A steering return control method based on objective steering evaluation

Abstract

This invention, applicable to the field of automotive steering control technology, provides a steering return control method for objective steering evaluation. The method comprises the following steps: collecting vehicle state parameters; determining the driver's degree of adherence to three driving styles (conservative, normal, and sporty) to calculate the coefficients influencing return speed and lateral acceleration; generating a reference return speed; and using the reference return speed as a tracking target to generate a smooth return torque via MPC. This method is designed based on objective evaluation phenomena, eliminating the need for extensive field testing to calibrate relevant parameters in later development stages. This method, oriented towards objective evaluation and personalized driving experience, allows the driver to determine the emphasis of objective evaluation, thereby achieving personalized, objectively evaluated vehicle steering return control.

Description

Technical Field

[0001] The present invention belongs to the technical field of automobile steering control, and in particular relates to a steering return control method oriented to objective steering evaluation. Background Art

[0002] Electric power steering (EPS) systems are widely used in modern vehicles due to their increased energy efficiency and responsiveness. Good steering return performance ensures the vehicle quickly returns to a straight line after turning. This high-quality steering return performance improves vehicle stability and driving comfort.

[0003] The Chinese invention patent, "A Return Control Method for an Electric Power Steering System Based on Return Speed ​​Control," with publication number CN117864237A, triggers return control via a hands-off state determination module. A table lookup determines the return time based on the steering angle and vehicle speed at the moment of release. The desired return speed is then generated using a "bathtub curve." Finally, the compensation torque is calculated through position tracking. This method relies on a static table lookup and fixed formulas, without incorporating vehicle conditions such as lateral acceleration for closed-loop optimization. This results in return accuracy being significantly affected by operating conditions.

[0004] The Chinese invention patent, "An Electric Return-to-Center Compensation Control System and Method," with publication number CN112937674A, triggers return-to-center compensation by detecting torque signals. The system first sets a starting force based on torque to propel the steering wheel back to center; then, based on motor speed, it calculates friction compensation to continuously promote return-to-center. This system, with its core being an open-loop, segmented compensation mechanism, relies on motor data for low-cost control. However, it relies solely on motor parameters and does not incorporate vehicle conditions such as steering wheel angle and lateral acceleration, lacking objective evaluation criteria. Summary of the Invention

[0005] The purpose of the embodiments of the present invention is to provide a steering return control method oriented to objective steering evaluation, aiming to solve the problems raised in the above background technology.

[0006] The embodiment of the present invention is implemented as follows: a steering return control method for objective steering evaluation includes the following steps:

[0007] Step 1: Collect vehicle status parameters, including steering wheel angle , steering wheel angular velocity , lateral acceleration , vehicle speed , yaw angular velocity ;

[0008] Step 2: Determine the driver's degree of membership in the three driving styles of conservative, normal, and sporty , , thereby calculating the coefficient affecting the return speed and the coefficient affecting lateral acceleration The value of is:

[0009] ;

[0010] ;

[0011] Step 3: Generate reference return speed;

[0012] Steering return is based on objective evaluation indicators, namely return performance and stability. Return performance indicators include return efficiency, return residual and return torque. Based on the return efficiency, a reference return speed is established. :

[0013] ;

[0014] in, is the reference value for the return performance. is the stability reference;

[0015] Step 4: MPC tracking control;

[0016] Reference return speed To track the target, a smooth aligning torque is generated through a model predictive controller (MPC).

[0017] A further technical solution is that in step 2, The calculation of is as follows: Preset comfort , ordinary type , sports type , which can be listed as follows:

[0018] .

[0019] A further technical solution is that in step 3, and The calculation formula is:

[0020] ;

[0021] ;

[0022] in, is the return performance gain coefficient; is the stability gain coefficient; is the correction function of the return speed; is the stability correction function;

[0023] Introducing the correction function of the return speed based on the return residual , which is calculated as follows:

[0024] ;

[0025] in, is the correction attenuation factor; is the correction gain coefficient; is the maximum lateral acceleration during the return process;

[0026] By adjusting Suppress overshoot and adjust Reduce the lack of return; establish a stability correction function based on the high efficiency and stability of the return , the specific formula is as follows:

[0027] ;

[0028] in, Correct the attenuation factor for stability; is the return speed threshold; by adjusting and Improved stability compensation at the start of return to centering.

[0029] A further technical solution is to consider the system equation in step 4. , , we get the continuous-time state equation:

[0030] ;

[0031] in, is the equivalent damping of the steering system; is the equivalent moment of inertia of the steering system; is the aligning torque; is the output and reference return speed in this system equation Input ;

[0032] Using the forward Euler method to discretize it, we get:

[0033] ;

[0034] in, and is the coefficient matrix of the system state equation after the continuous system is discretized by the forward Euler method, ; ; is the system state in step k; is the input state in step k; the reference return speed For discrete processing, define the reference return speed in this step ;

[0035] The reference trajectory for objective evaluation is essentially the expected self-centering velocity taking into account stability. Therefore, the tracking goal is to make the steering wheel angular velocity track the reference trajectory.

[0036] Assume the prediction time domain is N steps, and construct the state prediction sequence:

[0037] ;

[0038] Cost function:

[0039] ;

[0040] The first term is the minimum tracking error, and the second term is the rate of change of torque;

[0041] State prediction equation:

[0042] ;

[0043] Output equation:

[0044] ;

[0045] Prediction output:

[0046] ;

[0047] in, ;

[0048] The cost function is transformed into:

[0049] ;

[0050] Where T is the matrix transpose symbol; Q represents the tracking error weight of the reference return velocity. The larger Q is, the smaller the tracking error is and the better the tracking accuracy is. R represents the weight of the output return torque fluctuation. The larger R is, the greater the return torque is.

[0051] The embodiment of the present invention provides a steering return control method for objective steering evaluation, which has the following beneficial effects:

[0052] (1) Design is guided by excellent objective evaluation phenomena, eliminating the need for extensive field testing to calibrate relevant parameters in the later stages of development;

[0053] (2) Aiming at objective evaluation and personalized driving experience, the driver is allowed to decide the emphasis of objective evaluation, thereby realizing personalized vehicle steering return control oriented to objective evaluation. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 A flowchart of a steering return control method for objective steering evaluation provided by an embodiment of the present invention;

[0055] Figure 2 is the return speed correction function Schematic diagram of the impact on objective evaluation indicators;

[0056] Figure 3 for Q and R Schematic diagram of the impact of the value on the return torque. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0058] The specific implementation of the present invention is described in detail below with reference to specific embodiments.

[0059] like Figure 1 As shown in FIG, a steering return control method based on objective steering evaluation is provided in one embodiment of the present invention. The method uses driving style membership to dynamically weight the objective evaluations emphasized by different drivers during the return process, that is, to map the driving style membership to a control parameter adjustment coefficient. The formula is as follows:

[0060] ;

[0061] in, is the coefficient that affects the return speed; The adjustment corresponds to the return performance gain coefficient in this paper The value of The adjustment corresponds to the modified attenuation factor in this paper and correction gain factor The comfort type focuses more on the residual value of the return to normal position, while the sport type focuses more on the efficiency of the return to normal position.

[0062] To further control the minimum torque fluctuation and optimal handling stability, an MPC controller with reference to the return speed was established to achieve the goals of smooth return torque and stable return handling. The specific operation steps are as follows:

[0063] Step 1: Collect vehicle status parameters, including steering wheel angle , steering wheel angular velocity , lateral acceleration , vehicle speed , yaw angular velocity ;

[0064] Step 2: Use the driving style recognition module to determine the driver's membership in the three driving styles of conservative, normal and sporty , , thereby calculating the coefficient affecting the return speed and the coefficient affecting lateral acceleration The value of is:

[0065] ;

[0066] ;

[0067] in The calculation of is as follows: Preset comfort , ordinary type , sports type , which can be listed as follows:

[0068] ;

[0069] Step 3: Generate reference return speed;

[0070] When steering back to center, the objective evaluation index is based on the back-to-center performance and stability. The back-to-center performance index includes back-to-center efficiency, back-to-center residual and back-to-center torque. The reference back-to-center speed is established based on the back-to-center efficiency. :

[0071] ;

[0072] in, is the reference value for the return performance. is the stability reference quantity, and its calculation formula is:

[0073] ;

[0074] ;

[0075] in, is the return performance gain coefficient; is the stability gain coefficient; is the correction function of the return speed; is the stability correction function;

[0076] Introducing the correction function of the return speed based on the return residual , which is calculated as follows:

[0077] ;

[0078] in, is the correction attenuation factor; is the correction gain coefficient; is the maximum lateral acceleration during the return process;

[0079] Return speed correction function Impact on objective evaluation indicators Figure 2 As shown, Figure 2 The description is shown in Table 1 below:

[0080] Table 1

[0081]

[0082] By adjusting Suppress overshoot and adjust Reduce the lack of return; establish a stability correction function based on the high efficiency and stability of the return , the specific formula is as follows:

[0083] ;

[0084] in, Correct the attenuation factor for stability; is the return speed threshold; by adjusting and Improved stability compensation at the start of return to centering.

[0085] Step 4: MPC tracking control;

[0086] Reference return speed To track the target, a smooth aligning torque is generated through MPC.

[0087] Consider the system equations , , we get the continuous-time state equation:

[0088] ;

[0089] in, is the equivalent damping of the steering system; is the equivalent moment of inertia of the steering system; is the aligning torque; is the output and reference return speed in this system equation Input ;

[0090] Using the forward Euler method to discretize it, we get:

[0091] ;

[0092] in, and is the coefficient matrix of the system state equation after the continuous system is discretized by the forward Euler method, ; ; is the predicted system state in step k; is the predicted input state in step k; the reference return speed For discrete processing, define the reference return speed in this step .

[0093] The reference trajectory for objective evaluation is essentially the expected self-centering velocity taking into account stability, so the tracking goal is to make the steering wheel angular velocity track the reference trajectory.

[0094] Assume the prediction time domain is N steps, and construct the state prediction sequence:

[0095] ;

[0096] Cost function:

[0097] ;

[0098] The first term is the minimum tracking error, and the second term is the rate of change of torque.

[0099] State prediction equation:

[0100] ;

[0101] Output equation:

[0102] ;

[0103] Prediction output:

[0104] ;

[0105] in, ;

[0106] Then the cost function can be transformed into:

[0107] ;

[0108] Where T is the matrix transpose symbol; the influence of the values ​​of Q and R on the aligning torque is as follows: Figure 3 As shown in the figure, Q represents the weight of the reference return speed tracking error. The larger Q is, the smaller the tracking error is and the better the tracking accuracy is. R represents the weight of the output return torque fluctuation. The larger R is, the smoother the return torque is. is the aligning torque, In order to increase the maximum steady-state aligning torque under the torque smoothing weight, is the maximum steady-state aligning torque ignoring torque smoothing, Smaller can enhance stability, maintain the peak value of the return torque longer without overshoot, and ensure the return efficiency.

[0109] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A steering return control method for objective steering evaluation, characterized in that: The following steps are involved: Step 1: Collect vehicle status parameters, including steering wheel angle , steering wheel angular velocity , lateral acceleration , vehicle speed , yaw angular velocity ; Step 2: Determine the driver's degree of membership in the three driving styles of conservative, normal, and sporty , , thereby calculating the coefficient affecting the return speed and the coefficient affecting lateral acceleration The value of is: ； ； Step 3: Generate reference return speed; Steering return is based on objective evaluation indicators, namely return performance and stability. Return performance indicators include return efficiency, return residual and return torque. Based on the return efficiency, a reference return speed is established. : ； in, is the reference value for the return performance. is the stability reference; Step 4: MPC tracking control; Reference return speed To track the target, a smooth aligning torque is generated through MPC.

2. The steering return control method for objective steering evaluation according to claim 1, characterized in that: In step 2, The calculation of is as follows: Preset comfort , ordinary type , sports type , as follows: 。 3. The steering return control method for objective steering evaluation according to claim 2, characterized in that: In step 3, and The calculation formula is: ； ； in, is the return performance gain coefficient; is the stability gain coefficient; is the correction function of the return speed; is the stability correction function; Introducing the correction function of the return speed based on the return residual , which is calculated as follows: ； in, is the correction attenuation factor; is the correction gain coefficient; is the maximum lateral acceleration during the return process; By adjusting Suppress overshoot and adjust Reduce the lack of return; establish a stability correction function based on the high efficiency and stability of the return , the specific formula is as follows: ； in, Correct the attenuation factor for stability; is the return speed threshold; by adjusting and Improved stability compensation at the start of return to centering.

4. The steering return control method for objective steering evaluation according to claim 3, characterized in that: In step 4, consider the system equation , , we get the continuous-time state equation: ； in, is the equivalent damping of the steering system; is the equivalent moment of inertia of the steering system; is the aligning torque; is the output and reference return speed in this system equation Input ; Using the forward Euler method to discretize it, we get: ； in, and is the coefficient matrix of the system state equation after the continuous system is discretized by the forward Euler method, ; ; is the system state in step k; is the input state in step k; the reference return speed For discrete processing, define the reference return speed in this step ; The reference trajectory for objective evaluation is essentially the expected self-centering velocity taking into account stability. Therefore, the tracking goal is to make the steering wheel angular velocity track the reference trajectory. Assume that the prediction time domain is N steps and construct the state prediction sequence: ； Cost function: ； The first term is the minimum tracking error, and the second term is the rate of change of torque; State prediction equation: ； Output equation: ； Prediction output: ； in, ; The cost function is transformed into: ； Where T is the matrix transpose symbol; Q represents the tracking error weight of the reference return velocity. The larger Q is, the smaller the tracking error is and the better the tracking accuracy is. R represents the weight of the output return torque fluctuation. The larger R is, the greater the return torque is.

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