Control method and device of steer-by-wire system, electronic equipment and storage medium

Abstract

The present application relates to a kind of control method, device, electronic equipment and storage medium of steer-by-wire system.The control method of steer-by-wire system includes: according to the steering related data of the driving control state data of vehicle and steer-by-wire system, determine basic feedback torque and road feel feedback torque;According to the output proportion coefficient of the driving control state data corresponding to basic feedback torque and road feel feedback torque;Determine the target feedback torque of the upper conversion motor based on basic feedback torque, road feel feedback torque, the output proportion coefficient corresponding to basic feedback torque and road feel feedback torque.This application embodiment can allocate different output proportion coefficients for basic feedback torque and road feel feedback torque according to driving control state data, superimposed output obtains the target feedback torque of the upper conversion motor, so that driver can obtain good steering feel similar to traditional EPS, both can flexibly control vehicle to steer, and can also perceive the change of actual road, early risk prediction, improve driving safety.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of steer-by-wire systems, and in particular to a control method and device for a steer-by-wire system, an electronic device, and a storage medium. BACKGROUND

[0002] With the continuous development of the automotive industry, consumers' requirements for vehicle driving performance and use convenience are constantly increasing. In order to meet the increasingly intelligent and diversified needs of vehicles, the steering system has also undergone multiple iterations, from the initial mechanical steering, hydraulic steering, electric power steering, to the current steer-by-wire system.

[0003] The steer-by-wire system includes an upper steering feel simulation mechanism and a lower front wheel drive mechanism. After the mechanical connection is cancelled, the decoupling between the steering wheel and the steering wheel can be realized, which provides great flexibility for the layout and design of the steering control system and is conducive to the integration of the vehicle system. The control precision and response speed of the steer-by-wire system are high, which can facilitate the integration and data sharing with other subsystems of the vehicle, significantly improve the steering stability and safety of the vehicle, and facilitate the realization of higher-order intelligent driving.

[0004] However, due to the decoupling characteristics of the steer-by-wire system, the traditional tire friction force transmitted to the lower rack (generally represented by rack force) cannot be transmitted to the steering wheel through the mechanical intermediate shaft, so the steering feel control scheme of the traditional electric power steering system is not applicable to the upper steering feel simulation mechanism of the steer-by-wire system. It is necessary to redesign according to the characteristics of the steer-by-wire system, and the existing steer-by-wire steering feel simulation technology, some of which focus on mode scene switching and some of which focus on redundant scheme design, lacks research on the overall system scheme for improving the steering feel simulation effect. SUMMARY

[0005] To solve the above technical problems or at least partially solve the above technical problems, the present application provides a control method and device for a steer-by-wire system, an electronic device, and a storage medium.

[0006] In a first aspect, the present application provides a control method for a steer-by-wire system, comprising:

[0007] obtaining driving control state data of a vehicle and steering-related data of a steer-by-wire system;

[0008] determining a basic feedback torque and a road feel feedback torque according to the steering-related data and the driving control state data;

[0009] determining an output proportionality coefficient corresponding to the basic feedback torque and the road feel feedback torque according to the driving control state data;

[0010] Determine a target feedback torque of the upper rotating motor based on the base feedback torque, the road feedback torque, an output proportion coefficient corresponding to the base feedback torque and the road feedback torque, and control the upper rotating motor of the steer-by-wire system to output the target feedback torque.

[0011] Optionally, the steering-related data comprises a lower turning angle, a steering wheel angle and a steering wheel rotating speed, and the driving state data comprises a vehicle speed and driving mode information.

[0012] Determine a base feedback torque based on the steering-related data and the driving state data, comprising:

[0013] Calculate a comfortable rack force based on the lower turning angle and the vehicle speed.

[0014] Calculate the base feedback torque based on the comfortable rack force, the lower turning angle, the steering wheel angle, the steering wheel rotating speed, the vehicle speed and the driving mode information.

[0015] Optionally, calculate the comfortable rack force based on the lower turning angle and the vehicle speed, comprising:

[0016] Obtain a front wheel turning angle corresponding to the lower turning angle.

[0017] Determine a whole vehicle lateral force based on the front wheel turning angle and the vehicle speed.

[0018] Determine a comfortable rack force original value based on the whole vehicle lateral force.

[0019] Determine a rack force coefficient based on the lower turning angle and the vehicle speed.

[0020] Calculate a product of the comfortable rack force original value and the rack force coefficient.

[0021] Low-pass filter the product to obtain the comfortable rack force.

[0022] Optionally, calculate the base feedback torque based on the comfortable rack force, the lower turning angle, the steering wheel angle, the steering wheel rotating speed, the vehicle speed and the driving mode information, comprising:

[0023] Determine a base feedback torque initial value based on the comfortable rack force, the vehicle speed and the driving mode information.

[0024] Determine a damping coefficient based on the vehicle speed and the steering wheel rotating speed.

[0025] Determine a following feedback coefficient based on a difference between the steering wheel angle and the lower turning angle.

[0026] The product of the initial value of the basic feedback torque, the damping coefficient and the following feedback coefficient is calculated to obtain the basic feedback torque.

[0027] Optionally, the following feedback coefficient is determined according to a difference between the steering wheel angle and the lower steering angle, comprising:

[0028] It is determined whether the difference is within a preset deviation range;

[0029] If the difference is within the preset deviation range, the following feedback coefficient is determined as 1;

[0030] If the difference is outside the preset deviation range, the following feedback coefficient is determined according to a preset natural logarithm and exponential compound function.

[0031] Optionally, the steering related data comprises a lower steering motor speed, a lower steering motor torque, a steering wheel speed and an actual hand torque, and the driving control state data comprises a vehicle speed and driving mode information;

[0032] The road feeling feedback torque is determined according to the steering related data and the driving control state data, comprising:

[0033] The dynamic rack force is determined according to the lower steering motor speed and the lower steering motor torque;

[0034] The expected hand torque is determined according to the dynamic rack force, the vehicle speed and the driving mode information;

[0035] The road feeling feedback torque is determined according to the expected hand torque, the steering wheel speed and the actual hand torque.

[0036] Optionally, the dynamic rack force is determined according to the lower steering motor speed and the lower steering motor torque, comprising:

[0037] The lower steering motor speed and the lower steering motor torque are input into a dynamic mechanics model of the steer-by-wire system to obtain a dynamic rack force original value;

[0038] The dynamic rack force original value is dead zone processed to obtain the dynamic rack force.

[0039] Optionally, the road feeling feedback torque is determined according to the expected hand torque, the steering wheel speed and the actual hand torque, comprising:

[0040] The torque difference between the actual hand torque and the expected hand torque is calculated;

[0041] The integral coefficient is determined according to the steering wheel speed;

[0042] The torque difference is PID closed loop controlled according to the integral coefficient to obtain the road feeling feedback torque.

[0043] Optionally, the integral coefficient is determined according to the steering wheel speed, comprising:

[0044] determining whether the steering wheel speed is greater than an upper threshold value;

[0045] if the steering wheel speed is greater than the upper threshold value, determining that the integral coefficient is 1;

[0046] if the steering wheel speed is less than or equal to the upper threshold value, determining whether the steering wheel speed is less than a lower threshold value;

[0047] if the steering wheel speed is less than the lower threshold value, determining that the integral coefficient is 0;

[0048] if the steering wheel speed is greater than or equal to the lower threshold value, calculating the integral coefficient according to the steering wheel speed, the upper threshold value and the lower threshold value.

[0049] Optionally, the driving control state data comprises: vehicle speed and road feel opening relationship coefficient;

[0050] determining the output proportion coefficient corresponding to the basic feedback torque and the road feel feedback torque according to the driving control state data, comprising:

[0051] obtaining a feedforward value of a target feedback torque at a previous time;

[0052] determining a road feel feedback original weight coefficient according to the vehicle speed and the feedforward value;

[0053] calculating the product of the road feel feedback original weight coefficient and the road feel opening relationship coefficient to obtain a road feel feedback torque weight coefficient as the output proportion coefficient corresponding to the road feel feedback torque;

[0054] calculating the difference between 1 and the road feel feedback torque weight coefficient to obtain a basic feedback torque weight coefficient as the output proportion coefficient corresponding to the basic feedback torque.

[0055] Optionally, determining a target feedback torque of an upper rotating motor based on the basic feedback torque, the road feel feedback torque, the output proportion coefficient corresponding to the basic feedback torque and the road feel feedback torque, and controlling the upper rotating motor of the steer-by-wire system to output the target feedback torque, comprising:

[0056] calculating the product of the road feel feedback torque and the output proportion coefficient corresponding to the road feel feedback torque to obtain a road feel feedback torque component;

[0057] calculating the product of the basic feedback torque and the output proportion coefficient corresponding to the basic feedback torque to obtain a basic feedback torque component;

[0058] The sum of the road feel feedback torque component and the base feedback torque component is subjected to limiting processing to obtain the target feedback torque.

[0059] The upper conversion motor of the steer-by-wire system outputs the target feedback torque.

[0060] In a second aspect, the application provides a control device of a steer-by-wire system, comprising:

[0061] An acquisition module is configured to acquire driving control state data of a vehicle and steering-related data of a steer-by-wire system.

[0062] A first determination module is configured to determine a base feedback torque and a road feel feedback torque based on the steering-related data and the driving control state data.

[0063] A second determination module is configured to determine an output proportionality coefficient corresponding to the base feedback torque and the road feel feedback torque based on the driving control state data.

[0064] A third determination module is configured to determine a target feedback torque of an upper conversion motor based on the base feedback torque, the road feel feedback torque, and the output proportionality coefficient corresponding to the base feedback torque and the road feel feedback torque, and control the upper conversion motor of the steer-by-wire system to output the target feedback torque.

[0065] In a third aspect, the application provides an electronic device, comprising a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory are in communication with each other through the communication bus.

[0066] The memory is configured to store a computer program.

[0067] The processor is configured to execute the program stored in the memory to implement the control method of the steer-by-wire system according to any one of the first aspect.

[0068] In a fourth aspect, the application provides a computer readable storage medium, wherein the computer readable storage medium stores a program of a control method of a steer-by-wire system, and the program of the control method of the steer-by-wire system is executed by a processor to implement the steps of the control method of the steer-by-wire system according to any one of the first aspect.

[0069] The application has the following beneficial effects:

[0070] This application embodiment determines the basic feedback torque and road feel feedback torque based on the vehicle's steering-related data and driving control status data. Then, based on the driving control status data, it allocates different output ratio coefficients to the basic feedback torque and road feel feedback torque, and superimposes the outputs to obtain the target feedback torque of the upper motor. This allows the driver to obtain a good steering feel similar to that of a traditional EPS, enabling flexible control of the vehicle's steering and perception of changes in the actual road surface, allowing for early risk prediction and improved driving safety. Attached Figure Description

[0071] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0072] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0073] Figure 1 A flowchart illustrating a control method for a steer-by-wire system provided in this application embodiment;

[0074] Figure 2 A logic block diagram of a control method for a steer-by-wire system provided in an embodiment of this application;

[0075] Figure 3 for Figure 1 A flowchart of step S102;

[0076] Figure 4 A logic block diagram for calculating the basic feedback torque is provided in an embodiment of this application;

[0077] Figure 5 for Figure 1 Another flowchart for step S102;

[0078] Figure 6 A logic block diagram for calculating road feel feedback torque provided in an embodiment of this application;

[0079] Figure 7 A logic block diagram for calculating the target feedback torque is provided in an embodiment of this application;

[0080] Figure 8 A structural diagram of a control device for a steer-by-wire system provided in an embodiment of this application;

[0081] Figure 9 This is a structural diagram of an electronic device provided in an embodiment of this application. DETAILED DESCRIPTION

[0082] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0083] Due to the decoupling characteristics of the steer-by-wire system, after the actual traditional tire friction force is transmitted to the rack (generally represented by a rack force) that is turned downward, the rack force cannot be transmitted to the steering wheel through the mechanical intermediate shaft, so the steering feel control scheme of the traditional electric power steering system is not applicable to the steer-by-wire system, and needs to be redesigned according to the characteristics of the steer-by-wire system. The existing steer-by-wire steering feel simulation technology is biased towards mode scene switching and redundant scheme design, and lacks research on the overall system scheme for improving the steering feel simulation effect.

[0084] Therefore, the embodiments of the present application provide a control method and device of a steer-by-wire system, an electronic device and a storage medium, wherein the feedback torque of the upper turning motor for feel simulation is calculated according to the arbitration and mixing of a basic feedback torque and a road feel feedback torque through a certain strategy. The basic feedback torque is mainly calculated by referring to the running attitude of the vehicle, which can give the driver a basic hand feeling of operation, and is convenient for controlling and operating the running attitude of the vehicle. The road feel feedback torque is mainly calculated by referring to the actual running parameters of the lower turning motor through closed-loop control of the steering hand torque, which is sensitive and can truly reflect the actual road conditions to give the driver a clear road feel feedback. Finally, the basic feedback torque and the road feel feedback torque are allocated with different output proportion coefficients in different situations according to the vehicle speed and the strength of the actual request torque, so that the driver can obtain a good steering feel similar to the traditional EPS, that is, the driver can flexibly control the vehicle to turn and can also perceive the changes of the actual road surface, predict risks in advance and improve the driving safety.

[0085] The embodiments of the present application provide a control method of a steer-by-wire system, as shown in Figure 1 , comprising:

[0086] In step S101, the driving control state data of the vehicle and the steering related data of the steer-by-wire system are acquired.

[0087] In the embodiments of the present application, the driving state data refers to data reflecting the driving state and the control state of the vehicle, including: vehicle speed, driving mode information, and road sense opening coefficient. The vehicle speed can be detected by a vehicle speed sensor. The driving mode information refers to information of a driving mode set by a person. For example, the driving mode includes a sport mode and a comfort mode. The road sense opening coefficient can be set by a person through a central control screen, and the value range is 0 to 1. When the value is 0, the road sense torque is completely closed, and the final output is only the basic feedback torque component. When the value is 1, the road sense feedback torque component is normally opened. When the value is 0 to 1, the strength of the road sense feedback can be adjusted.

[0088] The steering related data of the steer-by-wire system refers to core parameters of the steer-by-wire system, which determines the steering accuracy, response speed and driving feel of the system. The steering related data includes: the lower steering angle, the steering wheel angle, the steering wheel speed, the lower steering motor speed, the lower steering motor torque and the actual hand torque (i.e. the actual steering wheel hand torque). The lower steering angle refers to the actual angle value of the front wheel (or the steering wheel) of the vehicle deviated to the left or right from the “straight driving position”, which can be detected by a steering machine angle sensor. The steering wheel angle refers to the angle value of the steering wheel rotated to the left or right from the “neutral return position”, which can be detected by a steering wheel angle sensor. The steering wheel speed refers to the angle change rate of the steering wheel rotated in unit time, which can be obtained by “differential calculation” of the signal of the steering wheel angle sensor. The lower steering motor speed refers to the rotation speed of the motor driving the steering mechanism in the electric power steering system (EPS) or the steer-by-wire system, which can be obtained by the number of rotations of the motor rotor in unit time. The lower steering motor torque refers to the “rotational torque” output by the steering motor, which can be obtained by “current calculation” of the motor controller or directly detected by a torque sensor. The actual hand torque refers to the actual reaction torque of the steering wheel on the hands of the driver when the driver rotates the steering wheel, which can be directly detected by a torque sensor installed between the steering column and the steering machine.

[0089] In step S102, the basic feedback torque and the road sense feedback torque are determined according to the steering related data and the driving state data.

[0090] In the embodiments of the present application, the basic feedback torque is obtained by comprehensively calculating the steering wheel angle, the lower steering angle, the steering wheel speed and the vehicle speed, as well as the comfort rack force obtained from the steering related data and the driving state data. Since the basic feedback torque is mainly referenced to the steering related data and the driving state data, the basic feedback torque can more truly reflect the driving control state of the steer-by-wire and the vehicle, and provide the driver with basic hand operation feedback.

[0091] For example, the road sense opening coefficient is set to 0.5, the steering wheel angle is 0, the lower steering angle is 0, the steering wheel speed is 0, and the vehicle speed is 0. In this case, the basic feedback torque is 0, and the road sense feedback torque is 0.5*0=0. Therefore, the total feedback torque is 0.5*0=0. Figure 2As shown, the comfortable rack force can be calculated according to the under-steering angle in the steering related data and the vehicle speed in the driving state data, and the basic feedback torque can be calculated according to the comfortable rack force, the steering wheel angle in the steering related data, the under-steering angle, the steering wheel speed, and the vehicle speed in the driving state data. The road feel feedback torque is obtained by the dynamic rack force calculated from the under-steering motor operating parameters and the vehicle speed (the vehicle speed in the figure), and the target steering wheel hand torque, and then the actual steering wheel hand force is closed-loop operated, and the integral coefficient calculated from the speed is used to control the output of the integral part to avoid the torque step problem.

[0092] Since the road feel feedback torque is mainly calculated according to the dynamics model of the under-steering actuator and the motor operating parameters, and the motor rotor of the under-steering actuator is relatively sensitive, the road feel feedback torque is relatively sensitive, and can truly reflect the actual road condition state and provide the driver with a relatively clear road feel feedback.

[0093] Specifically, in an embodiment of the present application, as shown in Figure 3 Step S102 determines the basic feedback torque according to the steering related data and the driving state data, including:

[0094] Step S201 calculates the comfortable rack force according to the under-steering angle and the vehicle speed.

[0095] In this step, the front wheel steering angle corresponding to the under-steering angle can be obtained, the vehicle lateral force can be determined according to the front wheel steering angle and the vehicle speed, the comfortable rack force original value can be determined according to the vehicle lateral force, the rack force coefficient can be determined according to the under-steering angle and the vehicle speed, the product of the comfortable rack force original value and the rack force coefficient can be calculated, and the product is low-pass filtered to obtain the comfortable rack force.

[0096] The present application embodiment can pre-set the corresponding relationship between the under-steering angle and the front wheel steering angle, can find the front wheel steering angle corresponding to the under-steering angle in the corresponding relationship according to the under-steering angle in the steering related data, and can multiply the found front wheel steering angle by a preset coefficient (determined according to the vehicle dynamics parameters) to obtain the front wheel steering angle corresponding to the under-steering angle in the steering related data.

[0097] After the front wheel steering angle is obtained, the vehicle lateral force can be calculated according to the following lateral force calculation formula:

[0098] F_y= m*a y =m*[V 2 *δ / (L+K*V 2 )]

[0099] Wherein, F_y is the lateral force, m is the vehicle mass, a yis the lateral acceleration, V is the vehicle speed, L is the wheelbase of the vehicle, δ is the front wheel steering angle, K is the stability factor which is a constant parameter.

[0100] After the lateral force of the whole vehicle is calculated, the original value of the comfortable rack force can be calculated according to the following rack force calculation formula:

[0101] F_rack = (F_y *r_gear) / (i_sw×η)

[0102] wherein F_rack is the original value of the comfortable rack force, F_y is the lateral force, r_gear is the pitch circle radius of the gear (m), i_sw is the steering transmission ratio, and η is the mechanical efficiency.

[0103] The rack force coefficient can be calculated by the following steering angle and vehicle speed by using the bilinear interpolation table lookup method. In the corresponding table lookup data, the coefficient presents the following rules: it increases with the increase of the steering angle; when the steering angle is small, if the vehicle speed is also reduced, the coefficient will be further reduced. Exemplarily, the numerical range of the rack force coefficient is 0.8-1.5, and the role of the rack force coefficient is to increase the comfortable rack force output at large angles and high speeds.

[0104] After the original value of the comfortable rack force is multiplied by the comfortable rack force coefficient, a first-order low-pass filtering is performed to obtain the required comfortable rack force. The role of the first-order low-pass filtering is to filter out the high-frequency jitter part and focus more on the comfort output.

[0105] In step S202, the base feedback torque is calculated according to the comfortable rack force, the steering angle, the steering wheel speed, the vehicle speed and the driving mode information.

[0106] In this step, as shown in the following formula, the initial value of the base feedback torque can be determined according to the comfortable rack force, the vehicle speed and the driving mode information; the damping coefficient can be determined according to the vehicle speed and the steering wheel speed; the following feedback coefficient can be determined according to the difference between the steering angle and the steering angle; the product of the initial value of the base feedback torque, the damping coefficient and the following feedback coefficient is calculated to obtain the base feedback torque. Figure 4

[0107] ​In the embodiments of the present application, different basic feedback torque initial value tables can be set in advance according to the driving modes. The user expects a larger steering hand force in the Sport mode, and a smaller steering hand force in the Comfort mode. Therefore, the basic feedback torque initial values in the basic feedback torque initial value table in the Sport mode are set to be larger as a whole, and the basic feedback torque initial values in the basic feedback torque initial value table in the Comfort mode are set to be smaller as a whole. The basic feedback torque initial value table is a two-dimensional table. The "row" is the torque value based on the comfort rack force breakpoint, and the "column" is the torque value based on the vehicle speed breakpoint. The value of the basic feedback torque initial value increases with the increase of the comfort rack force and the increase of the vehicle speed.

[0108] On the basis of the basic feedback torque initial value table, the basic feedback torque initial value can be calculated in a bilinear difference lookup table manner according to the comfort rack force and the vehicle speed.

[0109] In the embodiments of the present application, a corresponding relationship among the vehicle speed, the steering wheel speed and the damping coefficient can be set in advance. The damping coefficient increases with the increase of the vehicle speed and the steering wheel speed. Based on the corresponding relationship among the vehicle speed, the steering wheel speed and the damping coefficient, the damping coefficient is calculated according to the vehicle speed and the steering wheel speed, so as to give stronger hand force feedback in the case of fast steering and high speed, and increase the steering stability.

[0110] In the calculation of the following feedback coefficient, the difference between the steering wheel angle and the lower corner angle is calculated first to obtain an angle deviation. If the angle deviation is within a preset deviation range (a markable value), the following feedback coefficient is 1. If the angle deviation is outside the preset deviation range, the following feedback coefficient can be obtained by using a natural logarithm and exponential compound function calculation manner, so as to linearly increase the following coefficient when the angle deviation is small, and quickly increase the feedback torque to slow down the speed when the angle difference is too large, thereby avoiding instability.

[0111] The formula of the natural logarithm and exponential compound function is as follows:

[0112]

[0113] wherein, is the angle deviation (unit: degree), and the absolute value is taken to ensure symmetry; k1 is an overall gain coefficient, k1>0, for adjusting the feedback intensity; k2 is a logarithmic sensitivity parameter, k2>0, for controlling the smoothness in the small angle region; and k3 is an exponential growth parameter, k3>0, for dominating the rapid enhancement in the large angle region (usually k3∈(0.05, 0.2)).

[0114] Thus, in the small angle deviation region , the natural logarithm dominates: (Taylor expansion linear approximation); the exponent term is approximately 1: The function simplifies to: It exhibits linear growth, avoiding high-frequency oscillations; in the large-angle deviation region... The index component dominates growth: Follow ( Exponential growth; logarithmic growth: To prevent excessive and rapid increases; compound effects: This enables rapid enhanced feedback and accelerates system convergence.

[0115] The basic feedback torque can be directly obtained by multiplying the initial value of the basic feedback torque by the damping coefficient and then by the following feedback coefficient. Alternatively, the amplitude of the output value can be limited, with the limit decreasing as the vehicle speed increases to ensure safety. Specifically, the basic feedback torque can be obtained by applying a lookup table to the torque based on the vehicle speed. The lookup table limit can refer to the motor parameters to limit the vehicle speed. For example, if the maximum output of the motor is 8 Nm, then the low-speed limit is 8 Nm and the high-speed limit is 6 Nm.

[0116] In this embodiment, the calculation of the basic feedback torque takes into account enhanced hand force feedback during high-speed and rapid steering to improve driving stability, and incorporates follow-up feedback for downward steering, making it easier for the driver to perceive the actual response state of the vehicle. Furthermore, the basic feedback torque also considers enhancing torque feedback through damping coefficients in rapid steering and high-speed driving scenarios, and when downward steering fails to follow upward steering in time, using a nonlinear follow-up feedback coefficient to rapidly increase the feedback torque and reduce steering wheel speed to prevent instability when the angle deviation is too large.

[0117] The basic feedback torque obtained by the above method can also be superimposed (summed) with the active self-centering torque, the end-of-pipe protection torque, or the torque requested by the driver assistance system. Specifically, the self-centering torque can be superimposed during self-centering, the end-of-pipe protection torque can be superimposed when entering the end-of-pipe state, and the requested torque can be superimposed when ADAS requests torque. See the appendix for details. Figure 4 The dotted line portion in the text.

[0118] In one embodiment of this application, such as Figure 5 As shown, step S102 determines the road feel feedback torque based on the steering-related data and the driving control state data, including:

[0119] Step S301: Determine the dynamic rack force based on the speed and torque of the lower motor;

[0120] In this step, the speed and torque of the lower-rotor motor can be input into the dynamic mechanical model of the steer-by-wire system to obtain the original value of the dynamic rack force; the original value of the dynamic rack force is then processed to obtain the dynamic rack force.

[0121] The dynamic model considers the combined effect of friction and inertia of the steering system, and its formula is as follows:

[0122]

[0123] wherein, is the original value of the dynamic rack force, is the transmission ratio of the motor torque to the dynamic rack force, is the moment of inertia, is the motor angle, represents the second-order derivative of the motor angle, which means the motor angular acceleration, is the friction torque, is the motor torque.

[0124] The dead zone is that when the speed is less than the speed threshold, the output torque is 0, which avoids frequent changes, and the speed threshold changes dynamically based on the vehicle speed, and the larger the vehicle speed, the larger the threshold. After the original value of the dynamic rack force is processed by the dead zone, the influence of the dead zone position on the output dynamic rack force can be eliminated, the dead zone control is introduced to avoid the output dynamic rack force being too sensitive, and the final feedback road feeling feedback torque is more realistic.

[0125] Step S302, determining an expected hand torque according to the dynamic rack force, the vehicle speed and the driving mode information;

[0126] The expected hand torque of the drive-by-wire system is the expected feedback torque, which is theoretically proportional to the rack force, that is, the larger the rack force, the larger the expected feedback torque, but the feedback torque is obtained through the motor reaction force of the upper motor, so a target hand torque is calculated first, and then the actual required motor torque is calculated in the subsequent road feeling feedback torque module.

[0127] Specifically, the expected hand torque can be calculated by a bilinear difference lookup table according to the dynamic rack force and the vehicle speed, and the expected hand torque can be set with different calibration parameters according to the input driving mode (for example, the driving mode has Sport or Comfort, the steering hand force is heavier in Sport, and the expected hand force is smaller in Comfort, so the expected hand torque value can be adjusted according to the driving mode to calibrate the expected hand torque value), so as to obtain a target hand torque with different intensity.

[0128] Step S303, determining a road feeling feedback torque according to the expected hand torque, the steering wheel speed and the actual hand torque.

[0129] In this step, a torque difference between the actual hand torque and the expected hand torque can be calculated; an integral coefficient can be determined according to the steering wheel speed; and a road feeling feedback torque can be obtained by PID closed-loop control of the torque difference according to the integral coefficient.

[0130] In actual application, as shown in FIG. 5, the road feeling feedback torque (i.e., motor torque) required can be calculated by PID closed-loop control according to a difference between the actual hand torque and the expected hand torque (i.e., expected hand torque). Figure 6

[0131] The integral coefficient can be determined according to the steering wheel speed, including: determining whether the steering wheel speed is greater than an upper threshold value; if the steering wheel speed is greater than the upper threshold value, determining that the integral coefficient is 1; if the steering wheel speed is less than or equal to the upper threshold value, determining whether the steering wheel speed is less than a lower threshold value; if the steering wheel speed is less than the lower threshold value, determining that the integral coefficient is 0; and if the steering wheel speed is greater than or equal to the lower threshold value, calculating the integral coefficient according to the steering wheel speed, the upper threshold value and the lower threshold value. Specifically, integral coefficient = (steering wheel speed - lower threshold value) * 1 / (upper threshold value - lower threshold value).

[0132] That is, when the steering wheel speed is greater than the upper threshold value (the upper threshold value is a calibration value set according to experience, and the value range is between 5-10° / s, and an exemplary upper threshold value can be 8° / s), the coefficient value is set to 1; when the steering wheel speed is less than the lower threshold value (the lower threshold value is a calibration value set according to experience, and the value range is between 0-3° / s, and an exemplary lower threshold value can be 1° / s), the coefficient is set to 0. When the steering wheel speed is between the two, the integral coefficient = (steering wheel speed - 1) * 1 / (8 - 1), so that the integral coefficient can change linearly with the linear increase or linear decrease of the steering wheel speed, which can linearly decrease from 1 to 0, or linearly increase from 0 to 1, so as to ensure that there is no abrupt hand feeling when the steering direction is changed slowly, and to avoid that the integral accumulation hand feeling is too sensitive when the direction is changed at low speed. The integral coefficient is multiplied behind the I integral accumulator in the PID control to control the size of the entire integral part.

[0133] The steering wheel speed is used to reduce the integral coefficient (specifically, the lower the speed, the smaller the integral coefficient, and when the speed is less than the lower threshold value, the integral coefficient is reduced to 0, i.e., the integral is cleared) by the integral coefficient calculation unit when the steering wheel speed is low, and the output of the integral part is reduced according to the integral coefficient in the PID calculation unit, so that the road feeling feedback torque part is more accurate by the PID closed-loop method, which is different from the open-loop control of the comfort torque. The integral coefficient avoids the torque step caused by integral saturation when the steering wheel is finely adjusted at low speed, thereby avoiding excessive fluctuation of the output road feeling feedback torque.

[0134] ​Step S103, determining the output proportionality coefficient corresponding to the basic feedback torque and the road feel feedback torque according to the driving control state data;

[0135] In this step, different output proportionality coefficients can be assigned to the basic feedback torque and the road feel feedback torque according to the driving control state data, so as to obtain the output proportionality coefficient of the basic feedback torque and the output proportionality coefficient corresponding to the road feel feedback torque.

[0136] In an embodiment of the present application, step S103 determines the road feel feedback torque of the upper conversion motor according to the driving control state data, the basic feedback torque and the road feel feedback torque, including: obtaining the feedforward value of the target feedback torque at the previous moment; determining the road feel feedback original weight coefficient according to the vehicle speed and the feedforward value; calculating the product of the road feel feedback original weight coefficient and the road feel opening relationship number to obtain the road feel feedback torque weight coefficient as the output proportionality coefficient corresponding to the road feel feedback torque; calculating the difference between 1 and the road feel feedback torque weight coefficient to obtain the basic feedback torque weight coefficient as the output proportionality coefficient corresponding to the basic feedback torque.

[0137] In actual application, as shown in FIG. 6, the road feel feedback original weight coefficient B can be obtained by querying Table 1 through a bilinear table method according to the vehicle speed and the feedforward value of the target feedback torque (the final feedback torque). Figure 7 Figure 7 The road feel feedback original weight coefficient B has the characteristics that the value range is 0 to 1, the weight coefficient B decreases with the increase of the vehicle speed, the weight value is larger at low vehicle speed, and the weight value is smaller at high vehicle speed. The table for obtaining the road feel feedback original weight coefficient B is shown in Table 1, wherein the "row" is the torque breakpoint, and the "column" is the vehicle speed breakpoint. The specific parameters are obtained according to the vehicle model tuning.

[0138] Table 1

[0139]

[0140] The road feel feedback torque weight coefficient C is obtained by multiplying the road feel feedback original weight coefficient B and the road feel opening relationship number A, and the basic feedback torque weight coefficient is 1-C, wherein B represents the proportion of the road feel feedback torque in the target feedback torque under the default condition, and multiplying the road feel feedback original weight coefficient B and the road feel opening relationship number A represents reducing the proportion of the road feel feedback torque in the target feedback torque according to the road feel opening relationship number A, so as to reduce the proportion of the road feel feedback torque in the target feedback torque.

[0141] ​For example, if the initial weighting coefficient B for road feedback is 0.5, it means that by default, the proportion of road feedback torque to the target feedback torque at a certain vehicle speed is 0.5. If the road feedback switching coefficient A is 0.4, then B*A=0.2, which means reducing the proportion of road feedback torque in the target feedback torque to 0.2. If the road feedback switching coefficient A is set to 0, it means that the proportion of road feedback torque in the target feedback torque is 0, that is, it does not include road feedback torque. If the road feedback switching coefficient A is set to 1, it means that the proportion of road feedback torque in the target feedback torque is the default factory setting proportion.

[0142] Step S104: Determine the target feedback torque of the upper steering motor based on the basic feedback torque, the road feel feedback torque, the basic feedback torque, and the output ratio coefficient corresponding to the road feel feedback torque, and control the upper steering motor of the steer-by-wire system to output the target feedback torque.

[0143] In one embodiment of this application, step S104 determines the target feedback torque of the steering motor based on the basic feedback torque, the road feel feedback torque, the basic feedback torque, and the output proportion coefficient corresponding to the road feel feedback torque, and controls the steering motor of the steer-by-wire system to output the target feedback torque, including: calculating the product of the road feel feedback torque and the output proportion coefficient corresponding to the road feel feedback torque to obtain a road feel feedback torque component; calculating the product of the basic feedback torque and the output proportion coefficient corresponding to the basic feedback torque to obtain a basic feedback torque component; summing the road feel feedback torque component and the basic feedback torque component, limiting the sum to obtain the target feedback torque, and controlling the steering motor of the steer-by-wire system to output the target feedback torque.

[0144] Since the preceding text uses the road feel feedback torque weighting coefficient as the output proportion coefficient corresponding to the road feel feedback torque, and the basic feedback torque weighting coefficient as the output proportion coefficient corresponding to the basic feedback torque, as follows: Figure 7 As shown, the road feedback torque component is obtained by multiplying the road feedback torque by the road feedback torque weighting coefficient C, and the basic feedback torque component is obtained by multiplying the basic feedback torque by (1-C). The road feedback torque component and the basic feedback torque component are then superimposed, and after passing through the torque slope change limit and upper and lower amplitude limits, the final feedback torque is obtained. Specifically, the torque slope change limit and upper and lower amplitude limits refer to the following: when the output torque change rate is greater than the slope change limit, the torque change is performed according to the maximum limit of the slope change rate; when the output torque value exceeds the torque amplitude limit, the maximum limit is applied.

[0145] Through the above design, more road feeling feedback torque components can be distributed when the vehicle is at low speed and large torque, so that the driver can perceive the specific driving road surface state, and less road feeling feedback torque components can be distributed when the vehicle is at high speed, so that the vehicle driving posture is more stable and easier to control.

[0146] By controlling the road feeling opening coefficient, personalized customization requirements can be realized. The control coefficient can indirectly control the proportion of the road feeling feedback torque in the target feedback torque, so that the road feeling strength can be adjusted. Different driving settings can be realized according to the driving preferences of different drivers, and diversified driving requirements can be met.

[0147] The embodiment of the application first calculates the comfortable rack force and the dynamic rack force according to the output signal and the vehicle parameters, then calculates the basic feedback torque according to the comfortable rack force, calculates the target hand torque and the road feeling feedback torque according to the dynamic rack force, and then outputs the basic feedback torque and the road feeling feedback torque after arbitration according to the vehicle speed and the torque size: the road feeling feedback torque accounts for a larger proportion in the case of low vehicle speed and large torque, and the road feeling is more emphasized; the basic feedback torque accounts for a larger proportion in the case of high vehicle speed and small torque, and the comfort is more emphasized. Then, when the external road feeling opening coefficient A is not 1, the road feeling is closed or the strength of the road feeling feedback is adjusted according to the road feeling opening coefficient A, personalized adjustment is realized, different driving settings are realized according to the driving preferences of different drivers, and diversified driving requirements are met.

[0148] The embodiment of the application determines the basic feedback torque and the road feeling feedback torque according to the steering related data of the vehicle and the driving control state data of the vehicle, and then allocates different output proportion coefficients to the basic feedback torque and the road feeling feedback torque according to the driving control state data, so that the target feedback torque of the upper steering motor is obtained after superposition output, so that the driver can obtain a good steering hand feeling similar to the traditional EPS, which can flexibly control the vehicle to steer and can perceive the actual road surface changes, predict risks in advance, and improve driving safety.

[0149] In another embodiment of the application, a control device of a steer-by-wire steering system is also provided, as shown in Figure 8 , comprising:

[0150] The acquisition module 11 is configured to acquire the driving control state data of the vehicle and the steering related data of the steer-by-wire steering system.

[0151] The first determination module 12 is configured to determine the basic feedback torque and the road feeling feedback torque according to the steering related data and the driving control state data.

[0152] The second determination module 13 is configured to determine the output proportion coefficient corresponding to the basic feedback torque and the road feeling feedback torque according to the driving control state data.

[0153] The third determination module 14 is configured to determine a target feedback torque of the up-conversion motor based on the basic feedback torque, the road feeling feedback torque, and output proportionality coefficients corresponding to the basic feedback torque and the road feeling feedback torque, and control the up-conversion motor of the steer-by-wire system to output the target feedback torque.

[0154] In yet another embodiment of the present application, an electronic device is provided, comprising a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory communicate with each other through the communication bus;

[0155] The memory is configured to store a computer program.

[0156] The processor is configured to execute the program stored in the memory to implement the control method of the steer-by-wire system according to any one of the preceding method embodiments.

[0157] The electronic device provided by the embodiment of the present application is configured to determine the basic feedback torque and the road feeling feedback torque according to the steering related data of the vehicle and the driving control state data of the vehicle by executing the program stored in the memory, and then assign different output proportionality coefficients to the basic feedback torque and the road feeling feedback torque according to the driving control state data, so as to obtain the target feedback torque of the up-conversion motor after superimposed output, so that the driver can obtain a good steering feel similar to the traditional EPS, and can flexibly control the vehicle to steer and also perceive the actual road surface changes, predict risks in advance, and improve driving safety.

[0158] The communication bus 1140 mentioned in the above electronic device can be a peripheral component interconnect (PCI) bus or an extended industry standard architecture (EISA) bus, etc. The communication bus 1140 can be divided into an address bus, a data bus, a control bus, etc. For the convenience of representation, Figure 9 Only one thick line is used in the above-mentioned communication bus 1140, but it does not mean that there is only one bus or one type of bus.

[0159] The communication interface 1120 is configured to communicate between the above-mentioned electronic device and other devices.

[0160] The memory 1130 can include a random access memory (RAM) and can also include a non-volatile memory, such as at least one disk memory. Optionally, the memory can also be at least one storage device located away from the processor.

[0161] The processor 1110 described above can be a general processor, including a central processing unit (CPU), a network processor (NP), etc.; can also be a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component.

[0162] In yet another embodiment of the present application, a computer readable storage medium is also provided, and a program of a control method of a steer-by-wire system is stored on the computer readable storage medium, and the program of the control method of the steer-by-wire system, when executed by a processor, implements the steps of the control method of the steer-by-wire system according to any one of the method embodiments.

[0163] It should be noted that, in this document, relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. In other words, "comprising" does not exclude the presence of additional elements.

[0164] The above description is merely that of specific embodiments of the present application, and enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the present application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control method of a steer-by-wire system, characterized by, The method comprises: acquiring driving control state data of a vehicle and steering related data of a steer-by-wire system; determining a basic feedback torque and a road feel feedback torque according to the steering related data and the driving control state data; determining an output proportionality coefficient corresponding to the basic feedback torque and the road feel feedback torque according to the driving control state data; the driving control state data comprises vehicle speed and road feel opening coefficient; determining an output proportionality coefficient corresponding to the basic feedback torque and the road feel feedback torque according to the driving control state data comprises: acquiring a feedforward value of a target feedback torque at a previous time; determining a road feel feedback original weight coefficient according to the vehicle speed and the feedforward value; calculating a product of the road feel feedback original weight coefficient and the road feel opening coefficient to obtain a road feel feedback torque weight coefficient as the output proportionality coefficient corresponding to the road feel feedback torque; calculating a difference between 1 and the road feel feedback torque weight coefficient to obtain a basic feedback torque weight coefficient as the output proportionality coefficient corresponding to the basic feedback torque; determining a target feedback torque of an upper steering motor based on the basic feedback torque, the road feel feedback torque, the output proportionality coefficient corresponding to the basic feedback torque and the output proportionality coefficient corresponding to the road feel feedback torque, and controlling the upper steering motor of the steer-by-wire system to output the target feedback torque.

2. The control method of the steer-by-wire system according to claim 1, characterized by, the steering related data comprises a lower steering angle, a steering wheel angle and a steering wheel speed, and the driving control state data comprises vehicle speed and driving mode information; determining a basic feedback torque according to the steering related data and the driving control state data comprises: calculating a comfortable rack force according to the lower steering angle and the vehicle speed; calculating the basic feedback torque according to the comfortable rack force, the lower steering angle, the steering wheel angle, the steering wheel speed, the vehicle speed and the driving mode information.

3. The control method of the steer-by-wire system according to claim 2, characterized by, calculating a comfortable rack force according to the lower steering angle and the vehicle speed comprises: acquiring a front wheel steering angle corresponding to the lower steering angle; determining a whole vehicle lateral force according to the front wheel steering angle and the vehicle speed; determining a comfortable rack force original value according to the whole vehicle lateral force; determining a rack force coefficient according to the lower steering angle and the vehicle speed; calculating a product of the comfortable rack force original value and the rack force coefficient; performing low-pass filtering on the product to obtain the comfortable rack force.

4. The control method of the steer-by-wire system according to claim 2, characterized by, calculating the basic feedback torque according to the comfortable rack force, the lower steering angle, the steering wheel angle, the steering wheel speed, the vehicle speed and the driving mode information comprises: determining a basic feedback torque initial value according to the comfortable rack force, the vehicle speed and the driving mode information; determining a damping coefficient according to the vehicle speed and the steering wheel speed; determining a following feedback coefficient according to a difference between the steering wheel angle and the lower steering angle; calculating a product of the basic feedback torque initial value, the damping coefficient and the following feedback coefficient to obtain the basic feedback torque.

5. The control method of the steer-by-wire system according to claim 4, characterized by, determining a following feedback coefficient according to a difference between the steering wheel angle and the lower steering angle comprises: determining whether the difference is within a preset deviation range; if the difference is within the preset deviation range, the following feedback coefficient is determined as 1; If the difference is out of a preset deviation range, the following feedback coefficient is determined according to a preset natural logarithm and exponential compound function.

6. The control method of the steer-by-wire system according to claim 1, characterized by, The steering-related data includes a down motor speed, a down motor torque, a steering wheel speed and an actual hand torque, and the driving state data includes a vehicle speed and driving mode information. The road feeling feedback torque is determined according to the steering-related data and the driving state data, including: The dynamic rack force is determined according to the down motor speed and the down motor torque. The expected hand torque is determined according to the dynamic rack force, the vehicle speed and the driving mode information. The road feeling feedback torque is determined according to the expected hand torque, the steering wheel speed and the actual hand torque.

7. The control method of the steer-by-wire system according to claim 6, characterized by, The dynamic rack force is determined according to the down motor speed and the down motor torque, including: The down motor speed and the down motor torque are input into a dynamic mechanics model of the steer-by-wire system to obtain a dynamic rack force original value. The dynamic rack force original value is dead zone processed to obtain a dynamic rack force.

8. The control method of the steer-by-wire system according to claim 6, characterized by, The road feeling feedback torque is determined according to the expected hand torque, the steering wheel speed and the actual hand torque, including: A torque difference between the actual hand torque and the expected hand torque is calculated. An integral coefficient is determined according to the steering wheel speed. The torque difference is PID closed loop controlled according to the integral coefficient to obtain the road feeling feedback torque.

9. The control method of the steer-by-wire system according to claim 8, characterized by, The integral coefficient is determined according to the steering wheel speed, including: It is determined whether the steering wheel speed is greater than an upper threshold value. If the steering wheel speed is greater than the upper threshold value, the integral coefficient is determined as 1. If the steering wheel speed is less than or equal to the upper threshold value, it is determined whether the steering wheel speed is less than a lower threshold value. If the steering wheel speed is less than the lower threshold value, the integral coefficient is determined as 0. If the steering wheel speed is greater than or equal to the lower threshold value, the integral coefficient is calculated according to the steering wheel speed, the upper threshold value and the lower threshold value.

10. The control method of the steer-by-wire system according to claim 1, characterized by, The target feedback torque of the up motor is determined based on the basic feedback torque, the road feeling feedback torque, the output proportion coefficient corresponding to the basic feedback torque and the road feeling feedback torque, and the up motor of the steer-by-wire system is controlled to output the target feedback torque, including: A road feeling feedback torque component is obtained by calculating a product of the road feeling feedback torque and the output proportion coefficient corresponding to the road feeling feedback torque. A basic feedback torque component is obtained by calculating a product of the basic feedback torque and the output proportion coefficient corresponding to the basic feedback torque. The target feedback torque is obtained by limiting a sum of the road feeling feedback torque component and the basic feedback torque component. The up motor of the steer-by-wire system is controlled to output the target feedback torque.

11. A control device of a steer-by-wire system characterized by comprising: The method includes: An acquisition module is configured to acquire driving state data of a vehicle and steering-related data of a steer-by-wire system. A first determination module is configured to determine a basic feedback torque and a road feeling feedback torque according to the steering-related data and the driving state data. The second determining module is configured to determine the output proportionality coefficient corresponding to the basic feedback torque and the road feeling feedback torque according to the driving control state data, wherein the driving control state data comprises a vehicle speed and a road feeling opening relationship coefficient; determining the output proportionality coefficient corresponding to the basic feedback torque and the road feeling feedback torque according to the driving control state data comprises: obtaining a feedforward value of the target feedback torque at a previous moment; determining a road feeling feedback original weight coefficient according to the vehicle speed and the feedforward value; calculating a product of the road feeling feedback original weight coefficient and the road feeling opening relationship coefficient to obtain a road feeling feedback torque weight coefficient as the output proportionality coefficient corresponding to the road feeling feedback torque; and calculating a difference between 1 and the road feeling feedback torque weight coefficient to obtain a basic feedback torque weight coefficient as the output proportionality coefficient corresponding to the basic feedback torque; The third determining module is configured to determine a target feedback torque of an upper rotating motor based on the basic feedback torque, the road feeling feedback torque, the output proportionality coefficient corresponding to the basic feedback torque and the road feeling feedback torque, and control the upper rotating motor of the steer-by-wire system to output the target feedback torque.

12. An electronic device, comprising: The device comprises a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory are in communication with each other through the communication bus; The memory is configured to store a computer program. The processor is configured to execute the program stored on the memory to implement the control method of the steer-by-wire system according to any one of claims 1-10.

13. A computer-readable storage medium, characterized in that, The computer readable storage medium stores a program of the control method of the steer-by-wire system, and the program of the control method of the steer-by-wire system is executed by the processor to implement the steps of the control method of the steer-by-wire system according to any one of claims 1-10.

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