Abstract:
A step motor includes a plurality of stator cores. Each of the stator cores have a coil unit coiled therearound. The step motor includes a rotor that includes a rotation shaft and a plurality of permanent magnets and is configured to rotate by magnetic interaction between the stator cores and the permanent magnets. The step motor also includes a plurality of conducting parts on one cross-sectional surface of the rotor. The step motor further includes a printed circuit board (PCB) including electric elements that are arranged at certain positions and are disposed to face the conducting parts. The conducting parts and the electric elements are configured to electrically or magnetically interact as the rotor rotates to change electrical signals generated by the electric elements.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY 
     The present application is related to and claims the benefit of Korean Patent Application No. 10-2014-0122034, filed on Sep. 15, 2014, 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 a step motor and a system for driving a step motor. 
     BACKGROUND 
     Step motors are a driving device that may control a rotation angle of a motor to be constant by using a simple controlling circuit which may accurately control a location of a subject of the driving without including a separate location sensor. 
     A step motor of the related art is driven by using a basic angle control scheme, which is referred to as a full step or half step control mode. When the step motor is controlled by using the basic angle control scheme, a shaft may vibrate as a motor rotates to a basic movement angle at a relatively large angle for every pulse input. The micro step control scheme is a technique that controls a step motor by increasing resolution of a rotation angle in a method of driving a step motor by dividing a step into angles (a micro step) smaller than the basic movement angle to drive a step motor. According to the micro step control, a decrease in a rotation angle of a motor per step may reduce shaft vibration and increase the resolution of the motor rotation angle. However, even when the micro step driving method is used, a location error of about ±5% may occur in general. 
     In order to compensate for the error, a magnetic sensor or an optical sensor that may sense a location of a rotator may be placed in a step motor, and thus a location error caused by driving a step motor may be sensed and compensated for. However, when a magnetic sensor or an optical sensor is placed in a step motor, a size of a driving unit may increase according to an external diameter of the sensor, and it may be difficult to place a microscopic sensor on a printed circuit board (PCB). 
     SUMMARY 
     To address the above-discussed deficiencies, it is a primary object to provide for use a step motor. 
     Provided is a step motor and a system for driving a step motor. Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented exemplary embodiments. 
     In a first embodiment, a step motor is provided. The step motor includes a stator that includes a plurality of stator cores. Each of the stator cores has a coil unit coiled therearound. The step motor also includes a rotor that includes a rotation shaft and a plurality of permanent magnets. The rotor is configured to rotate by magnetic interaction between the stator cores and the permanent magnets. The step motor further includes a plurality of conducting parts that are on one cross-sectional surface of the rotor. The step motor includes a printed circuit board (PCB) that includes electric elements that are arranged on the PCB and are spaced apart from the plurality of conducting parts by certain distance to face the plurality of conducting parts. The conducting parts and the electric elements electrically or magnetically interact with each other as the rotor rotates. The interaction changes electrical signals generated by the electric elements. 
     Each of the electric elements may include a plurality of pattern coils. The plurality of pattern coils can be arranged on one surface of the PCB and are spaced apart from each other by certain distance along a circumference of the rotation shaft. The plurality of conducting parts can be arranged on one cross-sectional surface of the rotor and are spaced apart from each other by certain distance along the circumference of the rotation shaft. An angle between neighboring pattern coils can be different from an angle between neighboring conducting parts. 
     The plurality of pattern coils can be arranged on one surface of the PCB and are spaced apart from each other by certain distance along a circumference of the rotation shaft. The plurality of conducting parts can include first conducting parts and second conducting parts. The first conducting parts have different thicknesses to the second conducting parts. The first conducting parts and the second conducting parts are alternately arranged on one cross-sectional surface of the rotor along the circumference of the rotation shaft. 
     The plurality of pattern coils can be arranged on one surface of the PCB and are spaced apart from each other by certain distance along a circumference of the rotation shaft. The plurality of conducting parts can include first conducting parts and second conducting parts. The first conducting parts are formed of different materials from the second conducting parts. The first conducting parts and the second conducting parts are alternately arranged on one cross-sectional surface of the rotor along the circumference of the rotation shaft. 
     The electric elements can include a plurality of capacitors. Each of the capacitors can include a first electrode, a second electrode, and an insulating layer between the first electrode and the second electrode. The first electrode and the second electrode are arranged in a longitudinal direction of the rotation shaft. The capacitor can further include a protection layer on the second electrode layer. The capacitor can include the first electrode, the second electrode, and the insulating layer between the first electrode and the second electrode. The first electrode and the second electrode are arranged along a circumference of the rotation shaft. The plurality of capacitors can be arranged on one surface of the PCB and are spaced apart from each other by certain distance along a circumference of the rotation shaft. The plurality of conducting parts can be arranged on one cross-sectional surface of the rotor and are spaced apart from each other by certain distance along the circumference of the rotation shaft. 
     An angle between neighboring capacitors can be different from an angle between neighboring conducting parts. The plurality of capacitors can be arranged on one surface of the PCB and are spaced apart from each other by certain distance along a circumference of the rotation shaft. The plurality of conducting parts can include first conducting parts and second conducting parts. The first conducting parts have different thicknesses from the second conducting parts. The first conducting parts and the second conducting parts are alternately arranged on one cross-sectional surface of the rotor along the circumference of the rotation shaft. 
     In a second embodiment, a system for driving the step motor is provided. The system includes a driving unit configured to provide a driving current to the step motor by using a standard signal corresponding to an operation mode of the step motor and electrical signals generated by electric elements. The system also includes a control unit configured to transmit the standard signal corresponding to an operation mode of the step motor and the electric signals generated by the electric elements to the driving unit. 
     The driving unit generates the driving current by comparing the electrical signal with the standard signal. The control unit can include an output signal generating unit configured to generate electric signals by using the electric elements. The control unit can also include a standard signal generating unit configured to generate the standard signal according to an operation mode of the step motor. 
     Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts: 
         FIG. 1  is a plan view of an example step motor on a printed circuit board (PCB) according to this disclosure; 
         FIGS. 2A and 2B  are cross-sectional views of an example step motor placed on a PCB according to this disclosure; 
         FIGS. 3A and 3B  are plan views of an example step motor placed on a PCB according to this disclosure; 
         FIG. 4  is a detection circuit for detecting an inductance according to this disclosure; 
         FIG. 5  is a plan view of an example step motor on a PCB including a coil unit placed on the PCB according to this disclosure; 
         FIG. 6  is a graph illustrating an example of a change in the inductance generated in a coil unit according to this disclosure; 
         FIGS. 7A and 7B  are plan views of an example step motor on a PCB according to this disclosure; 
         FIGS. 8A and 8B  are partial cross-sectional views of an example self-electrostatic capacitance type capacitor for measuring an electrostatic capacitance according to this disclosure; 
         FIGS. 9A and 9B  are partial cross-sectional views of an example mutual electrostatic capacitance type capacitor for measuring an electrostatic capacitance according to this disclosure; 
         FIG. 10  is a plan view of an example step motor on a PCB including a capacitor placed on the PCB according to this disclosure; and 
         FIG. 11  is a block diagram illustrating a schematic structure of an example system for driving the step motor according to this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 through 11 , discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged motor or system. Reference will now be made in detail to exemplary embodiments of a step motor and a system for driving a step motor, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present exemplary embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the exemplary embodiments are merely described below, by referring to the figures, to explain aspects. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
       FIG. 1  illustrates an example step motor  10  according to this disclosure.  FIGS. 2A and 2B  illustrate cross-sectional views of an example step motor  10  according to this disclosure. 
     Referring to  FIG. 1 , the step motor  10  includes a rotor  100 , a stator  200 , a housing (not shown) outside the rotor  100  and the stator  200 , and the PCB  300 . The rotor  100  includes a rotation shaft  110  and permanent magnets  120  that are fixed on the rotation shaft  110 . The permanent magnets  120  extend along a longitudinal direction of the rotation shaft  110  and are arranged so that North (N) and South (S) poles of the permanent magnets alternate along a circumference direction of the rotation shaft  110 . For example, the permanent magnets  120  can be a ring-type permanent magnet that surrounds the rotation shaft  110  and includes 6 teeth  121 , which are arranged along a circumference direction of the rotation shaft  110 . Here, each of the 6 teeth  121  can be arranged along a circumference direction of the rotation shaft  110  so that N and S poles of the permanent magnets alternate with each other. 
     The stator  200  can include a yoke  210  in the housing, a plurality of stator cores  220 , and a plurality of coil units  230 , each of which coils around the stator core  220 . The stator cores  220  are arranged at constant intervals along a circumference following an inner wall of the yoke  210 . For example, the number of the stator cores  220  formed in a circumference direction along the inner wall of the yoke  210  at constant intervals may be 8. The coil units  230  respectively coil around the stator cores  220  and change a magnetic property of the stator cores  220  according to an electrical signal transmitted to each step. 
     The PCB  300  has a hollow form through which the rotation shaft  110  passes. The PCB  300  is positioned on the rotation shaft  110  by using a bearing member  360  disposed on a hollow part. A plurality of electric elements  350  (see  FIGS. 2A and 2B ) faces a surface of the rotor  100  and senses rotation of the rotor  110 . For example, referring to  FIGS. 2A and 2B , the electric elements  350  are arranged on the PCB  300  to face a first end  101  or a second end  102  of the rotor  100 . The electric elements  350  are members that generate electrical signals that change by interacting with the rotor  100 , particularly, with conducting parts  150  each disposed on one cross-sectional surface of the permanent magnet  120 . Examples of the electric element  350  include a pattern coil  310  (see  FIG. 3 ) that generates inductance or a capacitor  320  (see  FIG. 7 ) that generates electrostatic capacitance. However, exemplary embodiments are not limited thereto, and the electric elements  350  vary depending on electrical signals that change by interacting with the conducting member  150  disposed on one cross-sectional surface of the permanent magnet  120 . 
       FIGS. 3A and 3B  illustrate an example step motor  10  according to this disclosure.  FIG. 4  illustrates an example circuit arrangement according to this disclosure. Referring to  FIGS. 2A, 2B and 3A , the conducting part  150  is disposed on one cross-sectional surface of the permanent magnet  120 . The conducting part  150  generates eddy currents by magnetic flux that occurs when a signal current is supplied to the electric element  350 , that is, the pattern coil  310 . For example, the conducting part  150  is formed of a conductive material such as aluminum, iron, copper, a wiring board, a conductive film, or a plastic material containing metal. The plurality of conducting parts  150  are arranged at predetermined intervals, and thus a region for interaction with the pattern coil  310  is distinguished by the presence of the conducting parts  150 . However, a region for interaction with the pattern coil  310  is distinguished by continuously arranging the plurality of conducting parts  150  that have different thicknesses or that are formed of different materials. For example, referring to  FIG. 3B , first conducting parts  151  and second conducting parts  152  that are formed of different materials or have different thicknesses from each other are alternately arranged along a circumference of the rotation shaft  110 . 
     The pattern coils  310  are arranged on a substrate  301  of the PCB  300  and, for example, include first to fourth pattern coils  311 ,  312 ,  313 ,  314  having a square spiral form. The pattern coils  310  face the conducting parts  150 . For example, each of the first to fourth pattern coils  311 ,  312 ,  313 ,  314  is arranged at an angular interval of 90 degrees. That is, the first pattern coil  311 , the second pattern coil  312 , the third pattern coil  313 , and the fourth pattern coil  314  are arranged at an angular interval of 90 degrees in the stated order. Also, the first pattern coil  311  and the third pattern coil  313  form an offset of 180 degrees which construct a first channel CH 1 , and the second pattern coil  312  and the fourth pattern coil  314  form an offset of 180 degrees which construct a second channel CH 2 . Here, the first pattern coil  311  and the second pattern coil  312  form a first system S 1 , and the third pattern coil  313  and the fourth pattern coil  314  form a second system S 2 . A circuit is designed to obtain detection signals from each of the first and second systems S 1  and S 2 . 
     According to an exemplary embodiment, a principle for detecting a rotation angle of the rotor  100  is schematically described herein. Referring to  FIG. 4 , the first and second systems S 1  and S 2 , respectively, are connected to an AC voltage source V in parallel to apply a voltage to a resonance circuit of the first and second systems S 1  and S 2 , and thus magnetic flux is generated at the first to fourth pattern coils  311 ,  312 ,  313 ,  314 . Here, when the conducting parts  150  face the first to fourth pattern coils  311 ,  312 ,  313 ,  314 , respectively, eddy currents are generated at the conducting parts  150 , and magnetic flux passing the first to fourth pattern coils  311 ,  312 ,  313 ,  314  decreases due to the eddy currents generated at the conducting parts  150 . As the magnetic flux changes in correspondence to the eddy currents generated at the conducting parts  150 , an amount of inductance of the first to fourth pattern coils  311 ,  312 ,  313 ,  314  changes. 
     When the rotor  100  rotates about the rotation shaft  110  as a center, the conducing parts  150  periodically face the first to fourth pattern coils  311 ,  312 ,  313 ,  314 . Alternatively, the first conducing parts  151  and the second conducting parts  152  that are formed at different heights or are formed of different materials from each other periodically face the first to fourth pattern coils  311 ,  312 ,  313 ,  314 . In this regard, when a magnetic flux is generated from the first to fourth pattern coils  311 ,  312 ,  313 ,  314 , an amount of inductance also periodically changes. 
     Since amplitudes, phases, or frequencies of output signals obtained from the first and second systems S 1  and S 2 , respectively, that are formed of the first to fourth pattern coils  311 ,  312 ,  313 ,  314  change due to a change in the amount of the inductance of the first to fourth pattern coils  311 ,  312 ,  313 ,  314 , a rotation angle of the rotor  100  is detected by sensing the change of the amplitudes, phases, or frequencies. For example, a phase comparing device M is connected to the first and second systems S 1  and S 2 , respectively, at nodes of the resonance circuit, and a rotation angle and a rotation direction of the rotor  100  are detected by detecting and comparing output signals by using phases of the inductances of the first and second systems S 1  and S 2 , respectively, from the phase comparing device M. 
     For example, referring to  FIGS. 5 and 6 , the first pattern coil  311  and the second pattern coil  312  that are neighboring each other and the third pattern coil  313  and the fourth pattern coil  314  that are neighboring each other are spaced apart at an angular interval of 90 degrees, and thus sine waves having a phase difference of 90 degrees are detected. Here, when the neighboring conducting parts  150  are spaced apart at an angular interval of 60 degrees, the first channel CH 1  and the second channel CH 2  detect output signals having different amount of inductances at the same time. In this case, the first channel CH 1  and the second channel CH 2  analyze different output signals, and thus a rotation direction as well as a rotation angle of the rotor  100  are detected. For example, depending on which output signal of the first channel CH 1  and the second channel CH 2  precedes the other, a rotation direction of the rotor  100  is sensed as a clockwise direction or a counter-clockwise direction. 
       FIGS. 7A and 7B  show an example step motor  10  according to this disclosure.  FIGS. 8A to 9B  illustrate an example structure of a capacitor  320  according to this disclosure. Referring to  FIG. 7A , the conducting part  150  is disposed on one cross-sectional surface of the permanent magnetic  120 . The conducting part  150  changes an electrostatic capacitance of the capacitor  320  by interacting with the electric element  350 , that is, the capacitor  320 . For example, the conducting part  150  is formed of a conductive material such as aluminum, iron, copper, a wiring board, a conductive film, or a plastic material containing metal. The plurality of conducting parts  150  are arranged at certain intervals, and thus a region for interaction with the capacitor  320  is distinguished by the presence of the conducting parts  150 . However, a region for interaction with the capacitor  320  is distinguished by continuously arranging the plurality of conducting parts  150  that have different thicknesses. For example, referring to  FIG. 7B , first conducting parts  151  and second conducting parts  152  that have different thicknesses from each other are alternately arranged along a circumference of the rotation shaft  110 . 
     A plurality of the capacitors  320  are arranged on the PCB  300 , and the capacitors  320  are disposed to face the conducting parts on one cross-sectional surface of a teeth part  121 . When the rotor  100  rotates, the conducting parts  150  periodically face the capacitors  320 , or the first conducting parts  151  and the second conducting parts  152  that have different thicknesses periodically face the capacitors  320 , and thus an electrostatic capacitance of the capacitors  320  changes periodically. 
     A technique for measuring an electrostatic capacitance of the capacitors  320  is determined depending on the arrangement of arranging the first electrode  321  and the second electrode  322 . For example, referring to  FIGS. 7 and 8A , when the first electrode  321  is disposed on the base substrate  323  and the second electrode  322  is disposed to face the first electrode  321  at a constant interval, an electrostatic capacitance of the capacitor  321  is measured by a self-electrostatic capacitance technique. 
     The first electrode  321  and the second electrode  322  are formed of a conductive material. Examples of the conductive material include an indium tin oxide, a tin oxide, an indium zinc oxide, an indium tin zinc oxide, a metallic single-walled carbon nanotube (SWCNT), and a conductive polymer poly 3,4-ethylenedioxythiophene (PEDOT). The first electrode  321  and the second electrode  322  face each other and thus are prepared in various shapes, of which coordinate information of an external input is measured. For example, the first electrode  321  and the second electrode  322  have a flat pattern shape including a continuous pattern of rhombuses or diamonds. 
     The insulating layer  324  is disposed between the first electrode  321  and the second electrode  322 . The insulating layer  324  insulates the first electrode  321  and the second electrode  322  so as not to contact each other. Also, the insulating layer  324  serves as a dielectric layer between the first electrode  321  and the second electrode  322 . The insulating layer  324  is formed by filling a space between the first electrode  321  and the second electrode  322  with an insulating material. 
     The protection layer  325  is disposed on the second electrode  322 . The protection layer  325  protects the second electrode  322  from the outside, and, in some embodiments, the protection layer  325  is omitted. 
     The schematic principle of detecting a rotation angle of the rotor  100  by the self-electrostatic capacitance technique according to another embodiment is as follows. In  FIGS. 8A and 8B , the first electrode  321  is defined by an X-axis electrode X, and the second electrode  322  is defined by a Y-axis electrode Y. The X-axis electrode X is grounded and becomes a reference voltage unit having a voltage of 0 V. The Y-axis electrodes Y become a measuring unit that measures a voltage or an electrostatic capacitance. Referring to  FIGS. 8A and 8B , when the rotor  100  rotates and the conducting parts  150  disposed at a first end part  101  and a second end part  102  face the second electrode  322 , the conducting part  150  becomes a new conducting plate. In this regard, a new capacitor is formed in the protection layer  325  that is disposed between the conducting part  150  and the second electrode  322 , and thus a second electrostatic capacitance C 2  is formed. Also, although not shown in  FIGS. 8A and 8B , the capacitor  320  according to an embodiment has a parasitic electrostatic capacitance C 9  that is formed of various electrostatic capacitances generated between the first electrode  321  and the second electrode  322 . Thus, with reference to the measuring unit, the Y-axis electrode Y, a first electrostatic capacitance C 1  between the first electrode  321  and the second electrode  322 , the parasitic electrostatic capacitance Cp, and a second electrostatic capacitance C 2  caused by the conducting part  150  are connected in parallel. 
     When the electrostatic capacitances C 1 , C 2 , Cp are in parallel, an electrostatic capacitance Ctot value measured at the Y-axis electrode Y is obtained by the sum of the electrostatic capacitances C 1 , C 2 , Cp. Thus, when the rotor  100  rotates with the rotation shaft  110  in the center, the conducting parts  150  facing the capacitors  320  change periodically, and thus a size of the electrostatic capacitance Ctot measured at the Y-axis electrode Y also changes periodically. 
     An output signal, an amplitude, a phase, or a frequency changes due to change in a size of the electrostatic capacitance Ctot measured at the Y-axis electrode Y, and thus a rotation angle and a rotation direction of the rotor  100  is detected by sensing the change in an amplitude, a phase, or a frequency. 
     Referring to  FIGS. 7 and 9A , for example, the first electrode  321  and the second electrode  322  are disposed side by side at a certain interval, and an electrostatic capacitor of the capacitor  320  is measured by the self-electrostatic capacitance technique when the first electrode  321  and the second electrode  322  are arranged as described herein. 
     In  FIGS. 9A and 9B , the first electrode  321  is defined by an X-axis electrode X, and the second electrode  322  is defined by a Y-axis electrode Y. The X-axis electrode X is grounded and becomes a reference voltage unit having a voltage of 0 V. The Y-axis electrodes Y become a measuring unit that measures a voltage or an electrostatic capacitance. Referring to  FIGS. 9A and 9B , when the rotor  100  rotates and the conducting parts  150  disposed at a first end part  101  and a second end part  102  face the first electrode  321  and the second electrode  322 , the conducting part  150  becomes a new conducting plate. In this regard, an electric field is formed between the conducting part  150  and the second electrode  322 , and an electrostatic capacitance C 3  measured at the Y-axis electrode Y changes. 
     Therefore, when the rotor  100  rotates with the rotation shaft  110  in the center, the conducting parts  150  facing the capacitors  320  change periodically, and thus a size of the electrostatic capacitance C 3  measured at the Y-axis electrode Y also changes periodically. An amplitude, a phase, or a frequency of an output signal changes due to change in a size of the electrostatic capacitance C 3  measured at the Y-axis electrode Y, and thus a rotation angle and a rotation direction of the rotor  100  is detected by sensing the change in an amplitude, a phase, or a frequency 
     According to an exemplary embodiment, output signals that are detected by an electrostatic capacitance differ depending on an arrangement of the capacitors  326 ,  327 ,  328 ,  329 , which are used as electric elements  350 . For example, referring to  FIG. 10 , when an interval between a first capacitor  326  and a second capacitor  327  or between a third capacitor  328  and a fourth capacitor  329  that are neighboring each other is different from an interval between the neighboring conducting parts  150  of the rotor  100 , output signals different from each other are detected at a plurality of channels, and a rotation angle as well as a rotation direction of the rotor  100  are detected by analyzing the output signals. Detailed description of the embodiment is the same with that of an exemplary embodiment and thus is omitted. 
     In the step motor  10  and the step motor driving system  1  according to an embodiment, a rotation angle and a rotation direction of the step motor  10  are sensed by using the electric elements  350  disposed on the PCB  300 , and thus the step motor  10  is miniaturized, and a manufacturing cost of the whole system is reduced. 
       FIG. 11  is a block diagram illustrating a schematic structure of an example system for driving the step motor driving system  1  according to this disclosure. 
     Referring to  FIG. 11 , the step motor driving system  1  drives the step motor  10  and includes a control unit  20  and a motor driving unit  30 . The control unit  20  generates a reference signal that corresponds to a driving mode of the step motor  10  and output signals generated by the electric elements  350 , and the signals are provided to the motor driving unit  30 . For example, in the control unit  20 , a reference signal for optimum control with respect to torque and vibration characteristics of the step motor  10  is certain, and output signals are determined by electric signals of the electric elements  350  of the step motor  10 . In this regard, the control unit  20  according to an embodiment includes an output signal generating unit  21  and a reference signal generating unit  22 . 
     The output signal generating unit  21  generates output signals of a clock type that express whether the step motor  10  operates or not and a rate of the step motor  10  by using an electric signal generated by the electric element  350  and provides the output signals to the motor driving unit  30 . 
     The reference signal generating unit  22  generates reference signals of an appropriate intensity based on torque and vibration characteristics corresponding to the driving mode of the step motor  10  and then provide the reference signals to the motor driving unit  30 . For example, the control unit  20  includes a certain memory and stores data that correspond to the driving mode of the step motor  10 . 
     The motor driving unit  30  supplies a driving current to the step motor  10  and drives the step motor  10 . Whether the step motor  10  operates or not and a rate of the operation is determined according to an amount of the driving current. For example, the motor driving unit  30  supplies the driving current to the step motor  10  by using the output signal input from the output signal generating unit  21  and the reference signal input from the reference signal generating unit  22 . For example, the motor driving unit  30  drives the step motor  10  by supplying a driving current, of which a position error is compensated based on difference in two signals, to the step motor  10  by receiving the output signal input from the output signal generating unit  21  and the reference signal input from the reference signal generating unit  22 . 
     The step motor  10  and the step motor driving system  1  compensates the position error by sensing the position error and a rotation direction of the step motor  10  by using electric elements disposed on a PCB. Therefore, a rotation sensor-type step motor system including a microscopic magnetic sensor or an optical sensor is disposed on the PCB is easily manufactured, and a size of the whole step motor system is miniaturized, and a manufacturing cost of the step motor system is reduced. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the inventive concept (especially in the context of the following claims) are to be construed to cover both the singular and the plural. Furthermore, recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. Also, the steps of all methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The inventive concept is not limited to the described order of the steps. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the inventive concept and does not pose a limitation on the scope of the inventive concept unless otherwise claimed. Numerous modifications and adaptations will be readily apparent to one of ordinary skill in the art without departing from the spirit and scope. 
     It should be understood that exemplary embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each exemplary embodiment should typically be considered as available for other similar features or aspects in other exemplary embodiments. 
     Although the present disclosure has been described with an exemplary embodiment, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims.