Active return control method and device of electric power steering system, vehicle and medium

Abstract

The application provides a kind of electric power steering system active return control method, device, vehicle and medium, belong to vehicle control technical field, this method includes: in the case where vehicle is in return state, according to current vehicle speed, determine current return characteristic angle;According to the size relation of the initial steering wheel angle when the vehicle returns with current return characteristic angle, determine the return control state of vehicle;According to the return control state of vehicle, using the current return control parameter corresponding to current vehicle speed, return control is carried out.The method can accurately determine the return control state of vehicle, so that accurate return control can be carried out based on the return state of vehicle at any speed.And, when return control is carried out, control parameters are determined according to current vehicle speed, the influence of speed on return performance is considered, so accurate return control can be realized at different speeds.In this way, a low-cost and high-accuracy active return control is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicle control, and in particular relates to a method and device for active straightening control of an electric power steering system, a vehicle and a medium. BACKGROUND

[0002] An electric power steering system (EPS) of a vehicle assists a driver in turning a steering wheel by means of a torque generated by an electric motor. Straightening performance is an important aspect of vehicle handling stability, and active straightening control of an electric power steering system can improve the straightening performance of a vehicle.

[0003] In related technologies, the straightening state of a vehicle is determined based on vehicle speed, and fixed parameters are used for straightening control in the corresponding straightening state. However, the method of determining the straightening state of a vehicle based on vehicle speed cannot accurately determine the straightening state of a vehicle in some vehicle speed ranges, and a high-cost intelligent control method is required to achieve straightening control. Moreover, the straightening performance at different vehicle speeds is different, and it is difficult to accurately control the straightening of a vehicle at different vehicle speeds based on fixed control parameters, which can result in insufficient straightening or over-straightening. Therefore, how to achieve low-cost and high-accuracy straightening control is a technical problem to be solved. SUMMARY

[0004] In view of the above problems, the embodiments of the present application provide a method and device for active straightening control of an electric power steering system, a vehicle and a medium, so as to overcome the above problems or at least partially solve the above problems.

[0005] In a first aspect, the embodiments of the present application provide a method for active straightening control of an electric power steering system, and the method comprises:

[0006] In a case where a vehicle is in a straightening state, a current straightening characteristic angle is determined according to a current vehicle speed, wherein the straightening characteristic angle is determined according to a vehicle speed and a straightening characteristic angle lookup table, and the straightening characteristic angle lookup table is used to represent the corresponding relationship between a vehicle speed and a straightening characteristic angle;

[0007] A straightening control state of the vehicle is determined according to the size relationship between the initial steering wheel angle of the vehicle when the vehicle is straightening and the current straightening characteristic angle;

[0008] According to the straightening control state of the vehicle, a current straightening control parameter corresponding to the current vehicle speed is used for straightening control.

[0009] Optionally, the method further comprises:

[0010] In a case where the current vehicle speed is less than or equal to a first vehicle speed threshold, the straightening control state of the vehicle is determined to be insufficient straightening;

[0011] If the current vehicle speed is greater than or equal to the second vehicle speed threshold, the vehicle's return-to-center control state is determined to be return-to-center overshoot.

[0012] Based on the relationship between the initial steering wheel angle when the vehicle returns to center and the current centering characteristic angle, the vehicle's centering control state is determined, including:

[0013] If the current vehicle speed is greater than the first vehicle speed threshold and less than the second vehicle speed threshold, and the initial steering wheel angle when the vehicle returns to center is not greater than the current centering characteristic angle, the vehicle's centering control state is determined to be under-centering; if the initial steering wheel angle when the vehicle returns to center is greater than the current centering characteristic angle, the vehicle's centering control state is determined to be over-centering.

[0014] Optionally, the method further includes:

[0015] If the direction of the steering wheel angle is opposite to the direction of the steering wheel angular velocity, and the duration of the opposite direction is greater than a first time threshold, the vehicle is determined to be in a straightened state.

[0016] When the vehicle is in the straightening state, determine whether the vehicle needs to be straightened based on the steering wheel torque and the steering wheel angle.

[0017] Based on the relationship between the initial steering wheel angle when the vehicle returns to center and the current centering characteristic angle, the vehicle's centering control state is determined, including:

[0018] When it is necessary to control the vehicle to return to center, the vehicle's return-to-center control state is determined based on the relationship between the initial steering wheel angle when the vehicle returns to center and the current return-to-center characteristic angle.

[0019] Optionally, when the vehicle is in the centering state, determining whether vehicle centering control is needed based on the steering wheel torque and the steering wheel angle includes:

[0020] Determine whether the steering wheel torque is less than or equal to a first torque threshold;

[0021] If the steering wheel torque is greater than the first torque threshold, it is determined that no vehicle return-to-center control is required.

[0022] If the steering wheel torque is less than or equal to the first torque threshold, it is initially determined that the vehicle needs to be returned to center.

[0023] If it is initially determined that the vehicle needs to be returned to center, determine whether the steering wheel angle is greater than or equal to the first angle threshold.

[0024] if the steering wheel angle is greater than or equal to the first angle threshold, it is finally determined that the vehicle needs to be controlled to return to normal;

[0025] if the steering wheel angle is less than the first angle threshold, it is finally determined that the vehicle does not need to be controlled to return to normal.

[0026] Optionally, after determining that the return-to-normal control state of the vehicle is under-return, the method further comprises:

[0027] determining whether the steering wheel angular velocity is less than or equal to a first angular velocity threshold;

[0028] controlling the vehicle to return to normal according to the return-to-normal control state of the vehicle and a current return-to-normal control parameter corresponding to a current vehicle speed, comprising:

[0029] in the case where the steering wheel angular velocity is less than or equal to the first angular velocity threshold, controlling the vehicle to return to normal in an under-return control mode by using a first control parameter corresponding to the current vehicle speed;

[0030] after determining that the return-to-normal control state of the vehicle is over-return, controlling the vehicle to return to normal in an over-return control mode by using a second control parameter corresponding to the current vehicle speed.

[0031] Optionally, in the case where the steering wheel angular velocity is less than or equal to the first angular velocity threshold, controlling the vehicle to return to normal in the under-return control mode by using the first control parameter corresponding to the current vehicle speed, comprising:

[0032] determining a first proportional link adjustment coefficient and an integral link adjustment coefficient according to the current vehicle speed and a proportional-integral control parameter lookup table, the proportional-integral control parameter lookup table being used to represent a corresponding relationship between vehicle speed and proportional-integral control parameter;

[0033] controlling the vehicle to return to normal according to a proportional-integral control method based on the first proportional link adjustment coefficient and the integral link adjustment coefficient.

[0034] Optionally, the method further comprises:

[0035] determining whether an initial steering wheel angle when the vehicle returns to normal is less than or equal to an under-return characteristic angle, the under-return characteristic angle representing a steering wheel angle threshold that needs to be compensated by integration;

[0036] in the case where the initial steering wheel angle when the vehicle returns to normal is less than or equal to the under-return characteristic angle, determining an integral compensation parameter according to the initial steering wheel angle when the vehicle returns to normal and an integral compensation parameter lookup table, the integral compensation parameter lookup table being used to represent a corresponding relationship between steering wheel angle and integral compensation parameter;

[0037] According to the first proportional link adjustment coefficient and the integral link adjustment coefficient, the return control is performed according to a proportional integral control method, including:

[0038] According to the integral compensation parameter, the first proportional link adjustment coefficient and the integral link adjustment coefficient, the return control is performed according to a proportional integral control method, and in a case where the initial steering wheel angle of the vehicle during the return is less than or equal to the under-return characteristic angle, an integral compensation parameter is determined according to an integral compensation parameter lookup table and the initial steering wheel angle of the vehicle during the return, the integral compensation parameter lookup table being used to represent a corresponding relationship between the steering wheel angle and the integral compensation parameter.

[0039] According to the first proportional link adjustment coefficient and the integral link adjustment coefficient, the return control is performed according to a proportional integral control method, including:

[0040] According to the integral compensation parameter, the first proportional link adjustment coefficient and the integral link adjustment coefficient, the return control is performed according to a proportional integral control method.

[0041] Optionally, after determining that the return control state of the vehicle is return overshoot, the return control is performed according to a return overshoot control mode by using a second control parameter corresponding to the current vehicle speed, including:

[0042] According to the current vehicle speed and a proportional differential control parameter lookup table, a second proportional link adjustment coefficient and a differential link adjustment coefficient are determined, the proportional differential control parameter lookup table being used to represent a corresponding relationship between the vehicle speed and the proportional differential control parameter.

[0043] According to the second proportional link adjustment coefficient and the differential link adjustment coefficient, the return control is performed according to a proportional differential control method.

[0044] Optionally, the method further includes:

[0045] In a case where a return control end condition is met, the return control of the vehicle is ended.

[0046] The return control end condition includes any one of the following:

[0047] The current steering wheel angle is less than a target steering wheel angle;

[0048] The current steering wheel torque is greater than a first torque threshold;

[0049] The direction of the current steering wheel angle is the same as the direction of the steering wheel angular velocity, and the duration of the same direction is greater than a second time threshold.

[0050] In a second aspect, an embodiment of the present application provides a device for active return control of an electric power steering system, and the device includes:

[0051] The first determining module is configured to determine a current alignment characteristic angle according to a current vehicle speed when the vehicle is in the alignment state, wherein the alignment characteristic angle is determined according to the vehicle speed and an alignment characteristic angle lookup table, and the alignment characteristic angle lookup table is used to represent a corresponding relationship between the vehicle speed and the alignment characteristic angle.

[0052] The second determining module is configured to determine an alignment control state of the vehicle according to a size relationship between the initial steering wheel rotation angle and the current alignment characteristic angle when the vehicle is being aligned.

[0053] The first control module is configured to perform alignment control by using a current alignment control parameter corresponding to the current vehicle speed according to the alignment control state of the vehicle.

[0054] In a third aspect, an embodiment of the present application provides a vehicle, which comprises:

[0055] The memory and the processor, wherein the memory stores a computer program which is run by the processor, and the computer program, when being run by the processor, causes the processor to perform the steps of the active alignment control method of the electric power steering system according to the first aspect.

[0056] In a fourth aspect, an embodiment of the present application provides a computer readable storage medium, which stores a computer program, and the program, when being executed by a processor, implements the steps of the active alignment control method of the electric power steering system according to the first aspect.

[0057] The embodiments of the present application have the following advantages:

[0058] In the embodiments of the present application, when the vehicle is in the alignment state, a current alignment characteristic angle is determined according to a current vehicle speed, wherein the alignment characteristic angle is determined according to the vehicle speed and an alignment characteristic angle lookup table, and the alignment characteristic angle lookup table is used to represent a corresponding relationship between the vehicle speed and the alignment characteristic angle; then, an alignment control state of the vehicle is determined according to a size relationship between the initial steering wheel rotation angle and the current alignment characteristic angle when the vehicle is being aligned; and finally, alignment control is performed by using a current alignment control parameter corresponding to the current vehicle speed according to the alignment control state of the vehicle.

[0059] The method can accurately determine the alignment control state of the vehicle according to the initial steering wheel rotation angle and the alignment characteristic angle, so as to accurately control the alignment of the vehicle according to the alignment control state without using an intelligent control method, thereby reducing the control cost. Moreover, the control parameter is determined according to the current vehicle speed when performing the alignment control, and the influence of the vehicle speed on the alignment performance is considered, so that accurate alignment control can be achieved at different vehicle speeds. In this way, the active alignment control with low cost and high accuracy is achieved.

[0060] The above description is only a summary of the technical solutions of the present application. In order to make the technical means of the present application more clear and understandable, and to make the above and other purposes, characteristics and advantages of the present application more obvious and easy to understand, the following will describe the specific embodiments of the present application in detail. BRIEF DESCRIPTION OF DRAWINGS

[0061] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the description of the embodiments of the present application. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0062] Figure 1 is a step flow chart of an active return control method of an electric power steering system provided by the embodiments of the present application;

[0063] Figure 2 is a step flow chart of another active return control method of an electric power steering system provided by the embodiments of the present application;

[0064] Figure 3 is a step flow chart of still another active return control method of an electric power steering system provided by the embodiments of the present application;

[0065] Figure 4 is a step flow chart of a return control according to a return deficiency control mode provided by the embodiments of the present application;

[0066] Figure 5 is a flow chart of a return control according to a proportional integral control method provided by the embodiments of the present application;

[0067] Figure 6 is a flow chart of a return control according to a proportional differential control method provided by the embodiments of the present application;

[0068] Figure 7 is a specific implementation flow chart of an active return control method of an electric power steering system provided by the embodiments of the present application;

[0069] Figure 8 is a structural schematic diagram of an electric power steering system provided by the embodiments of the present application;

[0070] Figure 9 is a structural schematic diagram of an active return control device of an electric power steering system provided by the embodiments of the present application. DETAILED DESCRIPTION

[0071] In order to make the above objectives, characteristics and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0072] The return-to-straight control state of the vehicle usually includes two states of return-to-straight insufficient and return-to-straight overshoot. In the related art, a proportional integral control method (PI) is used for return-to-straight insufficient control, and a proportional differential control method (PD) is used for return-to-straight overshoot control. However, the return-to-straight performance of the vehicle is different at different speeds, and it is difficult to accurately control the return-to-straight of the vehicle at different speeds with fixed PI or PD values, which may lead to return-to-straight insufficient or overshoot. Moreover, in the case that the return-to-straight state of the vehicle cannot be accurately judged, a fuzzy proportional control integral differential control method (PID) is used for return-to-straight control. However, the fuzzy control method belongs to intelligent control, and requires higher chip computing power, which may increase additional economic cost. Moreover, it is difficult to formulate accurate fuzzy rules, and the debugging period is also longer, so that additional time cost is increased.

[0073] In addition, the existing return-to-straight control method does not consider the influence of the size of the initial steering wheel angle of the vehicle in the return-to-straight insufficient state on the return-to-straight performance. In the case that the vehicle is in the return-to-straight insufficient state, the initial steering wheel angle of the vehicle is different when the vehicle returns to straight at the same speed, and the fixed PI value cannot accurately control the return-to-straight process of the vehicle. For example, in the case that the vehicle is in the return-to-straight insufficient state, the initial steering wheel angle of the vehicle is 300 deg when the vehicle starts to return to straight, and a set of calibrated PI values can accurately control the return-to-straight process of the vehicle at the initial return-to-straight angle, so that the steering wheel accurately returns to the middle position. However, when the speed is unchanged and the initial angle of the vehicle when it starts to return to straight is changed to 20 deg, the above PI value is difficult to accurately control the return-to-straight process of the vehicle, which may lead to return-to-straight insufficient.

[0074] To overcome the limitations of the related art, the embodiments of the present application provide an active return control method, device, vehicle and medium of an electric power steering system. The method determines the return characteristic according to the current vehicle speed, and accurately determines the return control state of the vehicle according to the initial steering wheel angle and the return characteristic angle, so as to accurately control the return control state by using the corresponding control method, without fuzzy control by fuzzy PID, and the control algorithm is simple and easy to implement, without the need to establish fuzzy control rules, and the requirement for chip computing power is not high, saving a large amount of economic and time costs. Moreover, the influence of vehicle speed on return performance is considered, the corresponding control parameters are determined according to the current vehicle speed and the return control state of the vehicle, and the return process under the current vehicle speed is controlled to improve the control precision. In some embodiments, the integral compensation parameter is determined by the initial steering wheel angle and the integral compensation parameter lookup table to compensate for the insufficient return control under small steering angles, further improving the return control precision.

[0075] The active return control method of the electric power steering system provided by the embodiments of the present application will be described in detail below.

[0076] Reference Figure 1 As shown in the figure, Figure 1 is a step flowchart of an active return control method of an electric power steering system provided by the embodiments of the present application. As shown in the figure, Figure 1 The active return control method of an electric power steering system provided by the embodiments of the present application can include steps S110 to S130:

[0077] Step S110: In the case that the vehicle is in a return state, the current return characteristic angle is determined according to the current vehicle speed; wherein the return characteristic angle is determined according to the vehicle speed and the return characteristic angle lookup table, and the return characteristic angle lookup table is used to represent the corresponding relationship between the vehicle speed and the return characteristic angle.

[0078] In the embodiments of the present application, the vehicle in the return state means that the vehicle needs to be controlled to return, the current vehicle speed is obtained through the EPS function module on the vehicle, the return characteristic angle is pre-calibrated, and is used to determine the return control state of the vehicle. Each vehicle speed corresponds to a return characteristic angle, and the corresponding relationship between the vehicle speed and the return characteristic angle is represented by the return characteristic angle lookup table, so that the return characteristic angle lookup table is looked up according to the current vehicle speed in the case that the vehicle is in the return state, and the current return characteristic angle corresponding to the current vehicle speed is obtained.

[0079] Step S120: According to the size relationship between the initial steering wheel angle and the current return characteristic angle when the vehicle returns, the return control state of the vehicle is determined.

[0080] In the embodiment of the present application, the return-to-center control state of the vehicle includes two states: return-to-center deficiency and return-to-center overshoot. The return-to-center deficiency refers to a state in which the steering wheel is not returned to the center after steering. The return-to-center overshoot refers to a state in which the steering wheel is returned to the center and the steering wheel angle exceeds the center, causing an overshoot. Each vehicle speed corresponds to a return-to-center characteristic angle. At this vehicle speed, if the steering wheel angle is greater than the return-to-center characteristic angle, the return-to-center control state of the vehicle is determined to be return-to-center deficiency. If the steering wheel angle is not greater than the return-to-center characteristic angle, the return-to-center control state of the vehicle is determined to be return-to-center overshoot. Thus, after the current return-to-center characteristic angle corresponding to the current vehicle speed is determined, the return-to-center control state of the vehicle is accurately determined according to the size relationship between the initial steering wheel angle of the vehicle during return-to-center and the current return-to-center characteristic angle.

[0081] Step S130: According to the return-to-center control state of the vehicle, the current return-to-center control parameter corresponding to the current vehicle speed is used to perform return-to-center control.

[0082] In the embodiment of the present application, the control performance corresponding to the return-to-center control state of the vehicle is different. When the return-to-center control state of the vehicle is return-to-center deficiency, the steering resistance is large at this time, and a large return-to-center torque is required to overcome the current steering resistance. When the return-to-center control state of the vehicle is return-to-center overshoot, the steering resistance is considered to be small, and the steering is easy to overshoot, causing the vehicle to shake. Therefore, in order to improve the control accuracy, the return-to-center control is performed according to the return-to-center control state of the vehicle. Moreover, considering that the control performance is different at different vehicle speeds, the current control parameter corresponding to the current vehicle speed is used to perform return-to-center control, thereby realizing accurate return-to-center control.

[0083] In the above implementation process, the return-to-center control state of the vehicle is accurately determined according to the initial steering wheel angle and the return-to-center characteristic angle, so that the vehicle is accurately controlled according to the return-to-center control state, without the need to use an intelligent control method, thereby reducing the control cost. Moreover, when performing return-to-center control, the control parameter is determined according to the current vehicle speed, and the influence of the vehicle speed on the return-to-center performance is considered, so that accurate return-to-center control can be realized at different vehicle speeds. In this way, a low-cost and high-accuracy active return-to-center control is realized.

[0084] Further referring to Figure 2 , Figure 2 is a step flowchart of another active return-to-center control method of an electric power steering system provided in the embodiment of the present application. The method includes the following steps S210 to S240:

[0085] Step S210: In the case where the direction of the steering wheel angle is opposite to the direction of the steering wheel angular velocity, and the duration of the opposite directions is greater than a first time threshold, it is determined that the vehicle is in a return-to-center state.

[0086] In the embodiment of the present application, when the vehicle is steering, steering control is realized by rotating the steering wheel. At this time, the direction of the steering wheel angle is the same as the direction of the steering wheel angular velocity. If the direction of the steering wheel angle is opposite to the direction of the steering wheel angular velocity, it indicates that the vehicle is in the straightening state after steering. In order to avoid misjudgment caused by steering jitter, a first time threshold (such as 0.1 second) is set. When the direction of the steering wheel angle is opposite to the direction of the steering wheel angular velocity, and the duration of the opposite directions is greater than the first time threshold, it is determined that the vehicle is in the straightening state.

[0087] Step S220: In the case that the vehicle is in the straightening state, whether the vehicle needs to be controlled to straighten is determined according to the steering wheel torque and the steering wheel angle.

[0088] In the embodiment of the present application, the vehicle straightening can be realized by the driver's active control or the straightening control method. The steering wheel torque of the driver's active control is different from the steering wheel torque of the driver's non-active control. Whether the vehicle needs to be controlled to straighten is determined by the steering wheel torque. In addition, due to the influence of errors, the steering wheel angle of the neutral state can not be zero. Therefore, whether the vehicle needs to be controlled to straighten is further determined by the steering wheel angle.

[0089] Specifically, in the case that the vehicle is in the straightening state, whether the vehicle needs to be controlled to straighten is determined according to the steering wheel torque and the initial steering wheel angle of the vehicle when straightening, including steps A1 to A6:

[0090] Step A1: Determine whether the steering wheel torque is less than or equal to a first torque threshold.

[0091] Step A2: In the case that the steering wheel torque is greater than the first torque threshold, it is determined that the vehicle does not need to be controlled to straighten.

[0092] Step A3: In the case that the steering wheel torque is less than or equal to the first torque threshold, it is preliminarily determined that the vehicle needs to be controlled to straighten.

[0093] Step A4: In the case that it is preliminarily determined that the vehicle needs to be controlled to straighten, it is determined whether the steering wheel angle is greater than or equal to a first angle threshold.

[0094] Step A5: If the steering wheel angle is greater than or equal to the first angle threshold, it is finally determined that the vehicle needs to be controlled to straighten.

[0095] Step A6: If the steering wheel angle is less than the first angle threshold, it is finally determined that the vehicle does not need to be controlled to straighten.

[0096] In this embodiment, the steering wheel torque actively controlled by the driver differs from the steering wheel torque not actively controlled by the driver. If the driver actively controls the steering wheel, the torque is larger; if the driver does not actively control it, the torque is smaller. Therefore, a first torque threshold is set to determine whether the driver is actively controlling the steering wheel. If the steering wheel torque is greater than the first torque threshold, it indicates that the driver is actively controlling the vehicle to return to center, and it is determined that no vehicle centering control is needed. If the steering wheel torque is less than or equal to the first torque threshold, it indicates that the driver is not actively controlling the steering wheel, and it is initially determined that vehicle centering control is needed.

[0097] Due to the influence of error, the steering wheel angle in the neutral position may not be zero. Therefore, a first torque threshold is set to further determine whether the vehicle needs to be returned to center. If the steering wheel angle is greater than or equal to the first angle threshold, it is considered that the steering wheel is not in the neutral position and the vehicle needs to be returned to center. If the steering wheel angle is less than the first angle threshold, it is considered that the steering wheel is in the neutral position and the vehicle does not need to be returned to center. This avoids the vehicle frequently entering and exiting the return to center control when the steering wheel is at a small angle.

[0098] Step S230: When it is necessary to control the vehicle to return to center, determine the vehicle's return to center control state based on the relationship between the initial steering wheel angle when the vehicle returns to center and the current return to center characteristic angle.

[0099] In this embodiment, the current return-to-center characteristic angle is determined based on the vehicle speed and a return-to-center characteristic angle lookup table, which represents the correspondence between vehicle speed and the return-to-center characteristic angle. The vehicle's return-to-center control state includes under-centering and over-centering. If the initial steering wheel angle when the vehicle returns to center is not greater than the current return-to-center characteristic angle, the vehicle's return-to-center control state is determined to be under-centering. If the initial steering wheel angle when the vehicle returns to center is greater than the current return-to-center characteristic angle, the vehicle's return-to-center control state is determined to be over-centering.

[0100] Step S240: Based on the vehicle's return-to-center control status, use the current return-to-center control parameters corresponding to the current vehicle speed to perform return-to-center control.

[0101] In this embodiment, the control performance varies depending on the vehicle's return-to-center control state. When the return-to-center control state is under-centering, the steering resistance is high, requiring a large return-to-center torque to overcome it. Conversely, when the return-to-center control state is over-correction, the steering resistance is considered low, making over-correction prone to causing vehicle vibration. Therefore, to improve control accuracy, return-to-center control is performed based on the vehicle's return-to-center control state. Furthermore, considering the different control performance at different vehicle speeds, return-to-center control is performed using the current control parameters corresponding to the current vehicle speed, thereby achieving precise return-to-center control.

[0102] From Figure 2 It can be seen that, compared with Figure 1 the corresponding embodiment, the active straightening control method of the electric power steering system in the embodiment of the application involves a step of determining whether the vehicle needs to be controlled to straighten. Therefore, the scheme described in the embodiment of the application can automatically determine whether the vehicle needs to be controlled to straighten according to the steering wheel angle, the steering wheel angular velocity and the steering wheel torque of the vehicle, so as to realize accurate straightening control based on the straightening control state and the current vehicle speed of the vehicle in the case of straightening control.

[0103] Further referring to Figure 3 , Figure 3 is another step flow chart of the active straightening control method of the electric power steering system provided in the embodiment of the application, and the method comprises the following steps S310 to S360:

[0104] Step S310: In the case that the direction of the steering wheel angle is opposite to the direction of the steering wheel angular velocity, and the duration of the opposite directions is greater than a first time threshold, it is determined that the vehicle is in a straightening state.

[0105] Step S320: In the case that the vehicle is in the straightening state, it is determined whether the vehicle needs to be controlled to straighten according to the steering wheel torque and the steering wheel angle.

[0106] In the embodiment of the application, steps 310 and 320 can refer to steps 210 and 220 of the corresponding embodiment, which will not be described here again. Figure 2

[0107] Step S330: In the case that the vehicle needs to be controlled to straighten, the straightening control state of the vehicle is determined according to the current vehicle speed and the initial steering wheel angle when the vehicle is straightened, and the straightening control state of the vehicle comprises under-straightening and over-straightening.

[0108] In the embodiment of the application, considering that the straightening performance of the vehicle is related to the current vehicle speed and the initial steering wheel angle when the vehicle is straightened, in order to accurately determine the straightening control state of the vehicle, the straightening control state of the vehicle is determined according to the current vehicle speed and the initial steering wheel angle when the vehicle is straightened.

[0109] Specifically, determining the straightening control state of the vehicle comprises:

[0110] B1: In the case that the current vehicle speed is less than or equal to a first vehicle speed threshold, it is determined that the straightening control state of the vehicle is under-straightening;

[0111] B2: In the case that the current vehicle speed is greater than or equal to a second vehicle speed threshold, it is determined that the straightening control state of the vehicle is over-straightening;

[0112] ​B3: in the case that the current vehicle speed is greater than the first vehicle speed threshold and less than the second vehicle speed threshold, if the initial steering wheel angle of the vehicle when the vehicle is straightening is not greater than the current straightening characteristic angle, determining that the straightening control state of the vehicle is straightening deficiency, and if the initial steering wheel angle of the vehicle when the vehicle is straightening is greater than the current straightening characteristic angle, determining that the straightening control state of the vehicle is straightening overshoot.

[0113] wherein the current straightening characteristic angle is determined according to the vehicle speed and a straightening characteristic angle lookup table, the straightening characteristic angle lookup table being used to represent the corresponding relationship between the vehicle speed and the straightening characteristic angle. The first vehicle speed threshold, the second vehicle speed threshold and the straightening characteristic angle are all related to the structural parameters of the vehicle, and the first vehicle speed threshold, the second vehicle speed threshold and the straightening characteristic angle of the vehicle can be calibrated through experiments.

[0114] For the vehicles with the same structural parameters, when the current vehicle speed is less than or equal to the first vehicle speed threshold, no matter how large the initial steering wheel angle of the vehicle when the vehicle is straightening is, the vehicle is always straightening deficiency; when the current vehicle speed is greater than or equal to the second vehicle speed threshold, no matter how large the initial steering wheel angle of the vehicle when the vehicle is straightening is, the vehicle is always straightening overshoot; when the current vehicle speed is between the first vehicle speed threshold and the second vehicle speed threshold, the straightening state of the vehicle at a fixed speed is related to the initial steering wheel angle of the vehicle when the vehicle is straightening, when the initial steering wheel angle of the vehicle when the vehicle is straightening is greater than the current straightening characteristic angle, the vehicle is always straightening overshoot; when the initial steering wheel angle of the vehicle when the vehicle is straightening is not greater than the current straightening characteristic angle, the vehicle is always straightening deficiency.

[0115] In the specific implementation, in the case that the vehicle is in the straightening state, the straightening state of the vehicle is determined preferentially according to the current vehicle speed, and when the straightening state of the vehicle cannot be determined according to the current vehicle speed, the straightening state of the vehicle is determined according to the initial steering wheel angle of the vehicle when the vehicle is straightening. Specifically, firstly, it is judged whether the current vehicle speed is less than or equal to the first vehicle speed threshold, in the case that the current vehicle speed is less than or equal to the first vehicle speed threshold, the straightening control state of the vehicle is determined to be straightening deficiency; in the case that the current vehicle speed is greater than the first vehicle speed threshold, it is then judged whether the current vehicle speed is greater than or equal to the second vehicle speed threshold, if the current vehicle speed is greater than or equal to the second vehicle speed threshold, the straightening control state of the vehicle is determined to be straightening overshoot; if the current vehicle speed is not greater than or equal to the second vehicle speed threshold, it indicates that the current vehicle speed is between the first vehicle speed threshold and the second vehicle speed threshold, i.e. the current vehicle speed is greater than the first vehicle speed threshold and less than the second vehicle speed threshold; at this time, the straightening control state of the vehicle is determined according to the size relationship between the initial steering wheel angle of the vehicle when the vehicle is straightening and the current straightening characteristic angle, i.e. the initial steering wheel angle of the vehicle when the vehicle is straightening is not greater than the current straightening characteristic angle, the straightening control state of the vehicle is determined to be straightening deficiency, and the initial steering wheel angle of the vehicle when the vehicle is straightening is greater than the current straightening characteristic angle, the straightening control state of the vehicle is determined to be straightening overshoot.

[0116] Step S340: After determining that the return-to-straight control state of the vehicle is insufficient return-to-straight, it is judged whether the steering wheel angular velocity is less than or equal to a first angular velocity threshold, and in the case that the steering wheel angular velocity is less than or equal to the first angular velocity threshold, the first control parameter corresponding to the current vehicle speed is used to perform return-to-straight control in the insufficient return-to-straight control mode.

[0117] In the embodiments of the present application, in order to prevent the insufficient return-to-straight control caused by the excessively large steering wheel angular velocity from leading to return-to-straight overshoot and causing a large impact on the steering wheel, the first angular velocity threshold is set according to the return-to-straight control performance, and the first angular velocity threshold is used to judge the size of the steering wheel angular velocity. When the steering wheel angular velocity is less than or equal to the first angular velocity threshold, it indicates that the steering wheel angular velocity is small, and the mechanical return-to-straight effect of the vehicle itself will disappear. At this time, the first control parameter corresponding to the current vehicle speed is used to perform return-to-straight control in the insufficient return-to-straight control mode.

[0118] The insufficient return-to-straight control mode refers to a proportional-integral control method, and the first parameter is a proportional-integral control parameter determined according to the current vehicle speed. In the case that the return-to-straight control state of the vehicle is insufficient return-to-straight, the steering resistance of the vehicle is large, and a large return-to-straight torque is needed to overcome the current steering resistance. Therefore, the proportional-integral control method is used to perform insufficient return-to-straight control.

[0119] Specifically, in the case that the steering wheel angular velocity is less than or equal to the first angular velocity threshold, the first control parameter corresponding to the current vehicle speed is used to perform return-to-straight control in the insufficient return-to-straight control mode, which includes: determining a first proportional link adjustment coefficient and an integral link adjustment coefficient according to the current vehicle speed and a proportional-integral control parameter lookup table, the proportional-integral control parameter lookup table being used to represent the corresponding relationship between the vehicle speed and the proportional-integral control parameter; and performing return-to-straight control according to the proportional-integral control method according to the first proportional link adjustment coefficient and the integral link adjustment coefficient.

[0120] In the embodiments of the present application, the return-to-straight performance is different at different vehicle speeds, different vehicle speeds correspond to different proportional-integral control parameters, and the corresponding relationship between the vehicle speed and the proportional-integral control parameter is represented by a proportional-integral control parameter lookup table. When performing insufficient return-to-straight control, the proportional-integral control parameter lookup table is looked up according to the current vehicle speed to obtain the corresponding proportional-integral control parameter, that is, the first proportional link adjustment coefficient and the integral link adjustment coefficient; and the insufficient return-to-straight control is realized according to the first proportional link adjustment coefficient and the integral link adjustment coefficient.

[0121] In some embodiments, in order to compensate for the influence of the initial steering wheel angle on the return-to-straight performance when the return-to-straight is insufficient, an integral compensation parameter is introduced to perform insufficient return-to-straight control. Specifically, as shown in FIG. 6, performing return-to-straight control in the insufficient return-to-straight control mode includes steps C1 to C4: Figure 4 C1: determining the first proportional link adjustment coefficient and the integral link adjustment coefficient according to the current vehicle speed and the proportional-integral control parameter lookup table;

[0122] Step C1: Determine whether the initial steering wheel angle when the vehicle returns to center is less than or equal to the insufficient return-to-center characteristic angle, where the insufficient return-to-center characteristic angle represents the steering angle threshold that requires integral compensation.

[0123] When the initial steering wheel angle is small when the vehicle returns to center, it affects the accuracy of undercenter control. The undercenter characteristic angle is used to determine whether integral compensation is needed. The undercenter characteristic angle is a pre-calibrated value. If the initial steering wheel angle when the vehicle returns to center is less than or equal to the undercenter characteristic angle, integral compensation is needed. In this case, step C2 is executed to determine the integral compensation parameter. If the initial steering wheel angle when the vehicle returns to center is greater than the undercenter characteristic angle, integral compensation is not needed, and the integral compensation parameter is 0.

[0124] Step C2: If the initial steering wheel angle when the vehicle returns to center is less than or equal to the under-centering characteristic angle, determine the integral compensation parameter according to the initial steering wheel angle when the vehicle returns to center and the integral compensation parameter lookup table. The integral compensation parameter lookup table is used to characterize the correspondence between the steering wheel angle and the integral compensation parameter.

[0125] Different steering wheel angles correspond to different compensation scenarios. The relationship between steering wheel angles and integral compensation parameters is represented by an integral compensation parameter lookup table. When integral compensation is required, the corresponding integral compensation parameters are obtained by looking up the integral compensation parameter lookup table based on the initial steering wheel angle when the vehicle returns to center.

[0126] Step C3: Determine the first proportional control adjustment coefficient and the integral control adjustment coefficient according to the current vehicle speed and the proportional-integral control parameter lookup table. The proportional-integral control parameter lookup table is used to characterize the correspondence between vehicle speed and proportional-integral control parameters.

[0127] Step C4: Perform homing control according to the integral compensation parameter, the first proportional element adjustment coefficient, and the integral element adjustment coefficient using the proportional-integral control method.

[0128] Specifically, such as Figure 5 As shown, with steering wheel angle deviation as the control target, the proportional-integral controller calculates the adjustment coefficients of the first proportional element and the integral element to obtain the first proportional return current and the integral return current. For example, the proportional-integral controller calculation is expressed as:

[0129] I=Kp*(θa-θ)+Ki*∫(θa-θ)dt,

[0130] Wherein, θa represents a desired target steering wheel return angle, generally set as 0; θ represents an actual steering wheel angle; Kp represents a first proportional link adjustment coefficient, obtained by looking up a proportional integral lookup table according to a current vehicle speed; Ki represents an integral link adjustment coefficient, obtained by looking up the proportional integral lookup table according to the current vehicle speed; Kp*(θa-θ) is a first proportional return current; Ki*∫(θa-θ)dt is an integral return current.

[0131] Then, the integral compensation current (i.e., integral compensation parameter) and the integral return current are added to obtain a total integral return current; in order to prevent the proportional integral controller from being unstable due to too large a change range of the angle, the proportional return current is dynamically integrated and limited to obtain a limited proportional return current, and the total integral return current is dynamically integrated and limited to obtain a limited total integral return current. Finally, the limited proportional return current and the limited total integral return current are added to obtain a final return current, which is applied to a power-assisted motor in the electric power-assisted steering system to generate a return-assisted control to return the steering wheel to a neutral position, thereby realizing return control.

[0132] Step S350: After determining that the return control state of the vehicle is return overshoot, return control is performed according to a return overshoot control mode by using a second control parameter corresponding to the current vehicle speed.

[0133] In the embodiments of the present application, the return overshoot control mode refers to a proportional differential control method, and the second parameter is a proportional differential control parameter determined according to the current vehicle speed. In the case where the return control state of the vehicle is return overshoot, the steering resistance of the vehicle is small, and the steering is prone to overshoot to cause vibration of the vehicle, so the proportional differential control method is used for return overshoot control.

[0134] Specifically, after determining that the return control state of the vehicle is return overshoot, return control is performed according to a return overshoot control mode by using a second control parameter corresponding to the current vehicle speed, which includes: determining a second proportional link adjustment coefficient and a differential link adjustment coefficient according to the current vehicle speed and a proportional differential control parameter lookup table, the proportional differential control parameter lookup table being used to represent a corresponding relationship between a vehicle speed and a proportional differential control parameter; and performing return control according to a proportional differential control method according to the second proportional link adjustment coefficient and the differential link adjustment coefficient.

[0135] In the embodiments of the present application, the return-to-center performance is different at different vehicle speeds, different vehicle speeds correspond to different proportional and differential control parameters, and the corresponding relationship between the vehicle speed and the proportional and differential control parameters is represented by a proportional and differential control parameter lookup table. When performing the return-to-center overshoot control, the proportional and differential control parameter lookup table is looked up according to the current vehicle speed to obtain the corresponding proportional and differential control parameters, i.e., the second proportional link adjustment coefficient and the differential link adjustment coefficient; and then the return-to-center overshoot control is realized according to the second proportional link adjustment coefficient and the differential link adjustment coefficient.

[0136] In specific implementation, as shown in Figure 6 According to the second proportional link adjustment coefficient and the differential link adjustment coefficient, the return-to-center control is performed according to the proportional and differential control method, specifically including: taking the steering wheel angle deviation as the control target, performing the return-to-center overshoot control by using the proportional and differential controller, and calculating the second proportional return-to-center current and the differential return-to-center current according to the second proportional link adjustment coefficient and the differential link adjustment coefficient.

[0137] For example, the dynamic PD controller calculation method is as follows:

[0138] I = Kp * (θa - θ) + Kd * [d(θa - θ) / dt],

[0139] wherein θa is the expected target steering wheel return-to-center angle, which is generally set to 0; θ is the actual steering wheel angle; Kp is the second proportional link adjustment coefficient, which is obtained by looking up the proportional and differential lookup table according to the current vehicle speed; Kd is the differential link adjustment coefficient, which is obtained by looking up the proportional and differential lookup table according to the current vehicle speed; Kp * (θa - θ) is the second proportional return-to-center current; and Kd * [d(θa - θ) / dt] is the differential return-to-center current.

[0140] In order to prevent the proportional and differential controller from being unstable due to too large steering angle range, dynamic proportional limiting is performed on the proportional return-to-center current to obtain the limited proportional return-to-center current, and dynamic differential limiting is performed on the differential return-to-center current to obtain the limited differential return-to-center current. Finally, the limited proportional return-to-center current and the limited differential return-to-center current are added to obtain the final return-to-center current; and the return-to-center current is applied to the assist motor in the electric power steering system to generate return-to-center assist control, so that the steering wheel returns to the center to realize the return-to-center control.

[0141] It can be understood that when the dynamic proportional limiting, dynamic integral limiting and dynamic differential limiting processing are performed, the amplitude is not fixed and needs to be adjusted dynamically according to the current vehicle speed.

[0142] Step 360: ending the return-to-center control of the vehicle when the return-to-center control ending condition is met;

[0143] The return-to-center control ending condition includes any one of the following:

[0144] F1: the current steering wheel angle is less than the target steering wheel angle;

[0145] F2: the current steering wheel torque is greater than a first torque threshold value;

[0146] F3: the direction of the current steering wheel angle is the same as the direction of the steering wheel angular velocity, and the duration of the same direction is greater than a second time threshold value.

[0147] Specifically, the satisfaction of the F1 term indicates that the steering wheel returns to the neutral position, the satisfaction of the F2 term indicates that the driver may actively control, and the satisfaction of the F3 term indicates that the vehicle is not in the self-recovery state. Therefore, in the case where any one of the above F1 term to F3 term is satisfied, the self-recovery control of the vehicle is ended.

[0148] From Figure 3 It can be seen that, compared with the embodiments corresponding to Figure 1 and Figure 2 The active self-recovery control method of the electric power steering system in the embodiment of the application involves the steps of determining whether the vehicle needs to be self-recovered, judging whether the steering wheel torque is less than or equal to the first torque threshold value, and performing integral compensation. Therefore, the scheme described in the embodiment of the application can automatically determine whether the vehicle needs to be self-recovered according to the steering wheel angle, the steering wheel angular velocity and the steering wheel torque, intervene in the self-recovery control when the mechanical self-recovery effect of the vehicle itself disappears, and compensate for the insufficient self-recovery control in the case of small steering angle, so as to realize accurate self-recovery control.

[0149] The determination process of the self-recovery state of the vehicle in the embodiment of the application will be described below with a specific implementation flow, as shown in Figure 7 , including steps H1 to H7:

[0150] Step H1: If the direction of the steering wheel angle is opposite to the direction of the steering wheel angular velocity, and the duration of the opposite direction is greater than the first time threshold value, it is determined that the vehicle is in the self-recovery state.

[0151] Step H2: If the condition of step H1 is met, it is further judged whether the steering wheel torque is less than or equal to the first torque threshold value. In the case where the steering wheel torque is greater than the first torque threshold value, it is determined that the vehicle does not need to be self-recovered; in the case where the steering wheel torque is less than or equal to the first torque threshold value, it is preliminarily determined that the vehicle needs to be self-recovered.

[0152] Step H3: In the case that it is preliminarily determined that the vehicle needs to be controlled to return to normal, it is further determined whether the steering wheel angle is greater than or equal to a first angle threshold. If the steering wheel angle is greater than or equal to the first angle threshold, it is finally determined that the vehicle needs to be controlled to return to normal; if the steering wheel angle is less than the first angle threshold, it is finally determined that the vehicle does not need to be controlled to return to normal.

[0153] Step H4: In the case that it is finally determined that the vehicle needs to be controlled to return to normal, it is determined whether the current vehicle speed is less than or equal to a first speed threshold. In the case that the current vehicle speed is less than or equal to the first speed threshold, it is determined that the vehicle return-to-normal control state is return-to-normal deficiency, and at this time, instead of directly performing return-to-normal deficiency control, step H7 is executed; in the case that the current vehicle speed is greater than the first speed threshold, step H5 is executed.

[0154] Step H5: It is determined whether the current vehicle speed is greater than or equal to a second speed threshold. In the case that the current vehicle speed is greater than or equal to the second speed threshold, it is determined that the vehicle return-to-normal control state is return-to-normal overshoot, and directly enters return-to-normal overshoot control, and uses the second control parameter corresponding to the current vehicle speed to perform return-to-normal control in the return-to-normal overshoot control mode; in the case that the current vehicle speed is less than the second speed threshold, step H6 is executed.

[0155] Step H6: If the condition in step H5 is not established, it means that the current vehicle speed is between the first speed threshold and the second speed threshold, i.e., the current vehicle speed is greater than the first speed threshold and less than the second speed threshold. At this time, according to the size relationship between the steering wheel initial angle when the vehicle returns to normal and the current return-to-normal characteristic angle, the vehicle return-to-normal control state is determined. If the steering wheel initial angle when the vehicle returns to normal is greater than the current return-to-normal characteristic angle, it is determined that the vehicle return-to-normal control state is return-to-normal overshoot, and directly enters return-to-normal overshoot control, and uses the second control parameter corresponding to the current vehicle speed to perform return-to-normal control in the return-to-normal overshoot control mode; if the steering wheel initial angle when the vehicle returns to normal is not greater than the current return-to-normal characteristic angle, it is determined that the vehicle return-to-normal control state is return-to-normal deficiency, and at this time, instead of directly performing return-to-normal deficiency control, step H7 is executed.

[0156] Step H7: It is determined whether the steering wheel angular velocity is less than or equal to a first angular velocity threshold, and in the case that the steering wheel angular velocity is less than or equal to the first angular velocity threshold, uses the first control parameter corresponding to the current vehicle speed to perform return-to-normal control in the return-to-normal deficiency control mode.

[0157] The method provided in this application accurately determines the vehicle's return-to-center control state based on the current vehicle speed, the initial steering wheel angle, and the return-to-center characteristic angle. This allows for accurate return-to-center control without the need for intelligent control methods, reducing control costs. Furthermore, the control parameters are determined based on the current vehicle speed, taking into account the impact of speed on return-to-center performance, thus enabling accurate return-to-center control at different speeds. In this way, a low-cost and highly accurate active return-to-center control is achieved.

[0158] This application also provides an electric power steering system for implementing the active return-to-center control method of the electric power steering system described in this application embodiment, such as... Figure 8 As shown, the system includes: an EPS return-to-center control module, a data processing module, a power assist motor, a steering angle sensor, a torque sensor, an EPS function module, and a steering column. The system is powered by a battery.

[0159] Specifically, the EPS (Electric Power Steering) module acquires vehicle speed signals, the steering angle sensor acquires torque signals, and the steering angle sensor acquires steering angle signals. These signals are processed by the data processing module. The electric power steering system connects to the vehicle's CAN network and communicates with other vehicle controllers via the CAN module. When the driver completes the steering action and returns to center, the EPS return-to-center control module determines whether return-to-center control is needed based on the torque, steering angle, and vehicle speed signals collected by the sensors, and the angular velocity signal calculated by the data processing module using the steering angle signal. It then determines the return-to-center control state based on the current vehicle speed and steering angle signals. Finally, based on the return-to-center control state, it performs return-to-center control using the current return-to-center control parameters corresponding to the current vehicle speed.

[0160] This application also provides an active return-to-center control device for an electric power steering system, see reference. Figure 9 As shown, Figure 9 This is a schematic diagram of the structure of an active return-to-center control device for an electric power steering system provided in an embodiment of this application. The device includes:

[0161] The first determining module 910 is used to determine the current alignment feature angle based on the current vehicle speed when the vehicle is in the alignment state; wherein, the alignment feature angle is determined based on the vehicle speed and the alignment feature angle lookup table, and the alignment feature angle lookup table is used to represent the correspondence between the vehicle speed and the alignment feature angle.

[0162] The second determining module 920 is used to determine the vehicle's return-to-center control state based on the relationship between the initial steering wheel angle when the vehicle returns to center and the current return-to-center characteristic angle.

[0163] The first control module 930 is used to perform centering control based on the centering control status of the vehicle and the current centering control parameters corresponding to the current vehicle speed.

[0164] In an optional embodiment, the device further includes:

[0165] The third determining module is used to determine that the vehicle's return-to-center control state is insufficient when the current vehicle speed is less than or equal to the first vehicle speed threshold.

[0166] The fourth determining module is used to determine that the vehicle's return-to-center control state is return-to-center overshoot when the current vehicle speed is greater than or equal to the second vehicle speed threshold.

[0167] The fifth determining module is used to determine the vehicle's return-to-center control state as insufficient return-to-center if the initial steering wheel angle when the vehicle returns to center is not greater than the current return-to-center characteristic angle, and to determine the vehicle's return-to-center control state as overshoot if the current vehicle speed is greater than the first vehicle speed threshold and less than the second vehicle speed threshold.

[0168] In an optional embodiment, the device further includes:

[0169] The sixth determining module is used to determine that the vehicle is in a straightening state when the direction of the steering wheel angle is opposite to the direction of the steering wheel angular velocity, and the duration of the opposite direction is greater than a first time threshold.

[0170] The seventh determining module is used to determine whether vehicle return-to-center control is needed based on the steering wheel torque and the steering wheel angle when the vehicle is in the return-to-center state.

[0171] The second determining module includes:

[0172] The first determining submodule is used to determine the vehicle's return-to-center control state based on the relationship between the initial steering wheel angle when the vehicle returns to center and the current return-to-center characteristic angle when the vehicle needs to be returned to center.

[0173] In an optional embodiment, the seventh determining module includes:

[0174] The first judgment module is used to determine whether the steering wheel torque is less than or equal to a first torque threshold.

[0175] The second determining submodule is used to determine that, when the steering wheel torque is greater than the first torque threshold, it is not necessary to perform return-to-center control on the vehicle.

[0176] a third determining sub-module, configured to preliminarily determine that the vehicle needs to be controlled to return to normal if the steering wheel torque is less than or equal to the first torque threshold value;

[0177] a second judging module, configured to judge whether the steering wheel angle is greater than or equal to a first angle threshold value if it is preliminarily determined that the vehicle needs to be controlled to return to normal;

[0178] a fourth determining sub-module, configured to finally determine that the vehicle needs to be controlled to return to normal if the steering wheel angle is greater than or equal to the first angle threshold value;

[0179] a fifth determining sub-module, configured to finally determine that the vehicle does not need to be controlled to return to normal if the steering wheel angle is less than the first angle threshold value.

[0180] In an optional embodiment, the seventh determining module comprises

[0181] a third judging module, configured to judge whether the steering wheel angular velocity is less than or equal to a first angular velocity threshold value;

[0182] the first control module comprises:

[0183] an under-steering control module, configured to control the vehicle to return to normal in an under-steering control mode by using a first control parameter corresponding to the current vehicle speed if the steering wheel angular velocity is less than or equal to the first angular velocity threshold value;

[0184] an over-steering control module, configured to control the vehicle to return to normal in an over-steering control mode by using a second control parameter corresponding to the current vehicle speed after it is determined that the vehicle is in an over-steering control state.

[0185] In an optional embodiment, the under-steering control module comprises:

[0186] a sixth determining sub-module, configured to determine a first proportional link adjustment coefficient and an integral link adjustment coefficient according to the current vehicle speed and a proportional-integral control parameter lookup table, the proportional-integral control parameter lookup table being used to represent a corresponding relationship between the vehicle speed and the proportional-integral control parameter;

[0187] a first control sub-module, configured to control the vehicle to return to normal in a proportional-integral control method according to the first proportional link adjustment coefficient and the integral link adjustment coefficient.

[0188] In an optional embodiment, the under-steering control module comprises:

[0189] a fourth judging module, configured to judge whether an initial steering wheel angle when the vehicle returns to normal is less than or equal to an under-steering characteristic angle, the under-steering characteristic angle representing a threshold value of the angle that needs to be compensated by integration;

[0190] a seventh determining sub-module, configured to, when the initial steering wheel angle during the vehicle returning is less than or equal to the under-returning characteristic angle, determine an integral compensation parameter according to the initial steering wheel angle during the vehicle returning and an integral compensation parameter lookup table, the integral compensation parameter lookup table being used to represent a corresponding relationship between the steering wheel angle and the integral compensation parameter;

[0191] a second control sub-module, configured to perform the returning control according to the integral compensation parameter, the first proportional link adjustment coefficient and the integral link adjustment coefficient according to a proportional-integral control method.

[0192] In an optional embodiment, the returning over-control control module comprises:

[0193] an eighth determining sub-module, configured to determine a second proportional link adjustment coefficient and a differential link adjustment coefficient according to the current vehicle speed and a proportional-differential control parameter lookup table, the proportional-differential control parameter lookup table being used to represent a corresponding relationship between the vehicle speed and the proportional-differential control parameter;

[0194] a third control sub-module, configured to perform the returning control according to the second proportional link adjustment coefficient and the differential link adjustment coefficient according to a proportional-differential control method.

[0195] In an optional embodiment, the device further comprises:

[0196] an end control module, configured to end the returning control of the vehicle when a returning control end condition is met;

[0197] The returning control end condition comprises any one of the following:

[0198] the current steering wheel angle is less than the target steering wheel angle;

[0199] the current steering wheel torque is greater than a first torque threshold;

[0200] the direction of the current steering wheel angle is the same as the direction of the steering wheel angular velocity, and the same direction duration is greater than a second time threshold.

[0201] Embodiments of the present application also provide a vehicle, comprising a memory and a processor, the memory storing a computer program which is run by the processor, the computer program, when run by the processor, causing the processor to perform the steps of the active returning control method of the electric power assisted steering system according to the embodiments of the present application.

[0202] The embodiment of the present application further provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the steps of the active return control method of the electric power steering system.

[0203] Each of the embodiments in the specification is described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between the embodiments can be referred to each other.

[0204] The embodiments of the present application are described with reference to the flowcharts and / or block diagrams of the method and device according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks can be implemented by computer program instructions. The computer program instructions can be provided to a general purpose computer, a special purpose computer, an embedded processor or other programmable data processing terminal equipment to produce a machine, so that the instructions executed by the computer or other programmable data processing terminal equipment produce a device for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one flow or multiple flows and / or blocks Figure 1 The device for implementing the functions specified in one block or multiple blocks.

[0205] The computer program instructions can also be stored in a computer readable memory capable of guiding the computer or other programmable data processing terminal equipment to work in a specific manner, so that the instructions stored in the computer readable memory produce a product including instruction devices, which implement the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one flow or multiple flows and / or blocks Figure 1 The device for implementing the functions specified in one block or multiple blocks.

[0206] The computer program instructions can also be loaded into the computer or other programmable data processing terminal equipment, so that a series of operation steps are performed on the computer or other programmable terminal equipment to produce a computer implemented process, so that the instructions executed on the computer or other programmable terminal equipment provide steps for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one flow or multiple flows and / or blocks Figure 1 The device for implementing the functions specified in one block or multiple blocks.

[0207] Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications to the embodiments once they know the basic inventive concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the embodiments of the present application.

[0208] Finally, it is to be understood that the phraseology or terminology such as "first" and "second" etc. used herein is merely intended to differentiate one entity or operation from another entity or operation, without necessarily requiring or implying any actual such relationship or order between such entities or operations. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0209] The above describes in detail the active return control method, device, vehicle and medium of the electric power steering system provided by the present application. The principles and implementation manners of the present application are described by using specific examples. The above description of the embodiments is only used to help understand the method of the present application and its core idea. Meanwhile, for those skilled in the art, the specific implementation manners and application ranges will be changed according to the idea of the present application. In summary, the content of the specification should not be understood as a limitation of the present application.

Claims

1. An active return-to-center control method for an electric power steering system, characterized in that, The method includes: If the direction of the steering wheel angle is opposite to the direction of the steering wheel angular velocity, and the duration of the opposite direction is greater than a first time threshold, the vehicle is determined to be in a straightened state. When the vehicle is in the centering state, the system determines whether vehicle centering control is needed based on the steering wheel torque and the steering wheel angle. This includes: determining whether the steering wheel torque is less than or equal to a first torque threshold; if the steering wheel torque is greater than the first torque threshold, determining that vehicle centering control is not needed; if the steering wheel torque is less than or equal to the first torque threshold, initially determining that vehicle centering control is needed; if vehicle centering control is initially determined to be needed, determining whether the steering wheel angle is greater than or equal to a first angle threshold; if the steering wheel angle is less than the first angle threshold, finally determining that vehicle centering control is not needed; if the steering wheel angle is greater than or equal to the first angle threshold, finally determining that vehicle centering control is needed. When the vehicle is in the straightening state, the current straightening feature angle is determined based on the current vehicle speed; wherein, the straightening feature angle is determined based on the vehicle speed and the straightening feature angle lookup table, the straightening feature angle lookup table is used to represent the correspondence between the vehicle speed and the straightening feature angle; If the current vehicle speed is less than or equal to the first vehicle speed threshold, the vehicle's return-to-center control state is determined to be insufficient return-to-center. If the current vehicle speed is greater than or equal to the second vehicle speed threshold, the vehicle's return-to-center control state is determined to be return-to-center overshoot. When the current vehicle speed is greater than the first vehicle speed threshold and less than the second vehicle speed threshold, the vehicle's return-to-center control state is determined based on the relationship between the initial steering wheel angle when the vehicle returns to center and the current return-to-center characteristic angle. Based on the vehicle's return-to-center control status, return-to-center control is performed using the current return-to-center control parameters corresponding to the current vehicle speed.

2. The method according to claim 1, characterized in that, The step of determining the vehicle's return-to-center control state based on the relationship between the initial steering wheel angle when the vehicle returns to center and the current return-to-center characteristic angle includes: If the initial steering wheel angle when the vehicle returns to center is not greater than the current centering characteristic angle, the vehicle's centering control state is determined to be under-centering; if the initial steering wheel angle when the vehicle returns to center is greater than the current centering characteristic angle, the vehicle's centering control state is determined to be over-centering.

3. The method according to claim 1, characterized in that, The method further includes: Based on the relationship between the initial steering wheel angle when the vehicle returns to center and the current centering characteristic angle, the vehicle's centering control state is determined, including: When it is necessary to control the vehicle to return to center, the vehicle's return-to-center control state is determined based on the relationship between the initial steering wheel angle when the vehicle returns to center and the current return-to-center characteristic angle.

4. The method according to claim 2, characterized in that, After determining that the vehicle's return-to-center control state is insufficient, the method further includes: Determine whether the steering wheel angular velocity is less than or equal to the first angular velocity threshold; Based on the vehicle's return-to-center control status, return-to-center control is performed using the current return-to-center control parameters corresponding to the current vehicle speed, including: When the steering wheel angular velocity is less than or equal to the first angular velocity threshold, return-to-center control is performed according to the insufficient return-to-center control mode using the first control parameter corresponding to the current vehicle speed. After determining that the vehicle's return-to-center control state is return-to-center overshoot, the return-to-center control is performed according to the return-to-center overshoot control mode using the second control parameter corresponding to the current vehicle speed.

5. The method according to claim 4, characterized in that, When the steering wheel angular velocity is less than or equal to the first angular velocity threshold, the steering wheel angular velocity is controlled according to the insufficient steering wheel angular velocity control mode using the first control parameter corresponding to the current vehicle speed, including: Based on the current vehicle speed and the proportional-integral control parameter lookup table, the first proportional link adjustment coefficient and the integral link adjustment coefficient are determined. The proportional-integral control parameter lookup table is used to characterize the correspondence between vehicle speed and proportional-integral control parameters. Based on the first proportional element adjustment coefficient and the integral element adjustment coefficient, homing control is performed according to the proportional-integral control method.

6. The method according to claim 5, characterized in that, The method further includes: Determine whether the initial steering wheel angle when the vehicle returns to center is less than or equal to the insufficient return-to-center characteristic angle, wherein the insufficient return-to-center characteristic angle represents the steering angle threshold that requires integral compensation; When the initial steering wheel angle when the vehicle returns to center is less than or equal to the insufficient return characteristic angle, the integral compensation parameter is determined according to the initial steering wheel angle when the vehicle returns to center and the integral compensation parameter lookup table. The integral compensation parameter lookup table is used to characterize the correspondence between the steering wheel angle and the integral compensation parameter. Based on the first proportional element adjustment coefficient and the integral element adjustment coefficient, homing control is performed according to the proportional-integral control method, including: Based on the integral compensation parameter, the first proportional element adjustment coefficient, and the integral element adjustment coefficient, homing control is performed according to the proportional-integral control method.

7. The method according to claim 4, characterized in that, After determining that the vehicle's return-to-center control state is in the return-to-center overshoot state, the return-to-center control is performed according to the return-to-center overshoot control mode using the second control parameter corresponding to the current vehicle speed, including: Based on the current vehicle speed and the proportional-derivative control parameter lookup table, the adjustment coefficients of the second proportional element and the derivative element are determined. The proportional-derivative control parameter lookup table is used to characterize the correspondence between vehicle speed and proportional-derivative control parameters. Based on the second proportional element adjustment coefficient and the derivative element adjustment coefficient, homing control is performed according to the proportional-derivative control method.

8. The method according to any one of claims 1-7, characterized in that, The method further includes: If the conditions for ending the return-to-center control are met, the return-to-center control of the vehicle is terminated. The termination condition for the return-to-center control includes any one of the following: The current steering wheel angle is less than the target steering wheel angle; The current steering wheel torque is greater than the first torque threshold; The current steering wheel angle is in the same direction as the steering wheel angular velocity, and the duration of this same direction is greater than the second time threshold.

9. An active return-to-center control device for an electric power steering system, characterized in that, The device includes: The sixth determining module is used to determine that the vehicle is in a straightening state when the direction of the steering wheel angle is opposite to the direction of the steering wheel angular velocity, and the duration of the opposite direction is greater than a first time threshold. The seventh determining module is used to determine whether vehicle return-to-center control is needed based on the steering wheel torque and the steering wheel angle when the vehicle is in the return-to-center state. The seventh determining module includes: a first determining module for determining whether the steering wheel torque is less than or equal to a first torque threshold; a second determining submodule for determining that, if the steering wheel torque is greater than the first torque threshold, no vehicle return-to-center control is required; a third determining submodule for initially determining that, if the steering wheel torque is less than or equal to the first torque threshold, vehicle return-to-center control is required; a second determining module for determining whether the steering wheel angle is greater than or equal to a first angle threshold when vehicle return-to-center control is initially determined to be required; a fourth determining submodule for ultimately determining that vehicle return-to-center control is required if the steering wheel angle is greater than or equal to the first angle threshold; and a fifth determining submodule for ultimately determining that vehicle return-to-center control is not required if the steering wheel angle is less than the first angle threshold. The first determining module is used to determine the current alignment feature angle based on the current vehicle speed when the vehicle is in the alignment state; wherein, the alignment feature angle is determined based on the vehicle speed and the alignment feature angle lookup table, and the alignment feature angle lookup table is used to represent the correspondence between the vehicle speed and the alignment feature angle. The third determining module is used to determine that the vehicle's return-to-center control state is insufficient when the current vehicle speed is less than or equal to the first vehicle speed threshold. The fourth determining module is used to determine that the vehicle's return-to-center control state is return-to-center overshoot when the current vehicle speed is greater than or equal to the second vehicle speed threshold. The second determining module is used to determine the vehicle's return-to-center control state based on the relationship between the initial steering wheel angle when the vehicle returns to center and the current return-to-center characteristic angle when the current vehicle speed is greater than the first vehicle speed threshold and less than the second vehicle speed threshold. The first control module is used to perform centering control based on the vehicle's centering control status and the current centering control parameters corresponding to the current vehicle speed.

10. A vehicle, characterized in that, The vehicles include: A memory and a processor, wherein the memory stores a computer program executed by the processor, the computer program, when executed by the processor, causes the processor to perform the steps of the active return-to-center control method for an electric power steering system as described in any one of claims 1 to 8.

11. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps of the active return-to-center control method for the electric power steering system as described in any one of claims 1 to 8.

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