Zero point learning method and device of braking system

Abstract

The embodiment of the invention provides a zero point learning method and device of a braking system, and relates to the technical field of motor control, and the method comprises the steps that starting of braking voltage building zero point learning is obtained, and a starting signal of the braking voltage building zero point learning is generated when a vehicle is powered on or powered off; based on a learning control method corresponding to the starting signal, a piston is controlled to move through a motor, the piston passes through a braking zero point in the movement process, and motor movement data of the motor are collected in real time in the movement process; and the change condition of the motor motion data is analyzed in real time, when the change condition meets the zero point change condition, the current position of the piston serves as the braking zero point, and the zero point change condition is obtained according to empirical data generated in the braking process of the motor. According to the method, zero point learning and correction can be flexibly and conveniently carried out, and the driving safety is improved.

Description

Technical Field

[0001] This application relates to the field of motor control technology, and in particular to a zero-point learning method and apparatus for a braking system. Background Technology

[0002] EMB (Electro-Mechanical Brake) is an advanced automotive braking system that abandons traditional hydraulic or pneumatic transmission methods, instead using an electric motor to directly drive the brake calipers or discs, achieving rapid and precise control of braking force. The core of the EMB system lies in its highly integrated electronic control unit (ECU) and precise sensor network, which can monitor wheel conditions in real time and quickly adjust braking force according to driving needs, ensuring driving safety. For typical vehicles, by controlling the output torque and rotation of four wheel-side motors, the transmission system pushes the friction pads to clamp or release the wheel-side brake discs, thereby controlling wheel-end deceleration and slip ratio. The entire braking process can be divided into three stages: eliminating the gap between the friction pads and the brake disc; the friction pads and brake disc begin to clamp until real-time braking torque is generated; and the motor retraction stage creates a gap between the friction pads and brake disc. To distinguish these three stages and implement different control strategies at different stages, and to achieve precise braking effects, it is necessary to accurately identify the position of the contact surface between the friction pads and the brake disc, i.e., the zero point of the braking system. However, the zero point of the braking system changes due to the wear of the friction pads and the influence of environmental factors such as disc temperature.

[0003] In related technologies, in order to solve the problem of zero-point variation, a zero-point calibration device is connected to the vehicle to calibrate the vehicle's zero point when the vehicle is not in use. This method is complicated to operate and cannot guarantee that the zero point of the vehicle is always accurate during use between two zero-point calibrations, which is not very safe.

[0004] Therefore, there is an urgent need for a zero-point learning method and device for braking systems that can flexibly and conveniently perform zero-point learning and correction, thereby improving driving safety. Summary of the Invention

[0005] This application provides a method and apparatus for zero-point learning of a braking system, which can flexibly and conveniently perform zero-point learning and correction, thereby improving driving safety.

[0006] In a first aspect, embodiments of this application provide a zero-point learning method for a braking system, the method comprising: Receive a start signal, which is generated when the vehicle is powered on or off; Based on the learning control method corresponding to the start signal, the piston is controlled by the motor to move, so that the piston passes through the braking zero point during the movement, and the motor motion data of the motor is collected in real time during the movement. The changes in the motor motion data are analyzed in real time. When the changes meet the zero-point change condition, the current position of the piston is taken as the braking zero point. The zero-point change condition is obtained based on the empirical data generated by the motor during the braking process.

[0007] Secondly, embodiments of this application provide a zero-point learning device for a braking system, the device comprising: The start signal for brake pressure build-up zero-point learning is acquired, and the start signal for brake pressure build-up zero-point learning is generated when the vehicle is powered on or off. The first processing unit is used to control the piston movement by a motor based on the learning control method corresponding to the start signal, so that the piston passes through the braking zero point during the movement, and to collect the motor movement data of the motor in real time during the movement. The second processing unit is used to analyze the changes in the motor motion data in real time. When the changes meet the zero-point change condition, the current position of the piston is taken as the braking zero point. The zero-point change condition is obtained based on the empirical data generated by the motor during the braking process.

[0008] Optionally, the start signal is a front wheel learning signal, which is used to learn the zero point of the front wheels of the vehicle to obtain the front wheel braking zero point; The first processing unit is specifically used for, The piston is controlled by the motor to retract in the opposite direction to the target position, where the reverse direction is the opposite direction of the brake disc relative to the direction in which the piston is located; Using an S-shaped cycloidal speed control method, the piston is pushed forward from the target position. When the piston's moving speed is the target speed, the first actual torque value of the motor is collected at a first time interval to obtain multiple first actual torque values. The first average torque of the multiple first actual torque values ​​is calculated. The target speed is the moving speed of the piston in the uniform speed stage under the control of the S-shaped cycloidal speed control method. While the piston is moving at the target speed and is decelerating, the second actual torque value of the motor, which is collected in real time according to the second time interval, is subjected to sliding average filtering to obtain the second average torque. The zero-point change condition includes the set torque difference of the motor. The second processing unit is specifically used to calculate the actual torque difference between the second average torque and the first average torque in real time. When the actual torque difference is greater than the set torque difference, the current position of the piston is taken as the zero point of the front wheel braking.

[0009] Optionally, the start signal is a front wheel learning signal, which is used to learn the zero point of the vehicle's front wheels to obtain the front wheel braking zero point; the zero point change condition includes a set rate of change of the motor's rotational speed. The first processing unit is specifically used for, The piston is controlled by the motor to retract in the opposite direction to the target position, where the reverse direction is the opposite direction of the brake disc relative to the direction in which the piston is located; An S-shaped cycloidal speed control method is used to propel the piston in the forward direction, and the rotational speed data of the motor is collected in real time during the propulsion process; The second processing unit is specifically used for, Analyze the rate of change of the motor's speed. When the rate of change of the motor's speed is greater than a set rate of change, take the current position of the piston as the zero point of the front wheel braking.

[0010] Optionally, the second processing unit is further configured to, Based on the motor, the piston is controlled to continue moving in the positive direction until the friction plate pushed by the piston clamps the brake disc, and the speed of the motor is zero. The piston end position when the speed of the motor is zero, the first motor output torque and the first brake disc temperature when the speed of the motor is zero are obtained. Obtain a first reasonable distance range corresponding to the output torque of the first motor and the temperature of the first brake disc. The first reasonable distance range is used to characterize the distance range between the friction pad and the brake disc from the theoretical zero point to the braking end point under the conditions of the output torque of the first motor, the temperature of the first brake disc, and the stiffness of the braking system. The theoretical zero point is used to characterize the piston position where the friction pad and the brake disc separate or come into contact during relative movement. The braking end point is used to characterize the piston position where the friction pad and the brake disc are clamped together and the speed of the motor is zero. If the distance between the piston end point and the front wheel braking zero point meets the first reasonable distance range, then the front wheel braking zero point is determined to be a reliable front wheel braking zero point.

[0011] Optionally, the first processing unit is further configured to, The friction pads are clamped to the brake disc by the rear wheel controller of the vehicle, or the lock-up valve is locked.

[0012] Optionally, the start signal is a rear wheel learning signal, which is used to perform zero-point learning on the rear wheels of the vehicle to obtain the rear wheel braking zero point; the zero-point change condition includes the minimum value of the motor output torque; The first processing unit is specifically used to control the motor to be in a zero-speed closed-loop control state or to control the motor to creep in the clamping direction and release the pawl; When the pawl is successfully released, the motor stops churning, and the piston is at rest, record the original position of the piston. The piston is controlled by the motor to retract in the reverse direction, and the third actual torque value of the motor is collected in real time according to the third time interval during the reverse retraction process. The reverse direction is the opposite direction of the brake disc relative to the piston. The second processing unit is specifically used for, The third actual torque value of the motor, which is collected in real time according to the third time interval, is smoothed until the minimum value of the output torque of the motor is obtained, and the current position of the piston is set as the zero point of the rear wheel braking.

[0013] Optionally, the second processing unit is further configured to, A second reasonable distance range corresponding to the output torque of the second motor and the temperature of the second brake disc is obtained. The output torque of the second motor and the temperature of the second brake disc are recorded when the pawl is successfully released and the piston is in a stationary state. The second reasonable distance range is used to characterize the distance range between the friction pad and the brake disc from the theoretical zero point to the braking endpoint under the conditions of the output torque of the second motor, the temperature of the second brake disc, and the stiffness of the braking system. The theoretical zero point is used to characterize the piston position where the friction pad and the brake disc separate or come into contact during relative movement. The braking endpoint is used to characterize the piston position where the friction pad and the brake disc are clamped together and the speed of the motor is zero. If the distance between the original position of the piston and the zero point of the rear wheel brake meets the second reasonable distance range, then the zero point of the rear wheel brake is a reliable zero point of the rear wheel brake.

[0014] Optionally, the second processing unit is further configured to, Obtain historical brake disc temperature and historical zero point, wherein the historical brake disc temperature is the temperature of the brake disc at the time when the historical zero point is obtained; The temperature difference between the second brake disc temperature and the historical brake disc temperature, as well as the zero-point difference between the rear wheel braking zero point and the historical zero point, are obtained. Analyze whether the relationship between the temperature difference and the zero point difference conforms to the set temperature zero point relationship. If so, determine that the rear wheel braking zero point is a reliable rear wheel braking zero point.

[0015] Optionally, the first processing unit is further configured to, The friction pads are clamped to the brake disc by the front wheel controller of the vehicle.

[0016] Thirdly, embodiments of this application provide a vehicle, including a vehicle capable of executing a zero-point learning method for a braking system in any possible design of the first aspect.

[0017] The beneficial effects of this application are: This application provides a zero-point learning method for a braking system. This method, when the vehicle is powered on or off, determines whether the starting signal is for the front wheels or the rear wheels based on the starting signal generated during power-on or power-off. If it is a front wheel starting signal, the corresponding learning control method for the front wheels is selected, controlling the piston movement via a motor. If it is a rear wheel starting signal, the corresponding learning control method for the rear wheels is selected, controlling the piston movement via a motor, causing the piston to pass through the braking zero point during its movement. During this movement, the motor's motion data is collected in real time. Thus, changes in motor motion, such as changes in motor speed and output torque, can be obtained based on the motor motion data. Generally, when the friction pads contact or separate from the brake disc (braking zero point), the motor motion exhibits special phenomena different from other times. Zero-point change conditions can be obtained using empirical data generated near the zero point. When the real-time changes obtained from the motor motion data analysis meet the zero-point change conditions, the braking zero-point position can be determined. Therefore, when the vehicle starts or stops, a new braking zero point can be automatically, accurately, and quickly acquired, improving the convenience of zero-point updating and vehicle safety. In particular, when the vehicle is turned off, the temperature of the brake disc is unstable, which may lead to inaccurate zero-point calculation. Therefore, preferably, zero-point learning can be performed only when the vehicle is powered on and started.

[0018] These or other implementations of this application will become clearer and easier to understand in the following description of the embodiments. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A schematic flowchart of a zero-point learning method for a braking system provided in this application embodiment; Figure 2A simplified schematic diagram of piston position provided for an embodiment of this application; Figure 3a A schematic diagram of the speed control stages in an S-shaped cycloidal speed control method provided in an embodiment of this application; Figure 3b A schematic diagram of the speed control stages in an S-shaped cycloidal speed control method provided in an embodiment of this application; Figure 4a A schematic diagram illustrating the process by which a piston reaches a target speed, as provided in an embodiment of this application. Figure 4b A schematic diagram illustrating the moving speed of a piston according to an embodiment of this application; Figure 5 A schematic flowchart of a zero-point learning method for the front wheel of a braking system provided in an embodiment of this application; Figure 6 A schematic flowchart of a zero-point learning method for the rear wheel of a braking system provided in an embodiment of this application; Figure 7 A schematic diagram illustrating the parameter changes of various components during an active process, provided as an embodiment of this application; Figure 8 This is a schematic diagram of a zero-point learning method device for a braking system provided in an embodiment of this application. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] In the description of this invention, the phrase "in one embodiment" does not necessarily refer to the same embodiment, although it may refer to the same embodiment. Similarly, the phrase "in some embodiments," as used herein, does not necessarily refer to the same embodiment when used multiple times, although it may refer to the same embodiment. As used herein, the term "or" is an inclusive "or" operator and is equivalent to the term "and / or," unless the context clearly specifies otherwise. The term "based on" is not exclusive and allows for reliance on additional factors not described, unless the context clearly specifies otherwise. The word "exemplary" herein means "used as an example, instance, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior to or better than other embodiments. The scope of this invention is limited only by the scope of the appended claims, and any examples set forth in this specification are not intended to be limiting, but merely illustrate some of the many possible embodiments of the claimed invention. The various embodiments provided in this invention should not be construed as limiting the scope of protection of this invention.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0024] Against the backdrop of rapid development in the automotive industry, the widespread application of electronic braking systems has placed higher demands on the precision and safety of braking performance. Accurate determination of the braking zero point has become a core element in ensuring braking effectiveness and vehicle handling stability. However, traditional braking zero-point calibration methods require external equipment to be connected while the vehicle is idle. This method requires professional personnel to operate the equipment, making the zero-point calibration process complex. Consequently, users typically do not perform multiple zero-point calibrations in a short period, which can lead to the braking system's zero point remaining uncalibrated for extended periods, significantly impacting driving safety.

[0025] Therefore, embodiments of this application provide a zero-point learning method flow for a braking system, such as... Figure 1 As shown, the method includes: Step 101: Obtain the start signal for brake pressure build-up zero-point learning. The start signal for brake pressure build-up zero-point learning is generated when the vehicle is powered on or off.

[0026] Step 102: Based on the learning control method corresponding to the start signal, the piston is controlled by the motor to move, so that the piston passes through the braking zero point during the movement, and the motor motion data of the motor is collected in real time during the movement.

[0027] Step 103: Analyze the changes in the motor motion data in real time. When the changes meet the zero-point change condition, take the current position of the piston as the braking zero point. The zero-point change condition is obtained based on the empirical data generated by the motor during the braking process.

[0028] In one embodiment, the learning control method corresponding to the start signal of the front wheel can be different from the learning control method of the start signal of the rear wheel. Therefore, after receiving the start signal for learning the brake pressure build-up zero point, the corresponding learning control method can be selected according to the start signal, and the piston can be controlled by the motor to move, so that the piston passes through the brake zero point during the movement, and the motor motion data of the motor can be collected in real time during the movement.

[0029] In one embodiment, the start signal may be generated when the user turns the car key and / or presses the brake or opens the car door, or it may be generated when the vehicle start and stop buttons are pressed, or it may be generated based on the driver's operation on a smart device. The specific method of generating the start signal is not limited here. It should be noted that, preferably, the start signal is generated when the vehicle is powered on, because the temperature of the friction pads and brake discs is usually at ambient temperature when the vehicle is powered on, resulting in minimal deformation. The obtained braking zero point is more accurate than the braking zero point obtained when the vehicle is powered off (when the brake discs and friction pads have likely undergone rapid friction, leading to a rapid temperature rise and deformation).

[0030] In one embodiment, if a vehicle has four or more wheels, and each wheel corresponds to a motor, then the motor can be any one or more motors corresponding to any one or more wheels in the vehicle. In other words, in the zero-point learning method of the braking system, the motors of one or more wheels can simultaneously perform zero-point learning to obtain their respective braking zero points.

[0031] In one embodiment, the learning control method can be set based on the piston speed. For example, if the starting signal is a front wheel starting signal, the corresponding learning control method could be to control the piston to move forward at a certain speed (towards the wheel) from a position opposite to the wheel direction and far from the true zero point, passing through the true zero point. During this process, the braking zero point (approximately equal to or equal to the true zero point) is determined by analyzing changes in motor motion data. Figure 2 The diagram shown is a simplified schematic of a piston position provided in an embodiment of this application. The wheel 201 is in the forward direction, and the piston 204 is in the opposite direction relative to the wheel 201. The piston 204 pushes the friction plate 203 to contact the brake disc 202 for friction braking.

[0032] In one embodiment, the learning control method can be set based on the torque of the motor. For example, if the start signal is the start signal of the rear wheel, the corresponding learning control method can be a method in which the piston is controlled by the wheel direction (forward) and the motor output torque (not exceeding the maximum output torque limit) to move in the opposite direction (away from the wheel) at a certain speed and pass through the true zero point. During this process, the braking zero point (approximately equal to or equal to the true zero point) is determined by analyzing the changes in the motor motion data.

[0033] In one embodiment, after obtaining the braking zero point, the braking zero point can be stored in a corresponding memory so that the vehicle can be braked according to the obtained braking zero point the next time the vehicle is braked.

[0034] In one embodiment, the zero-point change condition can be obtained through statistical analysis of empirical data corresponding to the specific behavior of the friction pads when they pass the zero point during braking, where the motor pushes the piston. For example, the output torque and speed of the motor will change at the instant the friction pads contact the brake disc.

[0035] In one embodiment, the zero-point learning method of the braking system described above in this application is used for EMBs with and without clamping force sensors.

[0036] The zero-point learning method for the braking system disclosed in this application solves the technical problem of braking zero-point changes caused by friction pad wear and environmental influences. This application receives a start signal generated based on changes in vehicle state, controls a motor to drive a piston, and collects motor motion data during the movement. By analyzing the changes in motion data, when the zero-point change condition is met, the current position of the piston is determined as the braking zero point. This application employs a specific learning control method for the motor and piston, combined with motor motion data analysis, to achieve accurate identification of the braking zero point. This method can adapt to friction pad wear and environmental changes, dynamically adjusting the braking zero point, thereby improving the braking accuracy and reliability of the EMB (Electronic Braking Machine), and laying the foundation for achieving precise braking control at different stages.

[0037] Based on the above Figure 1 The method flow in this application provides a zero-point learning method for a front wheel braking system. The start signal is a front wheel learning signal, which is used to perform zero-point learning on the front wheels of the vehicle to obtain the front wheel braking zero point. The zero-point change condition includes the set torque difference value of the motor. In step 102, based on the learning control method corresponding to the start signal, the piston is controlled by the motor to move, causing the piston to pass through the braking zero point during the movement, and the motor motion data is collected in real time during the movement, including: Step A1021: Control the piston to retract in the opposite direction to the target position via the motor. The opposite direction is the opposite of the direction in which the brake disc is located relative to the piston.

[0038] Step A1022: Using the S-shaped cycloidal speed control method, the piston is pushed forward from the target position. When the piston's moving speed is the target speed, the first actual torque value of the motor is collected according to the first time interval to obtain multiple first actual torque values, and the first average torque of the multiple first actual torque values ​​is calculated. The target speed is the moving speed of the piston in the uniform speed stage under the control of the S-shaped cycloidal speed control method.

[0039] Step A1023: When the piston is moving at the target speed and is in the process of deceleration, perform a sliding average filter on the second actual torque value of the motor collected in real time according to the second time interval to obtain the second average torque.

[0040] In step 103, the changes in motor motion data are analyzed in real time. When the changes meet the zero-point change conditions, the current position of the piston is taken as the braking zero point. This includes: calculating the actual torque difference between the second average torque and the first average torque in real time. When the actual torque difference is greater than the set torque difference, the current position of the piston is taken as the front wheel braking zero point.

[0041] In one embodiment, during the retraction process in step A1021 above, it is necessary to monitor the motor torque and the cumulative piston retraction displacement. Generally, since there is no load or a very small load when the motor retracts, the output torque of the retracting motor will also be very small. If the motor output torque significantly exceeds the torque required for speed planning retraction, or the piston retraction displacement far exceeds the displacement generated by speed planning (the piston retraction may be abnormal, which is not conducive to zero-point learning), then the current zero-point learning is terminated.

[0042] In one embodiment, after the piston is retracted to the target position by the motor in step A1021, it can be further analyzed and confirmed that during the piston retraction process, the motor output torque does not exceed the torque required for retraction under the retraction speed plan, or the piston retraction displacement does not exceed the displacement generated by the retraction speed plan. The retraction speed plan includes the piston retraction displacement generated by the piston based on the retraction speed plan, and the motor torque required during the piston retraction process based on the retraction speed plan.

[0043] In one embodiment, the retraction speed planning can be an S-curve speed control method, which includes seven stages: uniform acceleration, uniform acceleration, uniform deceleration, uniform speed, uniform acceleration / deceleration, uniform deceleration, and uniform deceleration / deceleration. This method can reduce noise during braking zero-point learning.

[0044] In one embodiment, such as Figure 3a The diagram shown is a schematic representation of the speed control stages in an S-shaped cycloidal speed control method provided in this application embodiment. The entire process can be divided into 7 stages. The target maximum speed of the motor is set (the target maximum speed (rotation speed) of the motor achieves the target speed of the piston during the corresponding constant speed phase). This is the maximum acceleration allowed by the system. The maximum allowable jerk of the system is set, and t1, t2, t3, t4, t5, t6, and t7 are the times for each stage. The formulas for setting the time and speed for each stage are as follows:

[0045] In the formula, - To define the seven velocity change nodes in the movement method, For the uniform acceleration stage, For the uniform acceleration stage, For the uniform acceleration phase, For the uniform speed stage, For the uniform acceleration / deceleration stage, For the uniform deceleration stage, During the uniform deceleration phase, and These are the speeds at the end of stages t1 and t2, respectively. For example, it can be set... It is 2000 rpm. It is 40,000 rpm / s. If the value is 1,000,000 rpm / s^2, then the speed at each stage can be calculated.

[0046] Furthermore, in the S-shaped cycloidal speed control method, the uniform velocity phase may be relatively short, such as... Figure 3b The diagram shown is a schematic diagram of the speed control stages in another S-shaped cycloidal speed control method provided in this application embodiment, wherein the maximum forward speed (rotation speed) of the front shaft of the motor achieves the target speed of the piston in the corresponding constant speed stage.

[0047] In one embodiment, after the motor-controlled piston retracts to the desired retraction stroke (the piston movement generates a retraction displacement and stops at the target position), the motor rotates to control the piston to advance, also using the S-shaped cycloidal speed control method, such as... Figure 3a As shown, the process of the piston reaching the target speed includes t1, t2, t3, and part or all of t4, then as follows: Figure 4aThe diagram illustrates the process of a piston reaching a target speed according to an embodiment of this application. It includes: t11 - uniform acceleration, t12 - uniform acceleration, t13 - uniform acceleration / deceleration, and t14 - constant speed. After learning the braking zero point, braking can be performed based on the learned front wheel braking zero point in response to the driver's braking request. When the motor's target speed reaches the set maximum constant speed stage, the actual motor speed is acquired. When the actual speed stabilizes within a very narrow error range of the target speed (e.g., ±3%), the first actual torque value of the motor's actual output is collected and accumulated. After collecting a large number of first actual torque values, the average of the specific number of first actual torque values ​​collected within this range is calculated to obtain the first average torque for this stage. .

[0048] In addition, such as Figure 4b The diagram shown is a schematic of the piston's moving speed according to an embodiment of this application. After the piston pushes the friction pad to contact the brake disc (i.e., zero point - front wheel braking zero point), the piston's moving speed decreases until the rebound force when the friction pad and brake disc are clamped causes the piston's moving speed to change to a negative value, and then returns to zero.

[0049] In one embodiment, when the S-shaped cycloidal speed control method controls the piston to move in the forward direction, it must ensure that from the point of forward movement to obtaining the first average torque... The entire stroke should not exceed the retraction displacement to avoid the brake disc-friction pads hitting the brake disc before the first average torque is calculated, which would lead to inaccurate calculation of the first average torque during the constant speed phase or failure to meet the calculation conditions. In other words, the piston's forward displacement can be continuously monitored. If it is determined that the piston's forward displacement is greater than the retraction displacement, the learning of the front wheel braking zero point should be abandoned.

[0050] In one embodiment, this application provides a retraction displacement. In step A1023, before acquiring the second actual torque value of the motor according to the second time interval when the piston's moving speed is the target speed and during deceleration, the method further includes: determining that when the piston's moving speed reaches the target speed, the relative displacement of the piston is not greater than the piston's retraction displacement. The retraction displacement is the displacement of the piston from its initial position back to the target position, and the relative displacement is the displacement of the piston moving in the forward direction. The initial piston position can be the piston position when the vehicle was last powered off, or it can be the piston position after a change based on the piston position when the vehicle was last powered off (e.g., accidental piston contact or vehicle movement may cause piston displacement). In other words, the piston position is the piston position at the most recent moment before executing the zero-point learning method of this braking system.

[0051] In one embodiment, after obtaining the first average torque of the aforementioned stage, the motor continues to move forward at a constant speed. At this time, the second actual torque values ​​of multiple subsequently collected points are subjected to moving average filtering, and the second average torque after moving average filtering is updated in real time. And calculate the moving average filter in real time. and The deviation.

[0052] When the torque value after moving average filtering first appears Greater than (Setting the torque difference) will set the piston position at this time as the zero point of the front wheel braking.

[0053] Based on the above Figure 1 In addition to the method flow in the previous embodiment, this application provides another method for zero-point learning of the front wheel braking system. The start signal is a front wheel learning signal, which is used to perform zero-point learning on the front wheels of the vehicle to obtain the front wheel braking zero point. The zero-point change condition includes a set rate of change of the motor speed. In step 102, based on the learning control method corresponding to the start signal, the piston is controlled by the motor to move, causing the piston to pass through the braking zero point during the movement, and the motor motion data is collected in real time during the movement, including: Step B1021: Control the piston to retract in the opposite direction to the target position via the motor. The opposite direction is the opposite of the direction in which the brake disc is located relative to the piston. Step B1022: Using the S-shaped cycloidal speed control method, the piston is pushed forward, and the motor speed data is collected in real time during the pushing process; In step 103, the changes in motor motion data are analyzed in real time. When the changes meet the zero-point change condition, the current position of the piston is taken as the braking zero point. This includes: analyzing the rate of change of motor speed. When the rate of change of motor speed is greater than the set rate of change, the current position of the piston is taken as the braking zero point of the front wheel.

[0054] In one embodiment, the rate of change of motor speed is obtained by analyzing the motor speed change data. At the rate of change of rotational speed Greater than the set rate of change When, the rate of change The current position of the corresponding piston is used as the zero point of the front wheel braking.

[0055] Based on the aforementioned zero-point learning methods for each front wheel, this application embodiment provides a front wheel zero-point verification method. In step 103, after setting the current position of the piston as the front wheel braking zero point, the method further includes: Step a: Based on the motor, control the piston to continue moving in the positive direction until the friction plate pushed by the piston clamps with the brake disc, and the motor speed is zero. Obtain the piston end position when the motor speed is zero, the first motor output torque and the first brake disc temperature when the motor speed is zero.

[0056] Step b: Obtain the first reasonable distance range corresponding to the output torque of the first motor and the temperature of the first brake disc. The first reasonable distance range is used to characterize the distance range between the friction pad and the brake disc from the theoretical zero point to the braking end point under the conditions of the output torque of the first motor, the temperature of the first brake disc, and the stiffness of the braking system. The theoretical zero point is used to characterize the piston position where the friction pad and the brake disc separate or come into contact during relative movement. The braking end point is used to characterize the piston position where the friction pad and the brake disc are clamped together and the motor speed is zero.

[0057] Step c: If the distance between the piston end position and the front wheel braking zero point meets the first reasonable distance range, then the front wheel braking zero point is determined to be a reliable front wheel braking zero point.

[0058] In one embodiment, that is, during the forward movement of the piston, after obtaining the front wheel braking zero point through braking zero-point learning, the piston continues to move forward until the friction pads pushed by the piston and the brake disc clamp together - the motor speed is zero - the piston end position. At this time, the piston end position, the output torque of the first motor and the temperature of the first brake disc are obtained. Based on the output torque of the first motor and the temperature of the first brake disc, the corresponding first reasonable distance range is obtained. The distance between the piston end position and the front wheel braking zero point is verified. If it is within the first reasonable distance range, the front wheel braking zero point is confirmed as a reliable front wheel braking zero point; otherwise, the front wheel braking zero point learned this time is discarded, and the previous front wheel braking zero point is used.

[0059] In one embodiment, because the output torque of the first motor, the temperature of the first brake disc, and the stiffness of the braking system affect the true zero point of contact and the clamping position between the friction pads and the brake disc, a first reasonable range corresponding to the stiffness of the braking system at different brake disc temperatures can be determined based on empirical data. Thus, a corresponding first reasonable range can be selected based on the output torque of the first motor and the temperature of the first brake disc. The obtained front wheel braking zero point can be judged using this first reasonable range. If the distance between the obtained front wheel braking zero point and the piston end position is within the first reasonable range, then the front wheel braking zero point is reliable; otherwise, it is unreliable. For example, if the output torque of the first motor is 0.4 Nm and the temperature of the first brake disc is 30°C, the distance between the front wheel braking zero point and the piston end position is 0.1 mm, and the first reasonable range is 0.09-0.11, then the front wheel braking zero point is reliable.

[0060] Based on the above methods for learning the zero point of each front wheel, this application provides a method for learning the zero point of a braking system. Before the piston is retracted to the target position by controlling the motor, the method further includes: clamping the friction pads to the brake disc by the vehicle's rear wheel controller, or locking the lock-up valve. This prevents the vehicle from moving and ensures the accuracy of the learned front wheel braking zero point.

[0061] Based on the above methods for learning the zero point of each front wheel, this application provides a method for learning the zero point of the front wheels of a braking system, such as... Figure 5 As shown, it includes: Step 501: Receive the start signal for brake pressure build-up zero-point learning. The start signal is generated when the vehicle is powered on.

[0062] In one embodiment, considering that the brake disc temperature may be very high when the vehicle is powered off, affecting the accuracy of the front wheel brake zero-point learning, the zero-point learning of the braking system is performed when the vehicle is powered on in this embodiment.

[0063] Step 502: The start signal is a start signal for the front wheels, which can be the left front wheel and / or the right front wheel. The rear wheel controller of the vehicle clamps the friction pads to the brake disc or locks the locking valve.

[0064] In one embodiment, after the vehicle is started, the driver presses the brake pedal, receives the start signal from the front wheels, and then clamps the brake discs or locks them via two controllers on the rear wheels.

[0065] Step 503: Control the piston to retract in the opposite direction to the target position via the motor. The opposite direction is the opposite of the direction in which the brake disc is located relative to the piston.

[0066] In one embodiment, for the front wheel ECU, during zero-point learning, the friction pads and brake disc may be in either stage (contact stage or gap stage). Therefore, to improve the reliability of zero-point learning, sufficient learning space needs to be provided, the control piston should be moved away from the brake disc, and the motor should stop rotating after reaching the target position.

[0067] Step 504: Monitor the motor output torque and piston retraction displacement during the retraction process. If the motor output torque significantly exceeds the output torque required for retraction, or the piston retraction displacement far exceeds the planned retraction displacement, terminate the current ignition cycle braking zero-position learning. If the motor output torque does not exceed the output torque required for retraction and the piston retraction displacement does not exceed the planned retraction displacement, proceed to step 505.

[0068] In one embodiment, the reason for terminating the braking zero-point learning of the current ignition cycle when the motor's output torque significantly exceeds the output torque required for retraction, or when the piston retraction displacement far exceeds the planned retraction displacement, is that, under normal circumstances, the motor retraction is unloaded or has a very small load, so the motor output torque during retraction will also be very small. However, if the motor's output torque significantly exceeds the output torque required for retraction, or the piston retraction displacement far exceeds the planned retraction displacement, it may be that the piston malfunctions during retraction. Under abnormal conditions, the accuracy of the front wheel braking zero point learned is questionable, that is, unreliable.

[0069] Step 505: Using the S-shaped cycloidal speed control method, the piston is pushed forward from the target position. When the piston's moving speed is the target speed, the first actual torque value of the motor is collected according to the first time interval to obtain multiple first actual torque values, and the first average torque of the multiple first actual torque values ​​is calculated. The target speed is the moving speed of the piston in the uniform speed stage under the control of the S-shaped cycloidal speed control method.

[0070] In one embodiment, the maximum output torque of the motor in the S-shaped cycloidal speed control method is limited to Tthd.

[0071] In one embodiment, it is important to ensure that the positive displacement-stroke of the piston throughout the entire process from forward movement to obtaining the first average torque does not exceed the piston retraction displacement, so as to avoid the friction plate and brake disc contacting before the first average torque is fully calculated, which would lead to inaccurate calculation of the first average torque during the constant speed phase.

[0072] Step 506: When the piston is moving at the target speed and is in the process of deceleration, perform a sliding average filter on the second actual torque value of the motor collected in real time according to the second time interval to obtain the second average torque.

[0073] Step 507: Calculate the actual torque difference between the second average torque and the first average torque in real time. When the actual torque difference is greater than the set torque difference, take the current position of the piston as the zero point of the front wheel braking.

[0074] Step 508: Using the S-shaped cycloidal speed control method, the piston is pushed forward, and the motor speed data is collected in real time during the pushing process; the motor speed change rate is analyzed, and when the motor speed change rate is greater than the set change rate, the current position of the piston is taken as the zero point of the front wheel braking.

[0075] Step 509: Based on the motor, control the piston to continue moving in the positive direction until the friction plate pushed by the piston clamps with the brake disc, and the motor speed is zero. Obtain the piston end position when the motor speed is zero, the first motor output torque and the first brake disc temperature when the motor speed is zero.

[0076] Step 510: Obtain the first reasonable distance range corresponding to the output torque of the first motor and the temperature of the first brake disc. If the distance between the piston end position and the zero point of the front wheel brake meets the first reasonable distance range, then determine the zero point of the front wheel brake as a reliable zero point of the front wheel brake.

[0077] In one embodiment, the electrically controlled piston moves forward, pushing the friction pad into contact with the brake disc and clamping it. During this process, the maximum output torque of the motor is limited to Tthd. As the motor-controlled piston moves forward, the load torque on the motor increases after the friction pad contacts the brake disc, causing the motor speed to gradually decrease until it reaches zero. When the motor output torque reaches Tthd, the motor speed is 0. The distance from contact to this point where the motor speed is zero is calculated, and it is confirmed whether this distance conforms to the first reasonable distance range corresponding to the first motor output torque and the first brake disc temperature. If it does, the zero-point of the front wheel brake learned in the previous step is confirmed to be reliable. Setting the first reasonable distance range requires consideration of the braking system stiffness, i.e., the relationship between the motor output torque and the piston stroke, as well as the influence of the first brake disc temperature and static friction torque.

[0078] It should be noted that the above method is not unique; for example, steps 507 and 508 can be performed simultaneously.

[0079] Based on the above Figure 1 The method flow in this application provides a zero-point learning method for a rear wheel braking system. The start signal is a rear wheel learning signal, which is used to perform zero-point learning on the rear wheels of the vehicle to obtain the rear wheel braking zero point. The zero-point change condition includes the minimum value of the motor output torque. In step 102, based on the learning control method corresponding to the start signal, the piston is controlled by the motor to move, causing the piston to pass through the braking zero point during the movement, and the motor motion data is collected in real time during the movement, including: Step C1021: Control the motor to be in a zero-speed closed-loop control state or control the motor to creep in the clamping direction to release the pawl.

[0080] Step C1022: When the pawl is successfully released, the motor stops churning, and the piston is stationary, record the original position of the piston.

[0081] Step C1023: Control the piston to retract in the reverse direction by the motor, and collect the third actual torque value of the motor in real time according to the third time interval during the reverse retraction process. The reverse direction is the opposite direction of the brake disc relative to the piston.

[0082] In step 103, the changes in motor motion data are analyzed in real time. When the changes meet the zero-point change condition, the current position of the piston is taken as the braking zero point. This includes: smoothing the third actual torque value of the motor collected in real time according to the third time interval until the minimum value of the motor's output torque is obtained, and taking the current position of the piston as the rear wheel braking zero point.

[0083] In one embodiment, when the vehicle is powered off, the pawl locks the parking gear. At this time, the friction pads clamp the brake disc, and the braking torque generated by the clamping force prevents the vehicle from moving. The friction pads and brake discs of the rear wheels are also relatively stationary.

[0084] In one embodiment, the motor can be controlled to creep in the clamping direction, so that the brake disc and friction pad are actually clamped, which can ensure the accuracy of the obtained original piston position.

[0085] In one embodiment, a pawl release signal is given, during which the motor is controlled at zero speed, and in order to maintain a constant clamping force between the friction plate and the brake disc, the output torque value of the motor jumps to 163mNm.

[0086] In one embodiment, after the vehicle is started and powered on, the driver will press the brake pedal. The EMB domain controller will issue a parking release command to the rear wheel EMB actuators, completing the brake zero-point learning for the rear wheels during static parking release. This minimizes the impact of brake zero-point learning on the timeliness of the driver's braking requests. Upon receiving the braking signal, the two controllers on the front wheels will clamp the brake discs or lock them using the lock-up valves.

[0087] In one embodiment, when the vehicle is powered on, the rear axle wheel-side controller receives a parking release request from the EMB central processor. Based on the motor, it controls the motor to zero-speed closed-loop control so that after the pawl is released, the motor output torque controls the piston position to remain unchanged so that the clamping force can remain unchanged, thereby maintaining the relative stillness between the friction plate and the brake disc. At this time, the motor output torque Trz when the motor speed is zero and the original piston position P1 are recorded.

[0088] In one embodiment, the pawl is then controlled to release the parking gear. Once released, since the brake disc and friction pads form an elastic system, the rebound force of the brake disc on the friction pads is overcome by the zero-speed controlled motor to maintain a constant clamping force. Finally, the motor's reverse speed control is set, causing the piston to move in the opposite direction from its original position P1. This reverse movement is the direction away from the brake disc. During this reverse movement, the zero point of pressure build-up in the rear wheel braking system is obtained. This zero point of pressure build-up in the rear wheel braking system corresponds to the point where the motor output torque is at its minimum.

[0089] The mechanical motion equations are satisfied during the reverse speed control of the rear wheel of the motor, as shown below:

[0090] In the formula, J is the system's moment of inertia, and ω is the motor speed. The derivative of the rotational speed, For the motor output torque, B is the torque of the elastic system, which is in the same direction as the motor's reverse motion. B is the damping coefficient, and the damping torque is in the opposite direction to the motor's motion. When the motor's speed is controlled in the negative direction (piston moves in the opposite direction), the elastic system is released, and its rebound torque gradually decreases until it reaches zero at the separation surface of the friction plate and brake disc. Therefore, the motor's output torque gradually transitions from a positive value to zero, then becomes a negative output torque and gradually increases to a stable trend. When the separation surface is reached, the speed has reached a steady state. =0, The value is 0. Therefore, the motor's output torque is also in a stable state after the separation surface. Thus, the zero-pressure point of the rear wheel braking system is the point corresponding to the minimum value of the motor's output torque.

[0091] In one embodiment, to find the piston position at the minimum value of the motor output torque, the third actual torque value of the motor, collected at a third time interval, first needs to be smoothed. This smoothing can employ techniques such as Savitzky-Golay filtering or moving average. When the speed stabilizes and the motor output torque hardly changes, the piston position P2 is recorded and set as the zero point of the rear wheel braking. ΔP = P2 - P1, where ΔP is the distance between the zero point of the rear wheel braking and the original piston position.

[0092] In one embodiment, before controlling the motor to be in a zero-speed closed-loop control state and releasing the pawl in step C1021, the method further includes: clamping the friction pads to the brake disc via the vehicle's front wheel controller, or locking the lock-up valve. This prevents vehicle movement and ensures the accuracy of the learned front wheel braking zero point.

[0093] Based on the above-described zero-point learning method for the rear wheel, this application embodiment provides a method for verifying the zero-point of rear wheel braking. In step 103, after setting the current position as the braking zero point, the method further includes: Obtain the second reasonable distance range corresponding to the current output torque of the second motor and the temperature of the second brake disc. The output torque of the second motor and the temperature of the second brake disc are recorded when the pawl is successfully released and the piston is in a stationary state. The second reasonable distance range is used to characterize the distance range from the theoretical zero point to the braking endpoint between the friction pad and the brake disc under the conditions of the output torque of the second motor, the temperature of the second brake disc, and the stiffness of the braking system. The theoretical zero point is used to characterize the piston position where the friction pad and the brake disc separate or come into contact during relative movement. The braking endpoint is used to characterize the piston position where the friction pad and the brake disc are clamped together and the motor speed is zero. If the distance between the initial position and the zero point of the rear wheel braking meets the second reasonable distance range, then the zero point of the rear wheel braking is designated as a reliable zero point of the rear wheel braking.

[0094] In one embodiment, when the motor's output torque is Trz (maximum limited output torque), the temperature of the second brake disc is recorded, the second reasonable distance range corresponding to the second brake disc temperature is obtained, and it is determined whether ΔP is within the second reasonable distance range. If so, it is confirmed that the learned rear wheel braking zero point is reliable.

[0095] Here, setting this second reasonable distance range requires consideration of the braking system stiffness, i.e., the relationship between the motor output torque and the piston displacement-stroke, while also taking into account the influence of brake disc temperature and static friction torque.

[0096] Based on the above-described zero-point learning method for the rear wheel, this application embodiment provides another method for verifying the zero-point of rear wheel braking. In step 103, after setting the current position as the braking zero point, the method further includes: Step ①: Obtain the historical brake disc temperature and historical zero point. The historical brake disc temperature is the temperature of the brake disc when the historical zero point is obtained.

[0097] Step 2: Obtain the temperature difference between the second brake disc temperature and the historical brake disc temperature, as well as the zero-point difference between the rear wheel braking zero point and the historical zero point.

[0098] Step 3: Analyze whether the relationship between the temperature difference and the zero point difference conforms to the set temperature zero point relationship. If so, determine that the braking zero point is a reliable rear wheel braking zero point.

[0099] In one embodiment, the historical zero point and historical brake disc temperature recorded when the vehicle was last powered off are read from the EEPROM, and the second brake disc temperature at this time is obtained from the disc temperature estimation module.

[0100] In other words, each time power is turned off, the ECU needs to store the current rear wheel braking zero point, the second brake disc temperature, and its verification data in the EEPROM to ensure data integrity and accuracy. It should be noted that each time power is turned off, the ECU can also store the current front wheel braking zero point, the first brake disc temperature, and its verification data in the EEPROM to ensure data integrity and accuracy.

[0101] In one embodiment, the historical brake disc temperature and historical zero point at the time of pawl locking during the previous ignition cycle are read from the non-volatile memory when the vehicle is powered on, and the current second brake disc temperature and rear wheel brake zero point at the time of ignition are obtained. The temperature difference between the second brake disc temperature and the historical brake disc temperature, as well as the zero point difference between the rear wheel brake zero point and the historical zero point, are obtained. The relationship between the temperature difference and the zero point difference is analyzed to see if it conforms to a set temperature zero point relationship. If so, the brake zero point is determined to be a reliable rear wheel brake zero point. The actual zero point may change due to variations in brake disc temperature; therefore, different brake disc temperatures may result in different actual zero point positions. However, the temperature difference between two brake disc temperatures and the zero point difference between these two actual zero points have a set temperature zero point relationship. This set temperature zero point relationship can be used to determine whether the rear wheel brake zero point is reliable.

[0102] In one embodiment, if the obtained rear wheel braking zero point conforms to at least one of the two verification methods for rear wheel braking zero points, the rear wheel braking zero point can be considered reliable.

[0103] Based on the aforementioned zero-point learning method for the rear wheel braking system, and two methods for verifying the zero-point of rear wheel braking, this application embodiment provides a flowchart of a zero-point learning method for the rear wheel braking system, as follows: Figure 6 As shown, it includes: Step 601: Receive the start signal, which is generated when the vehicle is powered on.

[0104] In one embodiment, considering that the brake disc temperature may be very high when the vehicle is powered off, affecting the accuracy of the rear wheel brake zero-point learning, the zero-point learning of the braking system is performed when the vehicle is powered on in this embodiment.

[0105] Step 602: The start signal is a start signal for the rear wheels, which can be the left rear wheel and / or the right rear wheel. The front wheel controller of the vehicle clamps the friction pads to the brake disc or locks the locking valve.

[0106] In one embodiment, after the vehicle is started, the driver presses the brake pedal, receives a start signal from the rear wheels, and then clamps the brake discs or locks them via two controllers on the front wheels.

[0107] Step 603: Control the motor to be in a zero-speed closed-loop control state or control the motor to creep in the clamping direction to release the pawl.

[0108] Step 604: When the pawl is successfully released, the motor stops creeping, and the piston is stationary, record the original position of the piston, the output torque of the second motor, and the temperature of the second brake disc.

[0109] Step 605: Control the piston to retract in the reverse direction via the motor, and collect the third actual torque value of the motor in real time according to the third time interval during the reverse retraction process. The reverse direction is the opposite direction of the brake disc relative to the piston.

[0110] Step 606: Smooth the third actual torque value of the motor collected in real time according to the third time interval until the minimum value of the output torque of the motor is obtained, and set the current position of the piston as the zero point of the rear wheel braking.

[0111] Step 607: Obtain the second reasonable distance range corresponding to the output torque of the second motor and the temperature of the second brake disc. If the distance between the original piston position and the zero point of the rear wheel brake meets the second reasonable distance range, then the zero point of the rear wheel brake is determined to be a reliable zero point. And / or obtain the historical brake disc temperature and historical zero point, obtain the temperature difference between the second brake disc temperature and the historical brake disc temperature, and the zero point difference between the zero point of the rear wheel brake and the historical zero point; analyze whether the relationship between the temperature difference and the zero point difference conforms to the set temperature-zero point relationship. If so, then the zero point of the rear wheel brake is determined to be a reliable zero point. If the distance between the original piston position and the zero point of the rear wheel brake does not meet the second reasonable distance range, and the relationship between the temperature difference and the zero point difference does not conform to the set temperature-zero point relationship, then the zero point of the rear wheel brake is determined to be an unreliable zero point, the zero point of the rear wheel brake learned this time is discarded, and the previous zero point of the rear wheel brake is used instead.

[0112] In one embodiment, such as Figure 7 The diagram shown is a schematic representation of the parameter changes of various components during an active process according to an embodiment of this application, including: motor output torque, actual clamping force between the friction plate and the brake disc, motor speed, piston position, zero-point recognition success mark and zero-point position, with the horizontal axis representing time.

[0113] The above method can learn and update the zero point of the braking system every time the vehicle is powered on and off. Learning the zero point of the braking system when the front and rear wheels are powered on and off reduces the time impact on the driver's braking demand response. The method is simple and reliable, increases the reliability check of braking zero point learning, reduces noise in the braking zero point learning process, and optimizes NVH (noise, vibration, and harshness).

[0114] Based on the same concept, embodiments of this application provide a zero-point learning device for a braking system. Figure 8 A schematic diagram of a zero-point learning device for a braking system provided in an embodiment of this application is shown below. Figure 8 The following are examples: Transceiver unit 801 is used to receive a start signal, which is generated when the vehicle is powered on or powered off. The first processing unit 802 is used to control the piston movement through the motor based on the learning control method corresponding to the start signal, so that the piston passes through the braking zero point during the movement, and to collect the motor movement data of the motor in real time during the movement. The second processing unit 803 is used to analyze the changes in the motor motion data in real time. When the changes meet the zero-point change condition, the current position of the piston is taken as the braking zero point. The zero-point change condition is obtained based on the empirical data generated by the motor during the braking process.

[0115] Optionally, the start signal is a front wheel learning signal, which is used to learn the zero point of the front wheels of the vehicle to obtain the front wheel braking zero point; The first processing unit 802 is specifically used for, The piston is controlled by the motor to retract in the opposite direction to the target position, where the reverse direction is the opposite direction of the brake disc relative to the direction in which the piston is located; Using an S-shaped cycloidal speed control method, the piston is pushed forward from the target position. When the piston's moving speed is the target speed, the first actual torque value of the motor is collected at a first time interval to obtain multiple first actual torque values. The first average torque of the multiple first actual torque values ​​is calculated. The target speed is the moving speed of the piston in the uniform speed stage under the control of the S-shaped cycloidal speed control method. While the piston is moving at the target speed and is decelerating, the second actual torque value of the motor, which is collected in real time according to the second time interval, is subjected to sliding average filtering to obtain the second average torque. The zero-point change condition includes the set torque difference of the motor. The second processing unit is specifically used to calculate the actual torque difference between the second average torque and the first average torque in real time. When the actual torque difference is greater than the set torque difference, the current position of the piston is taken as the zero point of the front wheel braking.

[0116] Optionally, the start signal is a front wheel learning signal, which is used to learn the zero point of the vehicle's front wheels to obtain the front wheel braking zero point; the zero point change condition includes a set rate of change of the motor's rotational speed. The first processing unit 802 is specifically used for, The piston is controlled by the motor to retract in the opposite direction to the target position, where the reverse direction is the opposite direction of the brake disc relative to the direction in which the piston is located; An S-shaped cycloidal speed control method is used to propel the piston in the forward direction, and the rotational speed data of the motor is collected in real time during the propulsion process; The second processing unit 803 is specifically used for, Analyze the rate of change of the motor's speed. When the rate of change of the motor's speed is greater than a set rate of change, take the current position of the piston as the zero point of the front wheel braking.

[0117] Optionally, the second processing unit 803 is further configured to, Based on the motor, the piston is controlled to continue moving in the positive direction until the friction plate pushed by the piston clamps the brake disc, and the speed of the motor is zero. The piston end position when the speed of the motor is zero, the first motor output torque and the first brake disc temperature when the speed of the motor is zero are obtained. Obtain a first reasonable distance range corresponding to the output torque of the first motor and the temperature of the first brake disc. The first reasonable distance range is used to characterize the distance range between the friction pad and the brake disc from the theoretical zero point to the braking end point under the conditions of the output torque of the first motor, the temperature of the first brake disc, and the stiffness of the braking system. The theoretical zero point is used to characterize the piston position where the friction pad and the brake disc separate or come into contact during relative movement. The braking end point is used to characterize the piston position where the friction pad and the brake disc are clamped together and the speed of the motor is zero. If the distance between the piston end point and the front wheel braking zero point meets the first reasonable distance range, then the front wheel braking zero point is determined to be a reliable front wheel braking zero point.

[0118] Optionally, the first processing unit 802 is further configured to, The friction pads are clamped to the brake disc by the rear wheel controller of the vehicle, or the lock-up valve is locked.

[0119] Optionally, the start signal is a rear wheel learning signal, which is used to perform zero-point learning on the rear wheels of the vehicle to obtain the rear wheel braking zero point; the zero-point change condition includes the minimum value of the motor output torque; The first processing unit 802 is specifically used to control the motor to be in a zero-speed closed-loop control state or to control the motor to creep in the clamping direction and release the pawl; When the pawl is successfully released, the motor stops creeping, and the piston is stationary, the original position of the piston is recorded; the piston is controlled by the motor to retract in the opposite direction, and the third actual torque value of the motor is collected in real time according to the third time interval during the retraction process, where the opposite direction is the opposite direction of the brake disc relative to the piston. The second processing unit 803 is specifically used for, The third actual torque value of the motor, which is collected in real time according to the third time interval, is smoothed until the minimum value of the output torque of the motor is obtained, and the current position of the piston is set as the zero point of the rear wheel braking.

[0120] Optionally, the second processing unit 803 is further configured to, A second reasonable distance range corresponding to the output torque of the second motor and the temperature of the second brake disc is obtained. The output torque of the second motor and the temperature of the second brake disc are recorded when the pawl is successfully released and the piston is in a stationary state. The second reasonable distance range is used to characterize the distance range between the friction pad and the brake disc from the theoretical zero point to the braking endpoint under the conditions of the output torque of the second motor, the temperature of the second brake disc, and the stiffness of the braking system. The theoretical zero point is used to characterize the piston position where the friction pad and the brake disc separate or come into contact during relative movement. The braking endpoint is used to characterize the piston position where the friction pad and the brake disc are clamped together and the speed of the motor is zero. If the distance between the original position of the piston and the zero point of the rear wheel brake meets the second reasonable distance range, then the zero point of the rear wheel brake is a reliable zero point of the rear wheel brake.

[0121] Optionally, the second processing unit 803 is further configured to, Obtain historical brake disc temperature and historical zero point, wherein the historical brake disc temperature is the temperature of the brake disc at the time when the historical zero point is obtained; The temperature difference between the second brake disc temperature and the historical brake disc temperature, and the zero-point difference between the rear wheel braking zero point and the historical zero point are obtained; Analyze whether the relationship between the temperature difference and the zero point difference conforms to the set temperature zero point relationship. If so, determine that the rear wheel braking zero point is a reliable rear wheel braking zero point.

[0122] Optionally, the first processing unit 802 is further configured to, The friction pads are clamped to the brake disc by the front wheel controller of the vehicle.

[0123] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0124] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to this application. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0125] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0126] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0127] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A zero-point learning method for a braking system, characterized in that, The method includes: The start signal for learning the brake pressure build-up zero point is obtained when the vehicle is powered on or off. Based on the learning control method corresponding to the start signal, the piston is controlled by the motor to move, so that the piston passes through the braking zero point during the movement, and the motor motion data of the motor is collected in real time during the movement. The changes in the motor motion data are analyzed in real time. When the changes meet the zero-point change condition, the current position of the piston is taken as the braking zero point. The zero-point change condition is obtained based on the empirical data generated by the motor during the braking process.

2. The zero-point learning method as described in claim 1, characterized in that, The start signal is a front wheel learning signal, which is used to learn the zero point of the vehicle's front wheels to obtain the front wheel braking zero point. The learning control method based on the start signal controls the piston movement via a motor, causing the piston to pass through the braking zero point during the movement, and collects the motor motion data in real time during the movement, including: The piston is controlled by the motor to retract in the opposite direction to the target position, where the reverse direction is the opposite direction of the brake disc relative to the direction in which the piston is located; Using an S-shaped cycloidal speed control method, the piston is pushed forward from the target position. When the piston's moving speed is the target speed, the first actual torque value of the motor is collected at a first time interval to obtain multiple first actual torque values. The first average torque of the multiple first actual torque values ​​is calculated. The target speed is the moving speed of the piston in the uniform speed stage under the control of the S-shaped cycloidal speed control method. While the piston is moving at the target speed and is decelerating, the second actual torque value of the motor, which is collected in real time according to the second time interval, is subjected to sliding average filtering to obtain the second average torque. The zero-point change condition includes the set torque difference of the motor. The real-time analysis of the changes in the motor motion data, when the changes meet the zero-point change condition, uses the current position of the piston as the braking zero point, including: The actual torque difference between the second average torque and the first average torque is calculated in real time. When the actual torque difference is greater than the set torque difference, the current position of the piston is taken as the zero point of the front wheel braking.

3. The zero-point learning method as described in claim 1, characterized in that, The start signal is a front wheel learning signal, which is used to learn the zero point of the vehicle's front wheels to obtain the front wheel braking zero point; the zero point change condition includes the set rate of change of the motor's speed; The learning control method based on the start signal controls the piston movement via a motor, causing the piston to pass through the braking zero point during the movement, and collects the motor motion data in real time during the movement, including: The piston is controlled by the motor to retract in the opposite direction to the target position, where the reverse direction is the opposite direction of the brake disc relative to the direction in which the piston is located; An S-shaped cycloidal speed control method is used to propel the piston in the forward direction, and the rotational speed data of the motor is collected in real time during the propulsion process; The real-time analysis of changes in the motor motion data, and when the changes meet the zero-point change condition, taking the current position of the piston as the braking zero point, includes: Analyze the rate of change of the motor's speed. When the rate of change of the motor's speed is greater than a set rate of change, take the current position of the piston as the zero point of the front wheel braking.

4. The zero-point learning method as described in claim 2 or 3, characterized in that, After setting the current position of the piston as the zero point of the front wheel braking, the method further includes: Based on the motor, the piston is controlled to continue moving in the positive direction until the friction plate pushed by the piston clamps the brake disc, and the speed of the motor is zero. The piston end position when the speed of the motor is zero, the first motor output torque and the first brake disc temperature when the speed of the motor is zero are obtained. Obtain a first reasonable distance range corresponding to the output torque of the first motor and the temperature of the first brake disc. The first reasonable distance range is used to characterize the distance range between the friction pad and the brake disc from the theoretical zero point to the braking end point under the conditions of the output torque of the first motor, the temperature of the first brake disc, and the stiffness of the braking system. The theoretical zero point is used to characterize the piston position where the friction pad and the brake disc separate or come into contact during relative movement. The braking end point is used to characterize the piston position where the friction pad and the brake disc are clamped together and the speed of the motor is zero. If the distance between the piston end point and the front wheel braking zero point meets the first reasonable distance range, then the front wheel braking zero point is determined to be a reliable front wheel braking zero point.

5. The zero-point learning method as described in claim 2 or 3, characterized in that, Before controlling the piston to retract to the target position via the motor, the method further includes: The friction pads are clamped to the brake disc by the vehicle's rear wheel controller, or the lock-up valve is locked.

6. The zero-point learning method as described in claim 1, characterized in that, The start signal is a rear wheel learning signal, which is used to perform zero-point learning on the rear wheels of the vehicle to obtain the rear wheel braking zero point; the zero-point change condition includes the minimum value of the motor output torque; The learning control method based on the start signal controls the piston movement via a motor, causing the piston to pass through the braking zero point during the movement, and collects the motor motion data in real time during the movement, including: Control the motor to be in a zero-speed closed-loop control state or control the motor to creep in the clamping direction to release the pawl; When the pawl is successfully released, the motor stops creeping, and the piston is stationary, the original position of the piston is recorded; the piston is controlled by the motor to retract in the opposite direction, and the third actual torque value of the motor is collected in real time according to the third time interval during the retraction process, where the opposite direction is the opposite direction of the brake disc relative to the piston. The real-time analysis of changes in the motor motion data, and when the changes meet the zero-point change condition, taking the current position of the piston as the braking zero point, includes: The third actual torque value of the motor, which is collected in real time according to the third time interval, is smoothed until the minimum value of the output torque of the motor is obtained, and the current position of the piston is set as the zero point of the rear wheel braking.

7. The zero-point learning method as described in claim 6, characterized in that, After setting the current position of the piston as the zero point of the rear wheel braking, the method further includes: A second reasonable distance range corresponding to the output torque of the second motor and the temperature of the second brake disc is obtained. The output torque of the second motor and the temperature of the second brake disc are recorded when the pawl is successfully released and the piston is in a stationary state. The second reasonable distance range is used to characterize the distance range between the friction pad and the brake disc from the theoretical zero point to the braking endpoint under the conditions of the output torque of the second motor, the temperature of the second brake disc, and the stiffness of the braking system. The theoretical zero point is used to characterize the piston position where the friction pad and the brake disc separate or come into contact during relative movement. The braking endpoint is used to characterize the piston position where the friction pad and the brake disc are clamped together and the speed of the motor is zero. If the distance between the original position of the piston and the zero point of the rear wheel brake meets the second reasonable distance range, then the zero point of the rear wheel brake is a reliable zero point of the rear wheel brake.

8. The zero-point learning method as described in claim 6, characterized in that, After determining the current position of the piston as the zero point of the rear wheel braking, the method further includes: Obtain historical brake disc temperature and historical zero point, wherein the historical brake disc temperature is the temperature of the brake disc at the time when the historical zero point is obtained; The temperature difference between the second brake disc temperature and the historical brake disc temperature, as well as the zero-point difference between the rear wheel braking zero point and the historical zero point, are obtained. Analyze whether the relationship between the temperature difference and the zero point difference conforms to the set temperature zero point relationship. If so, determine that the rear wheel braking zero point is a reliable rear wheel braking zero point.

9. The zero-point learning method as described in claim 6, characterized in that, Before controlling the motor to be in a zero-speed closed-loop control state or a peristaltic control state in the clamping direction, and before releasing the pawl, the method further includes: The friction pads are clamped to the brake disc by the vehicle's front wheel controller.

10. A zero-point learning device for a braking system, characterized in that, The device includes: The transceiver unit is used to acquire the start signal for brake pressure build-up zero-point learning, which is generated when the vehicle is powered on or off. The first processing unit is used to control the piston movement by a motor based on the learning control method corresponding to the start signal, so that the piston passes through the braking zero point during the movement, and to collect the motor movement data of the motor in real time during the movement. The second processing unit is used to analyze the changes in the motor motion data in real time. When the changes meet the zero-point change condition, the current position of the piston is taken as the braking zero point. The zero-point change condition is obtained based on the empirical data generated by the motor during the braking process.

11. A vehicle, characterized in that, The vehicle performs the method as described in any one of claims 1 to 9.

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