A method and device for steer-by-wire control

Abstract

This application provides a steer-by-wire control method and apparatus, applied to a steer-by-wire system. When the steer-by-wire actuator assembly is in a fault state, the assist torque provided by the steering motor at the target vehicle speed is obtained. The assist torque is determined based on the maximum current provided by the steering motor. The maximum steering wheel torque is obtained based on the assist torque and a first correspondence relationship. The first correspondence relationship is the relationship between steering wheel torque, assist torque, and vehicle speed in an electric power steering system. The maximum steering wheel angle is obtained based on the maximum steering wheel torque and a second correspondence relationship, and the steering wheel is limited based on the maximum steering wheel angle. The second correspondence relationship is the relationship between steering wheel torque, steering wheel angle, and vehicle speed in a steer-by-wire system. The maximum steering wheel rotation angle is determined based on the maximum assist torque provided by the steering motor, and the steering wheel is limited at this position to ensure that the steering wheel angle remains consistent with the expected wheel rotation angle.

Description

Technical Field

[0001] This application relates to the field of vehicles, and in particular to a steer-by-wire control method and device. Background Technology

[0002] The automotive steering system is a crucial component of a car, used to change or maintain its direction of travel. Currently, electric power steering (EPS) is the dominant system in automotive steering systems. Because there is a mechanical connection between the steering wheel and the steering actuator via an intermediate shaft, there is no safety issue related to the steering wheel angle not matching the expected wheel angle.

[0003] The modular structure and freely variable gear ratios of Steering-By-Wire Systems (SBS) offer significant advantages for vehicle performance enhancement, making them a growing trend. Therefore, addressing safety issues related to SBS failure modes is crucial. Current research primarily focuses on mechanical structure design and software control strategies, with limited research on fault handling methods. This is particularly relevant when the driver's steering wheel angle deviates from the expected wheel angle, potentially leading to accidents. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a steer-by-wire control method and device to ensure that the steering wheel angle is consistent with the expected wheel angle. The specific solution is as follows:

[0005] In a first aspect, this application provides a steer-by-wire control method, applied to a steer-by-wire system, comprising:

[0006] When the online steering actuator assembly is in a fault state, the assist torque provided by the steering motor at the target vehicle speed is obtained; the assist torque is determined based on the maximum current provided by the steering motor.

[0007] The maximum steering wheel torque is obtained based on the power assist torque and the first correspondence; the first correspondence is the relationship between steering wheel torque, power assist torque, and vehicle speed in an electric power steering system.

[0008] The maximum steering wheel angle is obtained based on the maximum steering wheel torque and the second correspondence, so as to limit the steering wheel according to the maximum steering wheel angle; the second correspondence is the correspondence between steering wheel torque, steering wheel angle and vehicle speed in the steer-by-wire system.

[0009] Optionally, the second correspondence is obtained based on the third and fourth correspondences; the third correspondence is the correspondence between steering wheel torque, rack force and vehicle speed in the steer-by-wire system, and the fourth correspondence is the correspondence between steering wheel angle, rack force and vehicle speed.

[0010] Optionally, the third correspondence is determined based on the first correspondence.

[0011] Optionally, after obtaining the maximum steering wheel angle based on the maximum steering wheel torque and the second correspondence, the method further includes:

[0012] At the maximum steering wheel angle, the steering wheel simulator assembly outputs a resistance torque of 10-100 N·m.

[0013] Optionally, the method further includes:

[0014] When the online steering actuator assembly is in a fault state, the fault state is sent to the CAN network.

[0015] Secondly, embodiments of this application also provide a steer-by-wire control device, applied to a steer-by-wire system, comprising:

[0016] The acquisition unit is used to acquire the assist torque provided by the steering motor at the target vehicle speed when the online steering actuator assembly is in a fault state; the assist torque is determined based on the maximum current provided by the steering motor.

[0017] The first determining unit is used to obtain the maximum steering wheel torque based on the power assist torque and the first correspondence relationship; the first correspondence relationship is the correspondence between steering wheel torque, power assist torque and vehicle speed in the electric power steering system.

[0018] The second determining unit is used to obtain the maximum steering wheel angle based on the maximum steering wheel torque and the second correspondence, so as to limit the steering wheel according to the maximum steering wheel angle; the second correspondence is the correspondence between the steering wheel torque, the steering wheel angle and the vehicle speed in the steer-by-wire system.

[0019] Optionally, the second determining unit is configured to:

[0020] The second correspondence is obtained based on the third and fourth correspondences; the third correspondence is the correspondence between the steering wheel torque, rack force and vehicle speed in the steer-by-wire system, and the fourth correspondence is the correspondence between the steering wheel angle and rack force and vehicle speed.

[0021] Optionally, the third correspondence is determined based on the first correspondence.

[0022] Optionally, the device further includes:

[0023] The output unit is used to control the steering wheel simulator assembly to output a drag torque of 10-100 N·m at the maximum steering wheel angle.

[0024] Optionally, the device further includes:

[0025] The notification unit is used to send the fault status to the CAN network when the online steering actuator assembly is in a fault state.

[0026] This application provides a steer-by-wire control method and apparatus, applied to a steer-by-wire system. When the steer-by-wire actuator assembly is in a fault state, the assist torque provided by the steering motor at the target vehicle speed is obtained; the assist torque is determined based on the maximum current provided by the steering motor; then, the maximum steering wheel torque is obtained based on the assist torque and a first correspondence relationship; the first correspondence relationship is the relationship between steering wheel torque, assist torque, and vehicle speed in an electric power steering system; finally, the maximum steering wheel angle is obtained based on the maximum steering wheel torque and a second correspondence relationship, so as to limit the steering wheel based on the maximum steering wheel angle; the second correspondence relationship is the relationship between steering wheel torque, steering wheel angle, and vehicle speed in a steer-by-wire system. It is evident that in redundant mode, when one or more branches of the steer-by-wire actuator assembly fail, resulting in insufficient steering motor assistance, the maximum steering wheel rotation angle is determined based on the maximum assist torque provided by the steering motor. The steering wheel is then limited at this position to ensure that the steering wheel angle does not exceed this position, thus maintaining a high degree of consistency between the steering wheel angle and the expected wheel angle. This fills the gap in current steer-by-wire system fault handling methods and ensures the safety and reliability of the steer-by-wire system. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the steer-by-wire system.

[0029] Figure 2 A schematic flowchart of a steer-by-wire control method provided in an embodiment of this application is shown;

[0030] Figure 3 A boost curve for EPS provided in an embodiment of this application;

[0031] Figure 4 A curve showing the relationship between steering wheel angle, rack force, and vehicle speed is provided for an embodiment of this application.

[0032] Figure 5 This is a structural block diagram of a steer-by-wire control device provided in an embodiment of this application. Detailed Implementation

[0033] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0034] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0035] As described in the background section, with steer-by-wire systems, there may be a discrepancy between the driver's steering wheel angle and the expected wheel angle, which can easily lead to safety accidents. (Reference) Figure 1 The diagram shows the structure of a steer-by-wire system. The system includes a steering wheel simulator assembly, a steering actuator assembly, and a main controller. The simulator control unit controls the steering wheel simulator assembly, which is controlled by the main controller and can be connected to a CAN network. The main function of the steering wheel simulator assembly is to convert the driver's steering intention (by measuring the steering wheel angle) into a digital signal and transmit it to the main controller. The actuator control unit controls the steering actuator assembly, which is also controlled by the main controller and can be connected to a CAN network. The function of the steering actuator assembly is to receive commands from the main controller and control the steering wheel rotation via the steering motor controller to achieve the driver's steering intention.

[0036] The inventors discovered that for steer-by-wire actuator assemblies with dual or multiple redundancy structures, there is a possibility of one or more branches malfunctioning. In this case, the steering actuator assembly enters a fail mode, causing the power assist provided by the steering motor to be only 3 / 4 or 1 / 2 of that under normal operating conditions. Because the system provides insufficient power assist, and there is no mechanical connection between the steering wheel simulator assembly and the steering actuator assembly, it is easy for the actuator assembly to not actually turn the steering wheel to the corresponding angle after a certain angle has been turned (i.e., the rack does not reach the appropriate position). This results in the driver turning the steering wheel at an angle greater than the expected wheel angle, potentially causing a safety accident.

[0037] Based on the above technical problems, this application provides a steer-by-wire control method and device, applied to a steer-by-wire system. When the steer-by-wire actuator assembly is in a fault state, the assist torque provided by the steering motor at the target vehicle speed is obtained; the assist torque is determined based on the maximum current provided by the steering motor; then, the maximum steering wheel torque is obtained based on the assist torque and a first correspondence; the first correspondence is the relationship between steering wheel torque, assist torque, and vehicle speed in an electric power steering system; finally, the maximum steering wheel angle is obtained based on the maximum steering wheel torque and a second correspondence, so as to limit the steering wheel based on the maximum steering wheel angle; the second correspondence is the relationship between steering wheel torque, steering wheel angle, and vehicle speed in a steer-by-wire system. It is evident that in redundant mode, when one or more branches of the steer-by-wire actuator assembly fail, resulting in insufficient steering motor assistance, the maximum steering wheel rotation angle is determined based on the maximum assist torque provided by the steering motor. The steering wheel is then limited at this position to ensure that the steering wheel angle does not exceed this position, thus maintaining a high degree of consistency between the steering wheel angle and the expected wheel angle. This fills the gap in current steer-by-wire system fault handling methods and ensures the safety and reliability of the steer-by-wire system.

[0038] For ease of understanding, the following detailed description, in conjunction with the accompanying drawings, provides an embodiment of a steer-by-wire control method and apparatus provided in this application.

[0039] refer to Figure 2 The diagram shown is a flowchart of a steer-by-wire control method provided in an embodiment of this application. The method may include the following steps.

[0040] S101, when the online steering actuator assembly is in a fault state, obtains the assist torque provided by the steering motor at the target vehicle speed.

[0041] In this embodiment, when an electrical fault occurs in a branch of the steering actuator assembly of the steer-by-wire system, the system enters a Fail Operation mode. This mode allows the system to acquire the assist torque provided by the steering motor at the target vehicle speed, where the assist torque is determined based on the maximum current provided by the steering motor. Specifically, the simulator control unit calculates the maximum assist torque T that the steering motor can provide based on the maximum current it can provide in the fault mode. fmax Under normal circumstances, the maximum assist torque in fault mode is 50% of the maximum assist torque in normal mode.

[0042] S102, the maximum steering wheel torque is obtained based on the power assist torque and the first correspondence.

[0043] In this embodiment, the electric power steering system (EPS) has a first correspondence, namely, the correspondence between steering wheel torque, assist torque, and vehicle speed. This first correspondence can also be applied to the steer-by-wire system (SBS), where the steering wheel torque is generated by the driver's hands acting on the steering wheel. Therefore, based on the correspondence between steering wheel torque and assist torque at the target vehicle speed, the steering wheel torque can be determined from the assist torque. Since the assist torque is at its maximum value, the steering wheel torque is also at its maximum value. The first correspondence, which is the relationship between steering wheel torque, assist torque, and vehicle speed in the electric power steering system, can be denoted as the Boost curve.

[0044] refer to Figure 3 The diagram shows a Boost curve for an EPS (Electric Power Steering) according to an embodiment of this application. The horizontal axis represents the steering wheel torque (Nm), and the vertical axis represents the power assist torque provided by the steering motor (Nm). Curves one through six represent the relationship between steering wheel torque and power assist torque at different vehicle speeds: v1 = 0 m / s, v2 = 10 m / s, v3 = 30 m / s, v4 = 50 m / s, v5 = 80 m / s, v6 ≥ 100 m / s. It can be seen that the curve becomes flatter as the vehicle speed increases, which ensures high steering sensitivity at low speeds and steering safety at high speeds. Furthermore, at the same vehicle speed, steering wheel torque and power assist torque are positively correlated. It is understood that the vehicle speed can be calibrated and changed according to different vehicles, and the maximum steering wheel torque T that can be achieved can be deduced from the Boost curve. handmax .

[0045] S103, the maximum steering wheel angle is obtained based on the maximum steering wheel hand torque and the second corresponding relationship, so as to limit the steering wheel according to the maximum steering wheel angle.

[0046] In this embodiment, the second correspondence is the relationship between steering wheel torque, steering wheel angle, and vehicle speed in the online steering system. Specifically, the actuator control unit can retrieve the "steering wheel torque - steering wheel angle - vehicle speed" relationship curve, based on T... handmax Based on the vehicle speed, calculate the maximum steering angle α that the steering wheel can achieve. fmax And send it to the CAN network. At the target vehicle speed v i The relationship between steering wheel torque and steering wheel angle is as follows:

[0047] α i =g i (T hand v = v i

[0048] In the formula, Thand The steering wheel torque is given by i = 1, 2, 3, 4, 5, 6, v1 = 0 m / s, v2 = 10 m / s, v3 = 30 m / s, v4 = 50 m / s, v5 = 80 m / s, and v6 ≥ 100 m / s. The vehicle speed can be calibrated and changed according to different vehicles.

[0049] In this embodiment, the second correspondence is obtained based on the third and fourth correspondences. The third correspondence is the correspondence between steering wheel torque, rack force, and vehicle speed in the online steering system, and is determined based on the first correspondence. The fourth correspondence is the correspondence between steering wheel angle, rack force, and vehicle speed, thus determining the correspondence between steering wheel torque, steering wheel angle, and vehicle speed.

[0050] Specifically, the steering motor in the SBS system provides the assist torque T SBS The power assist torque T provided by the steering motor in the EPS system can be used as a reference. EPS Once determined, the third correspondence can be determined based on the first correspondence. Since the steering wheel torque of a steer-by-wire system cannot be superimposed on the EPS power assist torque, the power assist torque provided by the motor needs to be increased by the steering wheel torque for a steer-by-wire system. This can be expressed by the following formula:

[0051] T SBS =T EPS +T hand / i

[0052] Among them, T SBS This indicates the assist torque provided by the steering motor at a given vehicle speed v; T EPS T represents the steering motor assist torque provided by the EPS at a certain vehicle speed v; hand The value of 'i' represents the steering wheel torque of EPS at a certain vehicle speed 'v'; 'i' represents the reduction ratio of the motor reduction mechanism of SBS.

[0053] In this embodiment, since SBS still requires steering wheel feel, this function is performed by the steering wheel simulator assembly, thus still having similar... Figure 3 The Boost curve shown is different from the EPS curve in that the SBS curve differs in the change of the ordinate, which is determined by T. EPS Replace with T SBS Furthermore, although the calibration results differ between different vehicle models, the logical relationship remains the same.

[0054] In this embodiment of the application, due to the assist torque T provided by the steering motor SBS and rack force F iProportional to each other, the vertical axis of the Boost curve can be represented by the rack force. Thus, based on the first correspondence, the third correspondence can be determined. That is, based on the correspondence between steering wheel torque, assist torque, and vehicle speed in the electric power steering system, the correspondence between steering wheel torque, rack force, and vehicle speed in the wire-controlled steering system can be determined. At different vehicle speeds v, the steering wheel torque T... hand and rack force F i The correspondence between them can be expressed by the following equation:

[0055] F i =f i (T hand v = v i

[0056] In the formula, i = 1, 2, 3, 4, 5, 6, v1 = 0 m / s, v2 = 10 m / s, v3 = 30 m / s, v4 = 50 m / s, v5 = 80 m / s, v6 ≥ 100 m / s. The vehicle speed can be calibrated and changed according to different vehicles.

[0057] In this embodiment, the fourth correspondence is the relationship between steering wheel angle, rack force, and vehicle speed. Since steering must be able to turn both left and right, the steering gear has a "left tie rod" and a "right tie rod," which can provide left and right rack forces. The total rack force is obtained by superimposing the left and right rack forces. (Refer to...) Figure 4 The figure shows a curve illustrating the relationship between steering wheel angle and rack force at a vehicle speed of 0, provided in an embodiment of this application. The horizontal axis represents the steering wheel angle in degrees, and the vertical axis represents the rack force in kN. As the vehicle speed increases, the rack force decreases at the same steering wheel angle. Therefore, at different vehicle speeds, the steering wheel angle α and rack force F... i The relationship between them can be expressed by the following equation:

[0058] F i =k i (α)v=v i

[0059] In the formula, i = 1, 2, 3, 4, 5, 6, v1 = 0 m / s, v2 = 10 m / s, v3 = 30 m / s, v4 = 50 m / s, v5 = 80 m / s, v6 ≥ 100 m / s. The vehicle speed can be calibrated and changed for different projects.

[0060] In this embodiment, the maximum steering wheel angle is obtained based on the maximum steering wheel torque and the second corresponding relationship, and the steering wheel is limited according to the maximum steering wheel angle. Specifically, the control unit of the steering wheel simulator assembly receives the position information α of the maximum steering wheel angle from the CAN network. fmaxThe system collects fault information and applies a software hard limit at this location to ensure that the steering wheel angle that the driver can turn does not exceed the calculated limit position.

[0061] In this embodiment, after obtaining the maximum steering wheel angle based on the maximum steering wheel hand torque and the second corresponding relationship, the steering wheel simulator assembly can be controlled to output a resistance torque of 10-100 N·m at the maximum steering wheel angle. A software hard limit method can be used to set the steering wheel simulator assembly to output the maximum current at this position, causing the steering wheel simulator assembly to generate the maximum resistance torque. This resistance torque can be 50 N·m or 80 N·m, ensuring that the hand torque of an adult under extreme conditions does not exceed the resistance torque provided by the steering wheel simulator assembly.

[0062] In this embodiment of the application, when the online steering actuator assembly is in a fault state, it can send the fault state to the CAN network, that is, set the fault state bit and send it to the CAN network.

[0063] In the embodiments of this application, the actuator assembly of the steer-by-wire system is generally a redundant structure. When one or more branches of the steer-by-wire actuator assembly fail, resulting in insufficient steering assistance, the steering wheel angle is guaranteed to remain highly consistent with the expected wheel angle. The method is simple, practical, ensures the safety of drivers and passengers, and improves the driving experience.

[0064] This application provides a steer-by-wire control method applied to a steer-by-wire system. When the steer-by-wire actuator assembly is in a fault state, the assist torque provided by the steering motor at the target vehicle speed is obtained. The assist torque is determined based on the maximum current provided by the steering motor. Then, the maximum steering wheel torque is obtained based on the assist torque and a first correspondence relationship. The first correspondence relationship is the relationship between steering wheel torque, assist torque, and vehicle speed in an electric power steering system. Finally, the maximum steering wheel angle is obtained based on the maximum steering wheel torque and a second correspondence relationship, so as to limit the steering wheel based on the maximum steering wheel angle. The second correspondence relationship is the relationship between steering wheel torque, steering wheel angle, and vehicle speed in a steer-by-wire system. It is evident that in redundant mode, when one or more branches of the steer-by-wire actuator assembly fail, resulting in insufficient steering motor assistance, the maximum steering wheel rotation angle is determined based on the maximum assist torque provided by the steering motor. The steering wheel is then limited at this position to ensure that the steering wheel angle does not exceed this position, thus maintaining a high degree of consistency between the steering wheel angle and the expected wheel angle. This fills the gap in current steer-by-wire system fault handling methods and ensures the safety and reliability of the steer-by-wire system.

[0065] Based on the above-described steer-by-wire control method, this application also provides a steer-by-wire control device, see reference. Figure 5The diagram shown is a structural block diagram of a steer-by-wire control device provided in an embodiment of this application. The device may include:

[0066] The acquisition unit 100 is used to acquire the assist torque provided by the steering motor at the target vehicle speed when the online steering actuator assembly is in a fault state; the assist torque is determined based on the maximum current provided by the steering motor.

[0067] The first determining unit 200 is used to obtain the maximum steering wheel torque based on the power assist torque and the first correspondence relationship; the first correspondence relationship is the correspondence between steering wheel torque, power assist torque and vehicle speed in the electric power steering system;

[0068] The second determining unit 300 is used to obtain the maximum steering wheel angle based on the maximum steering wheel torque and the second correspondence, so as to limit the steering wheel according to the maximum steering wheel angle; the second correspondence is the correspondence between the steering wheel torque, the steering wheel angle and the vehicle speed in the steer-by-wire system.

[0069] Optionally, the second determining unit is configured to:

[0070] The second correspondence is obtained based on the third and fourth correspondences; the third correspondence is the correspondence between the steering wheel torque, rack force and vehicle speed in the steer-by-wire system, and the fourth correspondence is the correspondence between the steering wheel angle and rack force and vehicle speed.

[0071] Optionally, the third correspondence is determined based on the first correspondence.

[0072] Optionally, the device further includes:

[0073] The output unit is used to control the steering wheel simulator assembly to output a drag torque of 10-100 N·m at the maximum steering wheel angle.

[0074] Optionally, the device further includes:

[0075] The notification unit is used to send the fault status to the CAN network when the online steering actuator assembly is in a fault state.

[0076] This application provides a steer-by-wire control device applied to a steer-by-wire system. The device includes an acquisition unit for acquiring the assist torque provided by the steering motor at a target vehicle speed when the steer-by-wire actuator assembly is in a fault state; the assist torque is determined based on the maximum current provided by the steering motor. A first determination unit is used to obtain the maximum steering wheel torque based on the assist torque and a first correspondence relationship; the first correspondence relationship is the relationship between steering wheel torque, assist torque, and vehicle speed in an electric power steering system. A second determination unit is used to obtain the maximum steering wheel angle based on the maximum steering wheel torque and the second correspondence relationship, so as to limit the steering wheel position based on the maximum steering wheel angle; the second correspondence relationship is the relationship between steering wheel torque, steering wheel angle, and vehicle speed in the steer-by-wire system. It is evident that in redundant mode, when one or more branches of the steer-by-wire actuator assembly fail, resulting in insufficient steering motor assistance, the maximum steering wheel rotation angle is determined based on the maximum assist torque provided by the steering motor. The steering wheel is then limited at this position to ensure that the steering wheel angle does not exceed this position, thus maintaining a high degree of consistency between the steering wheel angle and the expected wheel angle. This fills the gap in current steer-by-wire system fault handling methods and ensures the safety and reliability of the steer-by-wire system.

[0077] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on its differences from other embodiments. In particular, the apparatus embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0078] The above description is merely a preferred embodiment of this application. Although this application has disclosed preferred embodiments above, it is not intended to limit this application. Any person skilled in the art can make many possible variations and modifications to the technical solutions of this application using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of this application. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the content of the technical solutions of this application shall still fall within the protection scope of the technical solutions of this application.

Claims

1. A steer-by-wire control method, characterized in that, Applications in steer-by-wire systems include: When the online steering actuator assembly is in a fault state, the assist torque provided by the steering motor at a target vehicle speed is obtained; the target vehicle speed is a vehicle speed value pre-calibrated in the first correspondence and the second correspondence; the assist torque is determined based on the maximum current that the steering motor can provide in the fault mode; The maximum steering wheel torque is obtained based on the power assist torque and the first correspondence; the first correspondence is the relationship between steering wheel torque, power assist torque, and vehicle speed in an electric power steering system. The maximum steering wheel angle is obtained based on the maximum steering wheel torque and the second correspondence, and the steering wheel is limited according to the maximum steering wheel angle; the second correspondence is the relationship between steering wheel torque, steering wheel angle and vehicle speed in the steer-by-wire system. The second correspondence is obtained based on the third and fourth correspondences; the third correspondence is the correspondence between steering wheel torque, rack force and vehicle speed in the steer-by-wire system, and the fourth correspondence is the correspondence between steering wheel angle, rack force and vehicle speed. The third correspondence is determined based on the first correspondence, and the determination of the third correspondence includes: based on the first correspondence and the relation T. SBS =T EPS +T hand / i, determine the correspondence between steering wheel torque, power assist torque and vehicle speed in the steer-by-wire system, and convert the power assist torque in the correspondence into rack force based on the fact that the power assist torque in the steer-by-wire system is proportional to the rack force; Among them, T SBS T represents the assist torque provided by the steering motor of the steer-by-wire system at the target vehicle speed. EPS T represents the assist torque provided by the steering motor of the electric power steering system at the target vehicle speed. hand The electric power steering system represents the steering wheel torque at the target vehicle speed, and i represents the reduction ratio of the motor reduction mechanism of the steer-by-wire system. The determination of the fourth correspondence includes: superimposing the left rack force provided by the left tie rod corresponding to the steering gear of the steer-by-wire system with the right rack force provided by the right tie rod to obtain the total rack force, and determining the fourth correspondence based on the relationship between the steering wheel angle and the total rack force at different vehicle speeds; The actuator control unit of the steer-by-wire system sends the maximum steering wheel angle to the CAN network; the control unit of the steering wheel simulator assembly receives the maximum steering wheel angle and fault information from the CAN network, and performs a software hard limit at the maximum steering wheel angle.

2. The method according to claim 1, characterized in that, After obtaining the maximum steering wheel angle based on the maximum steering wheel torque and the second correspondence, the method further includes: At the maximum steering wheel angle, the steering wheel simulator assembly outputs a resistance torque of 10-100 N·m.

3. The method according to any one of claims 1-2, characterized in that, The method further includes: When the online steering actuator assembly is in a fault state, the fault state is sent to the CAN network.

4. A steer-by-wire control device, characterized in that, Applications in steer-by-wire systems include: An acquisition unit is used to acquire the assist torque provided by the steering motor at a target vehicle speed when the online steering actuator assembly is in a fault state; the target vehicle speed is a pre-calibrated vehicle speed value in a first correspondence relationship and a second correspondence relationship; the assist torque is determined based on the maximum current that the steering motor can provide in the fault mode; a first determination unit is used to obtain the maximum steering wheel torque based on the assist torque and the first correspondence relationship; the first correspondence relationship is the correspondence between steering wheel torque, assist torque and vehicle speed in the electric power steering system; The second determining unit is used to obtain the maximum steering wheel angle based on the maximum steering wheel torque and the second correspondence, so as to limit the steering wheel according to the maximum steering wheel angle; the second correspondence is the correspondence between steering wheel torque, steering wheel angle and vehicle speed in the steer-by-wire system; The second determining unit is further configured to obtain the second correspondence relationship based on the third and fourth correspondence relationships; the third correspondence relationship is the correspondence between steering wheel torque, rack force, and vehicle speed in the steer-by-wire system, and the fourth correspondence relationship is the correspondence between steering wheel angle, rack force, and vehicle speed; based on the first correspondence relationship and the formula T... SBS =T EPS +T hand / i, determine the correspondence between steering wheel torque, power assist torque and vehicle speed in the steer-by-wire system, and convert the power assist torque in the correspondence into rack force according to the fact that the power assist torque in the steer-by-wire system is proportional to the rack force, so as to obtain the third correspondence; Among them, T SBS T represents the assist torque provided by the steering motor of the steer-by-wire system at the target vehicle speed. EPS T represents the assist torque provided by the steering motor of the electric power steering system at the target vehicle speed. hand The electric power steering system represents the steering wheel torque at the target vehicle speed, and i represents the reduction ratio of the motor reduction mechanism of the steer-by-wire system. The second determining unit is also used to superimpose the left rack force provided by the left tie rod corresponding to the steering gear of the steer-by-wire system with the right rack force provided by the right tie rod to obtain the total rack force, and determine the fourth correspondence relationship according to the relationship between the steering wheel angle and the total rack force at different vehicle speeds; The second determining unit is further configured to send the maximum steering wheel angle to the CAN network, so that the control unit of the steering wheel simulator assembly receives the maximum steering wheel angle and fault information from the CAN network, and performs a software hard limit at the maximum steering wheel angle.

5. The apparatus according to claim 4, characterized in that, The device further includes: The output unit is used to control the steering wheel simulator assembly to output a drag torque of 10-100 N·m at the maximum steering wheel angle.

6. The apparatus according to any one of claims 4-5, characterized in that, The device further includes: The notification unit is used to send the fault status to the CAN network when the online steering actuator assembly is in a fault state.

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