WO2014101868A1

WO2014101868A1 - Method and apparatus for controlling electronic parking brake system

Info

Publication number: WO2014101868A1
Application number: PCT/CN2013/090883
Authority: WO
Inventors: Tiejun Wang; Chuanbo LI; Qili LI
Original assignee: Shenzhen Byd Auto R&D Company Limited; Byd Company Limited
Priority date: 2012-12-29
Filing date: 2013-12-30
Publication date: 2014-07-03
Also published as: CN103895518A; CN103895518B

Abstract

A method and an apparatus for controlling an electronic parking brake system are provided. The method includes: obtaining first and second detected current value by a sensing element and a sampling resistor respectively; obtaining first and second detected rotating speed values by a speed sensor and the sampling resistor respectively; comparing the first and second detected current values to obtain a first result, and comparing the first and second detected rotating speed values to obtain a second result; determining the current value and the rotating speed value according to the first and second results respectively; calculating a first and second temperature values; comparing the first and second temperature values to obtain a third result; determining the temperature value according to the third result; obtaining the braking force according to the current value, the rotating speed value and the temperature value; and controlling the parking motor according to the braking force.

Description

METHOD AND APPARATUS FOR CONTROLLING ELECTRONIC PARKING BRAKE

SYSTEM

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority and benefits of Chinese Patent Application No.

201210590093.9, filed with State Intellectual Property Office, P. R. C. on December 29, 2012, the entire content of which is incorporated herein by reference.

FIELD

Embodiments of the present disclosure generally relate to a vehicle braking technology field, more particularly, to a method and an apparatus for controlling an electronic parking brake system.

BACKGROUND

A brake system is configured to decelerate a vehicle during driving until stopping the vehicle and to keep the vehicle in a static state. The brake system includes a parking brake equipment.

An operation method for the parking brake equipment is that a driver operates a brake bar to drive a parking cable, and then the parking cable drives a brake connected with the cable to provide a braking force for the wheels, thus keeping the wheels in the static state. When the brake bar is released, the parking cable is loosened so as to release the braking force from the wheels. This type of parking brake equipment which uses a pulling force of the parking cable to apply the braking force to the wheels or release the braking force from the wheels is referred to as a cable brake type of parking brake equipment.

The cable brake works only when the driver operates the brake bar, moreover, it functions only when the driver pulls up the brake bar with great force, which not only influences a usage of the inner space of the vehicle, but also brings trouble to the driver, for example, a thin and weak driver may be unable to pull up the brake bar. Accordingly, an electronic parking brake system adopting a parking motor instead of the driver to pull up the brake bar has been proposed.

The electronic parking brake system includes an electronic control unit, a parking motor, a gear train, a screw, a threaded sleeve and a parking cable. The electronic control unit is communicated with the controller area network of the vehicle to obtain an intention of the driver so as to achieve the driving brake and the parking brake, in which the parking brake is the common function of the electronic parking brake system.

The brake process of the electronic parking brake system is described as follows.

When the electronic control unit receives a command and determines that the command is a valid command, the electronic control unit controls a relay to be turned on so as to electrify the parking motor, the parking motor generates a rotation after being electrified, and then the transfer gear train transmits the rotation to the threaded sleeve to drive the screw. Since the rotation of the screw is limited by the threaded sleeve, the screw moves along a straight line under the rotation of the threaded rod, so as to drive the parking cable to lengthen or shorten, in which the brake is tightened when the parking cable shortens, and the brake is released when the parking cable lengthens.

For the electronic control unit, the key is to determine a value of the cable force. When a sensor for detecting the cable force breaks down, it is hard to determine whether a required braking force is reached, thus causing a serious threat to the safety of the vehicle.

SUMMARY

Embodiments of the present disclosure seek to solve at least one of the problems existing in the prior art to at least some extent.

For this, one objective of the present disclosure is to provide a method for controlling an electronic parking brake system, which can effectively detect a fault of the electronic parking brake equipment so as to ensure an operation security of the electronic parking brake equipment.

Another objective of the present disclosure is to provide an apparatus for controlling an electronic parking brake system, which can effectively detect the fault of the electronic parking brake equipment so as to ensure the operation security of the electronic parking brake equipment.

According to embodiments of a first aspect of the present disclosure, a method for controlling an electronic parking brake system is provided. The method includes: obtaining a first detected current value, a first detected rotating speed value, a second detected current value and a second detected rotating speed value of a parking motor; calculating a difference between the first detected current value and the second detected current value to obtain a first current difference value and calculating a difference between the first detected rotating speed value and the second detected rotating speed value to obtain a first rotating speed difference value; comparing the first current difference value with a predetermined current difference threshold to obtain a first comparison result and comparing the first rotating speed difference value with a predetermined rotating speed difference threshold to obtain a second comparison result; determining a current value according to the first comparison result and determining a rotating speed value of the parking motor according to the second comparison result; calculating a first temperature value of the parking motor according to a maximum current value when the parking motor is started and calculating a second temperature value of the parking motor according to a working current and a working time of the parking motor; calculating a difference between the first temperature value and the second temperature value to obtain a temperature difference value; comparing the temperature difference value with a predetermined temperature difference threshold to obtain a third comparison result, and determining a temperature value of the parking motor according to the third comparison result; querying a predetermined reference table according to the current value, the rotating speed value and the temperature value of the parking motor to determine a braking force applied by the parking motor; and controlling the parking motor according to the braking force.

With the method for controlling an electronic parking brake system according to embodiments of the present disclosure, since both the current and the rotating speed of the parking motor are obtained, a dual protection for the current and the rotating speed is realized, thus increasing an accuracy of the braking force (this is because the braking force is estimated according to a combination of the current and the rotating speed). Furthermore, since no other element for measuring force is used, a mechanical structure of the electronic parking brake system is simplified and a manufacturing cost of the electronic parking brake system is reduced.

According to embodiments of a second aspect of the present disclosure, an apparatus for controlling an electronic parking brake system is provided. The electronic parking brake system comprises a parking motor, a sensing element for detecting a current of a parking motor to obtain a first detected current value, a speed sensor for detecting a rotating speed of the parking motor to obtain a first detected rotating speed value, and a sampling resistor connected with the parking motor. The apparatus comprises: a first obtaining module configured to read the first detected current value and the first detected rotating speed value and to obtain a second detected current value and a second detected rotating speed value according to a voltage across the sampling resistor; a first calculating module configured to calculate a difference between the first detected current value and the second detected current value to obtain a first current difference value, to calculate a difference between the first detected rotating speed value and the second detected rotating speed value to obtain a first rotating speed difference value, to compare the first current difference value with a predetermined current difference threshold to obtain a first comparison result, to compare the first rotating speed difference value with a predetermined rotating speed difference threshold to obtain a second comparison result, to determine a current value of the parking motor according to the first comparison result, and to determine a rotating speed value of the parking motor according to the second comparison result; a second obtaining module configured to obtain a maximum current value when the parking motor is started, a working current and a working time of the parking motor, to calculate a first temperature value of the parking motor according to the maximum current value when the parking motor is started and to calculate a second temperature value of the parking motor according to the working current and the working time of the parking motor; a second calculating module configured to calculate a difference between the first temperature value and the second temperature value to obtain a temperature difference value, to compare the temperature difference value with a predetermined temperature difference threshold to obtain a third comparison result, and to determine a temperature value of the parking motor according to the third comparison result; a reference table storage module configured to store a reference table indicating corresponding relationships between currents, rotating speeds, temperatures and torques of the parking motor; a braking force calculating module configured to query the reference table according to the current value, the rotating speed value and the temperature value of the parking motor so as to determine the braking force applied by the parking motor; and a control module configured to control the parking motor according to the determined braking force.

With the apparatus for controlling the electronic parking brake system according to embodiments of the present disclosure, since the current of the parking motor is detected by the sensing element and the sampling resistor connected with the parking motor respectively, and the rotating speed of the parking motor is detected by the speed sensor and the sampling resistor connected with the parking motor respectively, a dual protection for the current and the rotating speed is obtained, thus increasing an accuracy of the braking force (this is because the braking force is estimated according to a combination of the current and the rotating speed). Furthermore, since no other element for measuring force is used, a mechanical structure of the electronic parking brake system is simplified and a manufacturing cost of the electronic parking brake system is reduced.

Additional aspects and advantages of embodiments of present disclosure will be given in part in the following descriptions, become apparent in part from the following descriptions, or be learned from the practice of the embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and advantages of embodiments of the present disclosure will become apparent and more readily appreciated from the following descriptions made according to the accompanying drawings, in which:

Fig. 1 is a schematic diagram of an electronic parking brake equipment according to an embodiment of the present disclosure;

Fig. 2 is a block diagram of an electronic control unit according to an embodiment of the present disclosure;

Fig. 3 is a flow chart of a method for controlling an electronic parking brake system according to an embodiment of the present disclosure; and

Fig. 4 is a flow chart of a method for controlling an electronic parking brake system according to another embodiment of the present disclosure.

DETAILED DESCRIPTION

Reference will be made in detail to embodiments of the present disclosure. Embodiments of the present disclosure will be shown in drawings, in which the same or similar elements and the elements having same or similar functions are denoted by like reference numerals throughout the descriptions. The embodiments described herein according to drawings are explanatory and illustrative, not construed to limit the present disclosure.

The following description provides a plurality of embodiments or examples configured to achieve different structures of the present disclosure. In order to simplify the present disclosure, components and dispositions of the particular embodiment are described in the following, which are only explanatory and not construed to limit the present disclosure. In addition, the present disclosure may repeat the reference number and/or letter in different embodiments for the purpose of simplicity and clarity, and the repeat does not indicate the relationship of the plurality of embodiments and/or dispositions. Moreover, in description of the embodiments, the structure of the second characteristic "above" the first characteristic may include an embodiment formed by the first and second characteristic contacted directly, and also may include another embodiment formed between the first and the second characteristic, in which the first characteristic and the second characteristic may not contact directly.

In the description of the present disclosure, unless specified or limited otherwise, it should be noted that, terms "mounted," "connected" and "coupled" may be understood broadly, such as electronic connection or mechanical connection, inner communication between two elements, direct connection or indirect connection via intermediary. These having ordinary skills in the art should understand the specific meanings in the present disclosure according to specific situations.

With reference to the following descriptions and drawings, these and other aspects of embodiments of the present disclosure will be distinct. In the descriptions and drawings, some particular embodiments are described in order to shown means of the principles of embodiments according to the present disclosure, however, it should be appreciated that the scope of embodiments according to the present disclosure is not limited. On the contrary, embodiments of the present disclosure include all the changes, alternatives, and modifications falling into the scope of the spirit and principles of the attached claims.

Fig. 1 is a schematic diagram of an electronic parking brake equipment according to an embodiment of the present disclosure. As shown in Fig. 1, the electronic parking brake equipment is a cable brake type of electronic parking brake equipment, and comprises a parking motor 10, a gear train 20, a screw 25, a threaded sleeve 30 and a parking cable 40. The cable brake type of electronic parking brake equipment further comprises a speed sensor 110 for detecting a rotating speed of the parking motor 10 during an operation of the electronic parking brake equipment.

An electronic parking brake system comprises the above cable brake type of electronic parking brake equipment, a brake, wheels, a parking switch, an electronic control unit (ECU), a sensing element, a sampling resistor and a display unit. The electronic parking brake system further comprises a battery for supplying power to each component. The sensing element is small in size and may be integrated in the circuit board without involving in the current loop of the parking motor 10. The sensing element is configured to detect a current of the parking motor 10. The sampling resistor is connected in the current loop of the parking motor 10 and advantageously is a copper plate.

Under the operation of the parking switch, the ECU controls the parking motor 10 to rotate forwardly or reversely with the power provided by the battery, and then the parking motor 10 drives the parking cable 40 to shorten or lengthen via the gear train 20, the screw 25 and the threaded sleeve 30, so as to apply a braking force to the brake or release a braking force from the brake.

The ECU estimates the braking force applied to the brake according to an estimated temperature of the parking motor 10, currents of the parking motor 10 detected by the sensing element and the sampling resistor respectively, and rotating speeds of the parking motor 10 detected by the speed sensor 110 and the sampling resistor respectively, and then controls a rotation of the parking motor 10 according to the estimated braking force, so as to control a tension force of the cable and the braking force of the brake. By analyzing the currents and the rotating speeds detected by the sensing element, the speed sensor and the sampling resistor, the fault in the electronic parking brake equipment can be detected, and thus a corresponding warning can be generated, and a corresponding operation can be performed.

Fig. 2 is a schematic diagram of an electronic control unit according to an embodiment of the present disclosure.

As shown in Fig. 2, the ECU 100 comprises a first obtaining module 100a, a first calculating module 100b, a second obtaining module 100c, a second calculating module lOOd, a reference table storage module lOOe, a braking force calculating module lOOf and a control module lOOg.

The first obtaining module 100a is configured to read a first detected current value II of the sensing element and a first detected rotating speed value Rl of the speed sensor 110, and to obtain a second detected current value 12 and a second detected rotating speed value R2 according to a voltage across the sampling resistor. Specifically, the second detected current value 12 is calculated after amplifying the voltage across the sampling resistor by an amplifier. The second detected rotating speed value R2 is obtained as follows: firstly, a ripple voltage across the sampling resistor is amplified with a larger amplification coefficient to obtain a number of commutations occurring in a commutator bar of the parking motor, and then the number of commutations is divided by a number of commutations per circle to obtain the second detected rotating speed value R2.

The second obtaining module 100c is configured to obtain a maximum current value when the parking motor is started, a working current and a working time of the parking motor, to calculate a first temperature value Tl of the parking motor according to the maximum current value when the parking motor is started and to calculate a second temperature value T2 of the parking motor according to the working current and the working time of the parking motor. Specifically, a winding resistance of the parking motor 10 is firstly obtained by dividing the voltage (measurable) of the parking motor by the maximum current value, and then the first temperature value Tl can be obtained according to the winding resistance, since the winding resistance of the parking motor changes with the temperature. On the other hand, firstly, a total power of the parking motor is calculated according to the voltage, the working current, the working time and the time interval of the parking motor, and an output force is calculated according to the current value and the rotating speed value of the parking motor so as to determine a mechanical power of the parking motor, and then a heat energy generated by the parking motor is obtained by subtracting the mechanical power from the total power, finally, the second temperature value T2 of the parking motor 10 can be estimated by subtracting the heat dissipation during the time interval from the heat energy. The mechanical power may have a certain deviation, but the deviation only has a very little effect on the power difference value. When the current is used to calculate the output force of the parking motor, considering the influence of the temperature on the parking motor, an output torque of the parking motor corresponding to the current value may change slightly. Furthermore, when the torque is constant, the higher the temperature is, the greater the rotating speed change corresponding to a unit torque is. Thus, by detecting the temperature of the parking motor, the deviation of the output force of the parking motor can be corrected. When the temperature is too high or too low, in order to obtain a same braking force, certain corrected values of the current and the rotating speed are required.

The first calculating module 100b is configured to calculate a difference between the first detected current value II and the second detected current value 12 to obtain a first current difference value ΔΙ1, to calculate a difference between the first detected rotating speed value Rl and the second detected rotating speed value R2 to obtain a first rotating speed difference value ARl, to determine whether the first current difference value ΔΙ1 is less than a predetermined current difference threshold ΔΙ and the first rotating speed difference value ARl is less than a predetermined rotating speed difference threshold AR.

Specifically, when the first current difference value ΔΙ1 is less than or equal to the predetermined current difference threshold ΔΙ and the first rotating speed difference value ARl is less than or equal to the predetermined rotating speed difference threshold AR, everything is normal, then the first detected current value II may be determined as the current value and the first detected rotating speed value Rl may be determined as the rotating speed value to calculate the braking force.

When the first current difference value ΔΙ1 is not less than the predetermined current difference threshold ΔΙ but the first rotating speed difference value AR1 is less than or equal to the predetermined rotating speed difference threshold AR, a single fault alarm is generated, and the first calculating module 100b queries a predetermined correlation table of currents and rotating speeds according to the first detected rotating speed value Rl or the second detected rotating speed value R2 to obtain a standard current value 13, calculates a difference between the first detected current value II and the standard current value 13 to obtain a second current difference value ΔΙ2 and calculates a difference between the second detected current value 12 and the standard current value 13 to obtain a third current difference value ΔΙ3. When the second current difference value ΔΙ2 is less than or equal to the predetermined current difference threshold ΔΙ, the first calculating module 100b determines the first detected current value II as the current value. When the third current difference value ΔΙ3 is less than or equal to the predetermined current difference threshold ΔΙ, the first calculating module 100b determines the second detected current value 12 as the current value.

Similarly, when the first current difference value ΔΙ1 is less than or equal to the predetermined current difference threshold ΔΙ but the first rotating speed difference value AR1 is not less than the predetermined rotating speed difference threshold AR, a single fault alarm is generated, and the first calculating module 100b queries the predetermined correlation table of currents and rotating speeds according to the first detected current value II or the second detected current value 12 to obtain a standard rotating speed value R3, calculates a difference between the first detected rotating speed value Rl and the standard rotating speed value R3 to obtain a second rotating speed difference value AR2 and calculates a difference between the second detected rotating speed value R2 and the standard rotating speed value R3 to obtain a third rotating speed difference value AR3. When the second rotating speed difference value AR2 is less than or equal to the predetermined rotating speed difference threshold AR, the first calculating module 100b determines the first detected rotating speed value Rl as the rotating speed value. When the third rotating speed difference value AR3 is less than or equal to the predetermined rotating speed difference threshold AR, the first calculating module 100b determines the second detected rotating speed value R2 as the rotating speed value. When neither the first current difference value ΔΙ1 is less than the predetermined current difference threshold ΔΙ nor the first rotating speed difference value ARl is less than the predetermined rotating speed difference threshold AR, a big fault occurs in the system, then the control module lOOg turns off the parking motor 10 after a predetermined delay time (for example, three seconds in one embodiment) and generates an alarm. Alternatively, the first calculating module 100b may query the predetermined correlation table of currents and rotating speeds according to the first detected current value II and the second detected current value 12 respectively to obtain a first queried rotating speed value Rl' and a second queried rotating speed value R2', and then calculate a difference between the first detected rotating speed value Rl and the first queried rotating speed value Rl' to obtain a difference value ART and calculate a difference between the second detected rotating speed value R2 and the second queried rotating speed value R2' to obtain a difference value AR2' . When the difference value ART is less than or equal to the predetermined rotating speed difference threshold AR, the first calculating module 100b determines the first detected current value II and the first detected rotating speed value Rl as the current value and the rotating speed value for emergency usage. When the difference value AR2' is less than or equal to the predetermined rotating speed difference threshold AR, the first calculating module 100b determines the second detected current value 12 and the second detected rotating speed value R2 as the current value and the rotating speed value for emergency usage. Alternatively, the first calculating module 100b may query the predetermined correlation table of currents and rotating speeds according to the first detected rotating speed value Rl and the second detected rotating speed value R2 respectively and then executes the processes similar to the above description to determine the current value and the rotating speed value for emergency usage, which will be omitted herein for simplicity.

The second calculating module lOOd is configured to calculate a difference between the first temperature value Tl and the second temperature value T2 to obtain a temperature difference value ATI, to compare the temperature difference value ATI with a predetermined temperature difference threshold AT to obtain a comparison result, and to determine a temperature value of the parking motor 10 according to the comparison result. Specifically, when the temperature difference value ATI is less than or equal to the predetermined temperature difference threshold AT, the second calculating module lOOd calculates an average value of the first detected temperature value Tl and the second detected temperature value T2 as the temperature value of the parking motor 10. When the temperature difference value ΔΤ1 is greater than the predetermined temperature difference threshold ΔΤ, the second calculating module lOOd chooses one having a larger absolute value from the first detected temperature value Tl and the second detected temperature value T2 as the temperature value of the parking motor 10, and meanwhile the control module lOOg generates an alarm.

The reference table storage module lOOe is configured to store a reference table indicating corresponding relationships between currents, rotating speeds, temperatures and torques of the parking motor 10.

The braking force calculating module lOOf is configured to query the reference table according to the current value, the rotating speed value and the temperature value of the parking motor 10 so as to determine the output torque of the parking motor 10, and thus the braking force applied by the parking motor 10 is determined.

The control module lOOg is further configured to control the parking motor 10 according to the determined braking force.

Fig. 3 is a flow chart of a method for controlling an electronic parking brake system according to embodiments of the present disclosure. As shown in Fig. 3, the method comprises the following steps.

At step 101, a first detected current value II, a second detected current value 12, a first detected rotating speed value Rl and a second detected rotating speed value R2 are obtained. Specifically, the current of a parking motor is detected by a sensing element to obtain the first detected current value II, the rotating speed of the parking motor is detected by a speed sensor to obtain the first detected rotating speed value Rl, and the second detected current value 12 and the second detected rotating speed value R2 are obtained according to the voltage across a sampling resistor connected with the parking motor.

When the parking command is performed by the parking switch, a rotating force of the parking motor 10 is converted to a linear motion of the screw 25 via the gear train 20 and the threaded sleeve 30, and the parking cable 40 fastened at an end of the screw 25 is stretched by the linear motion of the screw 25. When a tension force of the brake reaches a target braking force, the vehicle is kept stable.

The tension force of the brake is controlled by the ECU 100. When the parking switch works and commands to tighten the parking cable 40, the controlling process starts, the circuit loop of the parking motor is switched on, the parking motor 10 starts to rotate forwardly, and the counter starts to time, the sensing element detects the first detected current value II and the second detected current value 12 is obtained according to an amplified signal of the voltage across the sampling resistor.

As describe above, the first detected current value II can be obtained by the sensing element.

The sensing element is small in size and may be integrated in the circuit board without involving in the circuit loop of the parking motor. The reliability of the current value detected by the sensing element is high. The second detected current value 12 is calculated after amplifying the voltage across the sampling resistor by an amplifier. The sampling resistor is generally a copper plate.

As described above, the rotating speed value of the parking motor can be detected by two different methods. One method is to integrate the speed sensor in the parking motor, and thus it is easy to directly read the value of the speed sensor to obtain the first detected rotating speed value Rl. The other method is to use the sampling resistor. Specifically, firstly, a ripple voltage across the sampling resistor is amplified with a larger amplification coefficient to obtain a number of changes occurring in a commutator bar of the parking motor, and then the number of commutations is divided by a number of commutations per circle to obtain the second detected rotating speed value R2.

At step 102, the difference between the first detected current value II and the second detected current value 12 is calculated to obtain the first current difference value ΔΙ1, and the difference between the first detected rotating speed value Rl and the second detected rotating speed value R2 is calculated to obtain the first rotating speed difference value ARl.

At step 103, the first current difference value ΔΙ1 is compared with the predetermined current difference threshold ΔΙ to obtain a first comparison result, and the first rotating speed difference value AR1 is compared with a predetermined rotating speed difference threshold AR to obtain a second comparison result.

As described above, the difference between two detected current values are compared with the predetermined current difference threshold ΔΙ and the difference between two detected rotating speed values are compared with a predetermined rotating speed difference threshold AR to determine whether the two detected current values and the two detected rotating speed values are within the usable range. Herein, the term "usable" means that the first current difference value ΔΙ1 is less than or equal to the predetermined current difference threshold ΔΙ and the first rotating speed difference value AR1 is less than or equal to the predetermined rotating difference threshold AR.

At step 104, the current value is determined according to the first comparison result and the rotating speed value is determined according to the second comparison result.

Specifically, when the first current difference value ΔΙ1 is less than or equal to the predetermined current difference threshold ΔΙ and the first rotating speed difference value AR1 is less than or equal to the predetermined rotating speed difference threshold AR, everything is normal, then the first detected current value II may be determined as the current value and the first detected rotating speed value Rl may be determined as the rotating speed value to calculate the braking force.

When the first current difference value ΔΙ1 is not less than the predetermined current difference threshold ΔΙ but the first rotating speed difference value AR1 is less than or equal to the predetermined rotating speed difference threshold AR, a single fault alarm is generated, and a predetermined correlation table of currents and rotating speeds is queried according to the first detected rotating speed value Rl or the second detected rotating speed value R2 to obtain a standard current value 13, a difference between the first detected current value II and the standard current value 13 is calculated to obtain a second current difference value ΔΙ2 and a difference between the second detected current value 12 and the standard current value 13 is calculated to obtain a third current difference value ΔΙ3. When the second current difference value ΔΙ2 is less than or equal to the predetermined current difference threshold ΔΙ, the first detected current value II is determined as the current value. When the third current difference value ΔΙ3 is less than or equal to the predetermined current difference threshold ΔΙ, the second detected current value 12 is determined as the current value.

Similarly, when the first current difference value ΔΙ1 is less than or equal to the predetermined current difference threshold ΔΙ but the first rotating speed difference value AR1 is not less than the predetermined rotating speed difference threshold AR, a single fault alarm is generated, and the predetermined correlation table of currents and rotating speeds is queried according to the first detected current value II or the second detected current value 12 to obtain a standard rotating speed value R3, a difference between the first detected rotating speed value Rl and the standard rotating speed value R3 is calculated to obtain a second rotating speed difference value AR2 and a difference between the second detected rotating speed value R2 and the standard rotating speed value R3 is calculated to obtain a third rotating speed difference value AR3. When the second rotating speed difference value AR2 is less than or equal to the predetermined rotating speed difference threshold AR, the first detected rotating speed value Rl is determined as the rotating speed value. When the third rotating speed difference value AR3 is less than or equal to the predetermined rotating speed difference threshold AR, the second detected rotating speed value R2 is determined as the rotating speed value.

When neither the first current difference value ΔΙ1 is less than the predetermined current difference threshold ΔΙ nor the first rotating speed difference value ARl is less than the predetermined rotating speed difference threshold AR, a big fault occurs in the system, then the parking motor 10 is controlled to be turned off after a predetermined delay time (for example, three seconds in one embodiment) and an alarm is generated. Alternatively, the predetermined correlation table of currents and rotating speeds may be queried according to the first detected current value II and the second detected current value 12 respectively to obtain a first queried rotating speed value Rl' and a second queried rotating speed value R2', and then a difference between the first detected rotating speed value Rl and the first queried rotating speed value Rl' is calculated to obtain a difference value ARV and a difference between the second detected rotating speed value R2 and the second queried rotating speed value R2' is calculated to obtain a difference value AR2'. When the difference value ARV is less than or equal to the predetermined rotating speed difference threshold AR, the first detected current value II and the first detected rotating speed value Rl are determined as the current value and the rotating speed value for emergency usage. When the difference value AR2' is less than or equal to the predetermined rotating speed difference threshold AR, the second detected current value 12 and the second detected rotating speed value R2 are determined as the current value and the rotating speed value for emergency usage. Alternatively, the predetermined correlation table of currents and rotating speeds may be queried according to the first detected rotating speed value Rl and the second detected rotating speed value R2 respectively and then the processes similar to the above description may be executed to determine the current value and the rotating speed value for emergency usage, which will be omitted herein for simplicity.

At step 105, a first temperature value Tl of the parking motor is calculated according to a maximum current value when the parking motor is started and a second temperature value T2 of the parking motor is calculated according to a working current and a working time of the parking motor.

As described above, the temperature of the parking motor can be measured by two different methods. One method is to calculate the first temperature value Tl of the parking motor according to the maximum current value when the parking motor is started. Specifically, a winding resistance of the parking motor is firstly obtained by dividing the voltage (measurable) of the parking motor by the maximum current value, and then the first temperature value Tl can be obtained according to the winding resistance, since the winding resistance of the parking motor changes with the temperature. The other method is to calculate the second temperature value T2 of the parking motor according to the working current and the working time of the parking motor. Specifically, firstly, a total power of the parking motor is calculated according to the voltage, the working current, the working time and the time interval of the parking motor, and an output force is calculated according to the current value and the rotating speed value of the parking motor so as to determine a mechanical power of the parking motor, and then a heat energy generated by the parking motor is obtained by subtracting the mechanical power from the total power, finally, the second temperature value T2 of the parking motor 10 can be estimated by subtracting the heat dissipation during the time interval from the heat energy. The mechanical power may have a certain deviation, but the deviation only has a very little effect on the power difference value. When the current is used to calculate the output force of the parking motor, considering the influence of the temperature on the parking motor, an output torque of the parking motor corresponding to the current value may change slightly. Furthermore, when the torque is constant, the higher the temperature is, the greater the rotating speed change corresponding to a unit torque is. Thus, by detecting the temperature of the parking motor, the deviation of the output force of the parking motor can be corrected. When the temperature is too high or too low, in order to obtain a same braking force, certain corrected values of the current and the rotating speed are required.

At step 106, a difference between the first temperature value Tl and the second temperature value T2 is calculated to obtain a temperature difference value ΔΤ.

At step 107, the temperature difference value ΔΤ is compared with a predetermined temperature difference threshold ΔΤ to obtain a third comparison result and a temperature value of the parking motor is determined according to the third comparison result.

Specifically, when the temperature difference value ΔΤ is less than or equal to the predetermined temperature difference threshold ΔΤ, an average value of the first detected temperature value Tl and the second detected temperature value T2 is calculated as the temperature value of the parking motor.

When the temperature difference value ΔΤ is greater than the predetermined temperature difference threshold ΔΤ, one having a larger absolute value from the first detected temperature value Tl and the second detected temperature value T2 is chosen as the temperature value of the parking motor and an alarm is generated.

At step 108, a predetermined reference table is queried according to the current value, the rotating speed value and the temperature value of the parking motor to determine a braking force applied by the parking motor.

Specifically, a reference table indicating corresponding relationships between currents, rotating speeds, temperatures and torques of the parking motor can be stored in a storage module of a single-chip. Thus, it is possible to query the reference table according to the above current value, rotating speed value and temperature value of the parking motor to obtain the output torque of the parking motor, thus determining the braking force.

At step 109, the parking motor is controlled according to the determined braking force.

Fig. 4 is a flow chart of a method for controlling an electronic parking brake system according to another embodiment of the present disclosure. As shown in Fig. 4, the method comprises the following steps.

At step 401, the electronic parking brake system starts to work.

At step 402, the electronic parking brake equipment is operated and the timing is started.

At step 403, the first detected current value II of the parking motor 10 is obtained. Specifically, the current of the parking motor 10 is detected by the sensing element to obtain the first detected current value II.

At step 404, the second detected current value 12 of the parking motor 10 is obtained. Specifically, the second detected current value 12 is obtained according to the voltage across the sampling resistor connected with the parking motor.

At step 405, the first detected rotating speed value Rl of the parking motor 10 is obtained. Specifically, the rotating speed of the parking motor 10 is detected by the speed sensor to obtain the first detected rotating speed value Rl.

At step 406, the second detected rotating speed value R2 of the parking motor 10 is obtained.

Specifically, the second detected rotating speed value R2 of the parking motor 10 is obtained according to the voltage across the sampling resistor connected with the parking motor.

At step 407, it is determined whether the difference value ΔΙ1 between the first detected current value II and the second detected current value 12 is within the predetermined current error range { ΔΙ}.

At step 408, it is determined whether the difference value ARl between the first detected rotating speed value Rl and the second detected rotating speed value R2 is within the predetermined rotating speed error range { AR}.

At step 409, the parking motor is turned off after the predetermined delay time and then step 417 is executed when All£{ Al} and AR1£{ AR}. In one embodiment, the predetermined delay time is three seconds. When one detected current value and one detected rotating speed value are abnormal, a big fault occurs in the system, and the parking motor should be turned off. Alternatively, the predetermined correlation table of currents and rotating speeds may be queried according to the first detected current value II and the second detected current value 12 respectively to obtain a first queried rotating speed value Rl' and a second queried rotating speed value R2', and then a difference between the first detected rotating speed value Rl and the first queried rotating speed value Rl ' is calculated to obtain a difference value ART and a difference between the second detected rotating speed value R2 and the second queried rotating speed value R2' is calculated to obtain a difference value AR2' . When the difference value ART is less than or equal to the predetermined rotating speed difference threshold AR, the first detected current value II and the first detected rotating speed value Rl can be determined as the current value and the rotating speed value for emergency usage. When the difference value AR2' is less than or equal to the predetermined rotating speed difference threshold AR, the second detected current value 12 and the second detected rotating speed value R2 can be determined as the current value and the rotating speed value for emergency usage. Alternatively, the predetermined correlation table of currents and rotating speeds may be queried according to the first detected rotating speed value Rl and the second detected rotating speed value R2 respectively and then the processes similar to the above description may be executed to determine the current value and the rotating speed value for emergency usage, which will be omitted herein for simplicity.

At step 410, a single fault alarm is generated when All£ { Al} but ARl £ { AR} and then step 413 is executed.

At step 411, a single fault alarm is generated when All £ { Al} but AR1£ { AR} and then step 414 is executed.

At step 412, the first detected current value II is determined as the current value of the parking motor, and the first detected rotating speed value Rl is determined as the rotating speed value of the parking motor, and then step 420 is executed.

At step 413, a standard current value 13 is obtained according to the first detected rotating speed value Rl or the second detected rotating speed value R2 and then step 415 is executed. Specifically, the predetermined correlation table of currents and rotating speeds is queried according to the first detected rotating speed value Rl or the second detected rotating speed value R2 to obtain the standard current value 13.

At step 414, a standard rotating speed value R3 is obtained according to the first detected current value II or the second detected current value 12 and then step 416 is executed. Specifically, the predetermined correlation table of currents and rotating speeds is queried according to the first detected current value II or the second detected current value 12 to obtain the standard rotating speed value R3.

At step 415, it is determined whether a difference ΔΙ2 between the first detected current value

11 and the standard current value 13 or a difference ΔΙ3 between the second detected current value

12 and the standard current value 13 is within the predetermined current error range { ΔΙ} . When neither ΔΙ2 nor ΔΙ3 is within the predetermined current error range { ΔΙ}, step 417 is executed. When either ΔΙ2 or ΔΙ3 is within the predetermined current error range { ΔΙ}, step 418 is executed.

At step 416, it is determined whether a difference AR2 between the first detected rotating speed value Rl and the standard rotating speed value R3 or a difference AR3 between the second detected rotating speed value R2 and the standard rotating speed value R3 is within the predetermined rotating speed error range { AR}. When neither AR2 nor AR3 is within { AR}, step 417 is executed. When either AR2 or AR3 is within { AR}, step 419 is executed.

At step 417, a serious fault alarm is generated.

At step 418, the first detected rotating speed value Rl is determined as the rotating speed value of the parking motor, and the detected current value Ix which satisfies IIx-131 G { ΔΙ} is determined as the current value of the parking motor, and then step 420 is executed. Specifically, when the difference ΔΙ2 is within the predetermined current error range { ΔΙ}, the first detected current value II is determined as the current value. When the difference ΔΙ3 is within the predetermined current error range { ΔΙ}, the second detected current value 12 is determined as the current value.

At step 419, the first detected current value II is determined as the current value of the parking motor, and the detected rotating speed value Rx which satisfies IRx-R3l £ { AR} is determined as the rotating speed value of the parking motor, and then step 420 is executed. Specifically, when the difference AR2 is within the predetermined rotating speed error range { AR}, the first detected rotating speed value Rl is determined as the rotating speed value. When the difference AR3 is within the predetermined rotating speed error range { AR}, the second detected rotating speed value R2 is determined as the rotating speed value.

At step 420, the temperature value of the parking motor is estimated.

In the present disclosure, firstly, a first temperature value Tl is calculated according to the maximum current value when the parking motor is started and a second temperature value T2 is calculated according to the working current and the working time of the parking motor, and then a difference value ΔΤ1 between the first temperature value Tl and the second temperature value T2 is compared with the predetermined temperature difference threshold ΔΤ. When the temperature difference value ΔΤ1 is less than or equal to the predetermined temperature difference threshold ΔΤ, an average value of the first detected temperature value Tl and the second detected temperature value T2 is calculated as the temperature value of the parking motor. When the temperature difference value ΔΤ1 is greater than the predetermined temperature difference threshold ΔΤ, one having a larger absolute value from the first detected temperature value Tl and the second detected temperature value T2 is chosen as the temperature value of the parking motor. Specifically, a winding resistance of the parking motor can be firstly obtained by dividing the voltage (measurable) of the parking motor by the maximum current value, and then the first temperature value Tl can be obtained according to the winding resistance, since the winding resistance of the parking motor changes with the temperature. On the other hand, firstly, a total power of the parking motor is calculated according to the voltage, the working current, the working time and the time interval of the parking motor, and an output force is calculated according to the current value and the rotating speed value of the parking motor so as to determine a mechanical power of the parking motor, and then a heat energy generated by the parking motor is obtained by subtracting the mechanical power from the total power, finally, the second temperature value T2 of the parking motor 10 can be estimated by subtracting the heat dissipation during the time interval from the heat energy. The mechanical power may have a certain deviation, but the deviation only has a very little effect on the power difference value. When the current is used to calculate the output force of the parking motor, considering the influence of the temperature on the parking motor, an output torque of the parking motor corresponding to the current value may change slightly. Furthermore, when the torque is constant, the higher the temperature is, the greater the rotating speed change corresponding to a unit torque is. Thus, by detecting the temperature of the parking motor, the deviation of the output force of the parking motor can be corrected. When the temperature is too high or too low, in order to obtain a same braking force, certain corrected values of the current and the rotating speed are required.

At step 421, the braking force applied to the brake is calculated.

At step 422, the parking motor is controlled according to the determined braking force.

With the method for controlling an electronic parking brake system according to embodiments of the present disclosure, since the current of the parking motor is detected by the sensing element and the sampling resistor connected with the parking motor respectively, and the rotating speed of the parking motor is detected by the speed sensor and the sampling resistor connected with the parking motor respectively, a dual protection for the current and the rotating speed is obtained, thus increasing an accuracy of the braking force (this is because the braking force is estimated according to a combination of the current and the rotating speed). Furthermore, since no other element for measuring force is used, a mechanical structure of the electronic parking brake system is simplified and a manufacturing cost of the electronic parking brake system is reduced.

Any process or method described in the flowing diagram or other means may be understood as a module, segment or portion including one or more executable instruction codes of the procedures configured to achieve a certain logic function or process, and the preferred embodiments of the present disclosure include other performances, in which the performance may be achieved in other orders instead of the order shown or discussed, such as in a almost simultaneous way or in an opposite order, which should be appreciated by those having ordinary skills in the art to which embodiments of the present disclosure belong.

The logic and/or procedures indicated in the flowing diagram or described in other means herein, such as a constant sequence table of the executable code for performing a logical function, may be implemented in any computer readable storage medium so as to be adopted by the code execution system, the device or the equipment (such a system based on the computer, a system including a processor or other systems fetching codes from the code execution system, the device and the equipment , and executing the codes) or to be combined with the code execution system, the device or the equipment to be used. With respect to the description of the present invention, "the computer readable storage medium" may include any device including, storing, communicating, propagating or transmitting program so as to be used by the code execution system, the device and the equipment or to be combined with the code execution system, the device or the equipment to be used. The computer readable medium includes specific examples (a non-exhaustive list): the connecting portion (electronic device) having one or more arrangements of wire, the portable computer disc cartridge (a magnetic device), the random access memory (RAM), the read only memory (ROM), the electrically programmable read only memory (EPROMM or the flash memory), the optical fiber device and the compact disk read only memory (CDROM). In addition, the computer readable storage medium even may be papers or other proper medium printed with program, as the papers or the proper medium may be optically scanned, then edited, interpreted or treated in other ways if necessary to obtain the program electronically which may be stored in the computer memory.

It should be understood that, each part of the present invention may be implemented by the hardware, software, firmware or the combination thereof. In the above embodiments of the present invention, the plurality of procedures or methods may be implemented by the software or hardware stored in the computer memory and executed by the proper code execution system. For example, if the plurality of procedures or methods is to be implemented by the hardware, like in another embodiment of the present invention, any one of the following known technologies or the combination thereof may be used, such as discrete logic circuits having logic gates for implementing various logic functions upon an application of one or more data signals, application specific integrated circuits having appropriate logic gates, programmable gate arrays (PGA), field programmable gate arrays (FPGA).

It can be understood by those having the ordinary skills in the related art that all or part of the steps in the method of the above embodiments can be implemented by instructing related hardware via programs, the program may be stored in a computer readable storage medium, and the program includes one step or combinations of the steps of the method when the program is executed.

In addition, each functional unit in the present disclosure may be integrated in one progressing module, or each functional unit exists as an independent unit, or two or more functional units may be integrated in one module. The integrated module can be embodied in hardware, or software. If the integrated module is embodied in software and sold or used as an independent product, it can be stored in the computer readable storage medium.

The computer readable storage medium may be, but not limited to read-only memories, magnetic disks, or optical disks.

Reference throughout this specification to "an embodiment," "some embodiments," "one embodiment", "another example," "an example," "a specific example," or "some examples," means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. Thus, the appearances of the phrases such as "in some embodiments," "in one embodiment", "in an embodiment", "in another example," "in an example," "in a specific example," or "in some examples," in various places throughout this specification are not necessarily referring to the same embodiment or example of the present disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that the above embodiments cannot be construed to limit the present disclosure, and changes, alternatives, and modifications can be made in the embodiments without departing from spirit, principles and scope of the present disclosure.

Claims

What is claimed is:

1. A method for controlling an electronic parking brake system, comprising:

obtaining a first detected current value, a first detected rotating speed value, a second detected current value and a second detected rotating speed value of a parking motor;

calculating a difference between the first detected current value and the second detected current value to obtain a first current difference value and calculating a difference between the first detected rotating speed value and the second detected rotating speed value to obtain a first rotating speed difference value;

comparing the first current difference value with a predetermined current difference threshold to obtain a first comparison result and comparing the first rotating speed difference value with a predetermined rotating speed difference threshold to obtain a second comparison result;

determining a current value according to the first comparison result and determining a rotating speed value of the parking motor according to the second comparison result;

calculating a first temperature value of the parking motor according to a maximum current value when the parking motor is started and calculating a second temperature value of the parking motor according to a working current and a working time of the parking motor;

calculating a difference between the first temperature value and the second temperature value to obtain a temperature difference value;

comparing the temperature difference value with a predetermined temperature difference threshold to obtain a third comparison result, and determining a temperature value of the parking motor according to the third comparison result;

querying a predetermined reference table according to the current value, the rotating speed value and the temperature value of the parking motor to determine a braking force applied by the parking motor; and

controlling the parking motor according to the braking force.

2. The method according to claim 1, wherein determining a current value according to the first comparison result and determining a rotating speed value of the parking motor according to the second comparison result comprises:

when the first current difference value is less than or equal to the predetermined current difference threshold and the first rotating speed difference value is less than or equal to the predetermined rotating speed difference threshold, determining the first detected current value as the current value and determining the first detected rotating speed value as the rotating speed value.

3. The method according to claim 1 or 2, wherein determining a current value according to the first comparison result and determining a rotating speed value of the parking motor according to the second comparison result comprises:

when the first current difference value is less than or equal to the predetermined current difference threshold and the first rotating speed difference value is greater than the predetermined rotating speed difference threshold, querying a predetermined correlation table of currents and rotating speeds according to the first detected current value or the second detected current value to obtain a standard rotating speed value;

calculating a difference between the first detected rotating speed value and the standard rotating speed value to obtain a second rotating speed difference value and calculating a difference between the second detected rotating speed value and the standard rotating speed value to obtain a third rotating speed difference value;

when the second rotating speed difference value is less than or equal to the predetermined rotating speed difference threshold, determining the first detected rotating speed value as the rotating speed value;

when the third rotating speed difference value is less than or equal to the predetermined rotating speed difference threshold, determining the second detected rotating speed value as the rotating speed value.

4. The method according to any of claims 1 to 3, wherein determining a current value according to the first comparison result and determining a rotating speed value of the parking motor according to the second comparison result comprises:

when the first current difference value is greater than the predetermined current difference threshold and the first rotating speed difference value is less than or equal to the predetermined rotating speed difference threshold, querying the predetermined correlation table of currents and rotating speeds according to the first detected rotating speed value or the second detected rotating speed value to obtain a standard current value;

calculating a difference between the first detected current value and the standard current value to obtain a second current difference value and calculating a difference between the second detected current value and the standard current value to obtain a third current difference value; when the second current difference value is less than or equal to the predetermined current difference threshold, determining the first detected current value as the current value;

when the third current difference value is less than or equal to the predetermined current difference threshold, determining the second detected current value as the current value.

5. The method according to any of claims 1 to 4, further comprising:

when the first current difference value is greater than the predetermined current difference threshold and the first rotating speed difference value is greater than the predetermined rotating speed difference threshold, turning off the parking motor after a predetermined delay time and generating an alarm.

6. The method according to any of claims 1 to 5, wherein determining a temperature value of the parking motor according to the third comparison result comprises:

when the temperature difference value is less than or equal to the predetermined temperature difference threshold, calculating an average value of the first detected temperature value and the second detected temperature value as the temperature value of the parking motor;

when the temperature difference value is greater than the predetermined temperature difference threshold, choosing one having a larger absolute value from the first detected temperature value and the second detected temperature value as the temperature value of the parking motor.

7. The method according to any of claims 1-6, wherein the first detected current value is obtained from detecting a current of the parking motor by a sensing element, the first detected rotating speed value is obtained from detecting a rotating speed of the parking motor by a speed sensor, the second detected current value and the second detected rotating speed value are obtained according to a voltage across a sampling resistor connected with the parking motor.

8. An apparatus for controlling an electronic parking brake system, wherein the electronic parking brake system comprises a parking motor, a sensing element for detecting a current of a parking motor to obtain a first detected current value, a speed sensor for detecting a rotating speed of the parking motor to obtain a first detected rotating speed value, and a sampling resistor connected with the parking motor, and the apparatus comprises:

a first obtaining unit configured to read the first detected current value and the first detected rotating speed value and to obtain a second detected current value and a second detected rotating speed value according to a voltage across the sampling resistor; a first calculating module configured to calculate a difference between the first detected current value and the second detected current value to obtain a first current difference value, to calculate a difference between the first detected rotating speed value and the second detected rotating speed value to obtain a first rotating speed difference value, to compare the first current difference value with a predetermined current difference threshold to obtain a first comparison result, to compare the first rotating speed difference value with a predetermined rotating speed difference threshold to obtain a second comparison result, to determine a current value of the parking motor according to the first comparison result, and to determine a rotating speed value of the parking motor according to the second comparison result;

a second obtaining module configured to obtain a maximum current value when the parking motor is started, a working current and a working time of the parking motor, to calculate a first temperature value of the parking motor according to the maximum current value when the parking motor is started and to calculate a second temperature value of the parking motor according to the working current and the working time of the parking motor;

a second calculating module configured to calculate a difference between the first temperature value and the second temperature value to obtain a temperature difference value, to compare the temperature difference value with a predetermined temperature difference threshold to obtain a third comparison result, and to determine a temperature value of the parking motor according to the third comparison result;

a reference table storage module configured to store a reference table indicating corresponding relationships between currents, rotating speeds, temperatures and torques of the parking motor;

a braking force calculating module configured to query the reference table according to the current value, the rotating speed value and the temperature value of the parking motor so as to determine the braking force applied by the parking motor; and

a control module configured to control the parking motor according to the determined braking force.

9. The apparatus according to claim 8, wherein the first calculating module is configured to: determine the first detected current value as the current value and determine the first detected rotating speed value as the rotating speed value when the first current difference value is less than or equal to the predetermined current difference threshold and the first rotating speed difference value is less than or equal to the predetermined rotating speed difference threshold.

10. The apparatus according to claim 8 or 9, wherein the first calculating module is configured to:

query a predetermined correlation table of currents and rotating speeds according to the first detected current value or the second detected current value to obtain a standard rotating speed value when the first current difference value is less than or equal to the predetermined current difference threshold and the first rotating speed difference value is greater than the predetermined rotating speed difference threshold;

calculate a difference between the first detected rotating speed value and the standard rotating speed value to obtain a second rotating speed difference value and calculate a difference between the second detected rotating speed value and the standard rotating speed value to obtain a third rotating speed difference value;

determine the first detected rotating speed value as the rotating speed value when the second rotating speed difference value is less than or equal to the predetermined rotating speed difference threshold ; and

determine the second detected rotating speed value as the rotating speed value when the third rotating speed difference value is less than or equal to the predetermined rotating speed difference threshold.

11. The apparatus according to any of claims 8 to 10, wherein the first calculating module is configured to:

query the predetermined correlation table of currents and rotating speeds according to the first detected rotating speed value or the second detected rotating speed value to obtain a standard current value when the first current difference value is greater than the predetermined current difference threshold and the first rotating speed difference value is less than or equal to the predetermined rotating speed difference threshold;

calculate a difference between the first detected current value and the standard current value to obtain a second current difference value and calculate a difference between the second detected current value and the standard current value to obtain a third current difference value;

determine the first detected current value as the current value when the second detected current difference value is less than or equal to the predetermined current difference threshold; and determine the second detected current value as the current value when the third detected current difference value is less than or equal to the predetermined current difference threshold.

12. The apparatus according to any of claims 8 to 11, wherein the control module is further configured to turn off the parking motor after a predetermined delay time and generate an alarm when the first current difference value is greater than the predetermined current difference threshold and the first rotating speed difference value is greater than the predetermined rotating speed difference threshold.

13. The apparatus according to any of claims 8 to 12, wherein the second calculating module is configured to:

calculate an average value of the first detected temperature value and the second detected temperature value as the temperature value of the parking motor when the temperature difference value is less than or equal to the predetermined temperature difference threshold; and

choose one having a larger absolute value from the first detected temperature value and the second detected temperature value as the temperature value of the parking motor when the temperature difference value is greater than the predetermined temperature difference threshold.