Methods and devices for protecting the rack ends of vehicles and electric power steering systems

Abstract

This invention discloses a method and device for protecting the rack end of a vehicle and an electric power steering system. The method includes: acquiring the steering wheel speed and steering wheel angle; when the steering wheel speed and steering wheel angle meet a first preset condition, acquiring the actual motor current and actual motor speed; acquiring the motor damping current based on the actual motor speed; and limiting the motor assist current based on the actual motor current, the motor damping current, and a target current limit to protect the rack end of the electric power steering system. The rack end protection method of this invention, when the rack end protection condition is met, limits the motor assist current based on the actual motor current, the target current limit, and the motor damping current that changes in real time with the motor speed. This effectively captures the driver's steering intention, ensures that the rate of decrease of the end protection current reaches the expected effect, avoids a sudden impact sensation at the rack end, and is applicable to current limiting under various operating conditions.

Description

Technical Field

[0001] This invention relates to the field of vehicle technology, and in particular to a method for protecting the rack end of an electric power steering system, a vehicle, and a rack end protection device for an electric power steering system. Background Technology

[0002] With the rapid advancements in automotive electrification, intelligence, and connectivity, the electric power steering (EPS) system, as a core automotive component, has become an indispensable element in evaluating overall vehicle performance, particularly in terms of its intelligence and integration with vehicle comfort.

[0003] The rack end protection function is an important part of the debugging of the EPS electronic control unit of the electric power steering system. It can replace the traditional mechanical method (by adding a mechanical limit sleeve or limit ring) for rack end protection and restriction, which is more intelligent, convenient and precise.

[0004] The significance of rack end protection: Electric power steering ultimately achieves wheel rotation through the left and right movement of the rack. When the steering wheel is turned to its limit, the inner ball joint rod connected to the rack end will impact the housing. Without rack end protection, the impact force between the inner ball joint rod and the mechanical housing would be excessive, easily causing damage to the mechanical assembly, reducing its lifespan, and the noise generated by the impact would cause driver discomfort. The sudden increase in steering wheel torque would also result in poor steering feel. The introduction of rack end protection reduces the motor's assist current at the rack end, reducing the impact force between the rod and the housing, effectively suppressing the above problems. Current control methods result in a weak sense of intervention after the end protection function is activated, and the rate of decrease in the end protection current does not meet the expected effect, failing to satisfy user needs. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the first objective of this invention is to propose a rack end protection method for an electric power steering system. When the rack end protection conditions are met, the motor assist current is limited by using the actual motor current, the target current limit, and the motor damping current that changes in real time with the motor speed. This effectively captures the driver's steering intentions, ensures that the end protection current decreases at the expected rate, avoids a sudden impact sensation at the rack end, and is applicable to current limiting under various operating conditions.

[0006] The second objective of this invention is to provide a vehicle.

[0007] The third objective of this invention is to provide a rack end protection device for an electric power steering system.

[0008] To achieve the above objectives, a first aspect of the present invention provides a method for protecting the rack end of an electric power steering system, comprising: acquiring a steering wheel rotation speed and a steering wheel angle; acquiring an actual motor current and an actual motor rotation speed when the steering wheel rotation speed and steering wheel angle meet a first preset condition; acquiring a motor damping current based on the actual motor rotation speed; and limiting the motor assist current based on the actual motor current, the motor damping current, and a target current limit to protect the rack end of the electric power steering system.

[0009] According to an embodiment of the present invention, a method for protecting the rack end of an electric power steering system first acquires the steering wheel speed and steering wheel angle. When the steering wheel speed and steering wheel angle meet a first preset condition, the actual motor current and actual motor speed are acquired. Then, the motor damping current is acquired based on the actual motor speed. Finally, the motor assist current is limited based on the actual motor current, the motor damping current, and a target current limit to protect the rack end of the electric power steering system. Thus, when the rack end protection condition is met, this method limits the motor assist current based on the actual motor current, the target current limit, and the motor damping current that changes in real time with the motor speed. This effectively captures the driver's steering intention, ensures that the rate of decrease of the end protection current reaches the expected effect, avoids a sudden impact sensation at the rack end, and is applicable to current limiting under various operating conditions.

[0010] In addition, the rack end protection method for the electric power steering system according to the above embodiments of the present invention may also have the following additional technical features:

[0011] According to one embodiment of the present invention, limiting the motor assist current based on the actual motor current, the motor damping current, and the target current limit includes: calculating the sum of the currents between the actual motor current, the motor damping current, and the target current limit, and limiting the motor assist current based on the sum of the currents.

[0012] According to one embodiment of the present invention, limiting the motor assist current based on the actual motor current, the motor damping current, and the target current limit further includes: determining the relationship between the sum of the currents and a preset minimum current threshold; limiting the motor assist current based on the sum of the currents when the sum of the currents is greater than the preset minimum current threshold; and limiting the motor assist current based on the preset minimum current threshold when the sum of the currents is less than or equal to the preset minimum current threshold.

[0013] According to one embodiment of the present invention, obtaining the motor damping current based on the actual motor speed includes: multiplying the actual motor speed by a preset coefficient to obtain the motor damping current, wherein the preset coefficient is a negative value.

[0014] According to an embodiment of the present invention, the above-described method for protecting the rack end of an electric power steering system further includes: obtaining the steering wheel exit angle; obtaining the current difference between the actual current of the motor and the set current; and correcting the motor damping current based on the steering wheel entry angle, the steering wheel exit angle, the current difference, and the steering wheel rotation speed.

[0015] According to one embodiment of the present invention, correcting the motor damping current based on the steering wheel entry angle, the steering wheel exit angle, the current difference, and the steering wheel rotation speed includes: obtaining the angle difference between the steering wheel entry angle and the steering wheel exit angle; determining a first time based on the steering wheel rotation speed and the angle difference; determining a correction value based on the first time and the current difference; and correcting the motor damping current based on the correction value.

[0016] According to an embodiment of the present invention, the above-described method for protecting the rack end of an electric power steering system further includes: determining the current operating condition of the steering wheel; when the current operating condition of the steering wheel is engaged, if the correction value is greater than a first correction threshold, then correcting the motor damping current according to the first correction threshold; if the correction value is less than or equal to the first correction threshold, then correcting the motor damping current according to the correction value; when the current operating condition of the steering wheel is disengaged, if the correction value is greater than a second correction threshold, then correcting the motor damping current according to the second correction threshold; if the correction value is less than or equal to the second correction threshold, then correcting the motor damping current according to the correction value.

[0017] According to one embodiment of the present invention, the corresponding steering wheel entry angle is obtained based on the steering wheel rotation speed. When the current steering wheel angle is greater than the corresponding steering wheel entry angle, it is determined that the steering wheel rotation speed and the steering wheel angle satisfy a first preset condition. When the steering wheel rotation speed is less than a first set rotation speed, or the vehicle speed is less than a second set vehicle speed and the steering wheel angle is greater than a set angle threshold, it is determined that the steering wheel rotation speed and the steering wheel angle do not satisfy the first preset condition.

[0018] To achieve the above objectives, a second aspect of the present invention provides a vehicle comprising: a memory, a processor, and a control program for an electric power steering system stored in the memory and executable on the processor. When the processor executes the control program for the electric power steering system, it implements the above-described method for protecting the rack end of the electric power steering system.

[0019] According to the vehicle of the present invention, when the processor executes the control program of the electric power steering system, the above-mentioned rack end protection method of the electric power steering system is realized. It can effectively capture the driver's steering intention, ensure that the end protection current decrease rate reaches the expected effect, avoid the sudden impact feeling at the rack end, and is applicable to current limitation under various operating conditions.

[0020] To achieve the above objectives, a rack end protection device for an electric power steering system is provided in a third aspect embodiment of the present invention, comprising: a first acquisition module for acquiring steering wheel speed and steering wheel angle; a second acquisition module for acquiring actual motor current and actual motor speed when the steering wheel speed and steering wheel angle meet a first preset condition; a third acquisition module for acquiring motor damping current based on the actual motor speed; and a determination module for limiting the motor assist current based on the actual motor current, the motor damping current, and a target current limit, so as to protect the rack end of the electric power steering system.

[0021] According to an embodiment of the present invention, a rack end protection device for an electric power steering system acquires steering wheel speed and steering wheel angle through a first acquisition module. When the steering wheel speed and steering wheel angle meet a first preset condition, the second acquisition module acquires the actual motor current and actual motor speed. Then, a third acquisition module acquires the motor damping current based on the actual motor speed. A determining module limits the motor assist current based on the actual motor current, the motor damping current, and a target current limit to protect the rack end of the electric power steering system. Thus, when the rack end protection condition is met, this device limits the motor assist current based on the actual motor current, the target current limit, and the motor damping current that changes in real time with the motor speed. This effectively captures the driver's steering intention, ensures that the rate of decrease of the end protection current reaches the expected effect, avoids a sudden impact sensation at the rack end, and is suitable for current limiting under various operating conditions.

[0022] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0023] Figure 1 A flowchart of a rack end protection method for an electric power steering system according to an embodiment of the present invention;

[0024] Figure 2 This is a coordinate diagram showing the relationship between the entry angle and the steering wheel speed in a rack end protection method for an electric power steering system according to an embodiment of the present invention.

[0025] Figure 3This is a schematic diagram of a rack end protection method for an electric power steering system according to an embodiment of the present invention.

[0026] Figure 4 A flowchart illustrating the working condition differentiation of a rack end protection method for an electric power steering system according to an embodiment of the present invention.

[0027] Figure 5 A schematic block diagram of a vehicle according to an embodiment of the present invention;

[0028] Figure 6 This is a block diagram of a rack end protection device for an electric power steering system according to an embodiment of the present invention. Detailed Implementation

[0029] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0030] The following description, with reference to the accompanying drawings, illustrates a method for protecting the rack end of an electric power steering system, a vehicle, and a rack end protection device for an electric power steering system, according to embodiments of the present invention.

[0031] Figure 1 This is a flowchart of a method for protecting the rack end of an electric power steering system according to an embodiment of the present invention.

[0032] like Figure 1 As shown, the rack end protection method for an electric power steering system according to an embodiment of the present invention may include:

[0033] S1, obtains the steering wheel speed and steering wheel angle.

[0034] Specifically, the steering wheel speed and angle can be directly obtained through the corresponding speed and angle sensors. Furthermore, since the steering wheel angle is related to the steering wheel speed, the current steering wheel angle can be determined based on the relationship between the steering wheel speed and angle after obtaining the steering wheel speed.

[0035] S2, when the steering wheel speed and steering wheel angle meet the first preset conditions, obtain the actual motor current and the actual motor speed.

[0036] According to one embodiment of the present invention, the corresponding steering wheel approach angle is obtained based on the steering wheel rotation speed. When the current steering wheel angle is greater than the corresponding steering wheel approach angle, it is determined that the steering wheel rotation speed and steering wheel angle meet a first preset condition. When the steering wheel rotation speed is less than a first set rotation speed, or the vehicle speed is less than a second set vehicle speed and the steering wheel angle is greater than a set angle threshold, it is determined that the steering wheel rotation speed and steering wheel angle do not meet the first preset condition. The first set rotation speed, the second set vehicle speed, and the preset angle threshold can be calibrated according to actual conditions.

[0037] Specifically, the steering wheel entry angle for the initial end protection has a one-to-one correspondence with the steering wheel rotation speed, such as... Figure 2 As shown, different steering wheel rotation speeds correspond to different steering wheel approach angles. When the steering wheel rotation speed is high, the resulting change in steering wheel angle also increases, and the relative speed of the rack relative to the housing also increases. Therefore, to ensure the end-protection effect, the steering wheel approach angle for initial end-protection decreases as the steering wheel rotation speed increases, with a one-to-one correspondence between the steering wheel approach angle and the steering wheel rotation speed. The one-to-one correspondence between steering wheel rotation speed and steering wheel approach angle is pre-stored. When the current steering wheel rotation speed is obtained, the correspondence is retrieved to determine the corresponding steering wheel approach angle. The current steering wheel angle is compared with the steering wheel approach angle to determine whether to enter end-protection mode. If the current steering wheel angle is greater than the corresponding steering wheel approach angle, it indicates that the rack's movement distance meets the end-protection requirements, meaning the distance between the inner ball joint rod connected to the rack end and the housing is less than the safety distance. This confirms that the steering wheel rotation speed and steering wheel angle meet the first preset condition. When the steering wheel rotation speed and steering wheel angle meet the first preset condition, the actual motor current and actual motor rotation speed are obtained, and the end-protection strategy is initiated.

[0038] Furthermore, to meet the requirements of slow-turn testing, the system sets a dead zone for end-of-pipe protection speed, i.e., a first set speed. This first set speed serves as the criterion for judging steering wheel speed. When the current steering wheel speed is less than the first set speed, it indicates that there will be no abrupt impact at the end, and end-of-pipe protection is not required, meaning the first preset condition is not met. Additionally, during vehicle movement, the system can determine whether to exit or not enter end-of-pipe protection based on actual conditions. For example, if the current vehicle speed is less than a second set speed and the front steering wheel angle is greater than a set angle threshold, it is assumed that the vehicle is making a U-turn or the road angle is large, and end-of-pipe protection is either not entered or exited, meaning the first preset condition is not met. This prevents problems such as the steering wheel not rotating to its maximum angle and the required operating force increasing during low-speed, large-angle U-turns.

[0039] It should be noted that the relationship between the steering wheel approach angle and the steering wheel speed can be determined by experimentally measuring the required safe distance between the inner ball joint rod connected to the end of the rack and the housing at different steering wheel speeds. This allows for the determination of the steering wheel approach angle, and further setting of the relationship coefficient between the steering wheel speed and the steering wheel approach angle. The safe distance can be set by technicians based on the parameters of the vehicle being used and the actual vehicle operating environment.

[0040] S3, obtain the motor damping current based on the actual motor speed.

[0041] According to one embodiment of the present invention, obtaining the motor damping current based on the actual motor speed includes: multiplying the actual motor speed by a preset coefficient to obtain the motor damping current, wherein the preset coefficient is a negative value.

[0042] Specifically, a damping current module is configured in the electric power steering system. This module operates independently of other damping modules in the system, taking effect only when the first preset condition is met and the end-of-life protection function is activated. The damping current generated by this module corresponds to the motor speed, ensuring the adjustability of the motor damping current and resulting in a more comfortable operating feel and better protection effect for the end-of-life protection. For example, the damping module generates a current in the opposite direction to the actual motor speed as the motor damping current, i.e., the preset coefficient is negative. The actual motor speed is multiplied by the preset coefficient to obtain the motor damping current. As can be seen from the method of obtaining the motor damping current, different damping current values ​​correspond to different motor speeds, achieving flexible adjustability of the motor damping current. This further enables adjustable end-of-life protection current limits, resulting in a smoother feel and better effect for the end-of-life protection.

[0043] Because the motor damping current changes in real time with the actual motor speed, limiting the motor assist current in conjunction with the motor damping current can effectively capture the driver's steering intentions and prevent the end-of-life protection current from failing to achieve the expected effect. For example, if the driver slowly turns the steering wheel into the end-of-life protection zone and then suddenly jerks the steering wheel to its limit in the previous direction in an emergency, even if the acceleration distance is too short, the motor damping current, being related to the actual motor speed, will increase rapidly with the instantaneous increase in motor speed, effectively limiting the end-of-life output current and meeting current limits under various operating conditions, thus avoiding a sudden impact at the end of the journey.

[0044] To prevent the motor damping current from rising and falling too rapidly, the motor damping current can be corrected. According to one embodiment of the present invention, obtaining the motor damping current based on the actual motor speed further includes: obtaining the steering wheel exit angle; obtaining the current difference between the actual motor current and the set current; and correcting the motor damping current based on the steering wheel entry angle, the steering wheel exit angle, the current difference, and the steering wheel speed. The set current is a preset motor current, the steering wheel exit angle is the steering wheel angle when exiting end protection, and the steering wheel entry angle is the steering wheel angle when entering end protection. The set current can be calibrated according to actual conditions and can be the minimum output current of the motor assist current.

[0045] Furthermore, according to one embodiment of the present invention, the motor damping current is corrected based on the steering wheel entry angle, the steering wheel exit angle, the current difference, and the steering wheel rotation speed, including: obtaining the angle difference between the steering wheel entry angle and the steering wheel exit angle; determining a first time based on the steering wheel rotation speed and the angle difference; determining a correction value based on the first time and the current difference; and correcting the motor damping current based on the correction value.

[0046] According to one embodiment of the present invention, the current operating condition of the steering wheel is determined; when the current operating condition of the steering wheel is engaged, if the correction value is greater than a first correction threshold, the motor damping current is corrected according to the first correction threshold; if the correction value is less than or equal to the first correction threshold, the motor damping current is corrected according to the correction value; when the current operating condition of the steering wheel is disengaged, if the correction value is greater than a second correction threshold, the motor damping current is corrected according to the second correction threshold; if the correction value is less than or equal to the second correction threshold, the motor damping current is corrected according to the correction value. The first and second correction thresholds can be calibrated according to actual conditions.

[0047] Specifically, the steering wheel entry angle is determined based on the steering wheel rotation speed, denoted as α. Assuming the steering wheel exit angle is β, then the steering wheel needs to rotate β-α during entry and exit, i.e., the angle difference is β-α. The time from entry to exit, i.e., the first time, can be obtained based on the current steering wheel rotation speed angle difference. The current difference between the actual motor current and the set current is obtained. Based on this current difference and the first time, the correction value for the motor damping current can be determined. The sum of this correction value and the motor damping current obtained in the above embodiment is taken as the final motor damping current, i.e., the corrected motor damping current.

[0048] Considering that the steering wheel has two states: turning in and turning out, when turning in, in order to reduce the abrupt impact at the end, the absolute value of the motor damping current needs to be increased (the motor damping current is negative); similarly, when turning out, in order to enable the driver to turn smoothly without jamming or the phenomenon of turning hard quickly, the absolute value of the motor damping current needs to be decreased (the motor damping current is positive).

[0049] For example, when the steering wheel is in the engaged position, with an engagement angle α of 500° and an exit angle β of 600°, the actual motor current is 50A, the set current is 20A, and the actual rotational speed is 450°sec / s. From the angle difference of 100° and the actual rotational speed of 450sec / s, we can obtain the first time interval 450 / 100 = 4.5s. Based on the current difference of 30A and the first time interval 4.5s, we can determine the rate of ascent 30 / 4.5 = 6.67A / s, meaning the motor damping current correction value is 6.67A. Conversely, when the steering wheel is in the disengaged position, the rate of descent can be determined.

[0050] To prevent steering wheel vibration, the maximum values ​​of the upward and downward slopes need to be calibrated; that is, the upward and downward slopes cannot be too large. When the steering wheel is in the "engaged" position, the correction value is negative. If the correction value is greater than the first correction threshold, the motor damping current is corrected according to the first correction threshold to prevent the upward speed from being too fast; if the correction value is less than or equal to the first correction threshold, the motor damping current is corrected according to the correction value. When the steering wheel is in the "de-engaged" position, the correction value is positive. If the correction value is greater than the second correction threshold, the motor damping current is corrected according to the second correction threshold to prevent the downward speed from being too fast; if the correction value is less than or equal to the second correction threshold, the motor damping current is corrected according to the correction value. This effectively prevents steering wheel vibration caused by excessively rapid increases and decreases in the motor damping current.

[0051] Furthermore, the distinction between the aforementioned injection and injection conditions can be achieved through methods such as... Figure 4 The judgment shown is used to distinguish between different angles. The specific operation method is as follows: First, input the steering wheel angle; then, use a signal filter processor to obtain the absolute value T of the angle at time -Δt (the previous time). -Δt The absolute value of the angle T at time +Δt (the current time). +Δt Make a judgment if T -Δt -T +Δt If T > 0, it can be determined that the steering wheel is in the "out of control" state; otherwise, if T > 0, it can be determined that the steering wheel is in the "out of control" state. -Δt -T +Δt If the value is less than 0, it can be determined that the steering wheel is in the engaged state.

[0052] At this point, if the driver enters the end-of-life protection zone by turning the steering wheel at a certain speed, and then, in an emergency, suddenly turns the steering wheel sharply in the opposite direction to exit the end-of-life protection zone, the above-mentioned... Figure 4 The system differentiates between end-of-pipe protection and steering input / output conditions. When the angle condition is met, the motor can quickly restore the required assist current, allowing the steering wheel to follow the driver's steering intention and turn smoothly without jamming or becoming heavy when turning quickly.

[0053] S4 limits the motor assist current based on the actual motor current, motor damping current, and target current limit to protect the rack end of the electric power steering system.

[0054] Specifically, in practical applications, when in the "entering" state (entering end protection), the target current limit should restrict the motor output current using the calibrated decreasing slope (fixed slope). When in the "exiting" state (exiting end protection), the calibrated increasing slope (fixed slope) should be used for exiting. Finally, the actual motor current, motor damping current, and target current limit can be determined by... Figure 3 The methods shown work together to limit the motor assist current, that is, to calculate the sum of the current between the actual motor current, the motor damping current and the target current limit, thereby protecting the rack end of the electric power steering system. This can effectively solve the problem that there is a blank stroke (not actually effective) between the maximum output current and the actual output current during the descent, which leads to the current limiting effect not reaching the expected effect and the end protection feeling not being strong.

[0055] According to one embodiment of the present invention, after limiting the motor assist current, the method further includes: determining the relationship between the sum of currents and a preset minimum current threshold; limiting the motor assist current based on the sum of currents when the sum of currents is greater than the preset minimum current threshold; and limiting the motor assist current based on the preset minimum current threshold when the sum of currents is less than or equal to the preset minimum current threshold.

[0056] Specifically, the electric power steering system is calibrated with a preset minimum current threshold, which serves as the minimum output current limit for end-of-life protection. The end-of-life protection function limits the output current to no less than this calibrated current (preset minimum current threshold) to prevent insufficient current from causing low system control and resulting in steering wheel rebound or kickback, which could adversely affect the customer's health. The specific operation is as follows: after acquiring the current sum, the relationship between the current sum and the preset minimum current threshold is determined. If the current sum is greater than the preset minimum current threshold, the current sum is used as the motor assist current output; if the current sum is less than the preset minimum current threshold, the preset minimum current threshold is used as the motor assist current output.

[0057] In summary, the rack end protection method for this electric power steering system first obtains the steering wheel speed and steering wheel angle. Then, after determining that the steering wheel speed and steering wheel angle meet the first preset condition, the intervention time for end protection is determined. The actual motor current and actual motor speed are obtained, and the damping module generates a motor damping current in the opposite direction to the actual motor speed. At the same time, the motor damping current can be corrected by the steering wheel entry angle, steering wheel exit angle, the current difference between the actual motor current and the set current, and the steering wheel speed. Finally, the motor assist current is jointly limited based on the actual motor current, the motor damping current, the target current limit, and the motor assist current to protect the rack end of the electric power steering system. This satisfies the current limit under various operating conditions, avoids a sudden impact feeling at the end, and can distinguish the end protection area when entering and exiting the steering wheel, achieving a strong end protection feel when entering the end protection area and a light feel when exiting the steering wheel.

[0058] In summary, the rack end protection method for an electric power steering system according to an embodiment of the present invention first obtains the steering wheel speed and steering wheel angle. When the steering wheel speed and steering wheel angle meet a first preset condition, the actual motor current and actual motor speed are obtained. Then, the motor damping current is obtained based on the actual motor speed. Finally, the motor assist current is limited based on the actual motor current, the motor damping current, and the target current limit to protect the rack end of the electric power steering system. Therefore, this rack end protection method, when the rack end protection conditions are met, limits the motor assist current based on the actual motor current, the target current limit, and the motor damping current that changes in real time with the motor speed. This effectively captures the driver's steering intention, ensures that the rate of decrease of the end protection current reaches the expected effect, avoids a sudden impact sensation at the rack end, and is applicable to current limiting under various operating conditions.

[0059] Corresponding to the above embodiments, the present invention also proposes a vehicle.

[0060] like Figure 5 As shown, the vehicle 100 of this embodiment may include: a memory 110, a processor 120, and a control program for an electric power steering system stored in the memory 110 and executable on the processor 120. When the processor 120 executes the control program for the electric power steering system, it implements the above-mentioned rack end protection method for the electric power steering system.

[0061] According to the vehicle of the present invention, when the processor executes the control program of the electric power steering system, the above-mentioned rack end protection method of the electric power steering system is realized. It can effectively capture the driver's steering intention, ensure that the end protection current decrease rate reaches the expected effect, avoid the sudden impact feeling at the rack end, and is applicable to current limitation under various operating conditions.

[0062] Corresponding to the above embodiments, the present invention also proposes a rack end protection device for an electric power steering system.

[0063] Figure 6 This is a block diagram of a rack end protection device for an electric power steering system according to an embodiment of the present invention.

[0064] like Figure 6 As shown, the rack end protection device of the electric power steering system of the present invention may include: a first acquisition module 10, a second acquisition module 20, a third acquisition module 30 and a determination module 40.

[0065] The system comprises three modules: a first acquisition module 10 for acquiring steering wheel speed and steering wheel angle; a second acquisition module 20 for acquiring actual motor current and actual motor speed when the steering wheel speed and steering wheel angle meet a first preset condition; a third acquisition module 30 for acquiring motor damping current based on actual motor speed; and a determination module 40 for limiting the motor assist current based on actual motor current, motor damping current, and a target current limit to protect the rack end of the electric power steering system.

[0066] According to one embodiment of the present invention, the determining module 40 limits the motor assist current based on the actual motor current, the motor damping current and the target current limit, including: calculating the sum of the currents between the actual motor current, the motor damping current and the target current limit, and limiting the motor assist current based on the sum of the currents.

[0067] According to one embodiment of the present invention, the determining module 40 is further configured to: determine the relationship between the current sum and a preset minimum current threshold; when the current sum is greater than the preset minimum current threshold, limit the motor assist current according to the current sum; when the current sum is less than or equal to the preset minimum current threshold, limit the motor assist current according to the preset minimum current threshold.

[0068] According to one embodiment of the present invention, the third acquisition module 30 acquires the motor damping current based on the actual motor speed, specifically for: multiplying the actual motor speed by a preset coefficient to obtain the motor damping current, wherein the preset coefficient is a negative value.

[0069] According to one embodiment of the present invention, the third acquisition module 30 is further configured to: acquire the steering wheel exit angle; acquire the current difference between the actual motor current and the set current; and correct the motor damping current based on the steering wheel entry angle, the steering wheel exit angle, the current difference, and the steering wheel rotation speed.

[0070] According to one embodiment of the present invention, the third acquisition module 30 corrects the motor damping current based on the steering wheel entry angle, the steering wheel exit angle, the current difference, and the steering wheel rotation speed. Specifically, it is used to: acquire the angle difference between the steering wheel entry angle and the steering wheel exit angle; determine a first time based on the steering wheel rotation speed and the angle difference; determine a correction value based on the first time and the current difference, and correct the motor damping current based on the correction value.

[0071] According to one embodiment of the present invention, the third acquisition module 30 corrects the motor damping current based on the steering wheel entry angle, steering wheel exit angle, current difference, and steering wheel speed. Specifically, it is used to: determine the current operating condition of the steering wheel; when the current operating condition of the steering wheel is the engagement condition, if the correction value is greater than a first correction threshold, then the motor damping current is corrected according to the first correction threshold; if the correction value is less than or equal to the first correction threshold, then the motor damping current is corrected according to the correction value; when the current operating condition of the steering wheel is the disengagement condition, if the correction value is greater than a second correction threshold, then the motor damping current is corrected according to the second correction threshold; if the correction value is less than or equal to the second correction threshold, then the motor damping current is corrected according to the correction value.

[0072] According to an embodiment of the present invention, the second acquisition module 20 is further configured to acquire the corresponding steering wheel entry angle based on the steering wheel rotation speed; when the current steering wheel angle is greater than the corresponding steering wheel entry angle, determine that the steering wheel rotation speed and steering wheel angle meet the first preset condition; when the steering wheel rotation speed is less than the first set rotation speed, or the vehicle speed is less than the second set vehicle speed and the steering wheel angle is greater than the set angle threshold, determine that the steering wheel rotation speed and steering wheel angle do not meet the first preset condition.

[0073] It should be noted that for details not disclosed in the rack end protection device of the electric power steering system in this embodiment of the invention, please refer to the details disclosed in the rack end protection method of the electric power steering system in this embodiment of the invention, which will not be repeated here.

[0074] The rack end protection device for the electric power steering system according to the present invention acquires the steering wheel speed and steering wheel angle through a first acquisition module. When the steering wheel speed and steering wheel angle meet a first preset condition, the actual motor current and actual motor speed are acquired through a second acquisition module. Then, the motor damping current is acquired through a third acquisition module based on the actual motor speed. A determining module limits the motor assist current based on the actual motor current, the motor damping current, and a target current limit to protect the rack end of the electric power steering system. Thus, when the rack end protection conditions are met, the device limits the motor assist current based on the actual motor current, the target current limit, and the motor damping current that changes in real time with the motor speed. This effectively captures the driver's steering intention, ensures that the rate of decrease of the end protection current reaches the expected effect, avoids a sudden impact sensation at the rack end, and is suitable for current limiting under various operating conditions.

[0075] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0076] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0077] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0078] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0079] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0080] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for protecting the rack end of an electric power steering system, characterized in that, include: Get the steering wheel speed and steering wheel angle; When the steering wheel speed and steering wheel angle meet the first preset conditions, the actual motor current and the actual motor speed are obtained; The motor damping current is obtained based on the actual motor speed, specifically by multiplying the actual motor speed by a preset coefficient to obtain the motor damping current, wherein the preset coefficient is a negative value. The motor assist current is limited based on the actual motor current, the motor damping current, and the target current limit to protect the rack end of the electric power steering system. Obtain the steering wheel exit angle; Obtain the current difference between the actual current of the motor and the set current; Obtain the angle difference between the steering wheel entry angle and the steering wheel exit angle; The first time is determined based on the steering wheel rotation speed and the angle difference; A correction value is determined based on the first time and the current difference, and the motor damping current is corrected based on the correction value. Determine the current operating condition of the steering wheel; When the current working condition of the steering wheel is engaged, if the correction value is greater than the first correction threshold, the motor damping current is corrected according to the first correction threshold. If the correction value is less than or equal to the first correction threshold, the motor damping current is corrected according to the correction value; When the current working condition of the steering wheel is the out position, if the correction value is greater than the second correction threshold, the motor damping current is corrected according to the second correction threshold. If the correction value is less than or equal to the second correction threshold, the motor damping current is corrected according to the correction value.

2. The method for protecting the rack end of an electric power steering system according to claim 1, characterized in that, The motor assist current is limited based on the actual motor current, the motor damping current, and the target current limit, including: Calculate the sum of the actual motor current, the motor damping current, and the target current limit, and limit the motor assist current based on the sum of the currents.

3. The method for protecting the rack end of an electric power steering system according to claim 2, characterized in that, Also includes: Determine the relationship between the current and a preset minimum current threshold; When the sum of the currents exceeds the preset minimum current threshold, the motor assist current is limited based on the sum of the currents. When the current is less than or equal to the preset minimum current threshold, the motor assist current is limited according to the preset minimum current threshold.

4. The method for protecting the rack end of an electric power steering system according to claim 1, characterized in that, The steering wheel entry angle is obtained based on the steering wheel rotation speed. When the current steering wheel angle is greater than the corresponding steering wheel entry angle, it is determined that the steering wheel rotation speed and the steering wheel angle meet the first preset condition. When the steering wheel rotation speed is less than the first preset rotation speed, or the vehicle speed is less than the second preset vehicle speed and the steering wheel angle is greater than the preset angle threshold, it is determined that the steering wheel rotation speed and the steering wheel angle do not meet the first preset condition.

5. A vehicle, characterized in that, include: The system includes a memory, a processor, and a control program for an electric power steering system stored in the memory and executable on the processor. When the processor executes the control program for the electric power steering system, it implements the rack end protection method for the electric power steering system as described in any one of claims 1-4.

6. A rack end protection device for an electric power steering system, characterized in that, For implementing a method for protecting the rack end of an electric power steering system as described in any one of claims 1-4, the apparatus comprises: The first acquisition module is used to acquire the steering wheel speed and steering wheel angle; The second acquisition module is used to acquire the actual motor current and the actual motor speed when the steering wheel speed and steering wheel angle meet the first preset conditions. The third acquisition module is used to acquire the motor damping current based on the actual speed of the motor. The determining module is used to limit the motor assist current based on the actual motor current, the motor damping current, and the target current limit, so as to protect the rack end of the electric power steering system.

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