Photoelectric sensing structure for electronic mechanical braking system, braking control method and parking control method

Abstract

The invention discloses a photoelectric sensing structure for an electronic mechanical braking system, a braking control method and a parking control method, and belongs to the field of vehicle braking. The photoelectric sensing structure comprises a light emitter and a light receiver which are arranged on the two sides of a locking disc respectively, and the light emitter is fixed to an electromagnetic locking mechanism through a support; detection holes are formed in the locking disc and correspond to detection light paths of the light emitter and the light receiver, and the detection holes, the center of the locking disc and the center of a locking groove in the locking disc are located on the same straight line; the light emitter and the light receiver are both electrically connected with the brake controller, and the brake controller is electrically connected with the brake motor. By adopting the photoelectric sensing structure for the electronic mechanical braking system, the braking control method and the parking control method, the problems of complicated structure, high precision requirement, weak interference resistance, high cost and the like in the prior art are solved on the premise of not reducing the control precision and reliability.

Description

Technical Field

[0001] This invention relates to the field of vehicle braking technology, and in particular to photoelectric sensing structures, braking control methods, and parking control methods for electromechanical braking systems. Background Technology

[0002] In the field of vehicle electromechanical braking technology, the core design concept of existing mainstream braking systems is to achieve braking control and parking lock functions through the independent working mode of dual sensors. For example, the "An Electromechanical Brake Parking Mechanism and Control Method" disclosed in patent CN202510694955.X drives a three-phase motor to output power, which is directly applied to the vehicle wheel end to achieve dynamic braking. This process relies on independently set motor position sensors (such as photoelectric encoders, magnetic encoders, etc.) to collect the motor rotor position signal, thereby completing the closed-loop control of motor speed and angle to ensure the accuracy of braking force adjustment. At the same time, an electromagnetic pin-type parking structure is adopted. The extension and retraction of the pin is controlled by an electromagnetic drive unit, so that it is inserted into the slot of the wheel disc at the motor shaft end to form a mechanical lock and realize the parking fixation of the vehicle. In order to determine whether the pin is fully inserted, a Hall sensor is also required to determine the pin locking state by detecting the magnetic signal characteristics of the wheel disc slot.

[0003] However, the above technical solutions have many prominent drawbacks in practical applications, as follows: 1. Stringent mechanical precision requirements and high assembly difficulty: The detection principle of the Hall sensor dictates that it must be precisely aligned with the wheel disc slot, requiring an alignment tolerance of ≤±0.1mm. This high precision requirement poses an extremely high challenge to the assembly process, necessitating the use of specialized high-precision positioning fixtures for assembly and debugging. This not only extends the production cycle and reduces production efficiency but also presents problems such as pin jamming and inability to smoothly insert into the slot due to excessive positioning deviations during assembly. These issues directly affect the reliability of the parking function and may even lead to safety hazards due to the pin failing to lock.

[0004] 2. Complex structural design and poor vibration stability: To achieve slot position detection, the detection end of the Hall sensor needs to extend to the edge area of ​​the wheel disk, and the distance between it and the wheel disk surface needs to be controlled within ≤2mm. This installation requirement forces the system to design additional auxiliary parts such as special brackets, fixing seats, and positioning pins, resulting in an increase of 3-5 parts in the overall structure. This not only increases the complexity of the structural design but also increases the risk of cumulative assembly errors. At the same time, the unavoidable vibration environment during vehicle operation will affect the Hall sensor fixed by the independent bracket, which may cause the sensor installation position to shift, disrupting its relative positioning relationship with the wheel disk slot, and thus causing abnormal detection signals.

[0005] 3. Weak resistance to electromagnetic interference and high risk of signal misjudgment: Hall sensors rely on changes in magnetic signals to detect position. However, the vehicle operating environment contains various strong electromagnetic interference sources, such as electromagnetic radiation generated by high-voltage wiring harnesses and alternating electromagnetic fields generated by three-phase motors. These interference signals are superimposed on the detection signal of the Hall sensor, causing problems such as irregular signal jumps and distortion. Actual operating condition tests show that the position information misjudgment rate of this solution is as high as 5%-8%. Misjudgment can lead to two serious consequences: first, misjudging that the latch is in place when it is not actually fully inserted, causing parking failure and the risk of vehicle rollover; second, misjudging that the latch is not in place causes the electromagnetic latch to repeatedly extend and retract, accelerating component wear and shortening its service life. Summary of the Invention

[0006] The purpose of this invention is to provide a photoelectric sensing structure, braking control method, and parking control method for an electromechanical braking system, thereby solving the aforementioned technical problems.

[0007] To achieve the above objectives, the present invention provides a photoelectric sensing structure for an electromechanical braking system, including a light emitter and a light receiver placed on both sides of a locking disc, wherein the light emitter is fixed to an electromagnetic locking mechanism by a bracket, and a detection hole is provided on the locking disc and on the detection optical path corresponding to the light emitter and the light receiver. The detection hole, the center of the locking disc, and the center of the locking groove on the locking disc are on the same straight line. Both the optical transmitter and the optical receiver are electrically connected to the brake controller, which in turn is electrically connected to the brake motor.

[0008] Preferably, the locking disc has multiple detection holes evenly arranged in a circumferential array, and the multiple detection holes correspond one-to-one with multiple locking grooves provided on the locking disc.

[0009] Preferably, the photoelectric sensing structure is an infrared through-beam sensor or a laser through-beam sensor.

[0010] A braking control method using a photoelectric sensing structure in an electromechanical braking system includes the following steps: Step Sa1: System initialization. Power on and start the photoelectric sensor structure, brake motor, and brake controller. The brake controller clears the cumulative pulse count to zero and sets the braking target angle and angle deviation accuracy threshold. Initialize the incremental PID control coefficients. The motor drive module enters standby mode. Step Sa2: The driver presses the brake pedal, and the vehicle controller sends a braking command to the brake controller. Step Sa3: The brake controller outputs a PWM drive signal to the brake motor. The output shaft of the brake motor drives the locking disc to rotate synchronously through a flat key. During the rotation of the locking disc, the detection holes distributed around its circumference periodically open or block the detection optical path of the photoelectric sensor structure. The light receiver converts the light signal into a pulse signal with alternating high and low levels and transmits it to the brake controller in real time. Step Sa4: Based on the acquired pulse signals, the brake controller calculates the real-time speed and current rotation angle of the brake motor; Step Sa5: The brake controller calculates the rotation angle deviation and determines whether the rotation angle deviation is greater than the angle deviation accuracy threshold. If so, it triggers incremental PID regulation, calculates the duty cycle of the brake motor drive voltage, and returns to step Sa3; otherwise, it determines that the brake motor has reached the target position and completes the brake closed-loop control.

[0011] Preferably, in step Sa1, the incremental PID control coefficients are set as follows: , , , , and These represent the proportional coefficient, integral coefficient, and differential coefficient, respectively. Angular deviation accuracy threshold .

[0012] Preferably, in step Sa4, the real-time speed of the brake motor is... The calculation formula is as follows: ; In the formula, Indicates the number of detection wells; Indicates the frequency of the pulse signal Current rotation angle The calculation formula is as follows: ; In the formula, Indicates the current cumulative pulse count; This indicates the initial number of pulses when the braking command is triggered.

[0013] Preferably, in step Sa5, the rotation angle deviation The calculation formula is as follows: ; In the formula, Indicates the angle of the braking target; when This triggers incremental PID control to calculate the duty cycle of the brake motor drive voltage: ; in, ; In the formula, and They represent the first The second sampling and the first The duty cycle of the brake motor drive voltage in the next sample; This represents the voltage duty cycle increment relative to the previous sampling time. and They represent the first The second sampling and the first Rotation angle deviation of the second sampling.

[0014] A parking control method using a photoelectric sensing structure in an electromechanical braking system includes the following steps: Step Sb1: Initialize the parking control parameters, set the brake motor positioning speed threshold to ≤30rpm, signal stability verification time to 30ms-100ms, high level percentage threshold to ≥96%, electromagnetic locking mechanism locking position detection timeout time to 300ms, and maximum retry count to 3 times. At the same time, clear the cumulative pulse count of the photoelectric sensor structure and the signal sampling counter of the brake controller. Step Sb2: After receiving the parking command from the vehicle controller and confirming the vehicle speed = 0 status signal, the brake controller starts the parking control process. Step Sb3: The brake controller outputs a drive signal to control the brake motor to rotate at a speed of ≤30rpm. The brake motor drives the locking disc to rotate synchronously through the keyway transmission. During the rotation of the locking disc, the photoelectric sensor structure continuously collects the optical path conduction signal. When the detection hole conducts the optical path, it outputs a high level and outputs a low level when the non-through hole area is blocked. The level signal is transmitted to the brake controller in real time. Step Sb4, Brake Controller Start Signal Stability Verification Algorithm: Within the verification time of 30ms-100ms, sample at least 48 times continuously. If the high level percentage threshold is ≥96%, it is determined that the locking disc and the photoelectric sensor structure are aligned. Since the detection hole and the locking groove are collinear, it is synchronously confirmed that the locking groove and the electromagnetic pin axis of the electromagnetic locking mechanism are aligned. The brake controller outputs a brake motor stop signal. Otherwise, the brake motor continues to rotate at a speed of ≤30rpm, repeating until the alignment determination is successful. Step Sb5: After successful alignment, the brake controller outputs a 12V drive voltage to the electromagnetic pin, controlling the electromagnetic pin to extend and insert into the locking groove within 30ms to achieve mechanical locking. Step Sb6: The locking status is detected in real time by the Hall feedback switch built into the electromagnetic pin. When the Hall feedback switch outputs a signal indicating that the electromagnetic pin is locked in place, it is determined that the electromagnetic pin is locked in place. If no signal indicating that the electromagnetic pin is locked in place is detected within a 300ms timeout period, the brake controller records a parking failure, controls the electromagnetic pin to retract to the initial position, and returns to step Sb3 until the number of failures reaches the set number. At this time, the brake controller outputs a parking failure alarm signal and sends feedback to the vehicle controller.

[0015] Therefore, the present invention, by employing the aforementioned photoelectric sensing structure, braking control method, and parking control method for electromechanical braking systems, has the following beneficial effects: 1. Significantly optimized cost and improved economy: By integrating dual functions (braking and parking) through a single set of photoelectric sensing structure, the independent motor position sensor in the traditional solution is eliminated, and the hardware cost of a single system is directly reduced by 20%-30%; there is no need to calibrate the two types of sensors separately in the later stage, the maintenance process is simplified, the maintenance cost is reduced by more than 15%, and the total cost of vehicle life cycle is greatly reduced. 2. Simplified and convenient structure, improved assembly efficiency: The elimination of four auxiliary parts, such as the Hall sensor special bracket, significantly reduces structural complexity; the installation tolerance is widened to ±0.5mm, eliminating the need for high-precision positioning tooling, reducing cumulative assembly errors, improving assembly efficiency by 15%, and avoiding pin jamming problems caused by assembly deviations. 3. Significantly enhanced anti-electromagnetic interference capability: Adopting the principle of optical signal transmission and detection, it is not affected by electromagnetic interference sources such as vehicle high-voltage wiring harnesses and motor electromagnetic fields; Combined with signal stability verification algorithm, the position signal misjudgment rate is reduced from 5%-8% in traditional solutions to below 0.1%, completely avoiding the risk of parking failure caused by signal jumps; 4. Precise and reliable control and parking, ensuring safety: During the braking phase, the motor speed and angle are calculated through pulse signals, and the motor position detection accuracy reaches ±1°. Combined with the PID algorithm, the braking force is smoothly adjusted. During the parking phase, the alignment error is ≤0.1mm. After 1000 cycle tests, the pin insertion success rate is 100%. With a maximum of 3 retry mechanism, the risk of vehicle slippage is effectively avoided. 5. Wide compatibility and strong adaptability: By adjusting parameters such as braking target angle and PID control coefficient, it can flexibly adapt to the braking needs of vehicles of different tonnages without redesigning the structure for specific vehicle models, thus broadening the application scenarios of the technical solution.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 This is a structural diagram of the photoelectric sensing structure for the electromechanical braking system described in this invention.

[0018] Figure Labels 1. Brake motor; 2. Electromagnetic locking mechanism; 3. Locking disc; 4. Detection hole; 5. Locking groove. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of the present invention and are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0020] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, such as a process, method, system, product, or server that includes a series of steps or units, not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or device.

[0021] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0022] like Figure 1 As shown, the electromechanical braking system uses a photoelectric sensing structure, including a light emitter and a light receiver positioned on both sides of a locking disc 3 (the locking disc is coaxially fixed to the output shaft of the brake motor 1). The light emitter is fixed to the electromagnetic locking mechanism 2 via a bracket. A detection hole 4 is provided on the locking disc 3, corresponding to the detection optical path of the light emitter and the light receiver. The detection hole 4, the center of the locking disc 3, and the center of the locking groove 5 on the locking disc 3 are on the same straight line. Both the light emitter and the light receiver are electrically connected to the brake controller, which is electrically connected to the brake motor. The light emitter has an emission wavelength of 940nm, an operating voltage of 5V, and a detection distance of 5mm-10mm.

[0023] The locking disc 3 (50mm in diameter) has multiple detection holes evenly arranged in a circumferential array, and each detection hole 4 corresponds to a locking groove on the locking disc 3. In this embodiment, the edge of the locking disc 3 has 6 locking grooves (8mm deep and 5mm wide) evenly arranged in a circumferential array, and correspondingly, 6 detection holes 4 (3mm in diameter) are provided.

[0024] The photoelectric sensing structure is either an infrared through-beam sensor or a laser through-beam sensor.

[0025] A braking control method using a photoelectric sensing structure in an electromechanical braking system includes the following steps: Step Sa1: System initialization. Power on and start the photoelectric sensor structure, brake motor, and brake controller. The brake controller clears the cumulative pulse count to zero and sets the braking target angle and angle deviation accuracy threshold. Initialize the incremental PID control coefficients. The motor drive module enters standby mode. Step Sa2: The driver presses the brake pedal, and the vehicle controller sends a braking command to the brake controller. Step Sa3: The brake controller outputs a PWM drive signal to the brake motor. The output shaft of the brake motor drives the locking disc to rotate synchronously via a flat key. During the rotation of the locking disc, the detection holes distributed around its circumference periodically open or block the detection optical path of the photoelectric sensor structure (when the through hole is open, the light receiver outputs a high level; when the non-through hole area is blocked, it outputs a low level). The light receiver converts the optical signal into a pulse signal with alternating high and low levels and transmits it to the brake controller in real time. Step Sa4: Based on the acquired pulse signals, the brake controller calculates the real-time speed and current rotation angle of the brake motor; Step Sa5: The brake controller calculates the rotation angle deviation and determines whether the rotation angle deviation is greater than the angle deviation accuracy threshold. If so, it triggers incremental PID regulation, calculates the duty cycle of the brake motor drive voltage, and returns to step Sa3; otherwise, it determines that the brake motor has reached the target position and completes the brake closed-loop control.

[0026] In step Sa1, the incremental PID control coefficients are set as follows: , , , , and These represent the proportional coefficient, integral coefficient, and differential coefficient, respectively; furthermore, , , .

[0027] Angular deviation accuracy threshold .

[0028] Preferably, in step Sa4, the real-time speed of the brake motor is... The calculation formula is as follows: ; In the formula, Indicates the number of detection wells; Indicates the frequency of the pulse signal Current rotation angle The calculation formula is as follows: ; In the formula, Indicates the current cumulative pulse count; This indicates the initial number of pulses when the braking command is triggered.

[0029] Preferably, in step Sa5, the rotation angle deviation The calculation formula is as follows: ; In the formula, Indicates the angle of the braking target; when This triggers incremental PID control to calculate the duty cycle of the brake motor drive voltage: ; in, ; In the formula, and They represent the first The second sampling and the first The duty cycle of the brake motor drive voltage in the next sample; This represents the voltage duty cycle increment relative to the previous sampling time. and They represent the first The second sampling and the first Rotation angle deviation of the second sampling.

[0030] A parking control method using a photoelectric sensing structure in an electromechanical braking system includes the following steps: Step Sb1: Initialize the parking control parameters, set the brake motor positioning speed threshold to ≤30rpm, signal stability verification time to 30ms-100ms, high level percentage threshold to ≥96%, electromagnetic locking mechanism locking position detection timeout time to 300ms, and maximum retry count to 3 times. At the same time, clear the cumulative pulse count of the photoelectric sensor structure and the signal sampling counter of the brake controller. Step Sb2: After receiving the parking command from the vehicle controller and confirming the vehicle speed = 0 status signal, the brake controller starts the parking control process. Step Sb3: The brake controller outputs a drive signal to control the brake motor to rotate at a speed of ≤30rpm. The brake motor drives the locking disc to rotate synchronously through the keyway transmission. During the rotation of the locking disc, the photoelectric sensor structure continuously collects the optical path conduction signal. When the detection hole conducts the optical path, it outputs a high level and outputs a low level when the non-through hole area is blocked. The level signal is transmitted to the brake controller in real time. Step Sb4, Brake Controller Start Signal Stability Verification Algorithm: Within the verification time of 30ms-100ms, sample at least 48 times continuously. If the high level percentage threshold is ≥96%, it is determined that the locking disc and the photoelectric sensor structure are aligned. Since the detection hole and the locking groove are collinear, it is synchronously confirmed that the locking groove and the electromagnetic pin axis of the electromagnetic locking mechanism are aligned. The brake controller outputs a brake motor stop signal. Otherwise, the brake motor continues to rotate at a speed of ≤30rpm, repeating until the alignment determination is successful. Step Sb5: After successful alignment, the brake controller outputs a 12V drive voltage to the electromagnetic pin (stroke 10mm, drive voltage 12V, extension time no more than 30ms) to control the electromagnetic pin to extend and insert into the locking groove within 30ms to achieve mechanical locking. Step Sb6: The locking status is detected in real time by the Hall feedback switch built into the electromagnetic pin. When the Hall feedback switch outputs a signal indicating that the electromagnetic pin is locked in place, it is determined that the electromagnetic pin is locked in place. If no signal indicating that the electromagnetic pin is locked in place is detected within a 300ms timeout period, the brake controller records a parking failure, controls the electromagnetic pin to retract to the initial position, and returns to step Sb3 until the number of failures reaches the set number. At this time, the brake controller outputs a parking failure alarm signal and sends feedback to the vehicle controller.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An optoelectronic sensor structure for electromechanical brake systems, characterized in that: The light emitter and the light receiver are arranged on both sides of the locking disc, and the light emitter is fixed on the electromagnetic locking mechanism through the support. The light emitter and the light receiver are electrically connected with the brake controller, and the brake controller is electrically connected with the brake motor.

2. The photoelectric sensing structure for an electromechanical brake system according to claim 1, characterized by: The locking disc is uniformly provided with a plurality of detection holes in a circumferential array, and the plurality of detection holes correspond one-to-one to a plurality of locking grooves arranged on the locking disc.

3. The photoelectric sensing structure for an electromechanical brake system according to claim 1, characterized by: The photoelectric sensing structure is an infrared or laser emitter-receiver.

4. The brake control method for the photoelectric sensing structure of the electromechanical brake system according to any one of claims 1 to 3, characterized by: The method comprises the following steps: Step Sa1, system initialization, power on the photoelectric sensing structure, brake motor, brake controller, the brake controller clears the cumulative pulse count, sets the brake target angle and angle deviation precision threshold, initializes the incremental PID control coefficient, and the motor drive module enters the standby state; Step Sa2, the driver steps on the brake pedal, and sends a brake instruction to the brake controller through the vehicle controller; Step Sa3, the brake controller outputs a PWM drive signal to the brake motor, and the brake motor output shaft drives the locking disc to rotate synchronously through a key, and in the process of rotating the locking disc, the circumferally distributed detection holes periodically turn on or shield the detection light path of the photoelectric sensing structure, the light receiver converts the light signal into a pulse signal with high and low levels alternately, and transmits the pulse signal to the brake controller in real time; Step Sa4, based on the collected pulse signal, the brake controller calculates the real-time rotating speed and the current rotating angle of the brake motor; Step Sa5, the brake controller calculates the rotating angle deviation, and judges whether the rotating angle deviation is greater than the angle deviation precision threshold, if yes, the incremental PID adjustment is triggered, the brake motor drive voltage duty cycle is calculated, and the step Sa3 is returned; otherwise, it is determined that the brake motor reaches the target position, and the brake closed-loop control is completed.

5. The brake control method of the photoelectric sensing structure for an electromechanical brake system according to claim 4, characterized by: In step Sa1, the incremental PID control coefficients are set as follows: , , , , and denote the proportional coefficient, the integral coefficient and the differential coefficient, respectively. Angle deviation accuracy threshold .

6. The brake control method of the photoelectric sensing structure for an electromechanical brake system according to claim 5, characterized by: In step Sa4, the real-time rotational speed of the motor is braked The calculation formula is as follows: ； In the formula, represents the number of detection holes; represents the frequency of the pulse signal Current rotation angle The calculation formula is as follows: ； In the formula, represents the current cumulative pulse number; represents the initial pulse number at the time of the brake command trigger.

7. The brake control method of the photoelectric sensing structure for an electromechanical brake system according to claim 6, characterized by: In step Sa5, the rotation angle deviation The calculation formula is as follows: ； In the formula, denotes the target braking angle. When If so, then the incremental PID regulation is triggered and the brake motor drive voltage duty cycle is calculated: ； Wherein, ； wherein, and respectively represent the braking motor drive voltage duty ratio of the first sampling and the second sampling; represents the voltage duty ratio increment of the previous sampling time relative to the last time; and respectively represent the rotation angle deviation of the first sampling and the second sampling.

8. The parking control method of the photoelectric sensing structure for an electromechanical brake system according to any one of claims 1 to 3, characterized by: The method comprises the following steps: Step Sb1, initialize the parking control parameters, set the brake motor positioning rotating speed threshold ≤ 30 rpm, the signal stability verification time 30 ms-100 ms, the high level duty cycle threshold ≥ 96%, the locking in-place detection timeout time of the electromagnetic locking mechanism 300 ms, and the maximum retry number 3 times, and clear the cumulative pulse count of the photoelectric sensing structure and the signal sampling counter of the brake controller; Step Sb2, the brake controller receives the parking instruction issued by the vehicle controller, and after confirming the vehicle speed = 0 state signal, the parking control process is started; Step Sb3, the brake controller outputs a drive signal to control the brake motor to rotate at a speed of ≤ 30 rpm, and the brake motor drives the locking disc to rotate synchronously through a key, and in the process of rotating the locking disc, the photoelectric sensing structure continuously collects the light path signal, the detection hole outputs a high level when the light path is turned on, and outputs a low level when the non-through hole region is shielded, and the level signal is transmitted to the brake controller in real time; Step Sb4, brake controller start signal stability verification algorithm: within 30-100 ms verification time, continuously sample at least 48 times, if high level proportion threshold≥96%, determine that the locking disc and the photoelectric sensing structure light path are aligned, because the detection hole and the locking groove are collinear, the locking groove and the electromagnetic locking mechanism electromagnetic bolt axis are confirmed synchronously, the brake controller outputs the brake motor stop signal; otherwise, the brake motor continues to rotate at a speed of≤30 rpm, and repeats until the alignment determination is successful; Step Sb5, after the alignment determination is successful, the brake controller outputs a 12V driving voltage to the electromagnetic bolt, controls the electromagnetic bolt to extend, and inserts into the locking groove within 30 ms to realize mechanical locking; Step Sb6, the locking state is detected in real time through the Hall feedback switch built in the electromagnetic bolt, when the Hall feedback switch outputs a to-position signal, it is determined that the electromagnetic bolt is locked in place; if the to-position signal is not detected within 300 ms timeout time, the brake controller records a parking failure, controls the electromagnetic bolt to retract to the initial position, and returns to execute step Sb3 until the number of failures reaches the set number, the brake controller outputs a parking fault alarm signal, and feeds back to the vehicle controller.

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