Control method and system for steer-by-wire torque

Abstract

The invention discloses a control method and system for steer-by-wire torque. The method comprises the following steps that S1, initial steering torque is obtained through calculation according to a steering wheel torque signal, a vehicle speed signal and an aligning torque signal; s2, suspension state parameters are collected, and whether secondary correction is triggered or not is judged based on the suspension state parameters; s3, when secondary correction is not triggered, steering control is executed with the initial steering torque; and if the secondary correction is triggered, correcting the initial steering torque based on the suspension state parameters to obtain a corrected steering torque, and executing steering control by using the corrected steering torque. The method has the advantages that secondary correction is added to the calculated output torque to meet the steering stability of the vehicle under special conditions, and potential safety hazards caused by unreasonable output of the torque are reduced; the defect that the torque output of a vehicle with the cross-country performance requirement is unreasonable under the condition that the left suspension and the right suspension are distorted greatly or under the high-speed unstable condition is overcome.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of precise control of steer-by-wire system, in particular to a control method and system of steer-by-wire torque. BACKGROUND

[0002] The automobile steering system has experienced mechanical steering system, hydraulic power steering (HPS) system, electro-hydraulic power steering (EHPS) system, electric power steering (EPS) system, steer-by-wire (SBW) system, etc. As a relatively advanced steering control and technology, the steer-by-wire system SBW reduces the mechanical steering column compared with the traditional steering system, which is beneficial to the protection of human body in vehicle collision, saves the front compartment space, and the steering machine is more flexible in layout.

[0003] In the steer-by-wire system, the torque output signal is mostly obtained by superimposing the torque request signal, the torque request enable signal, the steering wheel torque signal and the vehicle speed signal, that is, the steering intention of the driver is accepted by the steering wheel, the steering angle sensor and the torque sensor, and then the electronic signal is converted and the steering operation is executed by the actuator components such as the steering motor. However, the existing technology does not consider the vehicle stability and safety in special situations when controlling the steering torque, such as the vehicle with off-road performance requirements in off-road working conditions or the steering control in high-speed unstable conditions. In any working condition, the steering torque is obtained by using the traditional steering wheel torque, vehicle speed and return torque signal, which cannot meet the safety and reliability requirements of the vehicle in some special situations. SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art and provide a control method and system of steer-by-wire torque, which adds a secondary correction to the calculated output torque to meet the vehicle steering stability in special situations, reduces the safety hazards caused by unreasonable torque output, solves the defects of unreasonable torque output of the vehicle with off-road performance requirements in the case of large left and right suspension distortion or high-speed instability, improves the rationality of torque output and improves the steering safety and reliability of the vehicle.

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: a control method of steer-by-wire torque, comprising the following steps:

[0006] S1, calculating an initial steering torque according to the steering wheel torque signal, the vehicle speed signal and the return torque signal;

[0007] S2, collecting suspension state parameters and determining whether to trigger secondary correction based on the suspension state parameters;

[0008] S3, if the secondary correction is not triggered, the steering control is performed with the initial steering torque; if the secondary correction is triggered, the initial steering torque is corrected based on the suspension state parameter to obtain a corrected steering torque, and the steering control is performed with the corrected steering torque.

[0009] The suspension state parameter includes displacement signals of left and right suspensions, and the secondary correction is triggered when a displacement difference between the left and right suspensions is greater than a set threshold, otherwise the secondary correction is not triggered.

[0010] A displacement sensor is arranged to detect displacement signals of the suspensions, wherein a suspension stroke of the vehicle in an empty state on a flat road is set as a 0 point of the displacement sensor, and the displacement signal is positive when the suspension is upward, otherwise the displacement signal is negative; displacement signals of left and right suspensions are collected by the displacement sensor and a displacement difference between the left and right suspensions is obtained.

[0011] When the secondary correction is triggered, a vehicle tilt direction and degree are determined according to displacement signals of left and right suspensions of the vehicle, and an output torque is corrected based on the vehicle tilt direction and degree to obtain a corrected steering torque.

[0012] Left and right steering torque correction coefficients are respectively calculated according to the vehicle tilt direction and degree, and the initial steering torque is corrected by using the left and right steering torque correction coefficients.

[0013] The left and right steering torque correction coefficients are limited according to the vehicle tilt direction and degree; wherein the correction coefficient of one side of the tilt direction is less than 1, and the correction coefficient of the other side is greater than 1; and the correction coefficient is associated with the tilt degree.

[0014] When it is determined that the vehicle is left-tilted, the left steering torque correction coefficient is set to be less than 1 and the right steering torque correction coefficient is set to be greater than 1, and the size of the left steering torque correction coefficient decreases to a set minimum value with the increase of the tilt degree;

[0015] When it is determined that the vehicle is right-tilted, the right steering torque correction coefficient is set to be less than 1 and the left steering torque correction coefficient is set to be greater than 1, and the size of the right steering torque correction coefficient decreases to a set minimum value with the increase of the tilt degree;

[0016] The difference between the left steering torque correction coefficient and the right steering torque correction coefficient and the value 1 is the same.

[0017] In step S1, the steering torque is calculated according to the steering wheel torque signal, and the initial steering torque is obtained by superimposing and correcting the vehicle speed signal and the return torque signal.

[0018] A control system of a steer-by-wire steering torque, including an initial steering torque calculation unit, a triggering unit, a secondary correction unit and an execution unit.

[0019] The initial steering torque calculation unit calculates the initial steering torque according to the steering wheel torque signal, the vehicle speed signal and the aligning torque signal;

[0020] The trigger unit determines whether to trigger the secondary correction according to the suspension state parameter;

[0021] When the secondary correction is not triggered, the initial steering torque calculation unit sends the initial steering torque to the execution unit for execution;

[0022] When the secondary correction is triggered, the initial steering torque calculation unit sends the initial steering torque to the secondary correction unit, the secondary correction unit corrects the initial steering torque based on the suspension state parameter to obtain a corrected steering torque, and sends the corrected steering torque to the execution unit for execution of the steering control with the corrected steering torque.

[0023] The suspension state parameter is collected by a suspension displacement sensor connected to the trigger unit and the secondary correction unit, and is sent to the trigger unit and the secondary correction unit, respectively.

[0024] The present application has the advantages that the secondary correction is added to the calculated output torque to meet the vehicle steering stability in special situations, reduce the safety hazards caused by unreasonable output of the torque, solve the defects of unreasonable torque output of the vehicle with off-road performance requirements in the case of large left and right suspension distortion or high-speed instability, improve the rationality of torque output and improve the steering safety and reliability of the vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0025] The contents expressed by each figure of the present application specification and the marks in the figures are briefly described as follows:

[0026] Figure 1 It is the control method flow chart of the present application;

[0027] Figure 2 It is the control principle diagram of the steering torque of the present application. DETAILED DESCRIPTION

[0028] The specific embodiments of the present application are further described in detail below by comparing the figures and describing the optimal embodiments.

[0029] The prior art calculates the steering torque signal based on the steering wheel torque signal, the vehicle speed signal and the return torque signal regardless of the state of the vehicle, without considering the steering safety risk caused by the change of the vehicle suspension under off-road or high-speed conditions. In the present scheme, the suspension displacement parameter is introduced to judge the tilt and suspension change of the vehicle, and the steering torque is corrected based on the suspension displacement data, so as to better adapt to the steering of the vehicle and avoid the safety hazard caused by the lack of adjustment of the steering torque when the vehicle tilts under off-road or high-speed conditions. Specifically, the scheme solves the demand of outputting a more reasonable torque signal and shielding a dangerous steering signal to make the vehicle more stable, safe and have a better steering feel under the conditions of large left and right suspension distortion of the vehicle with off-road performance requirements or high-speed instability; the suspension displacement sensor is added, and the suspension displacement sensor displacement signal is added when the output steering torque is calculated, so as to shield some extreme steering misoperation signals by judging the attitude of the vehicle when steering.

[0030] As shown in Figure 1 、 2 The present embodiment provides a kind of control method of steer-by-wire steering torque, comprising the following steps:

[0031] S1, the initial steering torque is calculated according to steering wheel torque signal, vehicle speed signal, return torque signal;

[0032] S2, suspension state parameter is collected, and whether secondary correction is triggered based on suspension state parameter is judged;

[0033] S3, when not triggering secondary correction, the initial steering torque is executed steering control;If secondary correction is triggered, the initial steering torque is corrected based on suspension state parameter to obtain modified steering torque, and the modified steering torque is executed steering control.

[0034] Whether the initial steering torque is corrected based on suspension state data is judged, and the vehicle running state can be judged by suspension displacement.If left and right suspension displacements are same or difference is very small, it indicates that the vehicle is stable, and there is no off-road or turning condition, therefore, the initial steering torque can be used for steering control, when left and right suspension displacements are large, it indicates that the vehicle is tilted, if the initial steering torque calculated by the existing method is still used for control, it can cause safety hazard such as vehicle overturning, therefore, the present scheme uses secondary correction to output steering torque, and the secondary correction refers to limiting the steering torque of once tilt and reducing the steering torque. Specific scheme is as follows:

[0035] The suspension state parameters include the displacement signals of the left and right suspensions. When the displacement difference between the left and right suspensions is greater than a set threshold, the secondary correction is triggered, otherwise the secondary correction is not triggered. A displacement sensor is arranged to detect the displacement signal of the suspension. The displacement sensor is calibrated to the 0 point of the suspension stroke of the vehicle in the empty state on a flat road. When the suspension moves upward, the displacement signal is positive, otherwise the displacement signal is negative. The displacement signals of the left and right suspensions are collected by the displacement sensor and the displacement difference between the left and right suspensions is obtained.

[0036] When the secondary correction is triggered, the inclination direction and degree of the vehicle are determined according to the displacement signals of the left and right suspensions of the vehicle. The output torque is corrected based on the inclination direction and degree of the vehicle to obtain the corrected steering torque. The left steering torque correction coefficient and the right steering torque correction coefficient are calculated according to the inclination direction and degree of the vehicle. The initial steering torque is corrected by using the left steering torque correction coefficient and the right steering torque correction coefficient. The left steering torque correction coefficient and the right steering torque correction coefficient are limited according to the inclination direction and degree of the vehicle. The correction coefficient on one side of the inclination direction is less than 1, and the correction coefficient on the other side is greater than 1. The correction coefficient is associated with the inclination degree.

[0037] When the vehicle is judged to be left inclined, the left steering torque correction coefficient is set to be less than 1 and the right steering torque correction coefficient is set to be greater than 1. The size of the left steering torque correction coefficient decreases to a set minimum value with the increase of the inclination degree. When the vehicle is judged to be right inclined, the right steering torque correction coefficient is set to be less than 1 and the left steering torque correction coefficient is set to be greater than 1. The size of the right steering torque correction coefficient decreases to a set minimum value with the increase of the inclination degree.

[0038] The difference between the left steering torque correction coefficient and the right steering torque correction coefficient and the value 1 is the same, that is, the reduction of the correction coefficient on one side of the inclination direction is the same as the increase of the correction coefficient on the other side.

[0039] In the embodiment, the steering torque is calculated according to the steering wheel torque signal in step S1, and the initial steering torque is obtained by superimposing and correcting the vehicle speed signal and the return torque signal. The initial steering torque can be calculated in the conventional manner of the prior art.

[0040] The embodiment also provides a control system for the steering torque by wire, which includes an initial steering torque calculation unit, a trigger unit, a secondary correction unit and an execution unit. The initial steering torque calculation unit calculates the initial steering torque according to the steering wheel torque signal, the vehicle speed signal and the return torque signal. The trigger unit judges whether to trigger the secondary correction according to the suspension state parameters.

[0041] When the secondary correction is not triggered, the initial steering torque calculation unit sends the initial steering torque to the execution unit for execution.

[0042] When the secondary correction is triggered, the initial steering torque calculation unit sends the initial steering torque to the secondary correction unit, the secondary correction unit corrects the initial steering torque based on the suspension state parameters to obtain a corrected steering torque and sends the corrected steering torque to the execution unit to perform steering control with the corrected steering torque.

[0043] The suspension state parameters are collected by a suspension displacement sensor connected to the triggering unit and the secondary correction unit to send the suspension state parameters to the triggering unit and the secondary correction unit, respectively.

[0044] In this embodiment, the steer-by-wire system is composed of three modules: a steering wheel assembly, an ECU, and a steering execution assembly. The steering wheel assembly module is composed of a steering wheel and a road feel motor. The steering wheel is used to receive the input of the driver, and the road feel motor is used to generate resistance to simulate the road condition steering return torque hand feeling. The steering execution assembly module is composed of a steering motor, a gear and rack assembly, a suspension tie rod assembly, and a tire assembly. The module receives the torque signal input by the ECU according to the steering wheel system and other related signals of the vehicle, and the motor drives the gear and rack to move, and the tie rod moves to the final tire corner. When the driver turns the steering wheel, the angle sensor detects the signal and converts the angle signal into a digital signal to transmit to the ECU. The ECU corrects the signal according to the input signal, the return torque signal, and the vehicle speed signal according to the built-in filtering algorithm in the ECU to obtain a corrected torque signal. For example, after filtering the torque request signal to obtain a corrected signal, the corrected filtering and the vehicle speed signal are superimposed to obtain a superimposed torque signal. After correction and superposition, the first correction superposition signal is obtained. In the unloaded state of the vehicle on the flat road, the suspension travel is the displacement sensor 0 point, the upward movement is positive, and the downward movement is negative. In this context, the left and right suspension displacement signals are judged. If the difference between the two is less than the threshold, the corrected signal of the previous step is used as the output torque signal. If the difference between the two is greater than the preset threshold, the steering angle signal needs to be corrected again. For example, the left front displacement sensor displacement value is negative, the right front displacement sensor is positive, and the difference between the two is greater than the threshold. At this time, the vehicle is in a left low and right high state, and the ECU needs to determine the steering intention. If there is still a left limit steering demand in the case of serious left tilt of the vehicle, it will cause the vehicle to tilt more seriously or even overturn. Therefore, the output torque signal needs to be corrected again. Conversely, the same applies.

[0045] In this embodiment, the secondary correction includes a steering wheel torque signal correction process. First, the steering wheel angle data is collected by an angle sensor and converted into a digital signal to transmit to the ECU to obtain a preliminary torque signal. Then, the preliminary torque signal is dynamically compensated and corrected according to the vehicle speed signal. Different correction coefficients are set for different vehicle speed intervals, and the coefficient is dynamically adjusted between 1.8 and 0.75, which is inversely proportional to the vehicle speed.

[0046] At the same time, considering the influence of the displacement difference between the left and right sides of the suspension on the vehicle posture, when the displacement difference between the left and right suspensions exceeds the preset threshold, the ECU determines that the vehicle is in a tilting state, at this time, a secondary correction mechanism is introduced; according to the tilting direction and degree of the vehicle, the upper limit of the torque output is dynamically adjusted, for example, when tilting to the left, the left steering torque signal is limited to introduce a secondary coefficient (a value less than 1), the right steering assist is increased to introduce a secondary coefficient (a value greater than 1, and the absolute value of the difference between the left and right secondary coefficients and 1 is equal), in order to offset the tilting trend; eliminate the risk of excessive steering caused by tilting, improve the driving stability, and thus shield the dangerous signal of tilting or even overturning caused by the driver's continuous left turning instruction in the case of large left tilting. Conversely, when the vehicle tilts to the right, the right steering torque signal is limited and the left steering torque signal is increased.

[0047] In the embodiment, in order to improve the reliability of the collected data and avoid errors caused by data fluctuations, a low-pass filtering algorithm is introduced, which can effectively suppress undesirable high-value signals. By filtering the input signal, the signal is more stable and reliable, and misjudgment caused by instantaneous fluctuations is avoided. The low-pass filtering algorithm smooths the signal according to the set cutoff frequency, retains the effective signal of low frequency, and also introduces a Gaussian filtering algorithm to further optimize the signal, eliminate random noise interference and improve signal accuracy. Gaussian filtering is a linear filtering method for signal processing with good smoothing effect, which is suitable for variable steering signal input under complex road conditions to make it more linear.

[0048] Obviously, the specific implementation of the present application is not limited by the above-mentioned manner, and various non-essential improvements made by adopting the method concept and technical scheme of the present application are within the protection scope of the present application.

Claims

1. A control method of steer-by-wire torque, characterized by: The method comprises the following steps: S1, calculating an initial steering torque according to a steering wheel torque signal, a vehicle speed signal and a return torque signal; S2, collecting suspension state parameters and determining whether to trigger secondary correction based on the suspension state parameters; S3, if the secondary correction is not triggered, performing steering control with the initial steering torque; if the secondary correction is triggered, correcting the initial steering torque to obtain a corrected steering torque based on the suspension state parameters, and performing steering control with the corrected steering torque.

2. A control method of steer-by-wire torque as claimed in claim 1, characterized in that: The suspension state parameters include displacement signals of left and right suspensions, and the secondary correction is triggered when a displacement difference between the left and right suspensions is greater than a set threshold, otherwise the secondary correction is not triggered.

3. A control method of steer-by-wire torque as claimed in claim 2, characterized in that: A displacement sensor is arranged to detect the displacement signal of the suspension, wherein the displacement of the suspension in the empty state of the vehicle on the flat road is set as the 0 point of the displacement sensor, and the displacement signal is positive when the suspension moves upward, otherwise the displacement signal is negative. The displacement signals of the left and right suspensions are collected by the displacement sensor and the displacement difference between the left and right suspensions is obtained.

4. The control method of a steer-by-wire torque as set forth in claim 1, characterized by: When the secondary correction is triggered, the inclination direction and degree of the vehicle are determined according to the displacement signals of the left and right suspensions of the vehicle, and the output torque is corrected based on the inclination direction and degree of the vehicle to obtain the corrected steering torque.

5. A control method of steer-by-wire torque as claimed in claim 4, characterized in that: The left steering torque correction coefficient and the right steering torque correction coefficient are calculated according to the inclination direction and degree of the vehicle, and the initial steering torque is corrected by using the left steering torque correction coefficient and the right steering torque correction coefficient.

6. A steer-by-wire torque control method according to claim 5, characterized in that: The left steering torque correction coefficient and the right steering torque correction coefficient are limited according to the inclination direction and degree of the vehicle; wherein the correction coefficient on one side of the inclination direction is less than 1, and the correction coefficient on the other side is greater than 1; and the correction coefficient is associated with the inclination degree.

7. A control method of steer-by-wire torque as claimed in claim 6, characterized in that: When it is determined that the vehicle is inclined to the left, the left steering torque correction coefficient is set to be less than 1 and the right steering torque correction coefficient is set to be greater than 1, and the size of the left steering torque correction coefficient decreases to a set minimum value with the increase of the inclination degree; When it is determined that the vehicle is inclined to the right, the right steering torque correction coefficient is set to be less than 1 and the left steering torque correction coefficient is set to be greater than 1, and the size of the right steering torque correction coefficient decreases to a set minimum value with the increase of the inclination degree; wherein the difference between the left steering torque correction coefficient and the right steering torque correction coefficient and the value 1 is the same.

8. The control method of a steer-by-wire torque, according to claim 1, characterized in that: In step S1, the steering torque is calculated according to the steering wheel torque signal, and the initial steering torque is obtained by superimposing and correcting the vehicle speed signal and the return torque signal.

9. A steer-by-wire torque control system characterized by: The method comprises an initial steering torque calculation unit, a triggering unit, a secondary correction unit and an execution unit; the initial steering torque calculation unit calculates the initial steering torque according to the steering wheel torque signal, the vehicle speed signal and the return torque signal; the triggering unit determines whether to trigger the secondary correction according to the suspension state parameters; when the secondary correction is not triggered, the initial steering torque calculation unit sends the initial steering torque to the execution unit for execution; when the secondary correction is triggered, the initial steering torque calculation unit sends the initial steering torque to the secondary correction unit, the secondary correction unit corrects the initial steering torque based on the suspension state parameters to obtain the corrected steering torque, and sends the corrected steering torque to the execution unit for steering control.

10. A steer-by-wire torque control system as recited in claim 9, characterized in that: The suspension state parameters are collected by a suspension displacement sensor, which is connected with the triggering unit and the secondary correction unit, so as to send the suspension state parameters into the triggering unit and the secondary correction unit respectively.

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