the vehicle terminal  140 . In other words, the operation unit  128  may receive the input of an operation on/off command of the vehicle terminal  140 , allow the user to select at least one of the plurality of functions, and transmit the selected function to the vehicle terminal  140 . 
     For example, when a navigation function is selected, the operation unit  128  may receive destination information, and transmit the received destination information to the vehicle terminal  140 . When a DMB function is selected, the operation unit  128  may receive broadcast channel and volume information, and transmit the received information to the vehicle terminal  140 . When a radio function is selected, the operation unit  128  may receive radio channel and volume information, and transmit the received information to the vehicle terminal  140  or the display unit  130   b.    
     The operation unit  128  may include a touch panel integrated with the display unit of the vehicle terminal. The operation unit  128  may be displayed and activated in the form of a button on the display unit of the vehicle terminal  140 , and receive location information of the displayed button. 
     The operation unit  128  may further include a jog dial (not shown) or a touch pad for the input of a movement command, a selection command, and the like of a cursor displayed on the display unit of the vehicle terminal  140 . The operation unit  128  may transmit an operation signal of the jog dial or a touch signal activated on the touch pad to the vehicle terminal  140 . 
     Here, the jog dial or the touch pad may be provided on the center fascia. The operation unit  128  may also receive the input of an automatic channel switching command when the radio function is performed. 
     In addition, the user may input a control command that changes an operation mode of the vehicle  1  through the operation unit  128 , and may also input a control command with respect to each element of the vehicle  1 . 
     The display unit  130   b  may display the operation information of the head unit  126 , and display information that is input to the operation unit  128 . 
     For example, when the radio function is selected, the display unit  130   b  may display the radio channel and volume information input by the user. 
     When the radio function is performed, the display unit  130   b  may display information on the input of the automatic channel switching command and the execution of the automatic channel switching command. 
     The vehicle terminal  140  may be installed in a holder on the dashboard. 
     The vehicle terminal  140  may perform audio, video, navigation, DMB, radio, and GPS functions. 
     A chassis of the vehicle  1  includes a power generation system, a power transmission system, a running gear, a steering system, a braking system, a suspension system, a transmission system, a fuel supply system, wheels (front, rear, left, and right wheels), and the like. 
     In addition, the vehicle  1  may include a variety of safety devices for the safety of the driver and the occupants. 
     For example, the vehicle  1  may include various kinds of safety devices such as an airbag control device for the safety of the driver and the occupant(s) in the event of a vehicle collision, and an electronic stability control (ESC) device controlling the posture of the vehicle while accelerating or cornering. 
     In addition, the vehicle  1  may further include a variety of sensors such as a proximity sensor detecting obstacles and other vehicles to the rear or side of the vehicle, a rain sensor detecting whether it rains or not and measuring rainfall, a wheel speed sensor detecting the speed of the front, rear, left, and right wheels, an acceleration sensor detecting acceleration of the vehicle, an angular velocity sensor detecting an angular velocity of the vehicle. 
     The vehicle  1  may include an electronic control unit (ECU) controlling the operations of the power generation system, the power transmission system, the running gear, the steering system, the braking system, the suspension system, the transmission system, the fuel supply system, a battery management system, and various kinds of safety devices and sensors. 
     In addition, the vehicle  1  may further include electronic devices, such as a hands-free device, a Bluetooth device, a rear camera, a charging device for a user terminal, and a hi-pass system, for the convenience of the driver. 
     The vehicle  1  may further include a start button for inputting an operation command to a starter motor (not shown). In other words, when the start button is turned on, the vehicle  1  may operate the starter motor, and drive the power generation system, that is, an engine (not shown) through the operation of the starter motor. 
     The vehicle  1  may include a battery (not shown) electrically connected to the terminal, the audio system, indoor lights, the starter motor, and the other electronic devices to supply driving power. 
     The vehicle  1  may be an electric vehicle in which a battery for driving the vehicle is used. Here, the electric vehicle may be driven by charging the battery with electricity and driving a motor using the charged electricity. The electric vehicle battery may be charged using power from its own generator or the engine while the vehicle is driving, or may be charged in an electric charging station. 
     In addition, the vehicle  1  may further include a communication device for communications between various in-vehicle electronic devices and for communications with the external user terminal. The communication device may include a CAN communication module, a Wi-Fi communication module, a USB communication module, and a Bluetooth communication module. In addition, the communication device may further include a broadcasting communication module such as DMB TPEG, SXM, and RDS. 
       FIG. 3  illustrates the configuration of an apparatus for limiting vehicle speed according to an exemplary embodiment of the present disclosure. 
     As illustrated in  FIG. 3 , the apparatus for limiting vehicle speed according to the exemplary embodiment of the present disclosure, may include a memory  31 , a mode setting device  32 , a safety speed input device  33 , one or more processors  37 , and a controller  36 . The elements may be combined into a single unit according to methods for carrying out the invention, and some of the elements may be omitted according to methods for carrying out the invention. 
     The one or more processors  37  may have an associated non-transitory memory storing software instructions which, when executed by the one or more processors  37 , provide the functionalities of an economical speed determination module  34  and a torque calculation module  35 . 
     With respect to each of the aforementioned elements, the memory  31  may store programs corresponding to a variety of processes performed by the controller  36 , and store various types of data generated when the controller  36  performs the processes. 
     The memory  31  may include at least one non-transitory storage medium selected from among a flash memory, a hard disk, a solid status disk (SSD), a silicon disk drive (SDD), a multimedia card micro type memory, a card type memory (e.g., SD or XD memory), a random access memory (RAM), a static random access memory (SRAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a programmable read-only memory (PROM), a magnetic memory, a magnetic disk, and an optical disk. 
     The mode setting device  32  may be a module providing a user interface (e.g., a touch screen, etc.) or an input device such as a mouse, a joystick, a jog shuttle, a stylus pen, etc., provided with a display, and allow a user to set any one of a safety mode, a fuel economy mode, and a hybrid mode. 
     Here, the safety mode refers to a mode in which the speed of the vehicle is controlled on the basis of a safety speed set by a driver, the fuel economy mode refers to a mode in which the speed of the vehicle is controlled on the basis of an economical speed determined by the economical speed determination module  34 , and the hybrid mode in which the safety mode and the fuel economy mode are applied in combination, and the speed of the vehicle is controlled on the basis of a lower speed of the safety speed set by the driver and the economical speed determined by the economical speed determination module  34 . 
     The safety speed input device  33  may be a module which is activated when the driver selects the safety mode or the hybrid mode, and include a single button or a plurality of buttons to allow the driver to input a safety speed. 
     The economical speed determination module  34  of the one or more processors  37  may determine an economical speed corresponding to the driving environment of the vehicle. Here, the economical speed determination module  34  may be interlocked with a variety of sensors (a camera, a radar sensor, an infrared sensor, and the like), a driving assistance system, a navigation system mounted in the vehicle to acquire various information. For example, the economical speed determination module  34  may acquire road information (speed cameras, curves, speed bumps, intersections, tollgates, school zones, and the like), and information on front obstacles (preceding vehicles, pedestrians, objects, and the like). Here, the information that affects the speed of the vehicle (speed cameras, curves, speed bumps, intersections, tollgates, school zones, and the like) may also be regarded as front obstacles. 
     The economical speed determination module  34  may calculate the economical speed using the road information. Here, the economical speed refers to the speed of the vehicle required for environmentally friendly and economical driving. Such an economical speed may be set individually for each road information. In other words, the economical speed may be determined in a variety of settings according to the road information such as curves, ramps, school zones, speed bumps and the like. 
     In particular, the economical speed determination module  34  may calculate the economical speed using the road information. In addition, the economical speed determination module  34  may determine the economical speed in a variety of settings by applying a current speed of the vehicle and various models required to calculate the economical speed of the vehicle, such as a motion model, a fuel economy model, and a heat load model. In other words, the economical speed determination module  34  may calculate a variety of economical speeds that allow the vehicle to extend coasting (non-power driving) to reduce energy required to drive the vehicle for each road type by applying the road information and various models, and allow the vehicle to reach a corresponding appropriate speed with minimum energy by considering a distance from the current location of the vehicle to a road type ahead, travel time, the current speed of the vehicle, and the like. 
     For example, when a curve is detected in front of the vehicle as a result of analyzing the road information, the economical speed determination module  34  may calculate a driving speed corresponding to the curve, and calculate an economical speed to allow the vehicle to enter the curve at the corresponding driving speed. 
     In addition, when a school zone is detected in front of the vehicle as a result of analyzing the road information, the economical speed determination module  34  may detect a driving speed corresponding to the school zone, and calculate an economical speed to allow the vehicle to pass the school zone at the corresponding driving speed. 
     In addition, when a speed bump is detected in front of the vehicle as a result of analyzing the road information, the economical speed determination module  34  may detect a driving speed corresponding to the speed bump, and calculate an economical speed to allow the vehicle to pass the speed bump at the corresponding driving speed. 
     In addition, when the vehicle is driving on a ramp as a result of analyzing the road information, the economical speed determination module  34  may calculate a driving speed corresponding to the ramp, and calculate an economical speed to allow the vehicle to maintain the corresponding driving speed on the ramp. 
     Hereinafter, details of the configuration of the economical speed determination module  34  will be described with reference to  FIG. 4 . 
       FIG. 4  illustrates the configuration of an economical speed determination module in an apparatus for limiting vehicle speed according to an exemplary embodiment of the present disclosure. 
     As illustrated in  FIG. 4 , the economical speed determination module  34  according to the exemplary embodiment of the present disclosure may include a first speed calculator  41 , a second speed calculator  42 , a third speed calculator  43 , and an economical speed selector  44 . 
     The first speed calculator  41  may calculate an economical speed of a subject vehicle on the basis of a speed of a preceding vehicle and a speed of the subject vehicle acquired by the radar sensor. For example, an economical speed Va may be calculated on the basis of the following equation 1: 
         Va =( A×V   1 )+{(1− A )× V   2 )}  Equation 1
 
     Here, V 1  represents a cumulative average speed of the preceding vehicle, V 2  represents a cumulative average speed of the subject vehicle, and A represents a weighted constant value. 
     The second speed calculator  42  may calculate an economical speed on the basis of a slope of fuel economy according to the speed of the subject vehicle, as illustrated in  FIG. 8 . Here, the economical speed may be an inflection point of the slope, wherein the inflection point refers to a point where the slope suddenly changes (becomes gentle). 
     In addition, the second speed calculator  42  may calculate an economical speed on the basis of table  1  below. Here, the economical speed may be a maximum speed. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 Maximum 
                 Minimum 
               
               
                 Road 
                   
                 Speed 
                 Speed 
               
               
                 Classification 1 
                 Classification 2 
                 (km/h) 
                 (km/h) 
               
               
                   
               
             
            
               
                 General Road 
                 Two-lane 
                 60 
                   
               
               
                   
                 Four-lane 
                 80 
               
               
                 Motorway 
                   
                 90 
                 30 
               
               
                 Expressway 
                 Two-lane 
                 80 
                 50 
               
               
                   
                 Four-lane or more 
                 100-120 
                 50 
               
               
                 School Zone 
                   
                 30 
               
               
                 Pedestrian 
                   
                 60 
               
               
                 Congested Area 
               
               
                   
               
            
           
         
       
     
     In addition, the second speed calculator  42  may calculate a lower speed of the speed at the inflection point and the maximum speed of a corresponding road as an economical speed. 
     The third speed calculator  43  may calculate an economical speed on the basis of an economical speed profile according to a distance to a front obstacle, as illustrated in  FIG. 9 . In  FIG. 9 , “ 910 ” represents a speed profile during operation of a brake pedal, “ 920 ” represents a speed profile during coasting, and “ 930 ” represents an economical speed profile according to a distance to a front obstacle. 
     The economical speed selector  44  may select a minimum speed of a first speed calculated by the first speed calculator  41 , a second speed calculated by the second speed calculator  42 , and a third speed calculated by the third speed calculator  43  as an economical speed. 
     In addition, the economical speed determination module  34  may include its own memory to store the graph of the slope of the fuel economy according to the speed of the subject vehicle, the economical speed profile according to the distance to the front obstacle, and the like. Alternatively, the graph of the slope of the fuel economy according to the speed of the subject vehicle, and the economical speed profile according to the distance to the front obstacle may also be stored in the memory  31 . 
     The torque calculation module  35  of the one or more processors  37  may be interlocked with an accelerator position sensor (APS)  351  to calculate a required torque of the driver. In other words, the torque calculation module  35  may calculate the degree (0-100%) of opening of an accelerator pedal on the basis of a voltage value transmitted from the APS  351 , and calculate the driver&#39;s required torque of corresponding to the calculated degree of opening of the accelerator pedal. Here, the APS  351  may output a voltage value corresponding to the degree of opening of the accelerator pedal controlled by the driver. 
     The controller  36  generally controls the aforementioned respective elements to perform the functions thereof normally. The controller  36  may be in the form of hardware or software, or a combination of hardware and software. The controller  36  may preferably be a microprocessor, but is not limited thereto. 
     In addition, the controller  36  may perform a variety of processes on the basis of the programs stored in the memory. 
     In addition, the controller  36  may receive a specific mode which is set by the driver through the mode setting device  32 , and activate a module corresponding to the specific mode. 
     In other words, when receiving a safety mode set by the driver through the mode setting device  32 , the controller  36  may activate the safety speed input device  33  to allow the driver to directly input a safety speed. Here, the controller  36  may set the safety speed to a speed limit of the vehicle. 
     In addition, when receiving a fuel economy mode set by the driver through the mode setting device  32 , the controller  36  may activate the economical speed determination module  34  to allow the economical speed determination module  34  to calculate an economical speed. Here, the controller  36  may set the economical speed to a speed limit of the vehicle. 
     In addition, when receiving a hybrid mode set by the driver through the mode setting device  32 , the controller  36  may activate the safety speed input device  33  to allow the driver to directly input a safety speed, activate the economical speed determination module  34  to allow the economical speed determination module  34  to calculate an economical speed, and set a lower speed of the safety speed and the economical speed to a speed limit of the vehicle. 
     When the speed limit of the vehicle is set according to any one of the aforementioned methods, the controller  36  may calculate a torque corresponding to the set speed limit and limit the speed of the vehicle on the basis of the calculated torque, thereby improving the fuel economy of the vehicle. 
     When the speed limit of the vehicle is set according to any one of the aforementioned methods, the controller  36  may calculate a torque corresponding to the set speed limit, and compare the calculated torque with the required torque calculated by the torque calculation module  35  to determine a lower torque as a final torque of the vehicle. The controller  36  may limit the speed of the vehicle on the basis of the final torque, thereby improving the fuel economy of the vehicle. 
     The calculation of a torque corresponding to a speed in exemplary embodiments of the present disclosure may be performed by a variety of generally known methods, and is not limited by any one method. 
     When the present inventive concept is applied to a hybrid vehicle, the functions of the controller  36  may be performed by a hybrid controller (HCU). 
       FIG. 5  illustrates a flowchart of a method for limiting a speed of a vehicle according to an exemplary embodiment of the present disclosure. 
     First of all, the mode setting device  32  may receive an operation mode which is set by a driver in operation  501 . 
     Next, it may be determined whether the operation mode is a safety mode, an economy mode, or a hybrid mode in operation  502 . 
     As a result of determination in operation  502 , when the operation mode is a safety mode, the controller  36  may activate the safety speed input device  33  to receive a safety speed which is input by the driver in operation  503 . 
     As a result of determination in operation  502 , when the operation mode is an economy mode, the controller  36  may activate the economical speed determination module  34 , and the economical speed determination module  34  may determine an economical speed on the basis of the driving environment of the vehicle in operation  504 . 
     As a result of determination in operation  502 , when the operation mode is a hybrid mode, the controller  36  may activate the safety speed input device  33  and the economical speed determination module  34  in operation  505 . Thus, the safety speed input device  33  may receive a safety speed which is input by the driver, and the economical speed determination module  34  may determine an economical speed on the basis of the driving environment of the vehicle. 
     Then, the controller  36  may limit the speed of the vehicle on the basis of the safety speed or the economical speed according to a mode set by the driver in operation  506 . 
     In other words, the controller  36  limit the speed of the vehicle on the basis of the safety speed in the safety mode, limit the speed of the vehicle on the basis of the economical speed in the economy mode, and limit the speed of the vehicle on the basis of a lower speed of the safety speed and the economical speed in the hybrid mode. 
       FIG. 6  illustrates the configuration of an apparatus for limiting vehicle speed according to another exemplary embodiment of the present disclosure. 
     As illustrated in  FIG. 6 , the apparatus for limiting vehicle speed according to the exemplary embodiment of the present disclosure may include an economical speed determination processor  61 , a torque calculation processor  62 , and a controller  63 . Here, since the functions of the economical speed determination processor  61  and the torque calculation processor  62  are the same as those of the economical speed determination module  34  and the torque calculation module  35  illustrated in  FIG. 3 , a detailed description thereof will be omitted. 
     The controller  63  generally controls the aforementioned respective elements to perform the functions thereof normally. The controller  63  may be in the form of hardware or software, or a combination of hardware and software. The controller  63  may preferably be a microprocessor, but is not limited thereto. 
     In addition, the controller  63  may calculate a torque corresponding to an economical speed determined by the economical speed determination processor  61 , and limit the speed of the vehicle on the basis of the calculated torque, thereby improving the fuel economy of the vehicle. 
     In addition, the controller  63  may calculate a torque corresponding to an economical speed determined by the economical speed determination processor  61 , and compare the calculated torque with a required torque calculated by the torque calculation processor  62  to determine a lower torque as a final torque of the vehicle. The controller  63  may limit the speed of the vehicle on the basis of the final torque, thereby improving the fuel economy of the vehicle. 
       FIG. 7  illustrates a flowchart of a method for limiting a speed of a vehicle according to another exemplary embodiment of the present disclosure. 
     First of all, the economical speed determination processor  61  may determine an economical speed on the basis of the driving environment of the vehicle in operation  701 . 
     Next, the torque calculation processor  62  may calculate a required torque of the driver in operation  702 . 
     Thereafter, the controller  63  may limit the speed of the vehicle on the basis of a lower torque of a torque corresponding to the economical speed determined by the economical speed determination processor  61  and the driver&#39;s required speed calculated by the torque calculation processor  62  in operation  703 . 
       FIG. 10  illustrates a block diagram of a computing system by which a method for limiting a speed of a vehicle according to an exemplary embodiment of the present disclosure is executed. 
     Referring to  FIG. 10 , a computing system  1000  may include at least one processor  1100 , a bus  1200 , a memory  1300 , a user interface input device  1400 , a user interface output device  1500 , a storage  1600 , and a network interface  1700 , wherein these elements are connected through the bus  1200 . 
     The processor  1100  may be a central processing unit (CPU) or a semiconductor device processing commands stored in the memory  1300  and/or the storage  1600 . The memory  1300  and the storage  1600  include various types of volatile or non-volatile storage media. For example, the memory  1300  may include a read only memory (ROM) and a random access memory (RAM). 
     Therefore, the steps of the method or algorithm described in connection with the exemplary embodiments disclosed herein may be embodied directly in hardware, in a software module executed by the processor  1100 , or in a combination thereof. The software module may reside in a storage medium (i.e., the memory  1300  and/or the storage  1600 ), such as RAM, a flash memory, ROM, an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a register, a hard disk, a removable disk, and a CD-ROM. An exemplary storage medium may be coupled to the processor  1100 , such that the processor  1100  may read information from the storage medium and write information to the storage medium. Alternatively, the storage medium may be integrated with the processor  1100 . The processor  1100  and the storage medium may reside in an application specific integrated circuit (ASIC). The ASIC may reside in a user terminal. Alternatively, the processor  1100  and the storage medium may reside as discrete components in a user terminal. 
     As set forth above, the apparatus for limiting vehicle speed and the method thereof, according to exemplary embodiments of the present disclosure, can prevent the vehicle from exceeding a speed limit to secure safety and improve fuel economy by calculating an economical speed corresponding to the driving environment of the vehicle and limiting the driving speed of the vehicle on the basis of the calculated economical speed. 
     Hereinabove, although the present disclosure has been described with reference to exemplary embodiments and the accompanying drawings, the present disclosure is not limited thereto, but may be variously modified and altered by those skilled in the art to which the present disclosure pertains without departing from the spirit and scope of the present disclosure claimed in the following claims.