Shimmy compensation method, steering system and vehicle

Abstract

A shimmy compensation method, a steering system and a vehicle, relating to the technical field of vehicle steering systems. The shimmy compensation method comprises: acquiring a real-time vehicle speed, and calculating a shimmy frequency on the basis of the real-time vehicle speed; when the shimmy frequency is within a closed interval of a disturbance frequency band, acquiring a motor torque, a rack position and a mechanical parameter, and estimating a first rack force in real time; performing data preprocessing on the first rack force to determine a basic compensation torque; setting a torque compensation coefficient to determine an actual compensation torque; and setting the direction of the actual compensation torque to be opposite to that of the first rack force, and superimposing a torque at a motor end for output.

Description

A sway compensation method, steering system and vehicle

[0001] Cross-references

[0002] This application incorporates Chinese Patent Application No. 202411001141.5, filed on July 25, 2024, entitled “A Shock Compensation Method, Steering System and Vehicle”, which is incorporated herein by reference in its entirety. Technical Field

[0003] This application relates to the field of vehicle steering system technology, and in particular to sway compensation methods, steering systems and vehicles. Background Technology

[0004] The steering system is a complete mechanism that causes the steering wheels to deflect, thereby changing or maintaining the vehicle's direction of travel, whether forward or backward. The function of the steering system is to control the vehicle's direction according to the driver's intentions; its action is to change the vehicle's direction as needed by the driver turning the steering wheel. Currently, with the development of autonomous driving technology, vehicles may experience lateral swaying due to wheel imbalance or other disturbances, reducing the user experience. For example, wheel imbalance includes static imbalance and torque imbalance. When the wheel's axis of rotation is not aligned with the central principal axis of inertia, its mass distribution relative to the axis is uneven, generating centrifugal force and causing longitudinal and lateral swaying. When lateral swaying occurs under the influence of centrifugal force due to uneven mass distribution, this swaying occurs simultaneously with wheel rotation and is at the same frequency as the wheel's rotation. Currently, related technologies obtain compensation values ​​by performing lead-phase correction on the steering system's torque (TAS) and then compensate for swaying through the steering system.

[0005] The inventors have discovered at least the following problems with the related technologies: The related technical solutions require the installation of a TAS sensor, increasing costs; the compensation schemes of the related technologies mainly operate at the steering wheel end, using advanced phase correction, which requires transmission through the mechanical structure of the steering column to reduce driver perception when yaw occurs; however, in steer-by-wire systems with decoupled steering wheels, yaw directly affects the steering wheel and cannot be compensated for through the column. This compensation scheme can only be used in electric power steering systems and cannot be adapted to steer-by-wire systems. Furthermore, the parameter tuning of the related technical solutions is difficult, and the calculation process is complex.

[0006] Summary of the Invention

[0007] This application provides a sway compensation method, the method comprising: acquiring real-time vehicle speed, calculating sway frequency based on real-time vehicle speed; when the sway frequency is within a closed interval of the disturbance frequency band, acquiring motor torque, rack position and mechanical parameters, and estimating a first rack force in real time; performing data preprocessing on the first rack force to determine a basic compensation torque; setting a torque compensation coefficient to determine an actual compensation torque; setting the direction of the actual compensation torque to the opposite direction of the first rack force, and superimposing torque output at the motor end.

[0008] The step of calculating the sway frequency based on the real-time vehicle speed includes determining the sway frequency based on the ratio of the real-time vehicle speed to the circumference of the front wheels of the vehicle.

[0009] The data preprocessing includes converting the first rack force into a wave signal and acquiring the rack force frequency and rack force amplitude. The range of the wave signal includes the disturbance frequency band.

[0010] The data preprocessing further includes amplifying the wave signal in the disturbance frequency band to obtain first data.

[0011] The data preprocessing also includes high-pass filtering and setting a cutoff frequency that is less than the oscillation frequency.

[0012] The torque compensation coefficient includes a first coefficient, which is less than 1 and related to vehicle speed. When the real-time vehicle speed is less than a vehicle speed threshold, the first coefficient is positively correlated with the real-time vehicle speed. When the real-time vehicle speed is greater than the vehicle speed threshold, the first coefficient decreases and tends to zero. The vehicle speed threshold is set by default.

[0013] The torque compensation coefficient includes a second coefficient, which is less than 1 and is related to the rack force. When the first rack force is greater than the rack force threshold, the second coefficient is inversely related to the rack force and tends to zero. When the first rack force is greater than zero and less than the rack force threshold, the second coefficient is at its maximum value. The rack force threshold is set by default.

[0014] Wherein, the rack force of the actual compensation torque is not greater than the disturbance rack force.

[0015] This application also provides a steering system, including an electric power steering system or a steer-by-wire system, which applies the sway compensation method of this application.

[0016] This application also provides a vehicle for which the sway compensation method of this application is applied. Attached Figure Description

[0017] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments, and unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0018] Figure 1 is an exemplary flowchart of the sway compensation method according to an embodiment of this application;

[0019] Figure 2 is an exemplary schematic diagram of torque compensation coefficient one according to an embodiment of this application;

[0020] Figure 3 is an exemplary schematic diagram of torque compensation coefficient two according to an embodiment of this application. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, some embodiments of this application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0022] Some embodiments of this application relate to a sway compensation method, as shown in Figure 1. The method includes acquiring real-time vehicle speed and calculating sway frequency based on the real-time vehicle speed; when the sway frequency is within a closed interval of the disturbance frequency range, acquiring motor torque, rack position, and mechanical parameters, and estimating a first rack force in real time; performing data preprocessing on the first rack force to determine the basic compensation torque; setting a torque compensation coefficient to determine the actual compensation torque; setting the direction of the actual compensation torque to the opposite direction of the first rack force, and superimposing the torque output at the motor end.

[0023] In some embodiments, as shown in FIG1, the shimmy compensation method may include: in step 201, acquiring the real-time vehicle speed and calculating the shimmy frequency based on the real-time vehicle speed. Step 201 may acquire the real-time vehicle speed through sensors in the steering system and calculate the shimmy frequency through a processor. In some embodiments, the calculation of the shimmy frequency based on the real-time vehicle speed may be determined by the ratio of the real-time vehicle speed to the circumference of the front wheels of the vehicle.

[0024] As an example, the calculation of the oscillation frequency f includes:

[0025] Where f is the yaw frequency, v is the real-time vehicle speed, pi is π, and R is the radius of the vehicle wheel. For example, the radius of the vehicle wheel is preferably the free radius of the wheel, which is the distance from the center of the wheel to the outer edge of the tire. It should be noted that the actual meaning calculated by the above formula is the frequency of one revolution of the wheel. When the vehicle experiences lateral yaw due to wheel imbalance, one revolution of the wheel corresponds to one lateral yaw. This application uses the wheel rotation frequency as the equivalent wheel yaw frequency.

[0026] In some embodiments, the natural frequencies of the steering system's mechanical structures are between 8-20Hz. If the frequency of the shimmy disturbance is close to the natural frequency, displacement resonance will occur, significantly increasing the system's amplitude. The user will clearly feel the wheel swaying, which is detrimental to safe driving. For the above application scenario, disturbances with frequencies near the system's natural frequency are the compensation targets in this embodiment. It should be noted that due to the non-constant nature of the disturbance, when the compensated torque is not less than the actual disturbance torque, it is easily perceived by the driver, reducing the user experience. In practical applications, the compensated torque should be set to be less than the actual disturbance torque to ensure that the compensated torque is not perceived by the user, thereby improving the user experience.

[0027] In step 202, when the oscillation frequency is within the closed interval of the disturbance frequency range, the motor torque, rack position, and mechanical parameters are acquired, and the first rack force is estimated in real time. Step 202 can acquire the motor torque, rack position, and mechanical parameters through sensors in the steering system, and estimate the first rack force in real time through the processor of the steering system. In some embodiments, the disturbance frequency range can be set primarily for the inherent frequency of the system's mechanical structure, regardless of whether there is input from the driver or the autonomous driving controller. As an example, this method can set the disturbance frequency range according to the application scenario. When the oscillation frequency is within the closed interval of the disturbance frequency range (i.e., including the endpoints), the motor torque, rack position, and mechanical parameters are acquired, and the first rack force is estimated in real time. Alternatively, when the oscillation frequency is not within the closed interval of the disturbance frequency range, the other steps of process 200 are not executed.

[0028] In step 203, the first rack force is preprocessed to determine the basic compensation torque. Step 203 can be performed by the steering system's processor to preprocess the first rack force. In some embodiments, the data preprocessing may include converting the first rack force into a wave signal and acquiring the rack force frequency and rack force amplitude, wherein the wave signal range includes the disturbance frequency band. In some embodiments, the data preprocessing may further include amplifying the wave signal in the disturbance frequency band to obtain first data. In some embodiments, the data preprocessing may further include high-pass filtering and setting a cutoff frequency, wherein the cutoff frequency is less than the oscillation frequency.

[0029] In some embodiments, the data preprocessing may include performing a first-order derivative on the first rack force, and determining first data after differentiation. In some embodiments, determining the first data after differentiation includes: determining an amplification factor based on the frequency of the first rack force, wherein the amplification factor is positively correlated with the frequency; and amplifying the amplitude of the first rack force based on the amplification factor to obtain the first data. It should be noted that in real-world scenarios, in addition to disturbances and the rack force input by the driver, there is also noise. The main function of amplification is to make the amplified noise easier to filter out. At the same time, amplification is mainly for accuracy. In some scenarios where accuracy requirements are low, amplification may not be performed and is not a necessary step. As an example, when the process performs amplification, a certain frequency band can be selected for amplification, or the entire signal can be amplified; the embodiments of this application illustrate this by amplifying the disturbance frequency band.

[0030] In some embodiments, the data preprocessing may include performing a first-order high-pass filter on the first data, and determining the basic compensation torque after filtering. In some embodiments, the cutoff frequency of the filtering process is set to be lower than the oscillation frequency; when the frequency of the first data is lower than the cutoff frequency, it is attenuated, and the filtering process yields first data with a frequency higher than the cutoff frequency. As an example, the high-pass filter can pass high-frequency data through the first data and attenuate low-frequency data; for example, filtering the rack force after differential processing, the cutoff frequency of the high-pass filter is 8Hz, data higher than the cutoff frequency of 8Hz can pass through, and data lower than the cutoff frequency of 8Hz is attenuated. It should be noted that if the basic compensation torque is directly superimposed on the motor end for torque output, it may cause the motor to actively reverse; therefore, a correction coefficient for compensation needs to be further set to correct the basic compensation torque and improve the effect of oscillation compensation.

[0031] In step 204, a torque compensation coefficient is set, and the actual compensation torque is determined. Step 204 can determine the actual compensation torque through the steering system's processor. In some embodiments, the torque compensation coefficient can be set by acquiring vehicle state parameters, and the actual compensation torque can be determined based on the set torque compensation coefficient.

[0032] In some embodiments, the torque compensation coefficient includes a first coefficient, which is less than 1 and related to vehicle speed. When the real-time vehicle speed is less than a vehicle speed threshold, the first coefficient is positively correlated with the real-time vehicle speed; when the real-time vehicle speed is greater than the vehicle speed threshold, the first coefficient decreases and tends to zero; the vehicle speed threshold is set by default. As an example, the basic compensation torque is corrected by the first coefficient to solve problems such as directly superimposing the basic compensation torque on the motor for torque output, or causing the motor to actively reverse; the lower the vehicle speed, the lower the coefficient, that is, when the vehicle speed is low and the frequency is low, the actual compensation torque is less than the basic compensation torque, so as to ensure that the user does not perceive the compensation torque.

[0033] As shown in Figure 2, some embodiments of this application provide a torque compensation coefficient of less than 1 that varies with vehicle speed. For example, when the real-time vehicle speed is less than a vehicle speed threshold, the first coefficient is positively correlated with the real-time vehicle speed, meaning it increases with increasing vehicle speed and tends towards a maximum value (the maximum value is less than 1). When the real-time vehicle speed is greater than the vehicle speed threshold, the first coefficient decreases and tends towards 0. In some embodiments, when the vehicle speed causes the sway frequency to exceed the inherent resonant frequency, the first coefficient decreases, such as approaching 0, meaning no sway compensation is performed. The vehicle speed threshold is set by default, as shown in Figure 2. The inflection point of the first coefficient's variation with vehicle speed corresponds to the default vehicle speed threshold, for example, 100 km / h. In different application scenarios, the vehicle speed threshold can be set by default within the range of 60 km / h to 120 km / h.

[0034] In some embodiments, the torque compensation coefficient includes a second coefficient, which is less than 1 and related to the rack force. When the first rack force is greater than a rack force threshold, the second coefficient is inversely correlated with the rack force and tends to zero; when the first rack force is greater than zero and less than the rack force threshold, the second coefficient is at its maximum value; the rack force threshold is set by default. As an example, the second coefficient corrects the basic compensation torque, solving problems such as directly superimposing the basic compensation torque on the motor end for torque output, or causing the motor to actively reverse; when the rack force is larger, the coefficient is smaller, and the rack force can overcome disturbances; or, the user can automatically cancel it out in actual scenarios.

[0035] As shown in Figure 3, some embodiments of this application provide a second torque compensation coefficient, which is less than 1 and varies with the rack force. For example, when the first rack force is greater than a rack force threshold, the second coefficient is inversely correlated with the rack force and decreases with a second slope, tending towards 0, thus reducing the effectiveness of the compensation function. When the first rack force is greater than zero and less than the rack force threshold, the second coefficient decreases from its maximum value (maximum value less than 1) with a first slope. The rack force threshold is set by default, as shown in Figure 3, where the inflection point of the second coefficient's variation with the rack force corresponds to the default rack force threshold, for example, 500N. In different application scenarios, the rack force threshold can be set by default to correspond to different user steering requirements. For example, when the steering angle requirement is no greater than 30°, the second coefficient decreases with the increase of the rack force with a first slope; when the steering angle requirement is greater than 30°, the second coefficient decreases with the increase of the rack force with a second slope, tending towards 0. The rack force threshold is the rack force corresponding to a steering requirement angle of 30°. The first slope is less than the second slope. That is, when the rack force is greater than zero and less than the rack force threshold, the second coefficient changes slowly. When the rack force is greater than the rack force threshold, the second coefficient decreases sharply with the increase of the rack force and tends to 0.

[0036] In some embodiments, determining the actual compensation torque based on the first coefficient and the second coefficient may include determining the actual compensation torque by multiplying the first coefficient, the second coefficient, and the base compensation torque. In some embodiments, when there is no user input, the embodiments of this application may include steps such as signal amplification, high-pass filtering (filtering out low-frequency signals, mainly from noise), vehicle speed coefficient (first coefficient) correction, reversal, and compensation. For example, determining the actual compensation torque based on the first coefficient may include determining the actual compensation torque by multiplying the first coefficient and the base compensation torque. In some embodiments, when there is user input, the embodiments of this application may include steps such as amplification, filtering (filtering out low-frequency signals, from driver input and noise), vehicle speed coefficient (first coefficient) correction, rack force coefficient (second coefficient) correction, reversal, and compensation.

[0037] In step 205, the direction of the actual compensation torque is set to the opposite direction of the first rack force, and torque is superimposed and output at the motor end. Step 205 can be achieved by setting the direction of the actual compensation torque to the opposite direction of the first rack force through the steering system controller, and then superimposing torque on the motor end for output. In some embodiments, when it is determined that the direction of the actual compensation torque is opposite to the direction of the first rack force, the actual compensation torque is superimposed on the motor end for output. In some embodiments, the rack force of the actual compensation torque is not greater than the disturbance rack force, so as to ensure that the user does not perceive the compensation torque. As an example, the rack force of the actual compensation torque can be equal to the disturbance rack force, such as without correction by a torque compensation coefficient or by setting the torque compensation coefficient to 1; or, for example, the rack force of the actual compensation torque can be less than the disturbance rack force, such as with correction by a torque compensation coefficient; or, based on the real-time changes in the disturbance rack force, the rack force of the actual compensation torque can be adjusted to be no greater than the disturbance rack force. When the disturbance rack force randomly jumps to less than the calculated compensation value, the rack force of the actual compensation torque is reduced to the current disturbance rack force; or, when the disturbance rack force fluctuates and falls below the compensation threshold (such as the minimum disturbance rack force required for sway compensation), the rack force of the actual compensation torque is reduced to 0, i.e., no sway compensation is performed. In some embodiments, the superimposed torque output at the motor end can further include controlling the compensation timing. As an example, the compensation timing can be achieved through data processing and a compensation coefficient. When compensation is not required, the compensation torque signal cannot be obtained, i.e., no sway compensation is performed.

[0038] This application has at least the following beneficial effects:

[0039] 1. The yaw compensation method, steering system, and vehicle provided in this application, wherein the steering system may include an electric power steering system or a steer-by-wire system, and the yaw compensation method of this application is applied. The steering system using the yaw compensation method does not require the installation of a TAS sensor, reducing costs; simultaneously, it can be applied to both electric power steering systems and steer-by-wire systems, etc., to eliminate lateral yaw of the vehicle caused by wheel imbalance or other disturbances, and improve the user experience.

[0040] It should be noted that the above description of the shimmy compensation method is for ease of description only and should not be construed as limiting this application to the scope of the embodiments described. It is understood that those skilled in the art, based on the principle of this device, may arbitrarily combine the various structures, or combine substructures with other structures, without departing from the principle, to make various formal and detailed modifications and changes to the function of implementing the above-described device and operation. For example, the shimmy compensation method can be applied to cost-reduction schemes without TAS sensors, and is simultaneously applicable to electric power steering systems and steer-by-wire systems. As another example, the shimmy compensation method may further include controlling the compensation timing. Such modifications are all within the protection scope of this application.

Claims

1. A pendulum compensation method, wherein, The method comprises: acquiring real-time vehicle speed, calculating the hunting frequency according to the real-time vehicle speed; when the hunting frequency is in the closed interval of the perturbation frequency range, acquiring motor torque, rack position and mechanical parameters, and estimating the first rack force in real time; performing data preprocessing on the first rack force to determine the basic compensation torque; setting a torque compensation coefficient to determine the actual compensation torque, and setting the direction of the actual compensation torque as the opposite direction of the first rack force, and superimposing torque output at the motor end.

2. The method of claim 1, wherein, The calculation of the hunting frequency according to the real-time vehicle speed comprises: determining the hunting frequency according to the ratio of the real-time vehicle speed to the circumference of the front wheels of the vehicle.

3. The method of claim 1, wherein, The data preprocessing comprises: converting the first rack force into a wave signal, and collecting the rack force frequency and the rack force amplitude, wherein the interval of the wave signal comprises the perturbation frequency range.

4. The method of claim 3, wherein, The data preprocessing further comprises: amplifying the wave signal in the perturbation frequency range to obtain first data.

5. The method of claim 3, wherein, The data preprocessing further comprises high-pass filtering, and setting a cutoff frequency, wherein the cutoff frequency is less than the hunting frequency.

6. The method of claim 1, wherein, The torque compensation coefficient comprises a first coefficient, wherein the first coefficient is less than 1 and is related to the vehicle speed, when the real-time vehicle speed is less than a vehicle speed threshold, the first coefficient is positively correlated with the real-time vehicle speed, when the real-time vehicle speed is greater than the vehicle speed threshold, the first coefficient decreases and tends to zero, and the vehicle speed threshold is set by default.

7. The method of claim 1, wherein, The torque compensation coefficient comprises a second coefficient, wherein the second coefficient is less than 1 and is related to the rack force, when the first rack force is greater than a rack force threshold, the second coefficient is inversely correlated with the rack force and tends to zero, when the first rack force is greater than zero and less than the rack force threshold, the second coefficient is a maximum value. The rack force threshold is set by default.

8. The method of claim 1, wherein, The rack force of the actual compensation torque is not greater than the perturbation rack force.

9. A steering system comprising an electric power assisted steering system or a steer-by-wire system, wherein: The application of the hunting compensation method according to any one of claims 1 to 8.

10. A vehicle, wherein, The application of the hunting compensation method according to any one of claims 1 to 8.

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