A method and device for zero point learning of a brake system

Abstract

The embodiment of the application provides a brake system zero point learning method and device, relates to the motor control technical field, and comprises the following steps: obtaining the starting of brake pressure building zero point learning, the starting signal of brake pressure building zero point learning is generated when the vehicle is powered on or powered off; based on the learning control method corresponding to the starting signal, the movement of the motor control piston is controlled, the piston passes through the brake zero point in the movement process, and the motor movement data of the motor is collected in real time in the movement process; the change condition of the motor movement data is analyzed in real time, when the change condition meets the zero point change condition, the current position of the piston is taken as the brake zero point, and the zero point change condition is obtained according to the experience data generated by the motor in the braking process. The foregoing method can flexibly and conveniently learn and correct the zero point, and improves driving safety.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of motor control, in particular to a zero point learning method and device of a brake system. BACKGROUND

[0002] EMB (Electro-Mechanical Brake) is an advanced automotive braking system that abandons traditional hydraulic or pneumatic transmission methods and instead uses electric motors to directly drive brake calipers or brake 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 to ensure driving safety. For general vehicles, by controlling the output torque and rotation of the four wheel edge motors, the transmission system pushes the friction plate to clamp or release the wheel edge brake disc, thereby controlling the wheel end deceleration and slip rate. The entire braking process can be divided into three stages: eliminating the gap between the friction plate and the brake disc, the friction plate and the brake disc begin to clamp to the stage of generating real-time braking torque, and the motor retreats to generate a gap between the friction plate and the brake disc. In order to distinguish between these three stages and implement different control strategies in different stages, and to achieve precise braking effect, it is necessary to accurately identify the position of the friction plate and the brake disc contact surface, i.e. the zero point of the brake system. However, due to the influence of friction plate wear and environmental factors such as disc temperature, the brake zero point is changing.

[0003] In related technologies, in order to solve the problem of zero point change, a zero point correction device is connected to the vehicle to correct the zero point of the vehicle when the vehicle is not in use. This method is complex to operate, and cannot guarantee that the zero point of the vehicle during the interval between two zero point corrections is always accurate when the vehicle is in use, which is not safe.

[0004] Therefore, there is an urgent need for a brake system zero point learning method and device that can flexibly and conveniently learn and correct the zero point, and improve driving safety. SUMMARY

[0005] The embodiments of the present application provide a brake system zero point learning method and device that can flexibly and conveniently learn and correct the zero point, and improve driving safety.

[0006] In a first aspect, the embodiments of the present application provide a brake system zero point learning method, which comprises:

[0007] receiving a start signal, the start signal being generated when the vehicle is powered on or powered off;

[0008] The learning control method corresponding to the starting signal is used to control the movement of the piston by the motor, so that the piston passes through the brake zero point during the movement, and motor movement data of the motor is collected in real time during the movement;

[0009] The change of the motor movement data is analyzed in real time, and when the change meets a zero point change condition, a current position of the piston is taken as the brake zero point, the zero point change condition being obtained according to experience data generated by the motor during braking.

[0010] In a second aspect, the embodiments of the present application provide a zero point learning device of a brake system, which comprises:

[0011] A starting signal for brake pressure building zero point learning is obtained, the starting signal being generated when the vehicle is powered on or powered off;

[0012] A first processing unit is configured to control the movement of the piston by the motor based on a learning control method corresponding to the starting signal, so that the piston passes through the brake zero point during the movement, and motor movement data of the motor is collected in real time during the movement;

[0013] A second processing unit is configured to analyze the change of the motor movement data in real time, and when the change meets a zero point change condition, a current position of the piston is taken as the brake zero point, the zero point change condition being obtained according to experience data generated by the motor during braking.

[0014] Optionally, the starting signal is a front wheel learning signal, the front wheel learning signal being used for zero point learning of a front wheel of the vehicle to obtain a front wheel brake zero point;

[0015] The first processing unit is specifically configured to,

[0016] The piston is controlled to retreat to a target position in a reverse direction by the motor, the reverse direction being opposite to a direction of the brake disc relative to the piston;

[0017] The piston is pushed forward from the target position by an S-shaped cycloid speed control method, when the moving speed of the piston is a target speed, a first actual torque value of the motor is collected according to a first time interval, a plurality of first actual torque values are obtained, and a first average torque of the plurality of first actual torque values is calculated, the target speed being a moving speed of the piston in a uniform speed stage controlled by the S-shaped cycloid speed control method;

[0018] when the piston is moving at the target speed and in the deceleration process, performing a sliding average filtering on the second actual torque value of the motor collected in real time according to a second time interval to obtain a second average torque;

[0019] The zero point change condition includes a set torque difference value of the motor, and the second processing unit is specifically configured to: calculate an actual torque difference value between the second average torque and the first average torque in real time, and take the current position of the piston as the front wheel brake zero point when the actual torque difference value is greater than the set torque difference value.

[0020] Optionally, the start signal is a front wheel learning signal, the front wheel learning signal is used for zero point learning of the front wheel of the vehicle to obtain a front wheel brake zero point, and the zero point change condition includes a set change rate of the motor speed;

[0021] The first processing unit is specifically configured to:

[0022] The piston is controlled to retreat to a target position in a reverse direction by the motor, the reverse direction being opposite to the direction of the brake disc relative to the piston;

[0023] An S-shaped cycloid speed control method is adopted to push the piston in a forward direction, and the motor speed data is collected in real time during the pushing process;

[0024] The second processing unit is specifically configured to:

[0025] The change rate of the motor speed is analyzed, and the current position of the piston is taken as the front wheel brake zero point when the change rate of the motor speed is greater than a set change rate.

[0026] Optionally, the second processing unit is further configured to:

[0027] The piston is controlled to continue moving in the forward direction based on the motor until the friction plate pushed by the piston is clamped with the brake disc and the motor speed is zero, and an end position of the piston when the motor speed is zero, a first motor output torque when the motor speed is zero and a first brake disc temperature are obtained;

[0028] A first reasonable distance range corresponding to the first motor output torque and the first brake disc temperature is obtained, the first reasonable distance range being used to represent a distance range of the friction plate and the brake disc from a theoretical zero point to a brake end point under the conditions of the first motor output torque, the first brake disc temperature and brake system stiffness, the theoretical zero point being used to represent a piston position at which the friction plate and the brake disc separate or contact each other during relative movement, and the brake end point being used to represent a piston position at which the friction plate and the brake disc are clamped with each other and the motor speed is zero;

[0029] If the distance between the piston end position and the front wheel brake zero point meets the first reasonable distance range, the front wheel brake zero point is determined as a reliable front wheel brake zero point.

[0030] Optionally, the first processing unit is further configured to,

[0031] The friction plate is clamped with the brake disc or a lock valve is locked by a rear wheel controller of the vehicle.

[0032] Optionally, the start signal is a rear wheel learning signal, the rear wheel learning signal is used for zero point learning of a rear wheel of the vehicle to obtain a rear wheel brake zero point, and the zero point change condition includes a minimum value of the motor output torque.

[0033] The first processing unit is specifically configured to control the motor to be in a zero speed closed loop control state or control the motor to creep in a clamping direction to release the pawl.

[0034] When the pawl is successfully released, the motor stops creeping, and the piston is in a static state, the original position of the piston is recorded.

[0035] The piston is controlled by the motor to perform reverse rollback, and a third actual torque value of the motor is collected in real time according to a third time interval during the reverse rollback, and the reverse direction is opposite to a direction of the brake disc relative to the piston.

[0036] The second processing unit is specifically configured to,

[0037] The third actual torque value of the motor collected in real time according to the third time interval is smoothed until a minimum value of the motor output torque is obtained, and the current position of the piston is the rear wheel brake zero point.

[0038] Optionally, the second processing unit is further configured to,

[0039] A second reasonable distance range corresponding to a second motor output torque and a second brake disc temperature is obtained, the second motor output torque and the second brake disc temperature are recorded when the pawl is successfully released and the piston is in a static state, and the second reasonable distance range is used to represent a distance range of the friction plate and the brake disc from a theoretical zero point to a brake end point under the conditions of the second motor output torque, the second brake disc temperature and brake system stiffness, the theoretical zero point is used to represent a piston position at which the friction plate and the brake disc separate or contact during relative movement, and the brake end point is used to represent a piston position at which the friction plate and the brake disc are clamped and the motor speed is zero.

[0040] If the distance between the original position of the piston and the rear wheel brake zero point meets the second reasonable distance range, the rear wheel brake zero point is determined as a reliable rear wheel brake zero point.

[0041] Optionally, the second processing unit is further configured to,

[0042] acquire a historical brake disc temperature and a historical zero point, the historical brake disc temperature being the temperature of the brake disc when the historical zero point is acquired;

[0043] acquire a temperature difference between a second brake disc temperature and the historical brake disc temperature, and a zero point difference between the rear wheel brake zero point and the historical zero point;

[0044] analyze whether a relationship between the temperature difference and the zero point difference meets a set temperature-zero point relationship, and if yes, determine the rear wheel brake zero point as a reliable rear wheel brake zero point.

[0045] Optionally, the first processing unit is further configured to,

[0046] clench the friction plate and the brake disc by a front wheel controller of the vehicle.

[0047] In a third aspect, the embodiments of the present application provide a vehicle, which can execute the zero point learning method of the brake system in any of the possible designs in the first aspect.

[0048] The present application has the following beneficial effects:

[0049] The embodiment of the application provides a zero point learning method of a brake system, which is used for judging whether a starting signal is a starting signal of a front wheel or a starting signal of a rear wheel according to the starting signal generated when a vehicle is powered on or powered off; if the starting signal is the starting signal of the front wheel, a corresponding learning control method of the front wheel is selected, the piston is controlled to move through a brake zero point in a movement process of the piston and the motor movement data of the motor is collected in real time in the movement process of the piston; if the starting signal is the starting signal of the rear wheel, a corresponding learning control method of the rear wheel is selected, the piston is controlled to move through the brake zero point in the movement process of the piston and the motor movement data of the motor is collected in real time in the movement process of the piston. In this way, the change of the motor movement can be obtained according to the motor movement data, for example, the change of the rotating speed of the motor, the change of the output torque of the motor and the like. Generally, when the friction plate contacts or separates from the brake disc (the brake zero point), the motor movement will have a special phenomenon different from other times, the experience data generated near the zero point can be used to obtain the zero point change condition, and then the brake zero point position can be determined when the real-time change obtained by analyzing the motor movement data meets the zero point change condition. In this way, when the vehicle is started or turned off, the new brake zero point can be automatically and accurately obtained, and the convenience of zero point updating and the safety of the vehicle are improved. Generally, when the vehicle is turned off, the temperature change of the brake disc is unstable, which may cause inaccurate zero point calculation, therefore, preferably, the zero point learning can be performed only when the vehicle is powered on and started.

[0050] The implementation manners or other implementation manners of the application will be more apparent in the following description of the embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without any creative labor.

[0052] Figure 1 A flowchart of a zero point learning method of a brake system provided by the embodiment of the application is shown in the figure;

[0053] Figure 2 A simple schematic diagram of a piston position provided by the embodiment of the application is shown in the figure;

[0054] Figure 3a A schematic diagram of each stage of speed control in an S-shaped cycloid speed control method provided by the embodiment of the application is shown in the figure;

[0055] Figure 3b A schematic diagram of each stage of speed control in an S-shaped cycloid speed control method provided by the embodiment of the application is shown in the figure;

[0056] Figure 4a A piston moving speed reaching a target speed process schematic diagram provided for an embodiment of the application;

[0057] Figure 4b A piston moving speed schematic diagram provided for an embodiment of the application;

[0058] Figure 5 A front wheel zero point learning method flowchart schematic diagram of a brake system provided for an embodiment of the application;

[0059] Figure 6 A rear wheel zero point learning method flowchart schematic diagram of a brake system provided for an embodiment of the application;

[0060] Figure 7 A parameter change condition schematic diagram of each component in an active process provided for an embodiment of the application;

[0061] Figure 8 A zero point learning method device schematic diagram of a brake system provided for an embodiment of the application. DETAILED DESCRIPTION

[0062] In order to make the purposes, technical solutions and advantages of the application clearer, the application will be further described in detail below with reference to the drawings. Obviously, the described embodiments are only some of the embodiments of the application, but not all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0063] In the description of the application, the phrase "in an embodiment" does not necessarily refer to the same embodiment, although it can refer to the same embodiment. Similarly, the phrase "in some embodiments" as used herein, when used multiple times, does not necessarily refer to the same embodiment, although it can 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 dictates otherwise. The term "based on" is not exclusive and allows additional factors not described, unless the context clearly dictates otherwise. The word "exemplary" means "serving as an example, instance, or illustration" in this context. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. The scope of the application is only limited by the scope of the appended claims, and any example set forth in the specification is not intended to limit, but only to illustrate, some of the many possible embodiments of the claimed application. The various embodiments provided by the application should not be interpreted as limiting the scope of protection of the application.

[0064] In addition, the terms "first", "second", "third", etc. are used herein only to describe different instances, and are not used to indicate or imply relative importance or a number of indicated technical features. Thus, features defined with "first", "second", etc. can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0065] Under the background of rapid development of the automobile industry, the wide application of electronic brake systems puts forward higher requirements for the accuracy and safety of brake performance. The accurate determination of the brake zero point is the core link to ensure the brake effect and the stability of vehicle control. However, the traditional brake zero point correction method needs to access external equipment for zero point correction in the idle state of the vehicle. This method requires professional personnel to operate the equipment for zero point correction, and the operation of zero point correction is complex. Therefore, users usually do not perform zero point correction for a short time, which leads to the fact that the brake zero point of the brake system may not be corrected for a long time, which has a great negative impact on the safety of driving vehicles.

[0066] In view of this, the embodiments of the present application provide a brake system zero point learning method process, as shown in Figure 1 The method comprises the following steps:

[0067] Step 101, obtaining the starting of brake pressure building zero point learning. The starting signal of brake pressure building zero point learning is generated when the vehicle is powered on or powered off.

[0068] Step 102, based on the learning control method corresponding to the starting signal, controlling the movement of the piston by the motor, so that the piston passes through the brake zero point in the movement process, and real-time collecting motor movement data of the motor in the movement process.

[0069] Step 103, real-time analyzing the change of the motor movement data, and when the change meets the zero point change condition, taking the current position of the piston as the brake zero point. The zero point change condition is obtained according to the experience data generated by the motor in the braking process.

[0070] In one embodiment, the learning control method corresponding to the starting signal of the front wheel can be different from the learning control method of the starting signal of the rear wheel. Therefore, after receiving the starting signal of brake pressure building zero point learning, the corresponding learning control method can be selected according to the starting signal, the movement of the piston is controlled by the motor, so that the piston passes through the brake zero point in the movement process, and the motor movement data of the motor is collected in real time in the movement process.

[0071] In one embodiment, the start signal can be generated when the user twists the car key, and / or steps on the brake or opens the door of the vehicle, or the start signal can be generated when the vehicle start and stop button is pressed, or the start signal can be generated based on the driver's operation on the smart device, and the specific generation of the start signal is not limited. It should be noted that preferably, the start signal is generated when the vehicle is powered on, because the temperature of the brake disc and the friction plate is usually at the ambient temperature when the vehicle is powered on, and the deformation is small, and the brake zero point obtained is more accurate than the brake zero point obtained when the vehicle is powered off (the brake disc and the friction plate have been rubbed quickly, and the quickly rubbed brake disc and the friction plate cause sharp temperature rise and deformation).

[0072] In one embodiment, if there are four or more wheels in the vehicle, each wheel corresponds to an electric motor, then the above-mentioned electric motor can be the electric motor corresponding to any one or more wheels in the vehicle, that is, in the zero point learning method of the above-mentioned brake system, one or more electric motors corresponding to one or more wheels can simultaneously learn the zero point and obtain the brake zero point of each wheel.

[0073] In one embodiment, the learning control method can be set according to the speed of the piston. For example, if the start signal is the start signal of the front wheel, the corresponding learning control method can be a method of controlling the piston to move in the positive direction (towards the wheel) at a certain speed and pass through the real zero point from the opposite direction of the wheel and away from the real zero point, and in this process, the brake zero point (approximately equal to or equal to the real zero point) is determined according to the change of the motor movement data. Figure 2 As shown in FIG. 8, it is a simple schematic diagram of the piston position provided by the embodiment of the present application, the wheel 201 is in the positive direction, and the piston 204 is in the opposite direction of the wheel 201, and the piston 204 pushes the friction plate 203 to contact and rub the brake disc 202.

[0074] In one embodiment, the learning control method can be set according to the torque of the electric motor. For example, if the start signal is the start signal of the rear wheel, the corresponding learning control method can be a method of controlling the piston to move in the opposite direction (away from the wheel) at a certain speed and pass through the real zero point from the direction of the wheel (positive direction) and the output torque of the electric motor (not exceeding the maximum output torque limit), and in this process, the brake zero point (approximately equal to or equal to the real zero point) is determined according to the change of the motor movement data.

[0075] In one embodiment, after obtaining the brake zero point, the brake zero point can be stored in the corresponding memory, so that the next time the vehicle is braked, the vehicle can be braked according to the obtained brake zero point.

[0076] In an embodiment, the zero point change condition can be obtained by analyzing experience data corresponding to special performance of the friction plate always having during the braking process when the friction plate passes the zero point according to the motor driving the piston. For example, the output torque of the motor changes and the rotation speed changes at the moment when the friction plate contacts the brake disc.

[0077] In an embodiment, the zero point learning method of the above-mentioned braking system of the application is used for the EMB with the clamping force sensor and the EMB without the clamping force sensor.

[0078] The zero point learning method of the above-mentioned braking system of the application solves the technical problem of the change of the brake zero point caused by the wear of the friction plate and the influence of the environment. The application receives the start signal generated based on the change of the vehicle state, controls the motor to drive the piston to move, and collects the motor motion data during the movement. By analyzing the change of the motion data, when the zero point change condition is met, the current position of the piston is determined as the brake zero point. The application uses a specific learning control method of the motor and the piston, and combines the analysis of the motor motion data to realize the accurate identification of the brake zero point. This method can adapt to the wear of the friction plate and the change of the environment, dynamically adjust the brake zero point, and thus improve the braking accuracy and reliability of the EMB, and lay a foundation for realizing accurate braking control in different stages.

[0079] Based on the method process in the above-mentioned Figure 1 , the embodiment of the application provides a zero point learning method of a braking system of a front wheel. The start signal is a front wheel learning signal, the front wheel learning signal is used for zero point learning of the front wheel of the vehicle to obtain a front wheel brake zero point; and the zero point change condition includes a set torque difference value of the motor.

[0080] In step 102, the motor is controlled to move the piston based on the learning control method corresponding to the start signal, so that the piston passes the brake zero point during the movement, and the motor motion data of the motor is collected in real time during the movement, including:

[0081] Step A1021, the piston is controlled to move reversely to the target position by the motor, and the reverse direction is the opposite direction of the direction of the brake disc relative to the piston.

[0082] Step A1022, the piston is pushed forward from the target position by using an S-shaped cycloid speed control method. When the moving speed of the piston is a target speed, the first actual torque value of the motor is collected according to a first time interval, a plurality of first actual torque values are obtained, and a first average torque of the plurality of first actual torque values is calculated. The target speed is the moving speed of the piston in the uniform speed stage controlled by the S-shaped cycloid speed control method.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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:

[0089]

[0090] wherein, - to set seven speed change nodes in the moving method, is a uniform acceleration phase, is a uniform acceleration phase, is a uniform deceleration phase, is a uniform speed phase, is a uniform acceleration-deceleration phase, is a uniform deceleration phase, is a uniform deceleration phase, and are the speeds at the end of t1 and t2 respectively. For example, it can be set that is 2000 rpm, is 40000 rpm / s, is 1000000 rpm / s^2, then the speed of each phase can be calculated.

[0091] In addition, the uniform speed phase in the S-shaped cycloid speed control method can be short in duration, as shown in Figure 3b which is a schematic diagram of the speed control phases in another S-shaped cycloid speed control method provided by an embodiment of the present application, in which the forward maximum speed (rotational speed) of the motor achieves the target speed of the piston in the corresponding uniform speed phase.

[0092] In an embodiment, after the motor is controlled to move the piston to retreat to the desired retreat stroke (the control of the piston movement generates a retreat displacement to reach the target position), the motor is rotated to control the piston to move forward, and the S-shaped cycloid speed control method is also used, as shown in Figure 3a which shows that the process of the piston moving speed reaching the target speed includes t1, t2, t3, and part or all of t4, and as shown in Figure 4a which is a schematic diagram of the process of the piston moving speed reaching the target speed provided by an embodiment of the present application, including: t11-uniform acceleration, t12-uniform acceleration, t13-uniform acceleration-deceleration, and t14-uniform speed. After learning the brake zero point, the brake can be performed based on the learned front wheel brake zero point according to the brake request of the driver. When the target rotational speed of the motor reaches the set maximum uniform speed phase, the actual rotational speed of the motor is obtained. When the actual rotational speed is stable within a very narrow error range (such as ±3%) of the target rotational speed, the first actual torque value of the actual output of the motor is collected and accumulated. After a certain number of first actual torque values are collected, the average value of the certain number of first actual torque values collected in this range is obtained as the first average torque of this phase .

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] Based on the above Figure 1The method flow in the method, and the embodiment of the application provides another zero point learning method of a front wheel brake system, a start signal is a front wheel learning signal, the front wheel learning signal is used for learning the zero point of the front wheel of the vehicle, and a front wheel brake zero point is obtained; the zero point change condition includes a set change rate of the rotating speed of the motor;

[0099] In step 102, based on the learning control method corresponding to the start signal, the piston is controlled to move by the motor, so that the piston passes through the brake zero point during the movement, and the motor movement data of the motor is collected in real time during the movement, including:

[0100] Step B1021, the piston is controlled to move reversely to the target position by the motor, and the reverse direction is the opposite direction of the direction of the brake disc relative to the piston;

[0101] Step B1022, the piston is pushed forward by using an S-shaped cycloidal speed control method, and the rotating speed data of the motor is collected in real time during the pushing process.

[0102] In step 103, the change of the motor movement data is analyzed in real time, and when the change meets the zero point change condition, the current position of the piston is taken as the brake zero point, including: the rotating speed change rate of the motor is analyzed, and when the rotating speed change rate of the motor is greater than the set change rate, the current position of the piston is taken as the front wheel brake zero point.

[0103] In one embodiment, the rotating speed change rate is obtained according to the rotating speed change data of the motor , and when the rotating speed change rate is greater than the set change rate , the change rate corresponding to the current position of the piston is taken as the front wheel brake zero point.

[0104] Based on the above zero point learning method of the front wheel, the embodiment of the application provides a zero point verification method of the front wheel, and after the current position of the piston is taken as the front wheel brake zero point in step 103, the method further includes:

[0105] Step a, based on the motor, the piston is controlled to continue to move forward until the friction plate pushed by the piston is clamped with the brake disc, and the rotating speed of the motor is zero, the piston end position when the rotating speed of the motor is zero, the first motor output torque when the rotating speed of the motor is zero and the first brake disc temperature are obtained.

[0106] Step b, obtaining a first reasonable distance range corresponding to the first motor output torque and the first brake disc temperature, the first reasonable distance range is used to represent the distance range of the friction plate and the brake disc from the theoretical zero point to the brake end point under the conditions of the first motor output torque, the first brake disc temperature and the brake system stiffness, the theoretical zero point is used to represent the piston position at which the friction plate and the brake disc are separated or contacted during relative movement, and the brake end point is used to represent the piston position at which the friction plate and the brake disc are clamped and the motor speed is zero.

[0107] Step c, if the distance between the piston end point position and the front wheel brake zero point meets the first reasonable distance range, the front wheel brake zero point is determined as a reliable front wheel brake zero point.

[0108] In one embodiment, that is, after learning the front wheel brake zero point during the positive movement of the piston, the piston continues to move positively until the friction plate and the brake disc pushed by the piston are clamped, the motor speed is zero, and the piston end point position, the first motor output torque and the first brake disc temperature at this time are obtained, the corresponding first reasonable distance range is obtained according to the first motor output torque and the first brake disc temperature, and the distance between the piston end point position and the front wheel brake zero point is verified. If it is within the first reasonable distance range, the front wheel brake zero point is confirmed as a reliable front wheel brake zero point, otherwise, the front wheel brake zero point learned this time is discarded, and the last front wheel brake zero point is used.

[0109] In one embodiment, because the first motor output torque, the first brake disc temperature and the brake system stiffness can affect the real zero point of contact and the clamping position between the friction plate and the brake disc, the first reasonable interval range corresponding to the brake system stiffness at different brake disc temperatures can be determined according to empirical data. In this way, the corresponding first reasonable interval range can be selected according to the first motor output torque and the first brake disc temperature, and the obtained front wheel brake zero point is judged by using the first reasonable interval range. If the distance between the obtained front wheel brake zero point and the piston end point position is within the first reasonable interval range, the front wheel brake zero point is reliable, otherwise, it is unreliable. For example, if the first motor output torque is 0.4 Nm, the first brake disc temperature is 30℃, the distance between the front wheel brake zero point and the piston end point position is 0.1 mm, and the first reasonable interval range is 0.09-0.11, the front wheel brake zero point is reliable.

[0110] Based on the above learning zero point method of each front wheel, the embodiment of the present application provides a zero point learning method of a brake system, before the piston is controlled to retreat to the target position in the reverse direction by the motor, the method further comprises: clamping the friction plate and the brake disc by the rear wheel controller of the vehicle, or locking the lock valve. In this way, the movement of the vehicle can be prevented, and the accuracy of the learned front wheel brake zero point can be ensured.

[0111] Based on the above learning zero point method of each front wheel, the embodiment of the present application provides a zero point learning method of a front wheel of a brake system, as shown in the formula (I): Figure 5 The formula (I) comprises the following steps:

[0112] Step 501, receiving a starting signal of brake pressure building zero point learning, the starting signal is generated when the vehicle is powered on.

[0113] In an embodiment, considering that the brake disc temperature may be high when the vehicle is powered off, which affects the accuracy of the front wheel brake zero point learning, the zero point learning of the brake system is performed when the vehicle is powered on in the embodiment.

[0114] Step 502, the starting signal is the starting signal of the front wheel, which can be the left front wheel and / or the right front wheel, and the friction plate is clamped with the brake disc or the lock valve is locked through the rear wheel controller.

[0115] In an embodiment, after the vehicle is started, the driver will step on the brake pedal, and the starting signal of the front wheel is received, and the brake disc is clamped or the lock valve is locked through the two controllers of the rear wheel.

[0116] Step 503, the motor controls the piston to retreat to a target position in a reverse direction, the reverse direction being the opposite direction of the direction of the brake disc relative to the piston.

[0117] In an embodiment, for the front wheel ECU, when the zero point learning is performed, the friction plate and the brake disc can be in any stage (contact stage or gap stage), therefore, in order to improve the reliability of the zero point learning, sufficient learning space is required, the piston is controlled to move away from the brake disc, and the motor is stopped after the piston reaches the target position.

[0118] Step 504, the motor output torque and the piston retreat displacement are monitored during the retreat process, when the motor output torque significantly exceeds the required output torque for the retreat, or the piston retreat displacement significantly exceeds the planned retreat displacement, the current ignition cycle brake zero position learning is terminated, if the motor output torque does not exceed the required output torque for the retreat and the piston retreat displacement does not exceed the planned retreat displacement, step 505 is performed.

[0119] In an embodiment, when the motor output torque significantly exceeds the required output torque for the retreat, or the piston retreat displacement significantly exceeds the planned retreat displacement, the reason for terminating the current ignition cycle brake zero position learning is that, generally, the motor has no load or small load during the retreat, therefore, the motor output torque during the retreat is also small, but when the motor output torque significantly exceeds the required output torque for the retreat, or the piston retreat displacement significantly exceeds the planned retreat displacement, it is possible that the piston has an abnormality during the retreat, and the accuracy of the learned front wheel brake zero point under the abnormal condition is questionable, i.e., unreliable.

[0120] Step 505, using the S-shaped cycloid speed control method, the piston is pushed forward from the target position, when the moving speed of the piston is the target speed, the first actual torque value of the motor is collected according to the first time interval, a plurality of first actual torque values are obtained, and the first average torque of the plurality of first actual torque values is calculated. The target speed is the moving speed of the piston in the uniform speed stage controlled by the S-shaped cycloid speed control method.

[0121] In one embodiment, the maximum output torque of the motor in the S-shaped cycloid speed control method is limited to Tthd.

[0122] In one embodiment, attention is paid to ensure that the forward displacement of the piston from the beginning to the end of obtaining the first average torque does not exceed the piston back displacement, so as to avoid the friction plate and the brake disc from contacting before the first average torque is calculated, resulting in inaccurate calculation of the first average torque in the uniform speed stage.

[0123] Step 506, when the moving speed of the piston is the target speed and in the deceleration process, the second actual torque value of the motor collected in real time according to the second time interval is subjected to sliding average filtering to obtain the second average torque.

[0124] Step 507, the actual torque difference between the second average torque and the first average torque is calculated in real time, and when the actual torque difference is greater than the set torque difference, the current position of the piston is taken as the front wheel brake zero point.

[0125] Step 508, using the S-shaped cycloid speed control method, the piston is pushed forward, and the speed data of the motor is collected in real time during the pushing process; the speed change rate of the motor is analyzed, and when the speed change rate of the motor is greater than the set change rate, the current position of the piston is taken as the front wheel brake zero point.

[0126] Step 509, based on the motor, the piston continues to move forward, until the friction plate pushed by the piston is clamped with the brake disc, and the speed of the motor is zero, the end position of the piston when the speed of the motor is zero and the first motor output torque and the first brake disc temperature when the speed of the motor is zero are obtained.

[0127] Step 510, a first reasonable distance range corresponding to the first motor output torque and the first brake disc temperature is obtained, and if the distance between the end position of the piston and the front wheel brake zero point meets the first reasonable distance range, the front wheel brake zero point is determined as a reliable front wheel brake zero point.

[0128] In one embodiment, after the electric control piston moves forward to push the friction plate to contact the brake disc, the motor output torque is limited to Tthd, and the load torque of the motor increases during the process of the electric control piston moving forward after the friction plate contacts the brake disc, so the motor speed gradually decreases until 0. When the motor output torque reaches Tthd, the motor speed is 0, the distance from the contact to the time when the motor speed is 0 is calculated and obtained, and it is determined whether the distance meets the first reasonable distance range corresponding to the first motor output torque and the first brake disc temperature. If it meets, it is determined that the front wheel brake zero point learned in the previous step is reliable. The first reasonable distance range needs to consider the relationship between the motor output torque and the piston stroke, and also consider the influence of the first brake disc temperature and the static friction torque.

[0129] It should be noted that the above method process is not unique, for example, process step 507 and process step 508 can be performed at the same time.

[0130] Based on the above Figure 1 method process, the embodiment of the present application provides a zero point learning method of a rear wheel brake system, a start signal is a rear wheel learning signal, the rear wheel learning signal is used for learning a zero point of a rear wheel of a vehicle to obtain a rear wheel brake zero point; and a zero point change condition includes a minimum value of a motor output torque;

[0131] In step 102, based on the learning control method corresponding to the start signal, the motor control piston is moved to pass through the brake zero point in the movement process, and the motor movement data of the motor is collected in real time in the movement process, including:

[0132] Step C1021, control the motor to be in a zero speed closed loop control state or control the motor to creep in a clamping direction to release the pawl.

[0133] Step C1022, when the pawl is successfully released, the motor stops creeping, and the piston is in a stationary state, the original position of the piston is recorded.

[0134] Step C1023, the motor control piston is moved in reverse, and the third actual torque value of the motor is collected in real time according to the third time interval in the reverse movement process, and the reverse direction is opposite to the direction of the brake disc relative to the piston.

[0135] In step 103, the change of the motor movement data is analyzed in real time, and when the change meets the zero point change condition, the current position of the piston is taken as the brake zero point, including: the third actual torque value of the motor collected in real time according to the third time interval is smoothed until the minimum value of the motor output torque is obtained, and the current position of the piston is taken as the rear wheel brake zero point.

[0136] In one embodiment, in the state of the vehicle power off, the pawl locks the parking gear, at this time the friction plate clamps the brake disc, the clamping force generates the brake torque, so that the vehicle cannot move, the friction plate and the brake disc of the rear wheel are also relatively static.

[0137] In one embodiment, the motor can be controlled to creep in the clamping direction, so that the brake disc and the friction plate are actually clamped, and the accuracy of obtaining the original position of the piston can be ensured.

[0138] In one embodiment, a release signal is given to a pawl, in this process, the motor is controlled at zero speed, and in order to maintain the clamping force between the friction plate and the brake disc unchanged, the output torque value of the motor jumps to 163 mNm.

[0139] In one embodiment, after the vehicle ignition is started and the vehicle is powered on, the driver will step on the brake pedal, and the EMB domain controller will send a parking release command to the rear wheel EMB actuator. The brake zero point learning of the rear wheel is completed when the static parking is released. In this way, the influence of brake zero point learning on the timeliness of the driver's brake request is minimized. The brake disc is clamped or locked by the two controllers of the front wheel.

[0140] In one embodiment, when the vehicle is powered on, the rear axle wheel side controller receives the parking release request sent by the EMB central processor, and controls the motor based on the motor zero speed closed loop control, so that the output torque of the motor is controlled unchanged when the pawl is released, so that the clamping force can be maintained unchanged, and the relative static state between the friction plate and the brake disc is maintained, and at this time the motor output torque Trz and the piston original position P1 when the motor speed is zero are recorded.

[0141] In one embodiment, the pawl is then controlled to release the parking gear, and after the pawl is released, because the brake disc and the friction plate are an elastic system, the rebound force of the brake disc on the friction plate is overcome by the motor controlled at zero speed, so as to maintain the clamping force unchanged. Finally, the motor is controlled in reverse speed, so that the piston moves reversely from the piston original position P1, and the reverse direction is the direction of the piston moving away from the brake disc. In the process of reverse movement, the zero point of the rear wheel brake system pressure building is obtained, and in this process, the zero point of the rear wheel brake system pressure building is the point corresponding to the minimum value of the motor output torque.

[0142] In one embodiment, the motor rear wheel reverse speed control process satisfies the mechanical motion equation as follows:

[0143]

[0144] In the formula, J is the rotational inertia of the system, ω is the motor speed, is the differential of the speed, is the motor output torque, is the elastic system torque, the direction of which is consistent with the reverse direction of the motor, B is the damping coefficient, and the direction of the damping torque is opposite to the direction of the motor. When the motor is controlled in the negative direction (the piston moves in the reverse direction), the elastic system is released, and the elastic torque gradually decreases until the elastic torque is 0 when the separation surface of the friction plate and the brake disc is reached. Therefore, the output torque of the motor gradually transitions from a positive value to 0 and then to a negative output torque and gradually increases to a stable trend. When the separation surface is reached, the speed is in a stable state. is 0, is 0. Therefore, the output torque of the motor is also in a stable state after the separation surface. Therefore, the build-up zero point of the rear wheel brake system is a point corresponding to the minimum value of the output torque of the motor.

[0145] In an embodiment, to find the piston position when the minimum value of the output torque of the motor is reached, the third actual torque value of the motor collected in the third time interval needs to be smoothed first. The smoothing can be performed by using a Savitzky-Golay filter, a moving average, or the like. When the speed is stable and the output torque of the motor is almost not changing, the piston position P2 at this time is recorded, and the piston position at this time is set as the zero point of the rear wheel brake. ΔP = P2-P1, and ΔP is the distance between the zero point of the rear wheel brake and the original position of the piston.

[0146] In an embodiment, before the step C1021, the method further includes: clamping the friction plate and the brake disc by a front wheel controller of the vehicle or locking a lock valve, so that the vehicle is prevented from moving and the accuracy of the learned zero point of the front wheel brake is ensured.

[0147] Based on the above-mentioned zero point learning method of the rear wheel brake, an embodiment of the present application provides a verification method of the zero point of the rear wheel brake. In step 103, the current position of the brake zero point is further included.

[0148] A second reasonable distance range corresponding to a current second motor output torque and a second brake disc temperature is obtained. The second motor output torque and the second brake disc temperature are recorded when the ratchet release is successful and the piston is in a static state. The second reasonable distance range is used to represent the distance range of the friction plate and the brake disc from a theoretical zero point to a brake end point under the conditions of the second motor output torque, the second brake disc temperature, and the brake system stiffness. The theoretical zero point is used to represent the piston position at which the friction plate and the brake disc are separated or contacted during relative movement. The brake end point is used to represent the piston position at which the friction plate and the brake disc are clamped and the motor speed is 0. If the distance between the initial position and the zero point of the rear wheel brake conforms to the second reasonable distance range, the zero point of the rear wheel brake is a reliable zero point of the rear wheel brake.

[0149] In one embodiment, when the output torque of the motor is Trz (the maximum limited output torque), the second brake disc temperature at this time is recorded, the second reasonable distance range corresponding to the second brake disc temperature is obtained, and it is determined whether the AP is in the second reasonable distance range. If yes, it is confirmed that the rear wheel brake zero point obtained through learning is reliable.

[0150] Here, the second reasonable distance range is set by considering the brake system stiffness, i.e., the relationship between the motor output torque value and the piston displacement-stroke, and considering the influence of the brake disc temperature and the static friction torque.

[0151] Based on the above-mentioned rear wheel zero point learning method, the embodiment of the present application provides another verification method of the rear wheel brake zero point. In step 103, after the current position is determined as the brake zero point, the method further includes:

[0152] Step 1: Obtain the historical brake disc temperature and the historical zero point. The historical brake disc temperature is the temperature of the brake disc when the historical zero point is obtained.

[0153] Step 2: Obtain the temperature difference between the second brake disc temperature and the historical brake disc temperature, and the zero point difference between the rear wheel brake zero point and the historical zero point.

[0154] Step 3: Analyze whether the relationship between the temperature difference and the zero point difference conforms to the set temperature-zero point relationship. If yes, it is determined that the brake zero point is a reliable rear wheel brake zero point.

[0155] In one embodiment, the historical zero point and the historical brake disc temperature recorded in the EEPROM when the vehicle is 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.

[0156] That is, each time the vehicle is powered off, the ECU needs to store the rear wheel brake zero point at this time, the second brake disc temperature and the verification data thereof into the EEPROM to ensure the completeness and accuracy of the data. It should be noted that each time the vehicle is powered off, the ECU can also store the front wheel brake zero point at this time, the first brake disc temperature and the verification data thereof into the EEPROM to ensure the completeness and accuracy of the data.

[0157] In one embodiment, the last ignition cycle vehicle power-off time history brake disc temperature, history zero point, and the current ignition time second brake disc temperature and rear wheel brake zero point are read from the power-off non-volatile memory when the vehicle is powered on. The temperature difference between the second brake disc temperature and the history brake disc temperature, and the zero point difference between the rear wheel brake zero point and the history zero point are obtained. The relationship between the temperature difference and the zero point difference is analyzed to determine whether it conforms to the set temperature-zero point relationship. If so, the brake zero point is determined to be a reliable rear wheel brake zero point. The true zero point may change due to changes in brake disc temperature, so the brake disc temperature is different, and the corresponding true zero point position may be different. The temperature difference between the two brake disc temperatures and the zero point difference between the two true zero points have a set temperature-zero point relationship, so this set temperature-zero point relationship can be used to determine whether the rear wheel brake zero point is reliable.

[0158] In one embodiment, the obtained rear wheel brake zero point conforms to at least one of the two rear wheel brake zero point verification methods, and the rear wheel brake zero point is considered reliable.

[0159] Based on the above-mentioned rear wheel brake system zero point learning method and the two rear wheel brake zero point verification methods, the embodiment of the present application provides a rear wheel brake system zero point learning method flow, as shown in Figure 6 , which includes:

[0160] Step 601, receive a start signal, the start signal is generated when the vehicle is powered on.

[0161] In one embodiment, when the vehicle is powered off, the brake disc temperature may be very high, which affects the accuracy of the rear wheel brake zero point learning. In this embodiment, the brake system zero point learning is performed when the vehicle is powered on.

[0162] Step 602, the start signal is the start signal of the rear wheel, which can be the left rear wheel and / or the right rear wheel, and the friction plate is clamped with the brake disc or the lock valve is locked through the front wheel controller.

[0163] In one embodiment, after the vehicle is started, the driver will press the brake pedal to receive the start signal of the rear wheel, and the brake disc is clamped or the lock valve is locked through the two controllers of the front wheel.

[0164] 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.

[0165] Step 604, when the pawl is successfully released, the motor stops creeping, and the piston is in a static state, the original position of the piston and the second motor output torque, and the second brake disc temperature are recorded.

[0166] Step 605, reverse back through the motor control piston, and in the reverse back process, the third actual torque value of the motor is collected in real time according to the third time interval, and the reverse direction of the direction of the brake disc relative to the piston is reversed.

[0167] Step 606, 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 output torque of the motor is obtained, and the current position of the piston is the rear wheel brake zero point.

[0168] Step 607, obtaining a second reasonable distance range corresponding to the second motor output torque and the second brake disc temperature, if the distance between the original position of the piston and the rear wheel brake zero point conforms to the second reasonable distance range, the rear wheel brake zero point is determined as a reliable rear wheel brake zero point. And / or obtaining a historical brake disc temperature and a historical zero point, obtaining a temperature difference value between the second brake disc temperature and the historical brake disc temperature, and a zero point difference value between the rear wheel brake zero point and the historical zero point; analyzing whether the relationship between the temperature difference value and the zero point difference value conforms to the set temperature zero point relationship, if yes, determining the rear wheel brake zero point as a reliable rear wheel brake zero point. If the distance between the original position of the piston and the rear wheel brake zero point does not conform to the second reasonable distance range, and the relationship between the temperature difference value and the zero point difference value does not conform to the set temperature zero point relationship, the rear wheel brake zero point is determined as an unreliable rear wheel brake zero point, the rear wheel brake zero point learned this time is discarded, and the rear wheel brake zero point of the last time is used.

[0169] In one embodiment, as shown in Figure 7 , a schematic diagram of parameter changes of various components in an active process is provided for the embodiment of the application, including: motor output torque, actual clamping force between friction plate and brake disc, motor speed, piston position, zero point identification success flag and zero point position, and the horizontal axis represents time.

[0170] The above method can learn and update the zero point of the brake system every time the vehicle is powered on and powered off. The zero point of the brake system is learned when the front wheels and the rear wheels are powered on and powered off, which shortens the time influence on the response of the driver's braking demand. The method is simple and reliable, increases the check of the reliability of the brake zero point learning, reduces the noise of the brake zero point learning process, and optimizes NVH (noise, vibration and harshness).

[0171] Based on the same idea, the embodiment of the application provides a zero point learning device of a brake system, Figure 8 A schematic diagram of a zero point learning device of a brake system is provided for the embodiment of the application, as shown in Figure 8 , which comprises:

[0172] The transceiver unit 801 is configured to receive a start signal, wherein the start signal is generated when the vehicle is powered on or powered off.

[0173] The first processing unit 802 is configured to control the piston to pass through the brake zero point during movement of the piston based on a learning control method corresponding to the starting signal, and collect motor movement data of the motor in real time during the movement of the piston.

[0174] The second processing unit 803 is configured to analyze a change condition of the motor movement data in real time, and take a current position of the piston as the brake zero point when the change condition meets a zero point change condition, the zero point change condition being obtained according to experience data generated by the motor during braking.

[0175] Optionally, the starting signal is a front wheel learning signal, and the front wheel learning signal is used for zero point learning of a front wheel of the vehicle to obtain a front wheel brake zero point.

[0176] The first processing unit 802 is specifically configured to,

[0177] The piston is controlled to retreat to the target position in a reverse direction by the motor, the reverse direction being a reverse direction of a direction of the brake disc relative to the piston;

[0178] The piston is pushed forward from the target position by the motor in an S-shaped cycloid speed control method, a first actual torque value of the motor is collected at a first time interval when a moving speed of the piston is a target speed, a plurality of first actual torque values are obtained, and a first average torque of the plurality of first actual torque values is calculated, the target speed being a moving speed of the piston in a uniform speed stage controlled by the S-shaped cycloid speed control method.

[0179] The second average torque is obtained by performing a sliding average filtering on a second actual torque value of the motor collected in real time at a second time interval when the moving speed of the piston is the target speed and in a deceleration process.

[0180] The zero point change condition includes a set torque difference value of the motor, and the second processing unit is specifically configured to calculate an actual torque difference value between the second average torque and the first average torque in real time, and take a current position of the piston as the front wheel brake zero point when the actual torque difference value is greater than the set torque difference value.

[0181] Optionally, the starting signal is a front wheel learning signal, and the front wheel learning signal is used for zero point learning of a front wheel of the vehicle to obtain a front wheel brake zero point; and the zero point change condition includes a set change rate of a rotating speed of the motor.

[0182] The first processing unit 802 is specifically configured to,

[0183] control the piston to retreat to a target position in a reverse direction by the motor, the reverse direction being opposite to a direction in which the brake disc is relative to the piston;

[0184] control the piston to advance in a forward direction by an S-shaped cycloid speed control method, and collect speed data of the motor in real time during the advancing process;

[0185] The second processing unit 803 is specifically configured to:

[0186] analyze a speed change rate of the motor, and take a current position of the piston as the front-wheel brake zero point when the speed change rate of the motor is greater than a set change rate.

[0187] Optionally, the second processing unit 803 is further configured to:

[0188] control the piston to continue to move in the forward direction based on the motor until the friction plate pushed by the piston is clamped with the brake disc and the speed of the motor is zero, and obtain a piston end position when the speed of the motor is zero, a first motor output torque when the speed of the motor is zero, and a first brake disc temperature;

[0189] obtain a first reasonable distance range corresponding to the first motor output torque and the first brake disc temperature, the first reasonable distance range being used to represent a distance range of the friction plate and the brake disc from a theoretical zero point to a brake end point under conditions of the first motor output torque, the first brake disc temperature, and brake system stiffness, the theoretical zero point being used to represent a piston position at which the friction plate and the brake disc are separated or contacted during relative movement, and the brake end point being used to represent a piston position at which the friction plate and the brake disc are clamped with each other and the speed of the motor is zero;

[0190] if a distance between the piston end position and the front-wheel brake zero point conforms to the first reasonable distance range, determine that the front-wheel brake zero point is a reliable front-wheel brake zero point.

[0191] Optionally, the first processing unit 802 is further configured to:

[0192] clamp the friction plate with the brake disc or lock a lock valve by a rear-wheel controller of the vehicle.

[0193] Optionally, the start signal is a rear-wheel learning signal, the rear-wheel learning signal being used to perform zero point learning on a rear wheel of the vehicle to obtain a rear-wheel brake zero point, and the zero point change condition includes a minimum value of the motor output torque.

[0194] The first processing unit 802 is specifically configured to control the motor to be in a zero-speed closed-loop control state or control the motor to creep in a clamping direction to release a pawl.

[0195] record the original position of the piston when the ratchet release is successful, the motor stops creeping, and the piston is in a static state; control the piston to perform reverse rollback by the motor, and collect a third actual torque value of the motor in real time according to a third time interval during the reverse rollback, the reverse being a reverse direction of the brake disc relative to the direction of the piston;

[0196] The second processing unit 803 is specifically configured to,

[0197] smoothly process the third actual torque value of the motor collected in real time according to the third time interval until a minimum value of the output torque of the motor is obtained, and the current position of the piston is the rear wheel brake zero point.

[0198] Optionally, the second processing unit 803 is further configured to,

[0199] obtain a second reasonable distance range corresponding to a second motor output torque and a second brake disc temperature, the second motor output torque and the second brake disc temperature being recorded when the ratchet release is successful and the piston is in a static state, the second reasonable distance range being used to represent a distance range of the friction plate and the brake disc from a theoretical zero point to a brake end point under the conditions of the second motor output torque, the second brake disc temperature, and the brake system stiffness, the theoretical zero point being used to represent a piston position at which the friction plate and the brake disc separate or contact during relative movement, and the brake end point being used to represent a piston position at which the friction plate and the brake disc are clamped and the rotation speed of the motor is zero;

[0200] if the distance between the original position of the piston and the rear wheel brake zero point conforms to the second reasonable distance range, the rear wheel brake zero point is determined as a reliable rear wheel brake zero point.

[0201] Optionally, the second processing unit 803 is further configured to,

[0202] obtain a historical brake disc temperature and a historical zero point, the historical brake disc temperature being a temperature of the brake disc when the historical zero point is obtained;

[0203] obtain a temperature difference value of the second brake disc temperature and the historical brake disc temperature, and a zero point difference value of the rear wheel brake zero point and the historical zero point;

[0204] analyze whether a relationship between the temperature difference value and the zero point difference value conforms to a set temperature-zero point relationship, and if so, determine that the rear wheel brake zero point is a reliable rear wheel brake zero point.

[0205] Optionally, the first processing unit 802 is further configured to,

[0206] clamping the friction plate to the brake disc by a front wheel controller of the vehicle.

[0207] Those skilled in the art will appreciate that embodiments of the present application can be devised for a method, a system, or a computer program product. Accordingly, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer readable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer readable program code.

[0208] The present application is described in reference to the flowchart illustrations and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will 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, create means for implementing the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 means for performing each of the one or more functions specified in the flowchart illustrations and / or block diagrams.

[0209] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 means for performing each of the one or more functions specified in the flowchart illustrations and / or block diagrams.

[0210] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 means for performing each of the one or more functions specified in the flowchart illustrations and / or block diagrams.

[0211] Obviously, numerous modifications and variations of the present application are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims and their equivalents, the application can be practiced otherwise than as specifically described.

Claims

1. A method of zero point learning for a brake system, characterized by, The method comprises: an initiation signal for brake pressure build-up zero point learning is acquired, the initiation signal being obtained when the vehicle is powered on or powered off; based on a learning control method corresponding to the initiation signal, a piston is moved by motor control, so that the piston passes through a brake zero point during movement, and motor movement data of the motor is collected in real time during the movement; changes in the motor movement data are analyzed in real time, and when the changes meet a zero point change condition, a current position of the piston is taken as the brake zero point, the zero point change condition being obtained according to experience data generated by the motor during braking; the initiation signal is a rear wheel learning signal, the rear wheel learning signal being used for zero point learning of rear wheels of the vehicle to obtain a rear wheel brake zero point, and the zero point change condition includes a minimum value of motor output torque; based on the learning control method corresponding to the initiation signal, the piston is moved by motor control, so that the piston passes through a brake zero point during movement, and motor movement data of the motor is collected in real time during the movement, comprising: the motor is controlled to be in a zero speed closed loop control state or to creep in a clamping direction to release a pawl; when the pawl is successfully released, the motor stops creeping, and the piston is in a stationary state, an original position of the piston is recorded, the piston is controlled in reverse by the motor, and a third actual torque value of the motor is collected in real time according to a third time interval during reverse movement, the reverse being a reverse direction of a direction of the brake disc relative to the piston; the changes in the motor movement data are analyzed in real time, and when the changes meet a zero point change condition, a current position of the piston is taken as the brake zero point, comprising: the third actual torque value of the motor collected in real time according to the third time interval is smoothed until a minimum value of motor output torque is obtained, and the current position of the piston is taken as the rear wheel brake zero point; after the current position of the piston is taken as the rear wheel brake zero point, further comprising: a second reasonable distance range corresponding to a second motor output torque and a second brake disc temperature is acquired, the second motor output torque and the second brake disc temperature being recorded when the pawl is successfully released and the piston is in a stationary state, the second reasonable distance range being used to represent a distance range of a friction plate and the brake disc from a theoretical zero point to a brake end point under conditions of the second motor output torque, the second brake disc temperature and brake system stiffness, the theoretical zero point being used to represent a piston position at which the friction plate and the brake disc separate or contact each other during relative movement, and the brake end point being used to represent a piston position at which the friction plate and the brake disc are clamped and the motor speed is zero; if a distance between the original position of the piston and the rear wheel brake zero point meets the second reasonable distance range, the rear wheel brake zero point is taken as a reliable rear wheel brake zero point.

2. The zero-point learning method as claimed in claim 1, characterized in that after the current position of the piston is taken as the rear wheel brake zero point, further comprising: acquiring a history brake disc temperature, which is the temperature of the brake disc when the history zero point is acquired, and the history zero point; acquiring a temperature difference between a second brake disc temperature and the history brake disc temperature, and a zero point difference between the rear wheel brake zero point and the history zero point; analyzing whether a relationship between the temperature difference and the zero point difference conforms to a set temperature zero point relationship, and if so, determining that the rear wheel brake zero point is a reliable rear wheel brake zero point.

3. The zero-point learning method as claimed in claim 1, characterized in that, The control of the motor in the zero speed closed loop control state or the creep control state in the clamping direction, and the release of the pawl, further comprises: clamping the friction plate and the brake disc through a front wheel controller of the vehicle.

4. A zero point learning device of a brake system characterized by comprising: The device is used for executing the method according to any one of claims 1 to 3. a transceiving unit, configured to acquire a starting signal of brake pressure building zero point learning, the starting signal being generated when the vehicle is powered on or powered off; a first processing unit, configured to control the movement of the piston through the brake zero point in a movement process based on a learning control method corresponding to the starting signal, and to collect motor movement data of the motor in real time in the movement process; a second processing unit, configured to analyze the change of the motor movement data in real time, and to take the current position of the piston as the brake zero point when the change conforms to a zero point change condition, the zero point change condition being obtained according to experience data generated by the motor in the braking process.

5. A vehicle characterized by comprising: The vehicle executes the method according to any one of claims 1 to 3.

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