Control method for switching process of EPS (electric power steering) power assisting mode and aligning mode

Abstract

The invention belongs to the technical field of automobile steering control, and particularly relates to an EPS power-assisted mode and return mode switching process control method which is composed of a steering mode switching judgment module, a switching time determination module, a torque curve processing module and a switching compensation torque determination module. By designing the switching time length determination module, the return time is determined according to the steering angle of the steering wheel and the vehicle speed at the current moment, the expectation of a driver is better met, the expected value of the switching compensation torque is obtained through torque processing of the Bizier curve according to calculation of different switching conditions, and therefore the accuracy of the switching compensation torque is improved. The switching compensation torque at any switching moment is obtained by tracking the switching torque curve graph, so that the steering mode switching process of the vehicle under different working conditions is smoother, and the steering comfort of a driver is greatly improved; the problem of pause caused by sudden change of hand torque felt by a driver when the power-assisted mode and the aligning mode of the current electric power-assisted steering automobile are switched is solved, and the driving experience is improved.

Description

Technical Field

[0001] The invention relates to the technical field of automobile steering control, and in particular to a method for controlling a switching process between an EPS power assist mode and a return mode. Background Art

[0002] In recent years, the automobile industry has developed rapidly, and consumers have put forward higher requirements for the quality of automobile movement. For steering movement, consumers are mainly concerned about the stability of movement, the steering feeling when turning, and the quality of returning to the center when letting go (or holding the steering wheel to return to the center). When the driver turns the steering wheel to a certain angle and tries to maintain this position, he will feel a noticeable drag if he slightly holds the steering wheel.

[0003] Invention patent CN118270096A discloses a vehicle steering wheel differential return method, device, vehicle and storage medium, the method includes: judging whether the driver controls the steering wheel by judging whether the hand torque applied by the driver on the steering wheel is less than a preset threshold, and differentially controlling the steering wheel based on the active disturbance rejection controller ADRC; distributing the target differential return compensation torque to the target wheel of the vehicle to obtain the control torque of the hub motor of the target wheel that meets the preset optimal conditions. However, in actual applications, when the driver is holding the steering wheel, the sudden change of the power torque may cause frustration, and the driver feels bad about driving.

[0004] Invention patent CN117022430A discloses an EPS system control method, device, electronic device and storage medium, the method comprising: according to the steering wheel hand force and the hand force threshold value Τ of the return mode min and Τ max The comparison results determine the EPS system working mode, which includes: steering mode, return mode and transition state mode; when it is in the return mode or steering mode, determine whether the current hand force control time change gradient is in the interval between the hand force rise time gradient and the hand force fall time gradient. When it is in the interval between the hand force rise time gradient and the hand force fall time gradient, adjust the hand force control time change gradient according to the change rate of the manual rotation torque received by the steering wheel, the rotation torque change coefficient, the manual rotation torque and the rotation torque coefficient until the hand force rise time gradient is reached, so that the hand force control time change gradient increases rapidly with the change rate of the manual rotation torque or the manual rotation torque. However, this method does not take into account the control of the switching time. The time required for mode switching at different vehicle speeds should be controlled and smoothed to improve the driver's driving feel. Summary of the invention

[0005] 1. Technical issues to be solved

[0006] In view of the deficiencies in the prior art, the present invention provides a method for controlling the switching process between the EPS power-assist mode and the return mode, which solves the problem that when the return mode and the power-assist mode of the current electric power steering vehicle are switched, the driver may feel a sense of frustration caused by the sudden change in steering wheel torque, thereby affecting the driving experience.

[0007] (II) Technical solution

[0008] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions:

[0009] A method for controlling the switching process between an EPS power assist mode and a return mode, the method comprising a steering mode switching judgment module, a switching time determination module, a torque curve processing module, and a switching compensation torque determination module, and comprising the following steps:

[0010] Step 1: The steering mode switching judgment module judges the target mode according to the vehicle speed, steering wheel torque, steering wheel angle and steering wheel speed signal. If the current mode is different from the target mode, the steering mode switching state is entered;

[0011] Step 2: The switching time determination module determines the expected switching time length according to the motion state of the vehicle before the steering mode is switched;

[0012] Step 3: The switching process torque change curve determination module divides the expected switching time into three equal parts according to different switching situations, uses B-spline to smooth the torque, and obtains the switching process torque change curve;

[0013] Step 4: The switching compensation torque determination module determines the switching compensation torque that the power-assisting motor needs to provide. By switching the compensation torque, a sudden change in the steering wheel torque felt by the driver when the steering mode is switched is avoided, so that the steering wheel torque felt by the driver can have a smooth transition.

[0014] Furthermore, in step 1, when any of the following conditions is met, it is determined that the switching state from the return mode to the power-assist mode is: (1) the steering wheel torque is greater than a certain threshold value, that is, the driver actively turns the steering wheel; (2) the steering wheel angle and speed are both less than a certain threshold value, that is, the steering wheel returns to the center area.

[0015] Furthermore, the switching state includes switching from active steering to a hands-off or steering-protected return state; and switching from a hands-off or steering-protected return state to an external active steering state.

[0016] Furthermore, the active steering state includes active external rotation and active internal rotation.

[0017] Furthermore, the expected switching time length is divided into: the time required for switching from the power-assisting mode to the return mode and the time required for switching from the return mode to the power-assisting mode.

[0018] Furthermore, in step 2, the switching time is determined according to the motion state of the vehicle at the start time of the switching.

[0019] Furthermore, in step 3, a 4th-order cubic B-spline curve is constructed, and 4 control vertices need to be determined; the switching time t tar Divide into three equal parts, the torque before switching and the stable torque after switching can determine two of the control vertices, and the other two control vertices can be obtained by the double circle tangent method;

[0020] Assuming that the coordinates of the four control vertices of the 3rd order 4th order B-spline curve are P0(x0,y0), P1(x1,y1), P2(x2,y2), and P3(x3,y3), the matrix expression of the B-spline curve is as follows:

[0021]

[0022] The component expressions of the B-spline curve are as follows;

[0023]

[0024] Constructing a B-spline curve requires solving three variables r s , Δt, that is, the design variable X of the B-spline curve optimization model is:

[0025]

[0026] Furthermore, in step 4, after detecting the start of the switching state, the torque in the switching process is controlled to reach the expected position in accordance with the size of the expected curve. It only takes effect when the driver lets go of the steering wheel, holds the steering wheel and is ready to take over the steering wheel. It does not take effect when the driver actively steers or actively returns to the center, at which time the compensation torque is zero.

[0027] Furthermore, the control method comprises the following specific steps:

[0028] Step 1: Determine whether the steering wheel is in a mode switching state according to the steering wheel torque, steering wheel angle and speed. If so, proceed to the following steps; otherwise, skip the following steps and the return compensation torque is directly zero;

[0029] Step 2: judging whether the steering wheel is in a switching state according to the vehicle speed, steering wheel torque, steering wheel angle and steering wheel speed signal, and judging the mode before switching and the mode after switching;

[0030] Step 3: According to the situation of the upcoming switching, the switching time is estimated, and the desired hand torque is smoothed based on the proposed B-spline curve analysis; B-spline curve equation: Where N is the B-spline basis function and P is the control point;

[0031] Step 4: After determining the desired hand torque curve, the compensation torque curve can be obtained through relationship calculation, so that each switch can achieve the expected comfort; the compensation torque calculation formula is: Mexp = MMtorgeett - Mhand.

[0032] (III) Beneficial effects

[0033] Compared with the prior art, the present invention provides a method for controlling the switching process between the EPS assist mode and the return mode, which has the following beneficial effects:

[0034] The present invention, by designing a switching time length determination module, determines the return time according to the steering wheel angle and vehicle speed at the current moment, so as to better meet the driver's expectations. Through the torque processing of the B-spline curve, the expected value of the switching compensation torque is obtained according to the calculation of different switching situations, and the switching compensation torque at any switching moment is obtained with the goal of tracking the switching torque curve diagram, so that the steering mode switching process of the vehicle under different working conditions is smoother, and the comfort of the driver when steering is greatly improved; the problem of the driver's feeling of frustration caused by the sudden change of hand torque when the current electric power steering vehicle switches between the power mode and the return mode is solved, and the driving experience is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the system of the present invention;

[0036] Figure 2 It is a schematic diagram of the torque variation curve of the switching process of the B-spline of the present invention;

[0037] Figure 3 Schematic diagram of the switching compensation torque calculation architecture of the present invention. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Example

[0040] like Figure 1-3 As shown, an embodiment of the present invention proposes a method for controlling the switching process between the EPS assist mode and the return mode, which is composed of a steering mode switching module, a switching time length determination module, a switching process torque change curve determination module, and a switching compensation torque determination module. The specific method includes the following steps:

[0041] Step 1: The steering mode switching judgment module judges the target mode according to the vehicle speed, steering wheel torque, steering wheel angle and steering wheel speed signal. If the current mode is different from the target mode, the steering mode switching state is entered;

[0042] The steering mode switching judgment module judges whether the steering wheel is in a switching state according to the vehicle speed, steering wheel torque, steering wheel angle and steering wheel speed signal, and judges the mode before switching and the mode after switching;

[0043] Step 2: The switching time determination module determines the expected switching time length according to the motion state of the vehicle before the steering mode is switched;

[0044] The switching time length determination module determines the expected switching time lengths according to the switching process between the power assist mode and the return mode;

[0045] Step 3: The switching process torque change curve determination module divides the expected switching time into three equal parts according to different switching situations, uses B-spline to smooth the torque, and obtains the switching process torque change curve;

[0046] Step 4: The switching compensation torque determination module determines the switching compensation torque that the power-assisting motor needs to provide, and avoids a sudden change in the steering wheel torque felt by the driver when the steering mode is switched by the switching compensation torque, so that the steering wheel torque felt by the driver can be smoothly transitioned;

[0047] The switching compensation torque determination module determines the expected value of the hand torque felt by the driver at the current speed, and obtains the expected value of the switching compensation torque based on calculations under different switching conditions. The switching compensation torque at any switching time is obtained by tracking the switching torque curve, so that the driver's hand force in operating the steering wheel meets the expected requirements.

[0048] As a further technical solution of the present invention: in step 1, when the following conditions are met at the same time, it is judged that the switching state from the power-assist mode to the return mode is: (1) the steering wheel angle and the speed are in the opposite directions, that is, the steering wheel is in the return state; (2) the steering wheel torque is less than a certain threshold value, that is, the driver releases the steering wheel; (3) the steering wheel angle is greater than a certain threshold value, that is, the vehicle is not in the center area.

[0049] As a further technical solution of the present invention: in step 1, when any of the following conditions is met, it is judged as the switching state from the return mode to the power-assisted mode: (1) the steering wheel torque is greater than a certain threshold value, that is, the driver actively turns the steering wheel; (2) the steering wheel angle and speed are both less than a certain threshold value, that is, the steering wheel returns to the center area.

[0050] The switching state includes switching from active steering to a hands-off or steering-protected return state; and switching from a hands-off or steering-protected return state to an external active steering state.

[0051] The active steering state includes active external rotation and active internal rotation.

[0052] We further divide the expected switching time into: the time required to switch from the power-assist mode to the return mode and the time required to switch from the return mode to the power-assist mode.

[0053] In step 2, the switching time is determined according to the motion state of the vehicle at the start time of the switching.

[0054] In step 3, to construct a 4th-order cubic B-spline curve, four control vertices need to be determined. tar Divide the force into three equal parts, and the torque before switching and the stable torque after switching can determine two of the control vertices, and the other two control vertices can be obtained by the double circle tangent method.

[0055] Assuming that the coordinates of the four control vertices of the 3rd order 4th order B-spline curve are P0(x0,y0), P1(x1,y1), P2(x2,y2), and P3(x3,y3), the matrix expression of the B-spline curve is as follows:

[0056]

[0057] The component expressions of the B-spline curve are shown below.

[0058]

[0059] Constructing a B-spline curve requires solving three variables r s , Δt, that is, the design variable X of the B-spline curve optimization model is:

[0060]

[0061] In step 4, after detecting the start of the switching state, the torque in the switching process is controlled to reach the expected position in accordance with the size of the expected curve. It only works when the driver lets go of the steering wheel, holds the steering wheel and is ready to take over the steering wheel. It does not work when the driver actively steers or actively returns to the center position, at which time the compensation torque is zero.

[0062] The specific control method steps for the switching process between EPS assist mode and return mode are as follows:

[0063] Step 1: Determine whether the steering wheel is in a mode switching state according to the steering wheel torque, steering wheel angle and speed. If so, proceed to the following steps; otherwise, skip the following steps and the return compensation torque is directly zero;

[0064] Step 2: judging whether the steering wheel is in a switching state according to the vehicle speed, steering wheel torque, steering wheel angle and steering wheel speed signal, and judging the mode before switching and the mode after switching;

[0065] Step 3: According to the situation of the upcoming switching, the switching time is estimated, and the desired hand torque is smoothed based on the proposed B-spline curve analysis; B-spline curve equation: Where N is the B-spline basis function and P is the control point;

[0066] Step 4: After determining the desired hand torque curve, the compensation torque curve can be obtained through relationship calculation, so that each switch can achieve the expected comfort. Compensation torque calculation formula: MxpMntaorgeb-Mhand O

[0067] The symbolic parameters used in the present invention are shown in Table 1 below.

[0068] Table 1: Symbol parameter description table:

[0069]

[0070]

[0071] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for controlling the switching process between EPS assist mode and return mode, the method comprising a steering mode switching judgment module, a switching time determination module, a torque curve processing module and a switching compensation torque determination module, and the method is characterized in that: The following steps are involved: Step 1: The steering mode switching judgment module judges the target mode according to the vehicle speed, steering wheel torque, steering wheel angle and steering wheel speed signal. If the current mode is different from the target mode, the steering mode switching state is entered; Step 2: The switching time determination module determines the expected switching time length according to the motion state of the vehicle before the steering mode is switched; Step 3: The switching process torque change curve determination module divides the expected switching time into three equal parts according to different switching situations, uses the Bizier curve to smooth the torque, and obtains the switching process torque change curve; Step 4: The switching compensation torque determination module determines the switching compensation torque that the power-assisting motor needs to provide. By switching the compensation torque, a sudden change in the steering wheel torque felt by the driver when the steering mode is switched is avoided, so that the steering wheel torque felt by the driver can have a smooth transition.

2. The EPS power assist mode and return mode switching process control method according to claim 1, characterized in that: In step 1, when any of the following conditions is met, it is determined that the switching state from the return mode to the power-assisted mode is: (1) the steering wheel torque is greater than a certain threshold value, that is, the driver actively turns the steering wheel; (2) the steering wheel angle and speed are both less than a certain threshold value, that is, the steering wheel returns to the center area.

3. The EPS power assist mode and return mode switching process control method according to claim 1, characterized in that: The switching state includes switching from active steering to a hands-off or steering-protected return state; and switching from a hands-off or steering-protected return state to an external active steering state.

4. The EPS power assist mode and return mode switching process control method according to claim 1, characterized in that: The active steering state includes active external rotation and active internal rotation.

5. The EPS power assist mode and return mode switching process control method according to claim 1, characterized in that: The expected switching time length is divided into: the time required for switching from the power-assist mode to the return mode and the time required for switching from the return mode to the power-assist mode.

6. The EPS power assist mode and return mode switching process control method according to claim 1, characterized in that: In step 2, the switching time is determined according to the motion state of the vehicle at the start time of the switching.

7. The EPS power assist mode and return mode switching process control method according to claim 1, characterized in that: In the step 3, a 4th-order 3rd-order B-spline curve is constructed, and 4 control vertices need to be determined; the switching time is divided into three equal parts, and the torque before the switching and the stable torque after the switching can determine two of the control vertices, and the other two control vertices can be obtained by the two-circle tangent method; Assuming that the coordinates of the four control vertices of the cubic 4th order B-spline curve are P0(x0,y0), P1(x1,y1), P2(x2,y2), and P3(x3,y3), the matrix expression of the B-spline curve is as follows: The component expressions of the B-spline curve are as follows; Constructing a B-spline curve requires solving three variables r s , that is, the design variable X of the B-spline curve optimization model is:

8. The EPS power assist mode and return mode switching process control method according to claim 1, characterized in that: In step 4, after detecting the start of the switching state, the torque in the switching process is controlled to reach the expected position in accordance with the size of the expected curve. It only works when the driver lets go of the steering wheel, holds the steering wheel and is ready to take over the steering wheel. It does not work when the driver actively steers or actively returns to the center position, at which time the compensation torque is zero.

9. A method for controlling the switching process between EPS power assist mode and return mode according to any one of claims 1 to 8, characterized in that: The specific steps are as follows: Step 1: Determine whether the steering wheel is in a mode switching state according to the steering wheel torque, steering wheel angle and speed. If so, proceed to the following steps; otherwise, skip the following steps and the return compensation torque is directly zero; Step 2: judging whether the steering wheel is in a switching state according to the vehicle speed, steering wheel torque, steering wheel angle and steering wheel speed signal, and judging the mode before switching and the mode after switching; Step 3: According to the situation of the upcoming switching, the switching time is estimated, and the desired hand torque is smoothed based on the proposed B-spline curve analysis; B-spline curve equation: Where N is the B-spline basis function and P is the control point; Step 4: After determining the desired hand torque curve, the compensation torque curve can be obtained through relationship calculation, so that each switch can achieve the expected comfort; the compensation torque calculation formula is: Mexp = MM target -Mhand.

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