Road feel simulation method, simulation system and simulation device for steer-by-wire steering system

Abstract

This invention discloses a road feel simulation method, simulation system, and simulation device for a steer-by-wire system, belonging to the field of motor vehicle technology. The method includes the following steps: acquiring vehicle driving status; calculating the additional steering angle of the steering wheels based on the driving status; calculating the additional steering angle of the steering wheel based on the additional steering angle and the steering ratio; generating a correction torque interpolation curve based on the additional steering angle and the current steering wheel angle; generating a correction torque based on the steering wheel angle and the correction torque curve; and generating a road feel simulation torque based on the correction torque. The interpolation curve ensures a smooth transition between the current steering wheel angle and the additional steering angle. After exceeding the additional steering angle, the torque increases rapidly to avoid oversteering. The correction torque guides the steering, avoiding excessive intervention in steering operations, giving the driver control of the steering, improving the steering experience, and preventing sudden steering changes.

Description

Technical Field

[0001] This invention relates to the field of motor vehicle technology, and more specifically to a road feel simulation method, simulation system, and simulation device for steer-by-wire systems. Background Technology

[0002] Steer-by-wire (SBW) systems eliminate the mechanical steering column, using electric motors to directly control wheel steering, offering advantages such as fast response and flexible spatial layout. Because SBW eliminates the rigid mechanical connection between the steering wheel and steering wheels, it typically incorporates an additional analog motor to simulate steering resistance torque, self-centering torque, and damping torque, providing feedback to the driver's steering wheel grip. Current road feel simulation methods primarily rely on dynamic simulation calculations or parameter fitting, but the feedback torque cannot meet the needs of various driving scenarios.

[0003] The patent document with publication number CN118405193A discloses a road feel simulation method, device, electronic device and storage medium, which corrects the output torque of the road feel by detecting the hand grip torque and the release coefficient.

[0004] For example, in vehicle steering scenarios, lateral acceleration and lateral displacement of the center of gravity are generated, causing the path to deviate. Existing road feel simulation methods cannot effectively reflect the lateral displacement of the center of gravity. Summary of the Invention

[0005] To address the aforementioned technical problems in the prior art, this invention provides a road feel simulation method, simulation system, and simulation device for a steer-by-wire system, which corrects the output torque by adjusting the lateral offset of the center of gravity.

[0006] The first aspect of this invention discloses a road feel simulation method for a steer-by-wire system, comprising the following steps: acquiring vehicle driving status; calculating the additional steering angle of the steering wheels based on the driving status; calculating the additional steering angle of the steering wheel based on the additional steering angle and the steering ratio; generating a correction torque interpolation curve or a correction torque lookup table based on the additional steering angle and the current steering wheel angle; generating a correction torque based on the steering wheel angle and the correction torque curve or correction torque lookup table; and generating a road feel simulation torque based on the correction torque.

[0007] Preferably, the method for obtaining the additional steering angle of the steering wheel includes: Calculate the target additional yaw moment of the vehicle based on the driving state; The additional steering angle of the steering wheel is obtained based on the additional yaw moment. The target additional yaw moment is used to overcome any one or a combination of the following yaw moments: a first additional yaw moment caused by steering center of gravity deflection, a second additional yaw moment generated by aerodynamics, and a third additional yaw moment generated by road surface slope or unevenness.

[0008] Preferably, the first additional yaw moment Mz1 The calculation formula is: ; in, Iz To bypass z moment of inertia of the shaft y de For the target yaw rate, y ac This is the actual yaw rate. The target yaw acceleration, This is the yaw acceleration. K Control coefficient ，C This is the centroid sideslip angle compensation coefficient. This is the centroid offset angle; The formula for calculating the second additional yaw moment Mz2 is: ; in, air density, v Where A is the vehicle speed, L is the frontal area, and L is the wheelbase. C mz This is the yaw moment coefficient; Third additional yaw moment Mz3 Represented as: ; in, The difference in vertical load between the left and right wheels (N). The coefficient of friction of the road surface. l f This is the distance from the front axle to the center of gravity. Target additional yaw moment Represented as: = -Mz1–Mz2 - Mz3 .

[0009] Preferably, the additional steering angle of the steering wheel Represented as: = Mz / (L f * C f ) ; in, Lf The distance from the vehicle's center of gravity to the front axle. C f The equivalent lateral stiffness of the front wheel can be estimated online based on real-time vehicle speed and tire model; Steering wheel additional steering angle Represented as: ; in, LT This refers to the steering ratio.

[0010] Preferably, the method for generating the modified torque curve includes: Obtain the first sample point of the current steering angle, wherein the sample point includes the current steering angle and the correction torque; Based on the current steering angle and the additional steering angle of the steering wheel, calculate the target steering angle and its correction torque to obtain the second sample point; Based on the target steering angle and the limit constant, calculate the limit steering angle and its correction torque to obtain the third sample point; Based on the interpolation method, interpolation is performed on the first sample point, the second sample point, and the third sample point to obtain the corrected torque curve or the corrected torque lookup table.

[0011] Preferably, the steering angle of the second sample point Sw ti+1 Represented as: ； in, Sw ti The steering wheel angle at the first sample point, the steering wheel angle at the third sample point Sw ti+2 Represented as: ； in, C3 This is the limit constant.

[0012] Preferably, the formula for calculating the road feel simulation torque is expressed as follows: T d = w1*T fric + w2*T damp + w3*T ar + w4*T rep + w5*T interia + w6*T m ; in, T d To simulate torque for road feel, Tfric The sensor provides feedback torque to simulate the forces acting on the tires and drivetrain. T damp For damping control torque, T ar To correct the torque, T rep For the end-stop torque, T m To correct the torque, w1 -w6 is the weighting coefficient; in, .

[0013] Preferably, the formula for calculating the road feel simulation torque is expressed as follows: T d = w1*T fric + w2*T damp + w3*T ar + w4*T rep + w5*T interia + w6*T m + w7*T hold ; in, T d To simulate torque for road feel, T fric For sensor feedback torque, T damp For damping control torque, T ar To correct the torque, T rep For the end-stop torque, T m To correct the torque, T hold To maintain torque for returning to positive position, w1 - w7 These are the weighting coefficients; ; in, C1 It is a constant, determined by empirical values. Q1 and Q2 These are two threshold values ​​for the steering wheel angle. Q1 It is a positive number. Q2 It is a negative number. sw This refers to the steering wheel angle.

[0014] Preferably, the method for obtaining the additional steering angle of the steering wheel includes: Obtain the dynamic model; The driving state is predicted based on a dynamic model, and the steering angle of the second steering wheel at the next moment is predicted. The additional steering angle is calculated based on the difference between the second steering wheel steering angle and the current steering wheel steering angle.

[0015] A second aspect of the present invention provides a simulation system for implementing the above-described road feel method, comprising a data acquisition module, an additional steering module, a correction module, and a road feel simulation torque generation module; The data acquisition module is used to collect the vehicle's driving status; The additional steering module is used to obtain the additional steering angle of the steering wheel based on the additional yaw moment; The correction module is used to calculate the additional steering angle of the steering wheel based on the additional steering angle and the steering ratio, generate a correction torque interpolation curve based on the additional steering angle and the current steering wheel angle, and generate a correction torque based on the steering wheel angle and the correction torque curve or correction torque lookup table. The road feel simulation torque generation module is used to generate a road feel simulation torque based on the corrected torque.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: the interpolation curve makes the transition between the current steering wheel angle and the additional steering angle smooth, and the torque rises rapidly after the additional steering angle is exceeded, avoiding oversteering; the steering is guided by the torque correction, avoiding excessive intervention in the steering operation, giving the driver the initiative in steering, improving the steering experience, and avoiding sudden steering changes. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the road feel simulation method for the steer-by-wire system of the present invention; Figure 2 This is a schematic diagram of the corrected torque curve; Figure 3 This is a simulation diagram of the road feel simulation torque structure; Figure 4 This is a logic block diagram of the simulation system of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The present invention will now be described in further detail with reference to the accompanying drawings: Example 1 provides a road feel simulation method for a steer-by-wire system, such as Figure 1 As shown, it includes the following steps: Step S1: Collect the vehicle's driving status.

[0020] Step S2: Calculate the target additional yaw moment of the vehicle based on the driving state.

[0021] Step S3: Obtain the additional steering angle of the steering wheel based on the additional yaw moment.

[0022] Step S4: Calculate the additional steering angle of the steering wheel based on the additional steering angle and steering ratio.

[0023] Step S5: Generate a correction torque interpolation curve or a correction torque lookup table based on the additional steering angle of the steering wheel and the current steering wheel angle.

[0024] Step S6: Generate the correction torque based on the steering wheel angle and the correction torque curve or correction torque lookup table.

[0025] Step S7: Generate a road feel simulation torque based on the corrected torque.

[0026] The correction torque is generated based on the interpolation curve, and the road feel torque is adjusted by the correction torque. The driver is guided to quickly rotate the steering wheel to the additional steering angle, while avoiding oversteering and overcoming the additional yaw torque caused by the center of gravity offset.

[0027] The interpolation curve ensures a smooth transition between the current steering wheel angle and the additional steering angle. Once the additional steering angle is exceeded, the torque increases rapidly to avoid oversteering. By correcting the torque, the steering is guided to avoid excessive intervention in steering operations, giving the driver control of the steering, improving the steering experience, and avoiding sudden steering changes.

[0028] The formula for calculating the road feel simulation torque is as follows: T d = w1*T fric + w2*T damp + w3*T ar + w4*T rep + w5*T interia + w6*T m (1); in, T d To simulate torque for road feel, T fric The sensor provides feedback torque to simulate the forces acting on the tires and drivetrain.T damp For damping control torque, T ar To correct the torque, T rep For the end-stop torque, T m To correct the torque, w1 - w6 These are the weighting coefficients.

[0029] In step S1, the driving status can be collected through onboard sensors, such as vehicle... v Steering wheel angle sw Steering wheel angular velocity Actual steering speed of the steering wheel, steering angle of the steering wheel Steering wheel angular velocity, tire longitudinal force, lateral acceleration, road surface adhesion coefficient, and steering wheel feedback torque, etc.

[0030] In step S2, the target additional yaw moment is used to overcome the first additional yaw moment caused by the deflection of the steering center of gravity, the second additional yaw moment generated by aerodynamics, and the third additional yaw moment generated by the road surface slope or unevenness.

[0031] The first additional yaw moment caused by the steering generates a deflection of the center of mass. Mz1 The calculation formula can be simplified to: (2); in, Iz To bypass z moment of inertia of the shaft y de For the target yaw rate, y ac This is the actual yaw rate. The target yaw acceleration, This is the yaw acceleration. K Control coefficient ，C This is the centroid sideslip angle compensation coefficient, typically 1000-2000 N·m / rad. This is the centroid offset angle.

[0032] Second additional yaw moment generated by aerodynamics Mz2 The calculation formula is: (3); in, air density (kg / m³). v Vehicle speed (m / s) A The windward area (m²) L The wheelbase is in meters (m). Cmz This is the yaw moment coefficient, which is dimensionless and related to the vehicle body shape and sideslip angle. It can be calculated from empirical values.

[0033] The third additional yaw moment caused by road surface slope or unevenness Mz3 Represented as: (4); in, The difference in vertical load between the left and right wheels (N). The coefficient of friction of the road surface. l f This is the distance (m) from the front axle to the center of mass.

[0034] Target additional yaw moment Represented as: (5).

[0035] It should be noted that Formulas 2-4 are merely illustrative of the calculation method for the corresponding additional yaw moment, and other publicly available formulas may be used instead of these calculation formulas.

[0036] In step S3, the additional steering angle of the steering wheel Represented as: = Mz / (L f * C f ) (6); in, L f The distance from the vehicle's center of gravity to the front axle. C f The equivalent lateral stiffness of the front wheel can be estimated online based on real-time vehicle speed and tire model.

[0037] In step S4, the steering wheel is adjusted to an additional steering angle. Represented as: (7); in, LT This refers to the steering ratio.

[0038] In step S5, the method for generating the corrected torque curve includes: Step 501: Obtain the first sample point of the current steering angle, whereby the sample point includes the current steering angle and the correction torque. This can be used to establish... According to the corrected torque lookup table, Match the corresponding correction torque 。

[0039] Step 502: Calculate the target steering angle and its correction torque based on the current steering angle and the additional steering angle of the steering wheel to obtain the second sample point.

[0040] Step 503: Calculate the limit steering angle and its correction torque based on the target steering angle and limit constant to obtain the third sample point.

[0041] The steering wheel angle of the second sample point Sw ti+1 Represented as, ; Sw ti The steering wheel angle at the first reference point, and the steering wheel angle or limit steering angle at the third reference point. Sw ti+2 Represented as, ，C3 This is the limit constant. The correction torque for the second sample point uses a preset value, such as between -3.5 and 3.5. In specific tests, the correction torque for the third sample point is the same as that for the first sample point, but it is not limited to this.

[0042] Step 504: Based on the interpolation method, interpolate the first sample point, the second sample point, and the third sample point to obtain the corrected torque curve or the corrected torque lookup table.

[0043] Interpolation methods can include fitting with smooth lines, logarithms, exponentials, polynomials, etc., but are not limited to these.

[0044] Figure 2 The specific correction torque curve is shown, with the horizontal axis representing the steering wheel angle and the vertical axis representing the correction torque. The current steering wheel angle (first point) is 5 degrees, and the correction torque is 0 N. The first sample point is at 2 degrees (7.1 degrees, -3.2 M / N*m), and the second sample point is between 5 and 7 degrees. The third sample point is at 9 degrees and 0 M / N*m. An interpolation curve is established using the three sample points, and the corresponding correction torque is queried through the interpolation curve.

[0045] To ensure that the road feel simulation torque and the aligning torque are in the same direction, the correction torque is constrained in the specific implementation: (8).

[0046] The return torque is opposite to the direction of the current steering wheel angle, and is expressed as: T ar= B1*Fy*(e1 + e2); in, B1 This is the positive return coefficient. Fy The lateral force exerted by the ground on the wheel. e1 For tire drag, e1 Main tilt trail。 The current steering wheel angle is less than a certain angle, such as less than 1 degree. Fy If the torque is reduced, the return torque will be insufficient to keep the steering wheel at 0 degrees, resulting in slow vibration or deflection of the steering wheel within the range of 0.1-0.2 degrees. This deflection cannot be eliminated by damping.

[0047] Example 2 provides a method for calculating the road feel simulation torque based on the return-to-center holding torque. The specific calculation formula is as follows: ： T d = w1*T fric + w2*T damp + w3*T ar + w4*T rep + w5*T interia + w6*T m + w7*T hold (9); T hold To maintain the return torque, w7 is a weighting coefficient, and each weighting coefficient can be determined through driving simulation.

[0048] ; in, C1 It is a constant, determined by empirical values. Q1 and Q2 The threshold value for steering wheel angle. Q1 It is a positive number. Q2 It is a negative number.

[0049] Example 3 provides model predictive control MPC The road feel simulation method includes the following steps: Step 301: Obtain the dynamic model.

[0050] The design method for dynamic models is existing technology and will not be elaborated upon in this invention.

[0051] Step 302: Predict the driving state based on the dynamic model and predict the direction of the second steering wheel at the next moment.

[0052] Step 303: Calculate the additional steering angle based on the difference between the second steering wheel steering angle and the current steering wheel steering angle, and execute steps S4-S7.

[0053] Additional steering angle The calculation method is as follows: ; in, for ti The steering angle of the steering wheel at any given moment. The direction of the second steering wheel's rotation at the next moment.

[0054] By combining the dynamic model of MPC to plan the trajectory, the steering angle deviation, i.e. the additional steering angle, is calculated through the planned trajectory. Without using autonomous driving, the road sense simulation is corrected by the planned trajectory, revealing the driver to make necessary steering without excessively interfering with the driver's subjective judgment.

[0055] Example 4 provides a simulation system for implementing the above-described road feel simulation method, such as... Figure 4 As shown, it includes: acquisition module 1, additional steering module 2, correction module 3, and road feel simulation torque generation module 4; The acquisition module 1 is used to acquire the vehicle's driving status; the additional steering module 2 is used to obtain the additional steering angle of the steering wheel based on the additional yaw moment; the correction module 3 is used to calculate the additional steering angle of the steering wheel based on the additional steering angle and the steering ratio, generate a correction torque interpolation curve based on the additional steering angle and the current steering wheel angle, and generate a correction torque based on the correction torque curve or the correction torque lookup table; the road feel simulation torque generation module 4 is used to generate a road feel simulation torque based on the correction torque.

[0056] Example 5 provides a simulation device, including a processor and a memory, wherein the memory stores code, and when the code is processed by the processor, it implements the above-described road feel simulation method.

[0057] Simulations were performed based on Carism and Veristand, with realistic road feel torque data provided by torque-angle sensor B. The simulation results are as follows: Figure 3 As shown, after introducing a correction torque within 4-5 seconds, the simulated road feel torque differs from the actual road feel. The correction torque guides the driver to adjust the steering angle.

[0058] This invention guides the driver's steering behavior through a corrective torque without excessive intervention, overcoming additional yaw moment and trajectory deviation, improving the user experience, avoiding sudden changes in steering angle caused by direct alteration / adjustment, and maintaining vehicle stability and safety. Simultaneously, it constrains the value of the corrective torque to prevent excessive torque from directly pushing the steering wheel.

[0059] Example 5 provides a simulation device that uses the simulation system described above.

[0060] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for simulating road feel in a steer-by-wire system, characterized in that, Includes the following steps: Collect vehicle driving status; Calculate the additional steering angle of the steering wheels based on the driving conditions; Calculate the additional steering angle of the steering wheel based on the additional steering angle and steering ratio; Based on the additional steering angle of the steering wheel and the current steering wheel angle, generate a correction torque interpolation curve or a correction torque lookup table; The correction torque is generated based on the steering wheel angle and the correction torque curve or correction torque lookup table. Based on the corrected torque, a road feel simulation torque is generated.

2. The road feel simulation method according to claim 1, characterized in that, Methods for obtaining the additional steering angle of the steering wheels include: Calculate the target additional yaw moment of the vehicle based on the driving state; The additional steering angle of the steering wheel is obtained based on the additional yaw moment. The target additional yaw moment is used to overcome any one or a combination of the following yaw moments: The first additional yaw moment is caused by the deflection of the steering center of gravity, the second additional yaw moment is caused by aerodynamics, and the third additional yaw moment is caused by the slope or unevenness of the road surface.

3. The road feel simulation method according to claim 2, characterized in that, First additional yaw moment Mz1 The calculation formula is: ； in, Iz To bypass z moment of inertia of the shaft y de For the target yaw rate, y ac This is the actual yaw rate. The target yaw acceleration, This is the yaw acceleration. K Control coefficient ，C This is the centroid sideslip angle compensation coefficient. This is the centroid offset angle; Second additional yaw moment Mz2 The calculation formula is: ； in, air density, v Where A is the vehicle speed, L is the frontal area, and L is the wheelbase. C mz This is the yaw moment coefficient; Third additional yaw moment Mz3 Represented as: ； in, The difference in vertical load between the left and right wheels. The coefficient of friction of the road surface. l f This is the distance from the front axle to the center of gravity. Target additional yaw moment Represented as: 。 4. The road feel simulation method according to claim 2, characterized in that, Additional steering angle of the steering wheel Represented as: = Mz / (L f * C f ) ; in, L f The distance from the vehicle's center of gravity to the front axle. C f This is the equivalent lateral stiffness of the front wheel; Steering wheel additional steering angle Represented as: ； in, LT This refers to the steering ratio.

5. The road feel simulation method according to claim 2, characterized in that, Methods for generating the corrected torque curve include: Obtain the first sample point of the current steering angle, wherein the sample point includes the current steering angle and the correction torque; Based on the current steering angle and the additional steering angle of the steering wheel, calculate the target steering angle and its correction torque to obtain the second sample point; Based on the target steering angle and the limit constant, calculate the limit steering angle and its correction torque to obtain the third sample point; Based on the interpolation method, interpolation is performed on the first sample point, the second sample point, and the third sample point to obtain the corrected torque curve or the corrected torque lookup table.

6. The road feel simulation method according to claim 5, characterized in that, The steering wheel angle of the second sample point Sw ti+1 Represented as: ； in, Sw ti The steering wheel angle at the first reference point, and the limit steering angle at the third reference point. Sw ti+2 Represented as: ； in, C3 This is the limit constant.

7. The road feel simulation method according to claim 1, characterized in that, The formula for calculating the simulated torque based on road feel is as follows: T d = w1*T fric +w2*T damp +w3*T ar +w4*T rep +w5*T interia + w6*T m ; in, T d To simulate torque for road feel, T fric The sensor provides feedback torque to simulate the forces acting on the tires and drivetrain. T damp For damping control torque, T ar To provide the restoring torque, T rep For the end-stop torque, T m To correct the torque, w1 - w6 These are the weighting coefficients; in, .

8. The road feel simulation method according to claim 1, characterized in that, The formula for calculating the simulated torque based on road feel is as follows: T d = w1*T fric + w2*T damp + w3*T ar + w4*T rep + w5*T interia + w6*T m + w7*T hold ； in, T d To simulate torque for road feel, T fric For sensor feedback torque, T damp For damping control torque, T ar To provide the restoring torque, T rep For the end-stop torque, T m To correct the torque, T hold To maintain torque for returning to positive position, w1-w7 These are the weighting coefficients; ； in, C1 It is a constant. Q1 and Q2 These are two threshold values ​​for the steering wheel angle. Q1 It is a positive number. Q2 It is a negative number. sw Steering wheel angle; Methods for obtaining the additional steering angle of the steering wheels include: Obtain the dynamic model; The driving state is predicted based on a dynamic model, and the steering angle of the second steering wheel at the next moment is predicted. The additional steering angle is calculated based on the difference between the second steering wheel steering angle and the current steering wheel steering angle.

9. A simulation system, characterized in that, The method for implementing the road feel simulation method as described in any one of claims 1-8 includes a data acquisition module, an additional steering module, a correction module, and a road feel simulation torque generation module; The data acquisition module is used to collect the vehicle's driving status; The additional steering module is used to obtain the additional steering angle of the steering wheel based on the additional yaw moment; The correction module is used to calculate the additional steering angle of the steering wheel based on the additional steering angle and the steering ratio, generate a correction torque interpolation curve based on the additional steering angle and the current steering wheel angle, and generate a correction torque based on the steering wheel angle and the correction torque curve or correction torque lookup table. The road feel simulation torque generation module is used to generate a road feel simulation torque based on the corrected torque.

10. A simulation device, characterized in that: The simulation system described in claim 9 is used.

Images