A motor control method for EMB system considering brake disc clearance adjustment

Abstract

The present invention discloses an EMB system motor control method that takes brake disc clearance adjustment into account. The method comprises identifying the vehicle state. When clearance adjustment conditions are met, the CDCU issues a brake disc clearance adjustment command, and the BCU enters a brake disc clearance adjustment strategy. The method also identifies the EMB caliper state, changes the parameter weights in the error tracking sliding mode function based on the identified caliper state, and adaptively controls the motor response based on the parameter weights so that the sliding mode function achieves the control target. The corresponding brake disc clearance at this point is output as the adjustment result. Through EMB caliper state identification and adaptive sliding mode control, the present invention ensures that the motor has excellent response time and tracking performance, resists the effects of sensor errors and external disturbances, and automatically adjusts the brake disc clearance when the vehicle meets the clearance adjustment conditions. This prevents variations in braking response time caused by wear of the brake disc and brake pads, ensures vehicle robustness and braking safety, and reduces vehicle cost and maintenance difficulty.

Description

Technical Field

[0001] The present invention relates to the field of vehicle motor control, and in particular to an EMB system motor control method considering brake disc clearance adjustment. Background Art

[0002] Compared with the existing EHB system, the electronic mechanical braking system EMB has a more compact structure, faster response speed, better controllability, more flexible braking control and higher control accuracy, giving it greater electronic control potential and intelligent advantages.

[0003] Factors such as initial braking velocity, maximum road adhesion, brake disc wear, tire tread and pressure, and brake application time all contribute to the vehicle's braking performance and safety in emergency situations. Maximum road adhesion is determined by road conditions and vertical wheel load. Brake application time, which encompasses the time it takes to eliminate brake disc play and the time it takes to reach the target clamping force, is determined by the braking system's control strategy. In actual vehicle use, severely worn brake discs reduce braking effectiveness and increase braking distance. Furthermore, caliper clearance increases due to wear between the brake disc and pads. Different target clamping forces lead to inconsistent drive motor speeds, resulting in inconsistent brake disc clearance elimination times, impacting vehicle braking safety.

[0004] Problems existing in the prior art are:

[0005] 1. The existing technology installs a displacement sensor on the caliper to collect the relative distance between the brake pad and the brake disc, calculates the wear amount based on the distance, and loads the wear amount on the motor rotation stroke. However, this will lead to a decrease in the braking response speed, and the sensor working environment is harsh, resulting in assembly difficulties and increased vehicle costs.

[0006] 2. The existing technology determines the size of the brake disc gap by monitoring the changes in the motor angle and torque values ​​during the vehicle's power-on self-test, and applies current control to eliminate the brake gap. However, this method does not take into account the wear and tear of the brake disc and brake pads caused by the actual vehicle operation, and does not consider the hysteresis effect that may be caused by the clamping force sensor. Current-based control cannot accurately control the rotation angle of the motor.

[0007] 3. The existing technology achieves automatic compensation of the brake disc gap by adding a mechanical automatic adjustment device with a gap compensation function. However, the addition of the device makes the EMB system structure bloated, occupies a large space, and is inconvenient to maintain. Summary of the Invention

[0008] The purpose of the present invention is to propose an EMB system motor control method that takes into account the brake disc gap adjustment. The CDCU is used to judge the vehicle status and the EMB system status. Within a defined driving distance or after a specified number of EMB clamping times, the EMB is automatically adjusted for the brake disc gap using an adaptive sliding mode control strategy of motor speed-clamping force-motor current-motor angle. By controlling the motor response in real time, the brake disc gap is quickly eliminated to ensure the safety of the braking process.

[0009] The technical solution adopted in the present invention is:

[0010] A motor control method for an EMB system considering brake disc clearance adjustment, the method comprising:

[0011] After identifying the vehicle status and meeting the clearance adjustment conditions, the CDCU issues a brake disc clearance adjustment command, and the BCU enters the brake disc clearance adjustment strategy;

[0012] Perform EMB caliper state identification, change the parameter weights in the error tracking sliding mode function according to the identified caliper state, and make the adaptive sliding mode control motor respond according to the parameter weights so that the sliding mode function reaches the control target, and output the corresponding brake disc clearance at this time as the adjustment result.

[0013] According to the above solution, the gap adjustment conditions are specifically as follows:

[0014] The vehicle travels within a defined distance or completes a specified number of EMB clamping times;

[0015] The vehicle is stationary;

[0016] The driver issues a braking request.

[0017] According to the above scheme, the adaptive sliding mode control motor response is specifically:

[0018] The EMB caliper state enters the gap elimination stage, and the adaptive sliding mode controls the motor to rotate forward until the brake pad and brake disc reach the critical contact point;

[0019] After reaching the critical contact point, the EMB caliper state enters the braking force following stage, and the adaptive sliding mode controls the motor to rotate forward until the braking purpose is achieved;

[0020] After completing the braking purpose, the EMB caliper state enters the gap generation stage, and the adaptive sliding mode control motor reverses until the brake pad and brake disc reach the separation critical point;

[0021] After reaching the separation critical point, the adaptive sliding mode controls the motor to reverse until the ideal gap is reached.

[0022] According to the above scheme, the sliding mode function of the error tracking is specifically:

[0023] The error value between the maximum clamping force that the EMB system can provide under normal conditions and the actual clamping force, the error value between the expected motor speed corresponding to the maximum clamping force and the actual speed, the error value between the expected motor current corresponding to the expected motor speed and the actual current, and the error value between the expected motor angle and the actual angle are weighted to obtain the error value;

[0024] The desired rotation angle of the motor is calculated based on the ideal clearance of the brake disc.

[0025] According to the above solution, the reaching of the critical contact point between the brake friction pad and the brake disc is specifically identified through a change signal of the motor speed and a sudden change signal of the motor current.

[0026] According to the above solution, the reaching of the separation critical point of the brake pad and the brake disc is specifically recognized by the differential signal of the motor current.

[0027] According to the above solution, reaching the ideal gap is specifically identified by the error between the expected rotation angle and the actual rotation angle of the motor being 0.

[0028] According to the above scheme, the sliding mode control law adopted by the adaptive sliding mode control is the exponential reaching law.

[0029] According to the above solution, the parameter weights in the sliding mode function of changing the error tracking are specifically:

[0030] When the EMB caliper state is in the gap elimination stage, the error value between the motor's expected speed and actual speed has the largest weight;

[0031] When the EMB caliper state is in the braking force following stage, the weight of the error between the maximum clamping force and the actual clamping force accounts for the largest proportion;

[0032] When the EMB caliper state is in the gap generation stage, the error value between the motor expected current and the actual current has the largest weight;

[0033] After the brake pad and brake disc reach the separation critical point, the error value between the motor's expected angle and the actual angle has the largest weight.

[0034] A computer-readable storage medium stores a computer program, which is called by a motor controller to implement the EMB system motor control method considering brake disc clearance adjustment as described above.

[0035] The beneficial effects produced by the present invention are:

[0036] 1. The present invention uses EMB caliper state recognition and adaptive sliding mode control to enable the motor to have good response time and tracking performance, effectively resist the influence of sensor errors and external disturbances, and ensure the robustness of the vehicle.

[0037] 2. The present invention automatically adjusts the brake disc clearance after the vehicle meets the clearance adjustment conditions, thereby preventing the difference in braking response time caused by the wear of the brake disc and brake pads, and ensuring the braking safety of the vehicle.

[0038] 3. The present invention utilizes the vehicle's chassis domain controller CDCU and brake control unit BCU to perform brake disc clearance adjustment judgment and adjustment, thereby reducing vehicle cost and maintenance difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the process of the present invention;

[0040] Figure 2 This is a schematic diagram of the working of the EMB system in the embodiment;

[0041] Figure 3 This is a control flow diagram of the chassis domain controller CDCU and the brake control unit BCU in the embodiment;

[0042] Figure 4 Schematic diagram of the EMB caliper state recognition and adaptive sliding mode control process in the embodiment;

[0043] Figure 5 Schematic diagram of the overall steps of another embodiment.

[0044] In the figure: 1-electronic pedal EPB switch module; 2-chassis domain controller CDCU module; 3-brake control unit BCU module; 4-caliper module. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0046] The abbreviations mentioned in the examples are explained as follows:

[0047] EHB: Electronic Hydraulic Brake System, electronic hydraulic brake system;

[0048] EMB: Electronic Mechanical Brake System, electronic mechanical brake system;

[0049] CDCU: Chassis Domain Control Unit, used to identify the driver's braking intention and send it to the brake control unit for execution;

[0050] BCU: Brake Control Unit, brake control unit, receives the braking request from the chassis domain controller and controls the wheel caliper motor to execute.

[0051] Example 1

[0052] The present invention provides an EMB system motor control method considering brake disc clearance adjustment, such as Figure 1 As shown, the method specifically includes:

[0053] S1. After identifying the vehicle status and meeting the clearance adjustment conditions, the CDCU issues a brake disc clearance adjustment command and the BCU enters the brake disc clearance adjustment strategy.

[0054] Based on the vehicle status recognition, it is determined whether the vehicle is within the defined driving distance or has completed the specified number of EMB clamping times. The CDCU also determines whether the vehicle is stationary and has received the driver's braking request.

[0055] The defined driving distance and the specified EMB clamping times may be obtained by calibration.

[0056] The control flow of the chassis domain controller CDCU and the brake control unit BCU in this embodiment is as follows: Figure 3 shown.

[0057] S2. Perform EMB caliper state identification, change the parameter weights in the error tracking sliding mode function according to the identified caliper state, and make the adaptive sliding mode control motor respond according to the parameter weights so that the sliding mode function reaches the control target, and output the corresponding brake disc clearance at this time as the adjustment result.

[0058] Figure 4 Schematic diagram of the EMB caliper state recognition and adaptive sliding mode control process in this embodiment.

[0059] The S2 step specifically includes the following steps:

[0060] S21, EMB caliper state enters the gap elimination stage, and the adaptive sliding mode controls the motor to rotate forward until the brake friction pad and brake disc reach the critical contact point.

[0061] The EMB caliper state enters the brake disc gap elimination stage. In this stage, the target clamping force is set to the maximum clamping force that the EMB system can provide under normal conditions. F max , set the desired motor speed to the corresponding F max Motor speed under ω tar , set the motor desired current to the corresponding ω tar Lower motor currentI tar , and calculate the expected motor angle signal δ tar ,Will F max 、 ω tar 、 I tar 、 δ tar The weighted error value corresponding to the actual value is e , defined as the sliding mode function of error tracking, as the selection of the sliding surface, and the exponential reaching law is used as the sliding mode control law of the adaptive sliding mode control.

[0062] The maximum clamping force F max Determined by the product model, the expected motor angle signal δ tar Calculated based on the ideal brake disc clearance L, in this embodiment, the ideal brake disc clearance L is 0.2 mm.

[0063] At this stage, the error value between the desired motor speed and the actual motor speed in the sliding mode function of error tracking has the largest weight, which is used to quickly eliminate the brake clearance, adaptively calculate the desired voltage through sliding mode control, and control the forward rotation of the motor; and identify whether the brake friction pad and the brake disc have reached the critical contact point through the change signal of the motor speed and the sudden change signal of the motor current.

[0064] S22. After reaching the contact critical point, the EMB caliper state enters the braking force following stage, and the adaptive sliding mode controls the motor to rotate forward until the braking purpose is achieved.

[0065] When the brake pad and disc reach the critical contact point, the brake clearance is considered to have been eliminated, and the EMB caliper enters the brake force following phase. During this phase, the error tracking sliding mode function, which determines the difference between the target and actual clamping forces, has the highest weight. This is used to accurately follow the driver's braking force request. Adaptive sliding mode control calculates the desired voltage and controls the motor's forward rotation. This also determines whether the braking objective has been achieved.

[0066] S23. After completing the braking purpose, the EMB caliper state enters the gap generation stage, and the adaptive sliding mode controls the motor to reverse until the brake pad and brake disc reach the separation critical point.

[0067] After braking, the EMB caliper enters the gap generation phase. During this phase, the error between the desired and actual motor currents in the error tracking sliding mode function has the highest weight, rapidly dissipating drag. Adaptive sliding mode control calculates the desired voltage and controls motor reversal. Simultaneously, the differential signal of the motor current is used to identify whether the brake pads and discs have reached the separation critical point.

[0068] S24. After reaching the separation critical point, the adaptive sliding mode controls the motor to reverse until the ideal gap is reached.

[0069] When it is identified that the brake friction pad and the brake disc have reached the separation critical point, the adaptive sliding mode control calculates the expected voltage. At this time, the error value between the expected motor angle and the actual angle in the error tracking sliding mode function has the largest weight, which is used to follow the ideal brake gap and ensure the gap adjustment accuracy. The adaptive sliding mode control motor reverses. When the error value between the expected motor angle and the actual angle is 0, it is determined that a fixed brake gap has been generated, and the brake disc gap is adjusted to the ideal brake gap. The sliding mode function reaches the control target, and the corresponding brake disc gap at this time is output as the adjustment result.

[0070] Meanwhile, the working process of the EMB system in this embodiment is as follows Figure 2 As shown, the system includes an electronic pedal (EPB) switch module, a chassis domain controller (CDCU) module, a brake control unit (BCU) module, and a caliper module. During system operation, the driver inputs a brake signal to the electronic pedal (EPB) switch module, which transmits the pedal travel and pedal force in the input signal to the chassis domain controller (CDCU) module. Vehicle data, such as WSS, SAS, and CAN, are also input to the chassis domain controller (CDCU) module. The chassis domain controller (CDCU) module calculates braking demand, distributes braking force, performs stability control, and implements parking brakes. Meanwhile, the brake disc clearance adjustment module in the module sends a clearance adjustment request to the brake control unit (BCU) module. Upon receiving the request, the brake control unit (BCU) module calculates the expected voltage and sends it to the caliper module. The caliper module then passes through the motor, transmission mechanism, friction disc, or locking mechanism. The motor has a motor angle sensor, and the friction disc has a force sensor. The motor angle sensor and force sensor provide feedback to the brake control unit (BCU) module for motor control. The motor angle sensor also provides feedback to the brake control unit (BCU) for clamping force control. The brake control unit (BCU) module performs clamping force control, motor control, and EPB control.

[0071] Example 2

[0072] This embodiment mainly includes: a vehicle state recognition module, a caliper state recognition module and a motor control module, and sets the target clamping force to the maximum clamping force that the EMB system can provide under normal conditions.F max , set the desired motor speed to the corresponding F max Motor speed under ω tar , set the motor desired current to the corresponding ω tar Lower motor current I tar , and calculate the expected motor angle signal δ tar ,Will F max 、 ω tar 、 I tar 、 δ tar The weighted error value corresponding to the actual value is e , defined as the sliding mode function of error tracking, as the selection of the sliding surface, and the exponential reaching law is used as the sliding mode control law of the adaptive sliding mode control.

[0073] The maximum clamping force F max Determined by the product model, the expected motor angle signal δ tar Calculated based on the ideal brake disc clearance L, in this embodiment, the ideal brake disc clearance L is 0.2 mm.

[0074] like Figure 5 As shown, the specific steps of this embodiment are as follows:

[0075] S01. The vehicle status recognition module determines whether the vehicle is within a defined driving distance (calibratable) or has completed a specified number of EMB clamping times (calibratable) based on the vehicle status recognition.

[0076] S02. The CDCU determines whether the vehicle is stationary and receives a braking request from the driver.

[0077] S03. CDCU issues a brake disc clearance adjustment command.

[0078] S04. The BCU receives a brake disc clearance adjustment instruction and enters a brake disc clearance adjustment control strategy.

[0079] S05: Enter the caliper status recognition module.

[0080] S06: The initial state enters the gap elimination stage.

[0081] S07. Adaptive sliding mode control calculates the expected voltage. At this time, the motor speed is given a larger weight in the selection of the sliding mode surface to quickly eliminate the braking gap.

[0082] S08. Identify the contact critical point between the brake friction pad and the brake disc through the motor speed change signal and the motor current mutation signal. If the contact critical point is reached, enter S09; otherwise, return to S06.

[0083] S09, EMB caliper state enters the braking force following stage.

[0084] S10, adaptive sliding mode control calculates the expected voltage. At this time, the expected clamping force is given a larger weight in the selection of the sliding mode surface to follow the driver's braking force request and ensure accuracy.

[0085] S11. Determine whether the braking purpose is completed. If so, proceed to S12; otherwise, return to S09.

[0086] S12, the EMB caliper state enters the gap generation stage.

[0087] S13. Adaptive sliding mode control calculates the expected voltage. At this time, the expected current has a larger weight in the selection of the sliding mode surface to quickly consume the drag force.

[0088] S14. Identify the separation critical point of the brake friction pad and the brake disc through the differential signal of the motor current.

[0089] S15, adaptive sliding mode control calculates the expected voltage and controls the motor to reverse. At this time, the motor angle weight is larger in the selection of the sliding mode surface to follow the ideal braking gap and ensure the gap adjustment accuracy.

[0090] S16: Determine whether the ideal brake clearance has been reached. If so, proceed to S17; otherwise, return to S15.

[0091] S17: Brake disc clearance adjustment is completed and motor control exits.

[0092] As another embodiment of the present invention, the present invention further provides a computer-readable storage medium storing a computer program, which is called by a motor controller to implement the EMB system motor control method considering the brake disc gap adjustment as described above.

[0093] The embodiment of the present invention uses EMB caliper state recognition and adaptive sliding mode control to ensure that the motor has good response time and tracking performance, effectively resists the influence of sensor errors and external disturbances, and ensures the robustness of the vehicle; and automatically adjusts the brake disc clearance after the vehicle meets the clearance adjustment conditions to prevent the difference in braking response time caused by wear of the brake disc and brake pads, thereby ensuring the braking safety of the vehicle; and uses the vehicle's chassis domain controller CDCU and brake control unit BCU to perform clearance adjustment judgment and adjustment, reducing vehicle cost and maintenance difficulty.

[0094] The size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0095] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A motor control method for an EMB system considering brake disc clearance adjustment, characterized in that: The method comprises: After identifying the vehicle status and meeting the clearance adjustment conditions, the CDCU issues a brake disc clearance adjustment command, and the BCU enters the brake disc clearance adjustment strategy; Perform EMB caliper state identification, change the parameter weights in the error tracking sliding mode function based on the identified caliper state, and make the adaptive sliding mode control motor respond according to the parameter weights so that the sliding mode function reaches the control target. The corresponding brake disc clearance at this time is output as the adjustment result; The sliding mode function of error tracking is defined as the weighted error between the target clamping force, the desired motor speed, the desired motor current, and the desired motor angle signal and the corresponding actual values. The target clamping force is the maximum clamping force that the EMB system can provide under normal conditions. The desired motor speed is the motor speed at the target clamping force, and the desired motor current is the motor current at the desired motor speed. The adaptive sliding mode control motor response is specifically: The EMB caliper state enters the gap elimination stage, and the adaptive sliding mode controls the motor to rotate forward until the brake pad and brake disc reach the critical contact point; After reaching the critical contact point, the EMB caliper state enters the braking force following stage, and the adaptive sliding mode controls the motor to rotate forward until the braking purpose is achieved; After completing the braking purpose, the EMB caliper state enters the gap generation stage, and the adaptive sliding mode control motor reverses until the brake pad and brake disc reach the separation critical point; After reaching the separation critical point, the adaptive sliding mode controls the motor to reverse until the ideal gap is reached.

2. The EMB system motor control method considering brake disc clearance adjustment according to claim 1, characterized in that: The gap adjustment conditions are specifically: The vehicle travels within a defined distance or completes a specified number of EMB clamping times; The vehicle is stationary; The driver issues a braking request.

3. The EMB system motor control method considering brake disc clearance adjustment according to claim 1, characterized in that: The sliding mode function of the error tracking is specifically: The error value between the maximum clamping force that the EMB system can provide under normal conditions and the actual clamping force, the error value between the expected motor speed corresponding to the maximum clamping force and the actual speed, the error value between the expected motor current corresponding to the expected motor speed and the actual current, and the error value between the expected motor angle and the actual angle are weighted to obtain the error value; The desired rotation angle of the motor is calculated based on the ideal clearance of the brake disc.

4. The EMB system motor control method considering brake disc clearance adjustment according to claim 1, characterized in that: The reaching of the critical contact point between the brake friction pad and the brake disc is specifically identified through a change signal of the motor speed and a sudden change signal of the motor current.

5. The EMB system motor control method considering brake disc clearance adjustment according to claim 1, characterized in that: The reaching of the separation critical point of the brake friction pad and the brake disc is specifically identified by the differential signal of the motor current.

6. The EMB system motor control method considering brake disc clearance adjustment according to claim 1, characterized in that: The reaching of the ideal gap is specifically identified by the error between the expected rotation angle and the actual rotation angle of the motor being 0.

7. The EMB system motor control method considering brake disc clearance adjustment according to claim 1, characterized in that: The sliding mode control law adopted by the adaptive sliding mode control is an exponential reaching law.

8. The EMB system motor control method considering brake disc clearance adjustment according to claim 1, characterized in that: The parameter weights in the sliding mode function of changing the error tracking are specifically: When the EMB caliper state is in the gap elimination stage, the error value between the motor's expected speed and actual speed has the largest weight; When the EMB caliper state is in the braking force following stage, the weight of the error between the maximum clamping force and the actual clamping force accounts for the largest proportion; When the EMB caliper state is in the gap generation stage, the error value between the motor expected current and the actual current has the largest weight; After the brake pad and brake disc reach the separation critical point, the error value between the motor's expected angle and the actual angle has the largest weight.

9. A computer-readable storage medium, characterized in that The computer program is stored therein, and after being called by the motor controller, the computer program implements the EMB system motor control method considering the brake disc gap adjustment as described in any one of claims 1-8.

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