Middle position calibration and tail end position self-learning method based on rear wheel steering system

Abstract

The invention provides a middle position calibration and tail end position self-learning method based on a rear wheel steering system, and the method is applied to the field of vehicles, and comprises the steps: obtaining a current rack middle position value and a rack middle position calibration value, and if a first difference absolute value of the current rack middle position value and the rack middle position calibration value is greater than or equal to a first preset error threshold value, determining that the tail end position is the middle position; if yes, the rear wheel steering system is controlled to conduct whole vehicle tail end self-learning, after the self-learning frequency reaches the first target frequency, a tail end position self-learning temporary value and a rack neutral position calibration value of the rear wheel steering system are obtained, and if a second difference absolute value of the tail end position self-learning temporary value and the rack neutral position calibration value is smaller than a second preset error threshold value, the rear wheel steering system is controlled to conduct whole vehicle tail end self-learning; if yes, when the whole vehicle is powered off, the tail end position self-learning value in the preset memory is updated based on the tail end position self-learning temporary value. According to the method, the accuracy and the reliability of a calibration result can be ensured based on the combination of the middle-position tail end self-learning of the rack and the tail end self-learning of the whole vehicle through multiple cycles and average value calculation.

Description

Technical Field

[0001] The present application relates to the field of vehicles, and more specifically, to a method for center position calibration and end position self-learning based on a rear-wheel steering system in the field of vehicles. Background Art

[0002] With the development of vehicle technology, RWS (Rear Wheel Steering) is widely used to improve the handling and stability of the vehicle. In order to ensure the normal operation of the rear-wheel steering system, it is necessary to ensure that the rear-wheel rack is in the middle position when the front wheel angle is 0 to avoid abnormal steering caused by deviation, thereby affecting driving safety. In addition, when the rear-wheel steering system cannot guarantee full functionality, the rack should return to the middle position and self-lock after power is restored.

[0003] In the related art, RWS usually uses manual calibration of the rack center position and limits the rack end position through a software limit method.

[0004] However, by manually calibrating the rack center position, the calibration efficiency and accuracy will be reduced because the internal displacement sensor is not calibrated in the center position. At the same time, when the rack end position is limited by the software limit method, the assembly process error cannot be effectively dealt with. The rear-wheel steering system has poor adaptability under different working conditions, which affects the accuracy and reliability of the rear-wheel steering system and needs to be solved urgently. Summary of the invention

[0005] The present application provides a method for mid-position calibration and end position self-learning based on a rear-wheel steering system. The method can combine the mid-position calibration of a test bench with the end position self-learning and the whole vehicle end position self-learning, and through multiple cycles and average value calculation, ensure the accuracy and reliability of the mid-position calibration results and the end position.

[0006] In the first aspect, a method for median calibration and end position self-learning based on a rear-wheel steering system is provided, the method comprising: obtaining a current rack median value and a rack median calibration value when the steering wheel angle is a target angle; if the absolute value of a first difference between the current rack median value and the rack median calibration value is greater than or equal to a first preset error threshold, controlling the rear-wheel steering system to perform vehicle end self-learning, and obtaining an end position self-learning temporary value of the rear-wheel steering system after the number of self-learning times of the rear-wheel steering system reaches a first target number; if the absolute value of a second difference between the end position self-learning temporary value and the rack median calibration value is less than a second preset error threshold, then when the vehicle is powered off, updating the end position self-learning value in the preset memory based on the end position self-learning temporary value.

[0007] Through the above technical solution, it is possible to combine the mid-terminal self-learning of the test bench with the terminal self-learning of the whole vehicle, and through multiple cycles and average value calculation, to ensure the accuracy and reliability of the calibration results.

[0008] In combination with the first aspect, in some possible implementations, before obtaining the current rack median value and rack median calibration value when the steering wheel angle is the target angle, it also includes: receiving a median calibration instruction of the rear-wheel steering system in a bench test; controlling the rack of the rear-wheel steering system to move to the end position of the rear-wheel steering system at a target speed based on the median calibration instruction, and after controlling the rack of the rear-wheel steering system to move a second target number of times, reading the end temporary position calibration value of the rack of the rear-wheel steering system at the end position; calculating the rack median calibration value of the rear-wheel steering system based on the end temporary position calibration value; obtaining the original median value of the rear-wheel steering system; judging whether the absolute value of the third difference between the rack median calibration value and the original median value is less than a third preset error threshold; if the absolute value of the third difference is less than the third preset error threshold, storing the rack median calibration value in the preset memory.

[0009] Through the above technical solution, the center position calibration values ​​are recorded through bench testing center position calibration to improve the calibration accuracy, thereby solving the problem of the internal center position calibration of the displacement sensor of the rear wheel steering system.

[0010] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, after determining whether the absolute value of the third difference between the rack median calibration value and the original median value is less than the third preset error threshold, it also includes: if the absolute value of the third difference is greater than or equal to the third preset error threshold, reassembling the rear-wheel steering system, controlling the rear-wheel steering system to perform terminal self-learning action in the bench test and recalibrating the terminal temporary position calibration value until the new absolute value of the third difference is less than the third preset error threshold.

[0011] Through the above technical solution, when the absolute value of the third difference between the rack median calibration value and the original median value is not within the normal range, the rear-wheel steering system is reassembled and self-learning is performed to improve the calibration accuracy.

[0012] In combination with the first aspect and the above implementation manner, in some possible implementation manners, after obtaining the current rack median value and the rack median calibration value when the steering wheel angle is the target angle, the method further includes:

[0013] If the absolute value of the first difference is less than the first preset error threshold, it is determined that the vehicle does not meet the vehicle terminal self-learning conditions.

[0014] Through the above technical solution, when the current rack median value and the rack median calibration value are within a normal range, the rear-wheel steering system is controlled not to perform self-learning.

[0015] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, before controlling the rear-wheel steering system to perform the whole vehicle terminal self-learning, it also includes: judging whether the rear-wheel steering system triggers the whole vehicle terminal self-learning action; if the rear-wheel steering system triggers the whole vehicle terminal self-learning action, then controlling the rear-wheel steering system to perform the whole vehicle terminal self-learning.

[0016] Through the above technical solution, it is determined whether the whole vehicle terminal self-learning action can be performed, so that the rear-wheel steering system is controlled to perform the whole vehicle terminal self-learning when the rear-wheel steering system triggers the whole vehicle terminal self-learning.

[0017] In combination with the first aspect and the above-mentioned implementation manner, in some possible implementation manners, the determining whether the rear-wheel steering system triggers the terminal self-learning action of the whole vehicle includes: obtaining at least one calibration quantity of the vehicle and the maximum duration of the at least one calibration quantity, wherein the at least one calibration quantity includes the driving speed, the rear-wheel steering system motor request torque, the rear-wheel steering system receiving the front wheel angle and the rear-wheel steering system rack speed; determining whether the driving speed is greater than or equal to the first vehicle speed and whether the driving speed is less than or equal to the second vehicle speed, and whether the rear-wheel steering system motor request torque is greater than or equal to a preset threshold, and whether the rear-wheel steering system receives the front wheel Whether the angle is greater than or equal to the preset angle, and whether the rack speed of the rear-wheel steering system is less than or equal to the preset speed, and whether the maximum duration is greater than or equal to the preset duration; if the driving speed is greater than or equal to the first speed and the driving speed is less than or equal to the second speed, and the rear-wheel steering system motor request torque is greater than or equal to the preset threshold, and the rear-wheel steering system receives a front wheel angle greater than or equal to the preset angle, and the rack speed of the rear-wheel steering system is less than or equal to the preset speed, and the maximum duration is greater than or equal to the preset duration, then it is determined that the rear-wheel steering system triggers the vehicle terminal self-learning action.

[0018] Through the above technical solution, by determining the specific content of the vehicle terminal self-learning, the vehicle terminal self-learning can be performed when the above conditions are met.

[0019] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, after obtaining the temporary value of the end position self-learning of the rear-wheel steering system, it also includes: if the absolute value of the second difference is greater than or equal to the second preset error threshold, continue to control the rear-wheel steering system to perform whole-vehicle terminal self-learning until the new second difference absolute value is less than the second preset error threshold.

[0020] Through the above technical solution, when the temporary value of the terminal position self-learning and the rack mid-position calibration value are not within the normal range, the rear-wheel steering system continues to be controlled to perform terminal self-learning of the whole vehicle to improve the calibration accuracy.

[0021] In the second aspect, a mid-position calibration and end-position self-learning device based on a rear-wheel steering system is provided, and the device includes: a first acquisition module, used to obtain the current rack mid-position value and the rack mid-position calibration value when the steering wheel angle is the target angle; a second acquisition module, used to control the rear-wheel steering system to perform vehicle end-position self-learning if the absolute value of the first difference between the current rack mid-position value and the rack mid-position calibration value is greater than or equal to a first preset error threshold, and to obtain the end-position self-learning temporary value of the rear-wheel steering system after the number of self-learning times of the rear-wheel steering system reaches a first target number; an updating module, used to update the end-position self-learning value in the preset memory based on the end-position self-learning temporary value when the vehicle is powered off if the absolute value of the second difference between the end-position self-learning temporary value and the rack mid-position calibration value is less than a second preset error threshold.

[0022] In combination with the second aspect, in some possible implementations, before obtaining the current rack median value and rack median calibration value when the steering wheel angle is the target angle, the first acquisition module further includes: a receiving unit for receiving a median calibration instruction of a rear-wheel steering system in a bench test; a reading unit for controlling the rack of the rear-wheel steering system to move to the end position of the rear-wheel steering system at a target speed based on the median calibration instruction, and after controlling the rack of the rear-wheel steering system to move a second target number of times, reading the end temporary position calibration value of the rack of the rear-wheel steering system at the end position; a calculation unit for calculating the rack median calibration value of the rear-wheel steering system based on the end temporary position calibration value; an acquisition unit for acquiring an original median value of the rear-wheel steering system; a first judgment unit for judging whether an absolute value of a third difference between the rack median calibration value and the original median value is less than a third preset error threshold; and a storage unit for storing the rack median calibration value in the preset memory if the absolute value of the third difference is less than the third preset error threshold.

[0023] In combination with the second aspect and the above-mentioned implementation methods, in some possible implementation methods, after determining whether the absolute value of the third difference between the rack median calibration value and the original median value is less than the third preset error threshold, the first judgment unit further includes: a calibration subunit, which is used to reassemble the rear-wheel steering system if the absolute value of the third difference is greater than or equal to the third preset error threshold, control the rear-wheel steering system to perform terminal self-learning action in the bench test and recalibrate the terminal temporary position calibration value until the new absolute value of the third difference is less than the third preset error threshold.

[0024] In combination with the second aspect and the above-mentioned implementation methods, in some possible implementation methods, after obtaining the current rack median value and the rack median calibration value when the steering wheel angle is the target angle, the first acquisition module also includes: a first judgment subunit, which is used to determine that the vehicle does not meet the terminal self-learning conditions of the whole vehicle if the absolute value of the first difference is less than the first preset error threshold.

[0025] In combination with the second aspect and the above-mentioned implementation methods, in some possible implementation methods, before controlling the rear-wheel steering system to perform the whole vehicle terminal self-learning, the second acquisition module also includes: a second judgment unit, used to judge whether the rear-wheel steering system triggers the whole vehicle terminal self-learning action; a first control unit, used to control the rear-wheel steering system to perform the whole vehicle terminal self-learning if the rear-wheel steering system triggers the whole vehicle terminal self-learning action.

[0026] In combination with the second aspect and the above-mentioned implementation manner, in some possible implementation manners, the second judgment unit includes: an acquisition subunit, used to acquire at least one calibration quantity of the vehicle and a maximum duration of the at least one calibration quantity, wherein the at least one calibration quantity includes a driving speed, a rear-wheel steering system motor request torque, a front wheel angle received by the rear-wheel steering system, and a rear-wheel steering system rack speed; a judgment subunit, used to judge whether the driving speed is greater than or equal to a first vehicle speed and whether the driving speed is less than or equal to a second vehicle speed, and whether the rear-wheel steering system motor request torque is greater than or equal to a preset threshold, and whether the rear-wheel steering system receives the front wheel angle is greater than or equal to a preset threshold. equal to a preset angle, and whether the rack speed of the rear-wheel steering system is less than or equal to a preset speed, and whether the maximum duration is greater than or equal to a preset duration; a second judgment subunit, for judging that the rear-wheel steering system triggers the vehicle terminal self-learning action if the driving speed is greater than or equal to the first speed and the driving speed is less than or equal to the second speed, and the rear-wheel steering system motor request torque is greater than or equal to the preset threshold, and the rear-wheel steering system receives a front wheel angle greater than or equal to the preset angle, and the rack speed of the rear-wheel steering system is less than or equal to the preset speed, and the maximum duration is greater than or equal to the preset duration.

[0027] In combination with the second aspect and the above-mentioned implementation methods, in some possible implementation methods, after obtaining the temporary value of the end position self-learning of the rear-wheel steering system, the second acquisition module also includes: a second control unit, which is used to continue to control the rear-wheel steering system to perform whole-vehicle terminal self-learning if the absolute value of the second difference is greater than or equal to the second preset error threshold, until the new second difference absolute value is less than the second preset error threshold.

[0028] In a third aspect, a vehicle is provided, comprising the mid-position calibration and end position self-learning method based on the rear-wheel steering system as described in the above embodiment.

[0029] In a fourth aspect, a computer program product is provided, comprising: a computer program code, which, when executed on a computer, enables the computer to execute the method in the first aspect or any possible implementation of the first aspect.

[0030] In a fifth aspect, a computer-readable storage medium is provided, which stores a computer program code. When the computer program code runs on a computer, the computer executes the method in the above-mentioned first aspect or any possible implementation manner of the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1is a flow chart of a method for mid-position calibration and end-position self-learning based on a rear-wheel steering system provided in an embodiment of the present application;

[0032] Figure 2 This is an overall implementation flow chart of an embodiment of the present application;

[0033] Figure 3 A block diagram of a method and device for mid-position calibration and end-position self-learning based on a rear-wheel steering system provided in an embodiment of the present application;

[0034] Figure 4 A schematic diagram of the structure of a vehicle provided for one embodiment of the present application. DETAILED DESCRIPTION

[0035] The technical solution in the present application will be described clearly and in detail below in conjunction with the accompanying drawings. In the description of the embodiments of the present application, unless otherwise specified, " / " means or, for example, A / B can mean A or B: "and / or" in the text is only a description of the association relationship of associated objects, indicating that there can be three relationships, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, "multiple" means two or more than two.

[0036] In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as suggesting or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features.

[0037] RWS is widely used to improve the handling and stability of vehicles. In order to ensure the normal operation of the rear-wheel steering system, for RWS rear-wheel steering products, it is necessary to ensure that the rear wheel rack is in the middle position when the front wheel angle is 0, so as to avoid abnormal steering caused by deviation, thereby affecting driving safety. When the rear-wheel steering system cannot guarantee full function, the rack should return to the middle position and self-lock after power is restored. At the same time, in order to avoid RWS receiving the front wheel angle signal excessively and causing the rack to collide at the extreme position, the control system will set the left and right end limits. When the rack approaches the limit, the control system will reduce the power assistance to prevent the end collision. However, in the related technology, the rack is manually calibrated. The center position will be reduced in calibration efficiency and accuracy because its internal displacement sensor has not been calibrated. At the same time, when the rack end position is limited by the software limit method, the small rear wheel travel and high precision characteristics are ignored. Therefore, the process error when installed on the vehicle will cause the vehicle end position to deviate. The software limit method cannot effectively deal with these errors, thus affecting the accuracy and reliability of the system. Therefore, there is an urgent need for an automated and high-precision method for center position calibration and end position self-learning to solve the above-mentioned problems, thereby improving the center position calibration accuracy and the reliability of end position management of the rear-wheel steering system.

[0038] Figure 1 It is a schematic flow chart of a method for mid-position calibration and end-position self-learning based on a rear-wheel steering system provided in an embodiment of the present application.

[0039] For example, Figure 1 As shown, the method includes:

[0040] In step S101, the current rack center value and the rack center calibration value when the steering wheel angle is the target angle are obtained.

[0041] Optionally, in one embodiment of the present application, before obtaining the current rack median value and rack median calibration value when the steering wheel angle is the target angle, it also includes: receiving a median calibration instruction of the rear-wheel steering system in a bench test; controlling the rack of the rear-wheel steering system to move to the end position of the rear-wheel steering system at a target speed based on the median calibration instruction, and after controlling the rack of the rear-wheel steering system to move a second target number of times, reading the end temporary position calibration value of the rack of the rear-wheel steering system at the end position; calculating the rack median calibration value of the rear-wheel steering system based on the end temporary position calibration value; obtaining the original median value of the rear-wheel steering system; judging whether the absolute value of the third difference between the rack median calibration value and the original median value is less than a third preset error threshold; if the absolute value of the third difference is less than the third preset error threshold, storing the rack median calibration value in a preset memory.

[0042] Optionally, in one embodiment of the present application, after determining whether the absolute value of the third difference between the rack median calibration value and the original median value is less than a third preset error threshold, it also includes: if the absolute value of the third difference is greater than or equal to the third preset error threshold, reassembling the rear-wheel steering system, controlling the rear-wheel steering system to perform terminal self-learning action in the bench test and recalibrating the terminal temporary position calibration value until the new absolute value of the third difference is less than the third preset error threshold.

[0043] Among them, the third preset error threshold can be set by those skilled in the art according to actual test requirements, or can be determined through a limited number of computer simulations, and is not specifically limited here.

[0044] Specifically, in order to overcome the low calibration efficiency, insufficient calibration accuracy and position deviation problems caused by the center position of the rack of the rear-wheel steering system during manual calibration, which is caused by the vehicle assembly process error based on the software limit method, the embodiment of the present application combines the center position calibration based on the bench test and the self-learning of the end position of the whole vehicle to improve the center position calibration accuracy of the rear-wheel steering system and the reliability of the end position management.

[0045] Specifically, in the mid-position calibration of the bench test, first, the rear-wheel steering system is fixed on the workbench, the assembly rods on both sides are placed and stuck at the ends, and a mid-position calibration command of the rear-wheel steering system is sent to the diagnosis of the rear-wheel steering system; secondly, after receiving the mid-position calibration command of the rear-wheel steering system, the rack of the rear-wheel steering system is controlled to move to the end positions of the rear-wheel steering system at a target speed based on the mid-position calibration command, including the left end position and the right end position. To ensure the reliability of the mid-position calibration, it is necessary to control the rack of the rear-wheel steering system to cycle the left and right end positions for a second target number of times (for example, more than 5 times). When moving to the left and right end positions, the rack of the rear-wheel steering system will change direction, that is, the rack of the rear-wheel steering system will change direction when moving to the left end position, continue to move to the right end position, and retain and update the maximum value of the left end position and the right end position, wherein the end position conversion conditions are as follows:

[0046] End position transition condition = (rear wheel steering system rack speed ≤ S1) & (motor request torque ≥ T1 / |T2|), while duration > t1;

[0047] Among them, S1, T1, and t1 are all internal calibration quantities. The rack direction is positive on the left and negative on the right. S1 is the maximum moving speed of the rack of the rear-wheel steering system. T1 is the minimum requested torque on the left, and T2 is the minimum requested torque on the right. The left and right are the same, only the units are different. t1 is the minimum duration. When all the end position conversion conditions are met, the rack of the rear-wheel steering system will move in the opposite direction.

[0048] Again, after the maximum value calibration update of the left end position and the right end position, the control system has an independent end temporary position, including the left end temporary position and the right end temporary position. Therefore, it is necessary to read the end temporary position calibration value of the rear wheel steering system rack at the end position, including the left end temporary position calibration value of the left end temporary position and the right end temporary position calibration value of the right end temporary position, and verify the left end temporary position and the right end temporary position. The specific verification method is as follows:

[0049] The temporary position of the left end is > L1;

[0050] The temporary position of the right end is > R1;

[0051] Among them, L1 and R1 are generally the minimum mechanical end strokes specified when the rear-wheel steering system is designed, and both are the same for left and right.

[0052] like Figure 2 As shown, after the left end temporary position and the right end temporary position are verified, the rack center position calibration value of the rear wheel steering system is calculated based on the left end temporary position and the right end temporary position, that is, the left end temporary position calibration value and the right end temporary position calibration value, wherein the rack center position calibration value calculation formula is as follows:

[0053] (Temporary position of the left end + temporary position of the right end) / 2 = rack center calibration value;

[0054] It should be noted that only when the left-side temporary position and the right-side temporary position meet the above-mentioned verification conditions, can the center calibration of the rear-wheel steering system pass and calculate the center calibration value of the rack; otherwise, the center calibration is judged to have failed and needs to be recalibrated.

[0055] Finally, after the rear-wheel steering system is calibrated, it is necessary to further obtain the original median value of the rear-wheel steering system, and determine whether the absolute value of the third difference between the rack median calibration value and the original median value is less than a third preset error threshold (e.g., Z1). If the absolute value of the third difference is less than the third preset error threshold, the rack median calibration value is stored in a preset memory (e.g., Nvm (Non-Volatile Memory)).

[0056] Among them, the original median value is the initial power-on of the rear-wheel steering system after off-line assembly. When the rear-wheel steering system receives the steering wheel angle as the target angle, such as the front wheel angle signal 0°, the displacement sensor will automatically read the median value. The absolute value of the third difference between the rack median calibration value and the original median value can be expressed as:

[0057] |Rack median calibration value - original median value|<Z1

[0058] Among them, Z1 is the calibration value. In order to avoid a large gap between the original median value and the rack median calibration value, the error value Z1 is set. If the absolute value of the third difference between the rack median calibration value and the original median value is less than the error value Z1, the Nvm write function is called when the system is powered off to store the rack median calibration value in Nvm.

[0059] Alternatively, if Figure 2 As shown, if the absolute value of the third difference between the rack median calibration value and the original median value is greater than or equal to the third preset error threshold, it means that there is a problem in the assembly process, and it is necessary to check the assembly process, reassemble the rear-wheel steering system, and further control the rear-wheel steering system to perform terminal self-learning action in the bench test and recalibrate the terminal temporary position calibration value until the new third difference absolute value is less than the third preset error threshold.

[0060] Furthermore, after the rear-wheel steering system of the embodiment of the present application completes the median calibration in the bench test, it needs to be assembled on the vehicle and read the steering wheel angle as the target angle (for example, 0°) when powered on. The current rack median value when the displacement instruction received by the rear-wheel steering system is 0 and the rack median calibration value stored in Nvm are compared, and it is determined whether the absolute value of the first difference between the current rack median value and the rack median calibration value is within the normal range, and further analysis is performed based on the error result.

[0061] In step S102, if the absolute value of the first difference between the current rack median value and the rack median calibration value is greater than or equal to the first preset error threshold, the rear-wheel steering system is controlled to perform vehicle terminal self-learning, and after the number of self-learning times of the rear-wheel steering system reaches the first target number, the terminal position self-learning temporary value of the rear-wheel steering system is obtained.

[0062] Optionally, in one embodiment of the present application, before controlling the rear-wheel steering system to perform vehicle terminal self-learning, it also includes: determining whether the rear-wheel steering system triggers the vehicle terminal self-learning action; if the rear-wheel steering system triggers the vehicle terminal self-learning action, then controlling the rear-wheel steering system to perform vehicle terminal self-learning.

[0063] Optionally, in one embodiment of the present application, determining whether the rear-wheel steering system triggers the terminal self-learning action of the whole vehicle includes: obtaining at least one calibration quantity of the vehicle and the maximum duration of at least one calibration quantity, wherein the at least one calibration quantity includes the driving speed, the rear-wheel steering system motor request torque, the rear-wheel steering system receiving the front wheel angle and the rear-wheel steering system rack speed; determining whether the driving speed is greater than or equal to the first speed and the driving speed is less than or equal to the second speed, and whether the rear-wheel steering system motor request torque is greater than or equal to a preset threshold, and the rear-wheel steering system receiving Whether the front wheel angle is greater than or equal to the preset angle, and the rack speed of the rear-wheel steering system is less than or equal to the preset speed, and the maximum duration is greater than or equal to the preset duration; if the vehicle speed is greater than or equal to the first speed and less than or equal to the second speed, and the rear-wheel steering system motor request torque is greater than or equal to the preset threshold, and the rear-wheel steering system receives a front wheel angle greater than or equal to the preset angle, and the rack speed of the rear-wheel steering system is less than or equal to the preset speed, and the maximum duration is greater than or equal to the preset duration, then it is determined that the rear-wheel steering system triggers the vehicle terminal self-learning action.

[0064] Among them, the first preset error threshold, the first vehicle speed, the second vehicle speed, the preset threshold, the preset angle, the preset speed and the preset duration can all be set by technical personnel in this field according to actual test requirements, or can be determined through a limited number of computer simulations, and are not specifically limited here.

[0065] Specifically, Figure 2 As shown, if the absolute value of the first difference between the current rack median value and the rack median calibration value is not within the normal range, that is, the absolute value of the first difference is greater than or equal to the first preset error threshold (for example, Z2), it means that the error between the current rack median value and the rack median calibration value is large, and the rear wheel steering system needs to be reassembled and controlled to perform vehicle terminal self-learning, wherein the difference between the current rack median value and the rack median calibration value can be expressed by the following formula:

[0066] |Rack median calibration value - current rack median value|≥Z2;

[0067] Specifically, the rear-wheel steering system on the whole vehicle system will not always be able to perform terminal self-learning like in the bench test. Since the rack of the rear-wheel steering system will not run to the extreme position in most driving scenarios, the self-learning function will only be triggered when the front wheel signal received by the rear-wheel steering system exceeds a certain angle. Therefore, before controlling the rear-wheel steering system to perform terminal self-learning of the whole vehicle, it is necessary to determine whether the rear-wheel steering system triggers the terminal self-learning action of the whole vehicle. If the rear-wheel steering system triggers the terminal self-learning action of the whole vehicle, the rear-wheel steering system is controlled to perform terminal self-learning of the whole vehicle.

[0068] First, at least one calibration quantity of the vehicle and the maximum duration of at least one calibration quantity are obtained, wherein the at least one calibration quantity includes a driving speed, a rear-wheel steering system motor request torque, a front wheel angle received by the rear-wheel steering system, and a rear-wheel steering system rack speed; secondly, it is determined whether the driving speed is greater than or equal to a first vehicle speed (for example, 0) and whether the driving speed is less than or equal to a second vehicle speed (for example, V1), whether the rear-wheel steering system motor request torque is greater than or equal to a preset threshold value (for example, T3 or T4), and whether the front wheel angle received by the rear-wheel steering system is greater than or equal to a preset angle ( For example, A1 or A2), and whether the rack speed of the rear-wheel steering system is less than or equal to the preset speed (for example, S2), and whether the maximum duration is greater than or equal to the preset duration (for example, t2), if the driving speed is greater than or equal to 0 and the driving speed is less than or equal to V1, and the rear-wheel steering system motor request torque is greater than or equal to T3, and the rear-wheel steering system receives the front wheel angle greater than or equal to A1, and the rack speed of the rear-wheel steering system is less than or equal to S2, and the maximum duration is greater than or equal to t2, then it is determined that the rear-wheel steering system triggers the vehicle terminal self-learning action, and the specific formula is as follows:

[0069] Self-learning left position = (0≤vehicle speed≤V1)&(rear wheel steering system motor request torque≥T3)&(rear wheel steering system receiving front wheel angle≥A1)&(rear wheel steering system rack speed≤S2)&(maximum duration≥t2);

[0070] Self-learning right position = (0≤vehicle speed≤V1)&(rear wheel steering system motor request torque≥T4)&(rear wheel steering system receiving front wheel angle≥A2)&(rear wheel steering system rack speed≤S2)&(maximum duration≥t2);

[0071] Among them, V1 is the limit of driving speed. The movement strategy of the rear-wheel steering system is to rotate with the front wheels at low speed and keep the neutral self-locking at high speed. The self-learning strategy can only be performed at low speed; T3 and T4 are the motor request torque of the rear-wheel steering system. Only when the power motor torque of the rear-wheel steering system exceeds a certain value can it be possible to indicate that the rack has moved to the end. However, if the motor request torque of the rear-wheel steering system does not exceed a certain value, it must not have moved to the end; A1 and A2 are the front wheel angle signals received by the rear-wheel steering system. Under normal circumstances, the rear-wheel steering The system rack stroke is relatively short, usually ±10°, so when the received front wheel steering wheel angle signal exceeds ±10°, the rear wheel steering system rack will move to the end at most; S2 is the rear wheel steering system rack speed, and the rack stops moving when it moves to the end, so when the rear wheel steering system rack speed is less than a certain value, it means that the rack has moved to the end; t2 is the maximum duration of all the above calibration quantities, to ensure whether the rack has moved to the end, so when the maximum duration of the above calibration quantities exceeds a certain value, it means that the rack position is accurately at the end.

[0072] Optionally, in one embodiment of the present application, after obtaining the current rack median value and the rack median calibration value when the steering wheel angle is the target angle, it also includes: if the absolute value of the first difference is less than a first preset error threshold, it is determined that the vehicle does not meet the terminal self-learning conditions of the whole vehicle.

[0073] Specifically, if the absolute value of the first difference between the current rack median value and the rack median calibration value is less than the first preset error threshold, that is, |rack median calibration value-current rack median value|<Z2, it means that the error between the current rack median value and the rack median calibration value is small, and there is no need to control the rear-wheel steering system for vehicle terminal self-learning.

[0074] Furthermore, to ensure the reliability of end position self-learning, the number of learning times for the left / right side must be greater than 5 times respectively, and the maximum value after 5 self-learning is compared to obtain the temporary value of end position self-learning and temporarily update it. That is, after the above conditions are met and the left and right sides have each learned for more than 5 times, the maximum value of the left and right positions is recorded, which is the temporary value of end position self-learning, and then the temporary value of end position self-learning is verified in the next system.

[0075] It should be noted that the verification steps for the self-learning position of the vehicle terminal are the same as the verification steps for the temporary position of the terminal in the above-mentioned bench test. To avoid redundancy, they will not be described in detail here.

[0076] In step S103, if the second absolute value of the difference between the terminal position self-learning temporary value and the rack center calibration value is less than the second preset error threshold, the terminal position self-learning value in the preset memory is updated based on the terminal position self-learning temporary value when the vehicle is powered off.

[0077] Optionally, in one embodiment of the present application, after obtaining the temporary value of the end position self-learning of the rear-wheel steering system, it also includes: if the absolute value of the second difference is greater than or equal to the second preset error threshold, continue to control the rear-wheel steering system to perform whole-vehicle terminal self-learning until the new absolute value of the second difference is less than the second preset error threshold.

[0078] The second preset error threshold may be set by those skilled in the art according to actual test requirements, or may be determined through a limited number of computer simulations, and is not specifically limited here.

[0079] Specifically, Figure 2As shown, after obtaining the temporary value of the terminal position self-learning, it is necessary to further verify the temporary value of the terminal position self-learning, that is, to determine whether the second difference absolute value between the temporary value of the terminal position self-learning and the rack mid-position calibration value is less than the second preset error threshold (for example, Z3). If the second difference absolute value between the temporary value of the terminal position self-learning and the rack mid-position calibration value is less than the second preset error threshold, then when the vehicle is powered off, the terminal position self-learning value in Nvm is updated based on the temporary value of the terminal position self-learning, wherein the difference formula between the temporary value of the terminal position self-learning and the rack mid-position calibration value is expressed as:

[0080] |Temporary value of end position self-learning - rack mid-position calibration value|<Z3;

[0081] Among them, Z3 is generally the maximum stroke value error of the mechanical design rack. As long as the error between the temporary self-learning value of the left and right end positions and the rack mid-position calibration value of the bench mid-position calibration is less than Z3, it means that the temporary self-learning value of the end position is reasonable, the verification passes, and the end position is updated and written into Nvm when power is off.

[0082] Furthermore, if the absolute value of the second difference between the temporary value of the end position self-learning and the rack median calibration value is greater than or equal to the second preset error threshold, that is, |temporary value of the end position self-learning - rack median calibration value|≥Z3, it means that the deviation between the temporary value of the end position self-learning and the rack median calibration value is large, and the end position self-learning is not in place, and the rear-wheel steering system needs to continue to be controlled to perform terminal self-learning of the whole vehicle until the new absolute value of the second difference is less than the second preset error threshold.

[0083] It should be noted that when the vehicle system is not powered off, if the number of self-learning cycles is greater than 5, and the temporary value of the terminal position self-learning is updated and verified to be reasonable, the temporary value of the terminal position self-learning is temporarily stored and is not written to Nvm in real time. When the vehicle system is powered off, the Nvm write function is directly called to update the current self-learning temporary value of the terminal position self-learning and write it to Nvm.

[0084] In summary, the embodiments of the present application, based on the above-mentioned specific discussion of the mid-position calibration and end position self-learning method based on the rear-wheel steering system, can achieve the following beneficial effects:

[0085] (1) By combining the bench mid-position calibration with the vehicle self-learning, the values ​​obtained at different stages are verified to ensure the accuracy of each self-learning result, thereby improving the calibration accuracy of the overall system and solving the problem of the internal mid-position calibration of the RWS displacement sensor and the problem of the end position deviation when the RWS is installed on the vehicle;

[0086] (2) By setting a limit on the number of self-learning times (e.g., 5 times), the system can be ensured to converge stably after multiple self-learnings and avoid over-adjustment, thereby enhancing the system adaptability;

[0087] (3) By verifying the error value, it is ensured that each self-learning result is within the allowable error range, thereby improving the reliability of the system.

[0088] In summary, according to the method for mid-position calibration and end-position self-learning based on the rear-wheel steering system of the embodiment of the present application, the current rack mid-position value and rack mid-position calibration value are obtained. If the absolute value of the first difference between the current rack mid-position value and the rack mid-position calibration value is greater than or equal to the first preset error threshold, the rear-wheel steering system is controlled to perform vehicle end-position self-learning, and after the number of self-learning times reaches the first target number, the end-position self-learning temporary value and rack mid-position calibration value of the rear-wheel steering system are obtained. If the absolute value of the second difference between the end-position self-learning temporary value and the rack mid-position calibration value is less than the second preset error threshold, when the vehicle is powered off, the end-position self-learning value in the preset memory is updated based on the end-position self-learning temporary value. This method can be based on the combination of the mid-position end-position self-learning of the test bench and the end-position self-learning of the vehicle, and through multiple cycles and average value calculation, to ensure the accuracy and reliability of the calibration results.

[0089] Figure 3 It is a structural schematic diagram of a mid-position calibration and end position self-learning device based on a rear-wheel steering system provided in an embodiment of the present application.

[0090] For example, Figure 3 As shown, the device may include: a first acquisition module 100 , a second acquisition module 200 and an update module 300 .

[0091] Wherein, the first acquisition module 100 is used to acquire the current rack median value and the rack median calibration value when the steering wheel angle is the target angle;

[0092] The second acquisition module 200 is used to control the rear-wheel steering system to perform vehicle terminal self-learning if the absolute value of the first difference between the current rack median value and the rack median calibration value is greater than or equal to a first preset error threshold, and to acquire a terminal position self-learning temporary value of the rear-wheel steering system after the number of self-learning times of the rear-wheel steering system reaches a first target number;

[0093] The updating module 300 is used to update the terminal position self-learning value in the preset memory based on the terminal position self-learning temporary value when the vehicle is powered off if the absolute value of the second difference between the terminal position self-learning temporary value and the rack mid-position calibration value is less than the second preset error threshold.

[0094] Optionally, in one embodiment of the present application, before obtaining the current rack median value and the rack median calibration value when the steering wheel angle is the target angle, the first obtaining module 100 further includes:

[0095] A receiving unit, used for receiving a mid-position calibration instruction of a rear wheel steering system in a bench test;

[0096] a reading unit, for controlling the rack of the rear-wheel steering system to move to the end position of the rear-wheel steering system at a target speed based on the mid-position calibration instruction, and reading the end temporary position calibration value of the rack of the rear-wheel steering system at the end position after controlling the rack of the rear-wheel steering system to move a second target number of times;

[0097] A calculation unit, used for calculating a rack mid-position calibration value of a rear-wheel steering system based on a terminal temporary position calibration value;

[0098] An acquisition unit, used for acquiring an original median value of a rear wheel steering system;

[0099] A first judging unit, used to judge whether a third absolute value of a difference between the rack median calibration value and the original median value is less than a third preset error threshold;

[0100] The storage unit is used to store the rack center calibration value in a preset memory if the absolute value of the third difference is less than a third preset error threshold.

[0101] Optionally, in one embodiment of the present application, after determining whether the absolute value of the third difference between the rack median calibration value and the original median value is less than a third preset error threshold, the first determination unit further includes:

[0102] The calibration subunit is used to reassemble the rear-wheel steering system if the absolute value of the third difference is greater than or equal to a third preset error threshold, control the rear-wheel steering system to perform terminal self-learning action in the bench test and recalibrate the terminal temporary position calibration value until the new absolute value of the third difference is less than the third preset error threshold.

[0103] Optionally, in one embodiment of the present application, after obtaining the current rack median value and the rack median calibration value when the steering wheel angle is the target angle, the first obtaining module 100 further includes:

[0104] The first determination subunit is used to determine that the vehicle does not meet the vehicle terminal self-learning conditions if the absolute value of the first difference is less than a first preset error threshold.

[0105] Optionally, in one embodiment of the present application, before controlling the rear wheel steering system to perform vehicle terminal self-learning, the second acquisition module 200 further includes:

[0106] The second judgment unit is used to judge whether the rear wheel steering system triggers the vehicle terminal self-learning action;

[0107] The first control unit is used to control the rear-wheel steering system to perform the whole vehicle terminal self-learning if the rear-wheel steering system triggers the whole vehicle terminal self-learning action.

[0108] Optionally, in one embodiment of the present application, the second judgment unit includes:

[0109] an acquisition subunit, configured to acquire at least one calibration quantity of the vehicle and a maximum duration of at least one calibration quantity, wherein the at least one calibration quantity includes a vehicle speed, a torque requested by a motor of a rear-wheel steering system, a front wheel angle received by the rear-wheel steering system, and a rack speed of the rear-wheel steering system;

[0110] a judgment subunit, used to judge whether the driving speed is greater than or equal to the first speed and the driving speed is less than or equal to the second speed, and whether the torque requested by the motor of the rear-wheel steering system is greater than or equal to a preset threshold, and whether the front wheel angle received by the rear-wheel steering system is greater than or equal to a preset angle, and whether the rack speed of the rear-wheel steering system is less than or equal to a preset speed, and whether the maximum duration is greater than or equal to a preset duration;

[0111] The second determination subunit is used to determine that the rear-wheel steering system triggers the terminal self-learning action of the whole vehicle if the driving speed is greater than or equal to the first speed and less than or equal to the second speed, and the rear-wheel steering system motor request torque is greater than or equal to a preset threshold, and the front wheel angle received by the rear-wheel steering system is greater than or equal to a preset angle, and the rack speed of the rear-wheel steering system is less than or equal to a preset speed, and the maximum duration is greater than or equal to a preset duration.

[0112] Optionally, in one embodiment of the present application, after acquiring the end position self-learning temporary value of the rear-wheel steering system, the second acquisition module 200 further includes:

[0113] The second control unit is used to continue controlling the rear-wheel steering system to perform vehicle terminal self-learning if the absolute value of the second difference is greater than or equal to the second preset error threshold, until the new absolute value of the second difference is less than the second preset error threshold.

[0114] In summary, according to the mid-position calibration and end position self-learning device based on the rear-wheel steering system of the embodiment of the present application, the current rack mid-position value and rack mid-position calibration value are obtained. If the absolute value of the first difference between the current rack mid-position value and the rack mid-position calibration value is greater than or equal to the first preset error threshold, the rear-wheel steering system is controlled to perform vehicle end self-learning, and after the number of self-learning times reaches the first target number, the end position self-learning temporary value and rack mid-position calibration value of the rear-wheel steering system are obtained. If the absolute value of the second difference between the end position self-learning temporary value and the rack mid-position calibration value is less than the second preset error threshold, when the vehicle is powered off, the end position self-learning value in the preset memory is updated based on the end position self-learning temporary value. This method can be based on the combination of the mid-position end self-learning of the test bench and the end self-learning of the vehicle, and through multiple cycles and average value calculation, to ensure the accuracy and reliability of the calibration results.

[0115] Figure 4 A schematic structural diagram of a vehicle provided in an embodiment of the present application.

[0116] It should be understood that the above-described method can be applied to Figure 4 In a vehicle of the structure shown.

[0117] In addition, an embodiment of the present application also protects a device, which may include a memory and a processor, wherein the memory stores an executable program code, and the processor is used to call and execute the executable program code to execute the mid-position calibration and end position self-learning method based on the rear-wheel steering system provided in the embodiment of the present application.

[0118] Furthermore, the device also includes: a communication interface 403 for communication between the memory 401 and the processor 402 .

[0119] In this embodiment, the functional modules of the device can be divided according to the above method example. For example, each functional module can be corresponded, or two or more functions can be integrated into one processing module. The above integrated module can be implemented in the form of hardware. It should be noted that the division of modules in this embodiment is schematic and is only a logical function division. There may be other division methods in actual implementation.

[0120] It should be noted that all relevant contents of each step involved in the above method embodiment can be referred to the functional description of the corresponding functional module, which will not be repeated here.

[0121] It should be understood that the device provided in this embodiment is used to execute the above-mentioned mid-position calibration and end position self-learning method based on the rear-wheel steering system, and thus can achieve the same effect as the above-mentioned implementation method.

[0122] In the case of an integrated unit, the device may include a processing module and a storage module. When the device is applied to a vehicle, the processing module may be used to control and manage the actions of the vehicle. The storage module may be used to support the vehicle in executing mutual program codes, etc.

[0123] The processing module may be a processor 402 or a controller, which may implement or execute various exemplary logic blocks, modules and circuits disclosed in the present application. The processor 402 may also be a combination that implements a computing function, such as a combination of one or more microprocessors, a combination of a digital signal processing (DSP) and a microprocessor, etc. The storage module may be a memory 401.

[0124] In addition, the device provided in the embodiments of the present application may specifically be a chip, a component or a module, and the chip may include a connected processor 402 and a memory 401; wherein the memory 401 is used to store instructions, and when the processor calls and executes the instructions, the chip can execute the mid-position calibration and end position self-learning method based on the rear-wheel steering system provided in the above embodiments.

[0125] This embodiment also provides a computer-readable storage medium, which stores computer program code. When the computer program code runs on a computer, the computer executes the above-mentioned related method steps to implement a mid-position calibration and end position self-learning method based on a rear-wheel steering system provided in the above embodiment.

[0126] This embodiment also provides a computer program product. When the computer program product runs on a computer, it enables the computer to execute the above-mentioned related steps to implement a mid-position calibration and end position self-learning method based on a rear-wheel steering system provided in the above embodiment.

[0127] Among them, the device, computer-readable storage medium, computer program product or chip provided in this embodiment is used to execute the corresponding method provided above. Therefore, the beneficial effects that can be achieved can refer to the beneficial effects in the corresponding method provided above, and will not be repeated here.

[0128] Through the description of the above implementation methods, technical personnel in the relevant field can understand that for the convenience and simplicity of description, only the division of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above.

[0129] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of modules or units is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0130] The above contents are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for mid-position calibration and end-position self-learning based on a rear-wheel steering system, characterized in that: The method comprises the following steps: Get the current rack center value and rack center calibration value when the steering wheel angle is the target angle; If the absolute value of the first difference between the current rack median value and the rack median calibration value is greater than or equal to a first preset error threshold, the rear-wheel steering system is controlled to perform vehicle terminal self-learning, and after the number of self-learning times of the rear-wheel steering system reaches a first target number, a terminal position self-learning temporary value of the rear-wheel steering system is obtained; If the second absolute value of the difference between the terminal position self-learning temporary value and the rack center position calibration value is less than a second preset error threshold, the terminal position self-learning value in the preset memory is updated based on the terminal position self-learning temporary value when the vehicle is powered off.

2. The method according to claim 1, characterized in that Before obtaining the current rack center value and the rack center calibration value when the steering wheel angle is the target angle, the method further includes: Receive the center calibration command of the rear wheel steering system during bench testing; Controlling the rack of the rear-wheel steering system to move to the end position of the rear-wheel steering system at a target speed based on the mid-position calibration instruction, and after controlling the rack of the rear-wheel steering system to move a second target number of times, reading the end temporary position calibration value of the rack of the rear-wheel steering system at the end position; Calculating a rack mid-position calibration value of the rear-wheel steering system based on the terminal temporary position calibration value; Obtaining an original median value of the rear wheel steering system; Determine whether a third absolute value of a difference between the rack median calibration value and the original median value is less than a third preset error threshold; If the absolute value of the third difference is smaller than the third preset error threshold, the rack center calibration value is stored in the preset memory.

3. The method according to claim 2, characterized in that After determining whether the absolute value of the third difference between the rack median calibration value and the original median value is less than the third preset error threshold, the method further includes: If the absolute value of the third difference is greater than or equal to the third preset error threshold, the rear-wheel steering system is reassembled, and the rear-wheel steering system is controlled to perform terminal self-learning action in the bench test and recalibrate the terminal temporary position calibration value until the new absolute value of the third difference is less than the third preset error threshold.

4. The method according to claim 1, characterized in that After obtaining the current rack center value and the rack center calibration value when the steering wheel angle is the target angle, the method further includes: If the absolute value of the first difference is less than the first preset error threshold, it is determined that the vehicle does not meet the vehicle terminal self-learning conditions.

5. The method according to claim 1, characterized in that Before controlling the rear wheel steering system to perform the vehicle terminal self-learning, the method further includes: Determining whether the rear-wheel steering system triggers a vehicle terminal self-learning action; If the rear-wheel steering system triggers the whole vehicle terminal self-learning action, the rear-wheel steering system is controlled to perform the whole vehicle terminal self-learning.

6. The method according to claim 5, characterized in that The determining whether the rear wheel steering system triggers the vehicle terminal self-learning action includes: Acquire at least one calibration quantity of the vehicle and a maximum duration of the at least one calibration quantity, wherein the at least one calibration quantity includes a vehicle speed, a rear-wheel steering system motor request torque, a front wheel angle received by the rear-wheel steering system, and a rack speed of the rear-wheel steering system; Determine whether the driving speed is greater than or equal to a first speed and less than or equal to a second speed, and whether the rear-wheel steering system motor request torque is greater than or equal to a preset threshold, and whether the rear-wheel steering system receives a front wheel angle greater than or equal to a preset angle, and whether the rear-wheel steering system rack speed is less than or equal to a preset speed, and whether the maximum duration is greater than or equal to a preset duration; If the driving speed is greater than or equal to the first speed and the driving speed is less than or equal to the second speed, and the rear-wheel steering system motor requested torque is greater than or equal to the preset threshold, and the front wheel angle received by the rear-wheel steering system is greater than or equal to the preset angle, and the rear wheel steering system rack speed is less than or equal to the preset speed, and the maximum duration is greater than or equal to the preset duration, it is determined that the rear-wheel steering system triggers the vehicle terminal self-learning action.

7. The method according to claim 1, characterized in that After obtaining the temporary value of the end position self-learning of the rear wheel steering system, the method further includes: If the absolute value of the second difference is greater than or equal to the second preset error threshold, the rear-wheel steering system continues to be controlled to perform vehicle terminal self-learning until the new absolute value of the second difference is less than the second preset error threshold.

8. A mid-position calibration and end position self-learning device based on a rear-wheel steering system, characterized in that: The device comprises: The first acquisition module is used to acquire the current rack median value and the rack median calibration value when the steering wheel angle is the target angle; A second acquisition module is used to control the rear-wheel steering system to perform vehicle terminal self-learning if the absolute value of the first difference between the current rack median value and the rack median calibration value is greater than or equal to a first preset error threshold, and to acquire a terminal position self-learning temporary value of the rear-wheel steering system after the number of self-learning times of the rear-wheel steering system reaches a first target number; An updating module is used to update the end position self-learning value in the preset memory based on the end position self-learning temporary value when the vehicle is powered off if the absolute value of the second difference between the end position self-learning temporary value and the rack mid-position calibration value is less than a second preset error threshold.

9. A vehicle, characterized in that: The vehicle comprises: a mid-position calibration and end-position self-learning method based on a rear-wheel steering system as described in any one of claims 1 to 7 above.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed, the method according to any one of claims 1 to 7 is implemented.

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