Abstract:
Disclosed herein are an electronic parking brake system and a method of controlling the same. The electronic parking brake system includes a wheel speed sensor which senses a movement of a vehicle; a vertical acceleration sensor which measures a vertical acceleration value; an electronic control unit (ECU) which determines whether the vehicle is rolling based on the movement of the vehicle and the vertical acceleration value; and a parking brake which brakes the vehicle based on the determination of whether the vehicle is rolling by the ECU.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 2015-0052966, filed on Apr. 15, 2015 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    Embodiments of the present disclosure relate to an electronic parking brake (EPB) system in a vehicle and a control method of the same, and more particularly, to an EPB system which restricts a brake re-clamp due to shaking of a vehicle being detected and misjudged as rolling. 
         [0004]    2. Description of the Related Art 
         [0005]    Generally, a brake system generally includes a parking brake such as a so called hand brake or side brake which maintains a vehicle in a stopped state. The parking brake is operated by a driver operating a parking lever provided at a side of the driver&#39;s seat in the vehicle. When the driver pulls the parking lever and a cable connected to the parking lever is pulled, a brake assembly of a side of a rear wheel connected to the cable is operated and braking power is generated, and conversely, when the parking lever is released and the cable is released, the braking power is released. 
         [0006]    However, since an operating method of the parking brake according to the parking lever is performed by a will of the driver, when the vehicle is parked at an inclined road without pulling the parking lever due to a carelessness of the driver, an unexpected accident such as the vehicle rolling down the inclined road may occur. 
         [0007]    In addition, since the driver has to operate the parking lever whenever parking the vehicle or starting to drive the vehicle, there are problems in that use is very cumbersome, and particularly, the use is further cumbersome to a weak woman or the elderly. 
         [0008]    Accordingly, recently, an electronic parking brake (EPB) system, which electrically controls driving a brake, is installed in a conventional disc brake and performs a parking brake function. 
         [0009]    Even though a driver does not manually operate the parking brake, the EPB system may automatically operate or release the parking brake according to a simple operation of a switch or control of an electronic control unit (ECU) which governs overall control of the EPB system. 
         [0010]    In addition, a vehicle on an inclined road may roll when a user manually operates the parking brake and fastening of the brake is incomplete, and the EPB system detects the rolling and automatically re-clamps the parking brake when the vehicle rolls on the inclined road. 
         [0011]    Such an EPB system includes an actuator having a motor which generates braking power, and an ECU for driving the actuator. The ECU includes a controller, a plurality of sensor interfaces, a motor driver, and a communication module. The ECU drives the actuator according to an operation state of a switch and operates or releases the EPB system. 
       SUMMARY 
       [0012]    Therefore, it is an aspect of the present disclosure to prevent false detection of movements of a driver or a passenger inside or outside a vehicle as a rolling of the vehicle. 
         [0013]    It is another aspect of the present disclosure to prevent unnecessary operations and to decrease a load of a vehicle and a system by determining whether it is a vehicle shaking mode or a vehicle rolling mode using a vertical acceleration sensor, re-clamping a parking brake when it is the vehicle rolling mode, and restricting a re-clamping of the parking brake when it is a simple vehicle shaking mode. 
         [0014]    Additional aspects of the disclosure will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the disclosure. 
         [0015]    In accordance with one aspect of the present invention, an electronic parking brake (EPB) system includes a wheel speed sensor which senses a movement of a vehicle; a vertical acceleration sensor which measures a vertical acceleration value; an electronic control unit (ECU) which determines whether the vehicle is rolling based on the movement of the vehicle and the vertical acceleration value; and a parking brake which brakes the vehicle based on the determination of whether the vehicle is rolling by the ECU. 
         [0016]    The ECU may include a comparator which determines whether an absolute value of the vertical acceleration value is greater than a predetermined reference value; a counting portion which counts a number of times when the absolute value of the vertical acceleration value is greater than the reference value; and a re-clamp restrictor which fastens the parking brake when the number is equal to or less than a predetermined reference counting number, and restricts fastening the parking brake when the number is greater than the predetermined reference counting number. 
         [0017]    The ECU may further include a rolling determination portion which determines that the vehicle is rolling when the number is equal to or less than the predetermined reference counting number; and a shaking determination portion which determines that the vehicle is shaking when the number is greater than the predetermined reference counting number. 
         [0018]    The ECU may disable a rolling detection of the vehicle by the wheel speed sensor of the vehicle, when the shaking is determined. 
         [0019]    In accordance with another aspect of the present invention, a method of an electronic parking brake (EPB) system includes a vertical acceleration sensor which measures a vertical acceleration value; an ECU which determines whether a vehicle is shaking based on the vertical acceleration value; and a parking brake which brakes the vehicle based on the determination of whether the vehicle is shaking by the ECU. 
         [0020]    The ECU may include a comparator which determines whether an absolute value of the vertical acceleration value is greater than a predetermined reference value; a counting portion which counts a number of times when the absolute value of the vertical acceleration value is greater than the reference value; and a re-clamp restrictor which fastens the parking brake when the number is equal to or less than a predetermined reference counting number, and restricts fastening the parking brake when the number is greater than the predetermined reference counting number. 
         [0021]    The ECU may further include a rolling determination portion which determines that the vehicle is rolling when the number is equal to or less than the predetermined reference counting number; and a shaking determination portion which determines that the vehicle is shaking when the number is greater than the predetermined reference counting number. 
         [0022]    The system may perform the counting when the vehicle is stopped. 
         [0023]    In accordance with another aspect of the present invention, a control method of an electronic parking brake (EPB) system includes sensing a movement of a vehicle by a wheel speed sensor of the vehicle; measuring a vertical acceleration value by a vertical acceleration sensor of the vehicle; determining whether the vehicle is rolling based on the vertical acceleration value and the movement of the vehicle; and re-clamping a parking brake of the vehicle based on the determining of whether the vehicle is rolling. 
         [0024]    The control method may further include restricting the re-clamping of the parking brake when the vehicle is determined to be shaking. 
         [0025]    The control method may further include disabling a rolling detection of the vehicle by the wheel speed sensor of the vehicle when the vehicle is determined to be shaking. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    These and/or other aspects of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
           [0027]      FIG. 1  is a perspective view illustrating a brake which may be used in one embodiment of the present disclosure. 
           [0028]      FIG. 2  is a view illustrating a control block diagram of an EPB system according to one embodiment of the present disclosure. 
           [0029]      FIG. 3  is a view illustrating a wheel speed sensor. 
           [0030]      FIG. 4  is a view illustrating a graph related to a voltage measured by the wheel speed sensor. 
           [0031]      FIG. 5  is a view illustrating a graph for showing a vertical acceleration value versus time (a time axis). 
           [0032]      FIG. 6  is a view illustrating a flow chart describing a control method of the EPB system according to one embodiment of the present disclosure. 
           [0033]      FIG. 7  is a view illustrating a block diagram of an EPB system according to another embodiment of the present disclosure. 
           [0034]      FIG. 8  is a view illustrating a flow chart of a control method of an EPB system according to another embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The following embodiments are examples to provide the scope of the present disclosure to those skilled in the art. The present disclosure is not limited to the following embodiments and may be implemented in different forms. In the drawings, portions which are not related to the description may be omitted for clarifying the present disclosure, and sizes of components may be exaggerated for understanding the present disclosure. 
         [0036]    According to one embodiment of the present disclosure,  FIG. 1  is a perspective view illustrating a brake which may be used in one embodiment of the present disclosure. 
         [0037]    Referring to  FIG. 1 , an electrical parking brake (EPB) system includes a motor  1  which is driven for operating or releasing an EPB, a multi stage gear  2  connected to the motor  1 , a gear wheel  3  mechanically linked to the multi stage gear  2 , a screw nut  4  integrally fixed to an inner circumferential surface of the gear wheel  3  and having a hollow shape, a spindle  5  gear-coupled to an inner circumferential surface of the screw nut  4  and moved along a shaft direction according to rotation of the gear wheel  3 , a parking cable  6  connected to an outlet side of the spindle  5  (an operation side of the parking cable) around the gear wheel  3 , and a stopper member  7  fixed to an outer circumferential surface of the spindle  5  connected to the parking cable  6  and configured to prevent the spindle  5  from being rotated by excessive pulling when the stopper member  7  is pulled to operate the brake. 
         [0038]    In addition, first and second springs  8  and  9 , which control power that pulls or releases the parking cable  6  by rotation of the gear wheel  3  and the screw nut  4  which are driven by the motor  1 , may be further installed between the gear wheel  3  and the stopper member  7 . 
         [0039]    A re-clamp operation refers to an operation which assists in the case of the spindle  5  being insufficiently pulled when the brake is operated and the parking cable  6  is pulled, wherein the vehicle rolls due to the parking cable  6  of a user being insufficiently fastened. 
         [0040]    A rolling phenomenon of a vehicle refers to the vehicle moving in a direction opposite to a traveling direction of the vehicle. 
         [0041]      FIG. 2  is a view illustrating a control block diagram of an EPB system according to one embodiment of the present disclosure. 
         [0042]    According to one embodiment of the present disclosure, the EPB system may include a vertical acceleration sensor  10 , a wheel speed sensor  20 , an electronic control unit (ECU)  30 , and a parking brake  40 . 
         [0043]    The vertical acceleration sensor  10  may sense an up and down movement (hereinafter, referred to as a vertical direction) of a vehicle. Such a vertical acceleration sensor  10 , which is a vertical sensor of an acceleration sensor and a component which detects a change in a vertical direction speed per unit of time, may sense and measure dynamic power such as an acceleration, a vibration, and an impact using principles of an inertial force, electrostriction, and a gyro. 
         [0044]    The wheel speed sensor  20  may sense a movement of the vehicle (a rolling or a shaking) and transmit a detection signal to the ECU  30 . In addition, rolling detection of the wheel speed sensor  20  may be controlled by the ECU  30  to be disabled. 
         [0045]    Specific structures and operations of the vertical acceleration sensor  10  and the wheel speed sensor  20  will be described in detail bellow. 
         [0046]    The ECU  30  totally controls the EPB system. 
         [0047]    The ECU  30  includes a comparator  50 , a counting portion  60 , a shaking determination portion  70 , a rolling determination portion  80 , and a re-clamp restrictor  90 . 
         [0048]    The comparator  50  determines whether an absolute value of a vertical acceleration value of the vertical acceleration sensor is greater than a preset reference value. 
         [0049]    According to the embodiment of the present disclosure, although the comparator  50  determines whether the absolute value of the vertical acceleration value is greater than the preset reference value, the comparator  50  is not limited thereto, and the comparator  50  may also determine whether the absolute value of the vertical acceleration value is less than the preset reference value. 
         [0050]    The counting portion  60  counts whether the number of points where the absolute value of the vertical acceleration value is greater than the preset reference value is greater than a preset arbitrary reference counting number. 
         [0051]    The shaking determination portion  70  determines that the vehicle is shaken by an external impact when a number counted by the counting portion  60  is greater than the preset arbitrary reference counting number. 
         [0052]    In addition, when the vehicle is determined to be shaken, the shaking determination portion  70  may disable a rolling detection of the wheel speed sensor  20 . 
         [0053]    When a traveling direction of the vehicle is represented as an X-axis, and a lateral direction of the vehicle is represented as a Y-axis, shaking of the vehicle means that the vehicle moves linearly back and forth, left and right, and up and down along the X-axis, Y-axis, or Z-axis direction. 
         [0054]    The rolling determination portion  80  determines that the vehicle is rolling when the number counted by the counting portion  60  is equal to or less than the preset arbitrary reference counting number. 
         [0055]    A re-clamp restrictor  90  may restrict re-clamping of the parking brake  40  of the vehicle when the shaking determination portion  70  determines that the vehicle is shaking. 
         [0056]    The parking brake  40  may be re-clamped through control of the ECU  30 . 
         [0057]      FIG. 3  is a view illustrating a wheel speed sensor, and  FIG. 4  is a view illustrating a graph related to a voltage measured by the wheel speed sensor. 
         [0058]    According to  FIG. 3 , the wheel speed sensor includes a sensor rotor  31  and a pick-up  33 , and when the rotor  31  rotates in a magnetic field having a predetermined intensity generated by a magnet included in the sensor rotor  31 , since a gap  32 , which is an interval between the sensor rotor  31  and the pick-up  33 , is increased or decreased proportionally to the number of revolutions, a magnetic resistance of a magnetic circuit including a pole piece  34  and a rotor  31  varies. 
         [0059]    The rotor  31  may rotate when the vehicle moves. Since the rotor  31  does not rotate when the vehicle is stopped, an induced voltage due to a magnet included in the sensor rotor  31  is not generated. 
         [0060]    Accordingly, a state in which the vehicle is moving may be sensed through the generation of the induced voltage. 
         [0061]    Since a level of the induced voltage generated through vehicle movement is proportional to a rotation speed of a wheel of the vehicle, the rotation speed of the wheel may be detected. 
         [0062]    The sensor rotor  31  includes a magnet and a coil, and the gap  32  is maintained in the range of 0.2 to 1.3 mm, and at this point, an alternating current (AC) flowing through the coil varies according to a variation of a magnetic flux. 
         [0063]    According to  FIG. 4 , a variation in an AC generated according to the magnetic flux may be converted into a sinusoidal signal by a digital signal. Accordingly, the signal is transmitted to the ECU  30  in a form of current signal by using pulse width modulation, and when the signal does not maintain a constant value and repeats in a form of a pulse type as illustrated in the graph in  FIG. 4 , a state in which the vehicle is moving may be sensed. 
         [0064]      FIG. 5  is a view illustrating a graph for showing a vertical acceleration value versus time (a time axis). 
         [0065]    According to the embodiment of the present disclosure, a predetermined reference value  51  is preset with respect to a vertical acceleration value, and the ECU counts when an absolute value of a varying vertical acceleration value is greater than the reference value  51 . 
         [0066]    The shaking determination portion  70  in the ECU  30  determines that the vehicle is shaking when a counted number is greater than a preset reference counting value, and the rolling determination portion  80  in the ECU  30  determines that the vehicle is rolling when the counted number is equal to or less than the preset reference counting value. 
         [0067]      FIG. 6  is a view illustrating a flow chart describing a control method of the EPB system according to one embodiment of the present disclosure. 
         [0068]    According to the embodiment of the present disclosure, whether a detected state is a shaking or a rolling of the vehicle is determined (S 100 ). 
         [0069]    When the detected state is a shaking or a rolling of the vehicle, the vertical acceleration sensor  10  measures a vertical acceleration value (S 200 ). 
         [0070]    The comparator  50  of the ECU  30  determines whether points where an absolute value of the measured vertical acceleration value is greater than a preset reference value exist (S 300 ). When points where the absolute value of the measured vertical acceleration value is greater than the preset reference value do not exist (NO in S 300 ), S 100  is restarted. 
         [0071]    When points where the absolute value of the measured vertical acceleration value is greater than the preset reference value exist (YES in  300 ), the counting portion  60  determines whether the number of counted points where the absolute value of the measured vertical acceleration value is greater than the preset reference value is greater than a reference counting value in a preset reference time (S 400 ). 
         [0072]    When the counted number is equal to or less than the preset reference counting value in the preset reference time (NO in S 400 ), the vehicle is determined to be rolling and a brake is re-clamped (S 900 ). 
         [0073]    When the counted number is greater than the preset reference counting value in the preset reference time (YES in S 400 ), the shaking determination portion  70  determines that the vehicle is shaking (S 500 ). 
         [0074]    When the shaking determination portion  70  in the ECU  30  determines that the vehicle is shaking (S 500 ), the re-clamp restrictor  90  restricts a re-clamping of the parking brake  40  (S 600 ). 
         [0075]    In addition, the ECU  30  restricts rolling detection of the wheel speed sensor (S 700 ). 
         [0076]      FIG. 7  is a view illustrating a block diagram of an EPB system according to another embodiment of the present disclosure. 
         [0077]    According to another embodiment of the present disclosure, an EPB system may include a vertical acceleration sensor  71 , an ECU  72 , and a parking brake  78 . 
         [0078]    The vertical acceleration sensor  71  may sense an up and down movement (hereinafter, referred to as a vertical direction) of a vehicle. Such a vertical acceleration sensor  71 , which is a vertical sensor of an acceleration sensor and a component which detects a vertical direction speed per unit of time, may sense and measure dynamic power such as an acceleration, a vibration, and an impact using principles of an inertia force, electrostriction, and a gyro. 
         [0079]    The ECU  72  totally controls the EPB system. 
         [0080]    The ECU  72  may perform a counting operation by comparing vertical acceleration values of the vertical acceleration sensor  71  only when the vehicle is stopped. 
         [0081]    The ECU  72  includes a comparator  73 , a counting portion  74 , a shaking determination portion  75 , a rolling determination portion  76 , and a re-clamp restrictor  77 . 
         [0082]    The comparator  73  determines whether an absolute value of a vertical acceleration value of the vertical acceleration sensor is greater than a preset reference value. 
         [0083]    Although the comparator  73  determines whether the absolute value of the vertical acceleration value is greater than the preset reference value, the comparator  73  is not limited thereto, and the comparator  73  may also determine whether the absolute value of the vertical acceleration value is less than the preset reference value. 
         [0084]    The counting portion  74  counts whether the number of counted points where the absolute value of the vertical acceleration value is greater than the preset reference value is greater than a preset arbitrary reference counting number. 
         [0085]    In addition, when the number counted by the counting portion  60  is greater than the preset arbitrary reference counting number, the vehicle is determined to be shaken by an external impact. 
         [0086]    When the number counted by the counting portion  74  is equal to or less than the preset arbitrary reference counting number, the rolling determination portion  76  determines that the vehicle is rolling. 
         [0087]    When the shaking determination portion  75  determines that the vehicle is shaking, the re-clamp restrictor  77  may restrict a re-clamping of the parking brake  78  of the vehicle. 
         [0088]    The parking brake  78  may be re-clamped through control of the ECU  72 . 
         [0089]      FIG. 8  is a view illustrating a flow chart of a control method of an EPB system according to another embodiment of the present disclosure. 
         [0090]    According to the embodiment of the present disclosure, whether a vehicle is stopped is determined (S 801 ). 
         [0091]    When the vehicle is stopped (YES in S 801 ), the vertical acceleration sensor  71  measures a vertical acceleration value (S 802 ). 
         [0092]    The comparator  73  in the ECU  72  determines whether points where an absolute value of the measured vertical acceleration value is greater than a preset reference value exist (S 803 ). When points where the absolute value of the measured vertical acceleration value is greater than the preset reference value do not exist (NO in S 803 ), S 801  is restarted. 
         [0093]    When points where the absolute value of the measured vertical acceleration value is greater than the preset reference value exist (YES in S 803 ), the counting portion  74  determines whether the number of the counted points where the absolute value of the measured vertical acceleration value is greater than the preset reference value is greater than a preset reference counting value in a preset reference time (S 804 ). 
         [0094]    When the counted number is equal to or less than the preset reference counting value in the predetermined time (NO in S 804 ), the vehicle is determined to be rolling, and the brake is re-clamped (S 807 ). 
         [0095]    When the counted number is greater than the preset reference counting value in the preset reference preset time (YES in S 804 ), the shaking determination portion  75  determines that the vehicle is shaking (S 805 ). 
         [0096]    When the shaking determination portion  75  in the ECU  72  determines that the vehicle is shaking (S 805 ), the re-clamp restrictor  77  restricts the re-clamping of the parking brake  78  (S 806 ). 
         [0097]    As is apparent from the above description, a vehicle shaking and a vehicle rolling can be distinguished using a wheel speed sensor in the EPB system and a vertical acceleration value. 
         [0098]    Accordingly, unnecessary operations and an excessive load on the EPB system can be prevented. 
         [0099]    Although embodiments of the present disclosure are illustrated and described as described above, the disclosed disclosure is not limited to the above-described specific embodiments, it should be understood that various changed embodiments may be made by those skilled in the art therein without departing from the spirit and scope of embodiments as defined by the appended claims, and such modified embodiments may not be individually understood from the disclosed disclosure.