A roll-over prevention motion planning method for a steer-by-wire multi-axle steering system

Abstract

The application discloses a rollover prevention motion planning method for a steer-by-wire multi-axle steering system, comprising the following steps: step one: based on a Bezier curve and a spline curve method, a trajectory candidate set generation model is constructed; step two: further introducing a vehicle dynamics constraint condition, considering a maximum steering angle, a maximum lateral acceleration and an influence of load forward movement on a front axle vertical load in a braking process under a multi-axle steering system, a nonlinear optimization model is established; step three: based on the accurate modeling of the load forward movement effect in step two, a rollover risk assessment model based on roll energy accumulation is proposed; step four: on the basis of step three, a speed profile optimization and trajectory mapping are carried out, a gradient descent method and a cooperative control strategy are used to ensure that the vehicle travels at a smooth speed under different path curvatures, and real-time response and accurate control of the vehicle to a complex dynamic environment are realized. The application realizes smooth transition of direction change, and effectively improves the accuracy and adaptability of path generation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of motion planning of intelligent electric trucks, and in particular to a rollover prevention motion planning method for a steer-by-wire multi-axle steering system. BACKGROUND

[0002] With the popularization of intelligent trucks, trajectory planning and motion planning technology as the core technology of intelligent truck safety and precise task execution directly affects its application and transformative role in the global economy. Current trajectory planning methods are mainly divided into two directions: fast planning based on geometric path and optimization planning based on dynamic model. However, these methods have limitations in dealing with the high center of gravity and large inertia characteristics of heavy trucks, especially the lack of consideration of rollover risk, which restricts the development of autonomous truck technology. In the existing research on rollover prevention motion planning methods, for example: Chinese invention patent application No. CN202011641346.1, named "path tracking optimization control method for distributed drive unmanned vehicle", the invention first determines the relevant parameters according to the vehicle rollover and sideslip conditions, then designs the active speed limit activation condition based on the speed distribution interval, so as to obtain the vehicle expected longitudinal force of the vehicle in different speed distribution intervals; then determine the optimal objective function of multiple constraints, and propose the weight coefficient adjustment method of different motor failure and failure form, and obtain the drive and brake torque of each motor through the effective set algorithm, finally, according to the vehicle dynamics model, the target function of vehicle trajectory tracking is proposed to realize trajectory tracking; Chinese invention patent application No. CN202211564129.6, named "multi-axle special vehicle safety trajectory planning method considering obstacle avoidance stability", the invention establishes a five-axle special vehicle dynamics model, refers to the relative motion state of surrounding vehicles and special vehicles, and establishes a five-axle special vehicle dynamics constraint model based on vehicle yaw stability and roll safety, so as to design an MPC trajectory planner to generate a safe driving trajectory. This method can generate a vehicle driving trajectory that realizes stable obstacle avoidance, and realizes safe and stable high-speed driving of multi-axle special vehicles.

[0003] However, the existing anti-rollover motion planning method has the following two potential problems: 1. The existing anti-rollover motion planning method has limitations in the accuracy and adaptability of path generation: Although existing anti-rollover technologies, such as Chinese invention patent application number CN202011641346.1: "Path tracking optimization control method for distributed drive unmanned vehicle", have achieved certain results on two-axle vehicles, these methods often ignore the smoothness and continuity in the path generation process, especially under the complex steering requirements of multi-axle vehicles. These methods fail to fully utilize suitable path planning techniques, resulting in inaccurate path generation and inability to adapt to changing road conditions and vehicle dynamics in practical applications. 2. The existing multi-axle vehicle anti-rollover motion planning does not fully integrate vehicle dynamics constraints and load forward shift effect: Existing multi-axle vehicle anti-rollover motion planning methods, such as Chinese invention patent application number CN202211564129.6: "Multi-axle special vehicle safety trajectory planning method considering obstacle avoidance stability", although they begin to consider the special requirements of multi-axle vehicles, they often fail to fully integrate vehicle dynamics constraints, especially under extreme conditions such as sudden braking, the impact of load forward shift on vehicle stability. These methods fail to establish a nonlinear optimization model that comprehensively considers the maximum steering angle, maximum lateral acceleration, and load forward shift effect during braking, resulting in insufficient path following ability and driving safety of the vehicle under complex dynamic conditions in practical applications.

[0004] Therefore, how to more accurately consider the dynamic characteristics of the vehicle in trajectory planning and motion planning, and optimize the anti-rollover performance, especially under the complex control requirements of multi-axle steering systems, has become a key factor restricting the further development of intelligent truck technology. SUMMARY

[0005] This section aims to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification to avoid obscuring the purpose of this section, abstract and title, and such simplifications or omissions cannot be used to limit the scope of the invention.

[0006] In view of the above-mentioned problems of the existing anti-rollover motion planning method for the steer-by-wire multi-axle steering system, the present invention is proposed.

[0007] Therefore, the purpose of the present invention is to provide an anti-rollover motion planning method for a steer-by-wire multi-axle steering system, which solves the problem in the prior art that the anti-rollover control strategy is too conservative and cannot effectively ensure the stability of the vehicle under complex road conditions when performing rollover risk assessment and motion planning due to the failure to fully consider the dynamic characteristics of the vehicle's center of gravity shift and the coordination between trajectory planning and motion planning.

[0008] To solve the above technical problems, the application provides the following technical scheme: a rollover prevention motion planning method for a drive-by-wire multi-axle steering system, comprising the following steps:

[0009] Step one: based on the Bezier curve and spline curve method, a trajectory candidate set generation model is constructed, a preliminary path candidate set is first generated, the smoothness and continuity of the path are ensured through curve interpolation technology, and the smoothness and continuity of the direction change are ensured by optimizing the path curvature and tangent direction;

[0010] Step two: on the basis of step one, further introduce the vehicle dynamics constraint condition, consider the maximum steering angle under the multi-axle steering system, the maximum lateral acceleration and the influence of load forward movement on the front axle vertical load in the braking process to establish a nonlinear optimization model, and through the optimization of path curvature and load forward movement effect, ensure that the generated path candidate set still has high stability under emergency braking conditions;

[0011] Step three: based on the accurate modeling of the load forward movement effect in step two, a rollover risk assessment model based on roll energy accumulation is proposed, the roll energy and its cumulative effect are calculated to establish a rollover risk assessment threshold, and it is coupled with the path curvature and vehicle speed to optimize the joint strategy of path and speed, so as to reduce the rollover risk and improve the driving efficiency;

[0012] Step four: on the basis of step three, the speed profile optimization and trajectory mapping are carried out, the gradient descent method and collaborative control strategy are used to ensure that the vehicle travels at a stable speed under different path curvatures, and through the collaborative adjustment of the multi-axle steering system, the optimized trajectory and speed are mapped to the wheel angle of each steering axle, so as to obtain the wheel angle motion planning result which can ensure the stability and rollover prevention performance of the vehicle, and realize real-time response and accurate control to complex dynamic environment.

[0013] As a preferred scheme of the rollover prevention motion planning method for the drive-by-wire multi-axle steering system, wherein: the step one specifically comprises:

[0014] 1.1) preliminary path candidate set generation: using the Bezier curve and spline curve method, a preliminary path candidate set is generated according to the preset path control points, assuming that the path control points are , the generated Bezier curve is represented as: , wherein, is a parameter, is the path point of the Bezier curve;

[0015] 1.2) based on the path candidate set in 1.1), the smoothness and continuity of the path is optimized: the path generated in 1.1) is smoothed by using the spline interpolation technology to ensure the continuity of the path, assuming that the spline interpolation function is Path curvature and tangent direction The optimization objective function is: By optimizing the above objective function, the smoothness and continuity of the path are ensured;

[0016] 1.3) Optimization of smoothness of direction change: Based on 1.2), further optimize the curvature κ(x) and tangent direction of the path. To ensure the smoothness of direction changes, the smoothness of path direction changes can be achieved by minimizing the second derivative of the path curvature: .

[0017] As a preferred embodiment of the anti-rollover motion planning method for a steer-by-wire multi-axis system described in this invention, step two specifically includes:

[0018] 2.1) Based on the optimized path in 1.3), considering vehicle dynamics constraints: introduce the maximum steering angle of the multi-axle steering system. and maximum lateral acceleration Due to limitations, the path curvature optimization model in 1.3) is adjusted to ensure vehicle stability under dynamic conditions. The optimization formula for path curvature becomes: Where v is the vehicle speed;

[0019] 2.2) Effect of load forward shift during braking on front axle vertical load: Considering the load forward shift effect during braking, adjust the front axle vertical load. Based on Newton's second law, the change in vertical load on the front axle caused by the forward shift of the load. Represented as: ,in, For the height of the center of mass, Wheelbase For vehicle quality, This refers to the vehicle's longitudinal acceleration;

[0020] 2.3) Based on the load shifting effect in 2.2), optimize the path curvature and load distribution: Incorporate the load shifting effect into the path optimization model, consider the influence of load distribution on path curvature, and ensure that the generated path candidate set still has high stability under emergency braking conditions. The adjusted optimization model is as follows: .

[0021] As a preferred embodiment of the anti-rollover motion planning method for a steer-by-wire multi-axis system described in this invention, step three specifically includes:

[0022] 3.1) Based on the load distribution in 2.3), a roll energy accumulation model is proposed: The roll energy is calculated. And its cumulative effect, to assess rollover risk, the roll energy is expressed as: ;

[0023] 3.2) Establishing the rollover risk assessment threshold: Based on the rollover energy accumulation effect in 3.1), the rollover risk assessment threshold is established . Assuming that the rollover risk threshold is (where γ is the safety factor), the rollover risk condition is: ;

[0024] 3.3) Coupling optimization of path curvature and speed: The rollover risk assessment threshold is combined with the path curvature κ(x) and the vehicle speed v(x), and the joint strategy of the path and the speed is optimized to reduce the rollover risk and improve the driving efficiency, and the optimization objective function is: .

[0025] As a preferred scheme of the anti-rollover motion planning method for the steer-by-wire multi-axle steering system, wherein: the step four specifically comprises:

[0026] 4.1) Speed profile optimization based on the coupling optimization results in 3.3): The gradient descent method is used to optimize the speed profile v(x) of the vehicle under different path curvatures, to ensure that the vehicle travels at a smooth speed, and the optimization objective function of the speed profile is:

[0027] 4.2) Cooperative adjustment of the multi-axle steering system: Based on the optimized speed profile and the path curvature in 4.1), the cooperative adjustment of the multi-axle steering system is performed, and the optimized speed profile is mapped to the wheel angle of each steering axle, and the formula is: , wherein L i is the wheelbase of the steering axle, and h i is the height of the steering axle;

[0028] 4.3) Real-time response and precise control: The wheel angle motion planning results in 4.2) are fed back to the central control system to ensure the stability and anti-rollover performance of the vehicle in complex dynamic environments, and to improve the real-time response ability of the system.

[0029] As a preferred scheme of the anti-rollover motion planning method for the steer-by-wire multi-axle steering system, wherein: the anti-rollover motion planning method for the steer-by-wire multi-axle steering system is based on the steer-by-wire multi-axle steering system, which includes: wheels, a sensor module, a central controller, a power steering device, a main drive device, a rollover warning system, a mechanical drive device, and a data bus module;

[0030] The input of the sensor module is the real-time dynamic data of the vehicle during driving, including lateral acceleration, longitudinal acceleration, vehicle speed, steering wheel angle, steering angle of each axle and side slip rate of the wheel; the output is processed vehicle dynamic parameter data, which is transmitted to the central controller;

[0031] The input of the central controller is the vehicle dynamic parameter data from the sensor module, and the central controller is connected with the power steering device, the active drive device and the rollover early warning system through the control bus or signal line to realize accurate control and information transmission; the output of the central controller is divided into three parts: the steering angle control instruction of each axle output to the power steering device, which is used to adjust the actual steering angle of each wheel; the steering adjustment torque control signal output to the active drive device to ensure that the active drive device executes the steering strategy set by the central controller; the lateral load transfer rate and the center of gravity position change information output to the rollover early warning system for rollover risk assessment;

[0032] The power steering device includes a steering motor, a steering motor controller, a steering wheel module, a CAN bus and a road feeling motor and a road feeling motor controller; the housing of the steering motor and the steering motor controller are integrally cast, the steering motor controller transmits the steering angle instruction of the central controller to the steering motor through the CAN bus, the steering motor is mechanically connected with the active drive device, the active drive device is directly connected with the wheel steering shaft through mechanical connection, the road feeling motor controller transmits the signal of the central controller to the road feeling motor through the CAN bus, and the road feeling motor is connected with the steering wheel module through a mechanical device to feedback the road feeling torque;

[0033] The input of the active drive device is the steering angle adjustment torque output by the power steering device, and the output is the actual steering angle of each steering axle; the specific components of the active drive device include a steering motor controller, a steering motor shaft, a planetary gear primary reduction device, a worm gear secondary reduction device, a steering column, a gear rack mechanism, a steering tie rod, a steering trapezoidal arm, a steering knuckle arm, a steering knuckle and an active drive controller; the specific connection relationship is that the steering motor controller controls the rotation of the steering motor, the steering motor is connected with the active drive controller through the steering motor shaft, the active drive controller is connected with the planetary gear primary reduction device, the primary planetary gear reduction mechanism is mechanically connected with the worm gear secondary reduction mechanism, the worm gear secondary reduction mechanism transmits power to the gear rack mechanism through the steering column, the gear rack mechanism drives the steering trapezoidal arm through the steering tie rod, and the steering trapezoidal arm is connected with the steering knuckle through the steering knuckle arm to drive the wheel to rotate;

[0034] The input of the rollover early warning system is the lateral load transfer rate and the center of gravity position change information provided by the central controller, and the output is a rollover risk early warning signal or an emergency operation instruction, which is fed back to the central controller and transmitted to the power steering device to adjust the steering strategy of the vehicle.

[0035] As a preferred scheme of the anti-rollover motion planning method for the drive-by-wire multi-axle steering system, each sensor of the sensor module is connected with the central controller through the data bus module and is responsible for providing real-time vehicle dynamic information for the central controller, and the module mainly comprises: lateral acceleration sensors located at the front and rear parts of the vehicle for measuring lateral acceleration; longitudinal acceleration sensors located near the center of gravity of the vehicle for measuring longitudinal acceleration; steering wheel angle sensors installed on the steering column for detecting the rotation angle and direction of the steering wheel; steering shaft angle sensors installed on the steering shaft for detecting the steering angle of the steering shaft, which are usually composed of multiple sensors; and wheel speed sensors installed on the non-rotating part of the wheel assembly for measuring the wheel speed; each sensor is connected with the central controller through the data bus module.

[0036] As a preferred scheme of the anti-rollover motion planning method for the drive-by-wire multi-axle steering system, the data bus module supports CAN, LIN, FlexRay and Ethernet protocols to meet different types of data transmission requirements.

[0037] The beneficial effects of the present application are as follows:

[0038] 1、The present application not only constructs a trajectory candidate set generation model based on the Bezier curve and the spline curve method to ensure the smoothness and continuity of the path, but also realizes the smooth transition of direction change on the basis of optimizing the path curvature and tangent direction, effectively improving the accuracy and adaptability of path generation.

[0039] 2、The present application further introduces vehicle dynamics constraints, comprehensively considers the maximum steering angle of the multi-axle steering system, the maximum lateral acceleration and the influence of load forward movement on the front axle vertical load during braking, and establishes a nonlinear optimization model. Through optimizing the path curvature and load distribution, the high stability of the generated path candidate set under extreme conditions such as emergency braking is ensured, and the path following ability and driving safety of the vehicle under complex dynamic conditions are improved.

[0040] 3、The application puts forward a rollover risk assessment model based on roll energy accumulation by accurately modeling the load forward effect. By establishing a rollover risk assessment threshold and coupling it with path curvature and vehicle speed, the joint strategy of path and speed is optimized, which effectively reduces the rollover risk and improves the driving efficiency, so that the system can maintain high stability and safety under complex road conditions;

[0041] 4、On the basis of evaluating the rollover risk, the application further optimizes the speed profile and trajectory mapping, through the gradient descent method and the collaborative control strategy of the multi-axle steering system, to ensure that the vehicle travels at a smooth speed under different path curvatures. Finally, through accurate wheel angle motion planning and real-time response control, the stability and rollover prevention performance of the vehicle in complex dynamic environment are realized, which greatly improves the dynamic response ability and overall control performance of the vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor. Among them:

[0043] Figure 1 It is the schematic diagram of the method of the application;

[0044] Figure 2 It is the architecture diagram of the application's line control multi-axle steering system;

[0045] Figure 3 It is the position diagram of the sensor module of the application;

[0046] Figure 4 It is the structure diagram of the active transmission module of the application;

[0047] Figure 5 It is the structure diagram of the power steering module of the application. DETAILED DESCRIPTION

[0048] In order to make the above-mentioned purposes, features and advantages of the application more obvious and easy to understand, the specific embodiments of the application will be described in detail below with reference to the drawings of the specification.

[0049] In the following description, many specific details are set forth in order to provide a thorough understanding of the application, but the application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the application, therefore the application is not limited by the specific embodiments disclosed below.

[0050] Second, the "one embodiment" or "an embodiment" referred to herein means a specific feature, structure, or characteristic under discussion. Thus, "at least one embodiment" does not mean some embodiments but rather means one or more embodiments.

[0051] Third, the present application is described in detail in conjunction with the schematic diagram. In the detailed description of the embodiments of the present application, the cross-sectional view of the device structure is partially enlarged without the general proportion for the convenience of description, and the schematic diagram is only an example, which should not limit the scope of protection of the present application. In addition, the three-dimensional spatial dimensions of length, width and depth should be included in actual production.

[0052] Referring to Figures 1-4 , a rollover prevention motion planning method for a steer-by-wire multi-axle steering system is provided, comprising the following steps:

[0053] Step one: based on the Bezier curve and spline curve method, a trajectory candidate set generation model is constructed. First, a preliminary path candidate set is generated, the smoothness and continuity of the path are ensured through curve interpolation technology, and the smoothness and continuity of the direction change are ensured by optimizing the path curvature and tangent direction;

[0054] Step two: on the basis of step one, further introduce the vehicle dynamics constraint condition, consider the maximum steering angle under the multi-axle steering system, the maximum lateral acceleration and the influence of load forward movement on front axle vertical load during braking, establish a nonlinear optimization model, through optimizing the path curvature and load forward movement effect, ensure that the generated path candidate set still has high stability under emergency braking condition;

[0055] Step three: based on the accurate modeling of load forward movement effect in step two, a rollover risk assessment model based on roll energy accumulation is proposed. The rollover risk assessment threshold is established by calculating the roll energy and its cumulative effect, and it is coupled with the path curvature and vehicle speed to optimize the joint strategy of path and speed, so as to reduce the rollover risk and improve the driving efficiency;

[0056] Step four: on the basis of step three, the speed profile optimization and trajectory mapping are carried out. The gradient descent method and cooperative control strategy are used to ensure that the vehicle travels at a smooth speed under different path curvatures, and the optimized trajectory and speed are mapped to the wheel angle of each steering axle through the cooperative adjustment of multi-axle steering system, so as to obtain the wheel angle motion planning result which can ensure the stability and rollover prevention performance of the vehicle, and realize the real-time response and accurate control to the complex dynamic environment.

[0057] Among them, step one specifically includes:

[0058] 1.1) Preliminary path candidate set generation: using Bezier curve and spline curve method, a preliminary path candidate set is generated according to preset path control points, assuming that the path control points are The generated Bezier curve is expressed as: Wherein, is a parameter, is a path point of the Bezier curve;

[0059] 1.2) Based on the path candidate set in 1.1), the smoothness and continuity of the path is optimized: the path generated in 1.1) is smoothed by using spline interpolation technology to ensure the continuity of the path, assuming that the spline interpolation function is The optimization objective function of the path curvature and the tangent direction is: By optimizing the above objective function, the smoothness and continuity of the path are ensured;

[0060] 1.3) Smoothness optimization of direction change: on the basis of 1.2), the curvature κ(x) and the tangent direction of the path are further optimized to ensure the smoothness of the direction change, and the smoothness of the direction change of the path can be realized by minimizing the second derivative of the path curvature: .

[0061] Further, step two specifically includes:

[0062] 2.1) Based on the optimized path in 1.3), considering the vehicle dynamics constraints: the maximum steering angle and the maximum lateral acceleration of the multi-axle steering system are introduced to adjust the path curvature optimization model in 1.3) to ensure the stability of the vehicle under dynamic working conditions, and the optimization formula of the path curvature becomes: Wherein, v is the vehicle speed;

[0063] 2.2) Effect of load forward movement on front axle vertical load during braking: considering the load forward movement effect during braking, the front axle vertical load is adjusted; based on Newton's second law, the change of the front axle vertical load caused by the load forward movement is expressed as: Wherein, is the height of the center of mass, is the wheelbase, is the mass of the vehicle, is the longitudinal acceleration of the vehicle;

[0064] 2.3) Optimize path curvature and load distribution based on load shift effect in 2.2: Incorporate load shift effect into path optimization model, consider the influence of load distribution on path curvature, ensure that the generated path candidate set still has high stability under emergency braking conditions, the adjusted optimization model is:

[0065] .

[0066] Further, step three specifically includes:

[0067] 3.1) Propose roll energy accumulation model based on load distribution in 2.3: Calculate roll energy and its accumulation effect to evaluate the rollover risk, roll energy is represented as: ;

[0068] 3.2) Establish rollover risk evaluation threshold: Based on the roll energy accumulation effect in 3.1, establish the rollover risk evaluation threshold . Assuming the rollover risk threshold is (where γ is the safety factor), the rollover risk condition is: ;

[0069] 3.3) Coupling optimization of path curvature and speed: Combine the rollover risk evaluation threshold with the path curvature κ(x) and vehicle speed v(x), optimize the joint strategy of path and speed to reduce rollover risk and improve driving efficiency, the optimization objective function is: .

[0070] Specifically, step four specifically includes:

[0071] 4.1) Speed profile optimization based on the coupling optimization results in 3.3: Use gradient descent method to optimize the speed profile v(x) of the vehicle under different path curvatures, ensure the vehicle to travel at a smooth speed, the optimization objective function of the speed profile is: ;

[0072] 4.2) Cooperative adjustment of multi-axis steering system: Based on the optimized speed profile and path curvature in 4.1, cooperative adjustment of multi-axis steering system is carried out, the optimized speed profile is mapped to the wheel angle of each steering axle , the formula is: , where L i is the wheelbase of the steering axle, h i is the height of the steering axle;

[0073] 4.3) Real-time response and precise control: feedback the wheel angle motion planning results in 4.2) to the central control system to ensure the stability and rollover prevention performance of the vehicle in complex dynamic environment, and improve the real-time response ability of the system.

[0074] The anti-rollover motion planning method for the steer-by-wire multi-axle steering system is based on the steer-by-wire multi-axle steering system, which includes a wheel 101, a sensor module 102, a central controller 107, a power steering device 104, a active transmission device 108, a rollover warning system 105, a mechanical transmission device 106, and a data bus module 103.

[0075] The input of the sensor module 102 is the real-time dynamic data of the vehicle during driving, including lateral acceleration, longitudinal acceleration, vehicle speed, steering wheel angle, steering angle of each axle, and side slip rate of the wheel; the output is the processed vehicle dynamic parameter data, which is transmitted to the central controller 107;

[0076] The input of the central controller 107 is the vehicle dynamic parameter data from the sensor module 102, and the central controller 107 is connected with the power steering device 104, the active transmission device 108 and the rollover warning system 105 through the control bus or signal line, realizing accurate control and information transmission; the output of the central controller is divided into three parts: the steering angle control command output to the power steering device for adjusting the actual steering angle of each wheel 101; the steering adjustment torque control signal output to the active transmission device 108 to ensure that the active transmission device 108 executes the steering strategy set by the central controller 107; the lateral load transfer rate and the center of gravity position change information output to the rollover warning system 105 for rollover risk assessment;

[0077] The power steering device 104 includes a steering motor 302, a steering motor controller 301, a steering wheel module 401, a CAN bus 103, a road feel motor 403, and a road feel motor controller 402; the housing of the steering motor 302 and the steering motor controller 301 are integrated by casting, the steering motor controller 301 transmits the steering angle command of the central controller 107 to the steering motor 302 through the CAN bus 103, the steering motor 302 is mechanically connected to the active transmission device 108, the active transmission device 108 is directly connected to the steering shaft of the wheel 101 through mechanical connection, the road feel motor controller 402 transmits the central controller signal to the road feel motor 403 through the CAN bus 103, and the road feel motor 403 is connected to the steering wheel module 401 through mechanical device to feedback the road feel torque;

[0078] The input of the active transmission 108 is the steering angle adjustment torque output by the power steering device 104, and the output is the actual steering angle of each steering shaft; the specific components include: a steering motor controller 301, a steering motor shaft 303, a planetary gear primary reduction device 304, a worm gear secondary reduction device 305, a steering column 312, a rack and pinion mechanism 306, a steering tie rod 307, a steering trapezoidal arm 311, a steering knuckle arm 310, a steering knuckle 309, an active transmission controller 313, and a steering motor 302; the specific connection relationship is that the steering motor controller 301 controls the rotation of the steering motor 302, the steering motor 302 is connected to the active transmission controller 313 through the steering motor shaft 303, the active transmission controller 313 is connected to the planetary gear primary reduction device 304, the primary planetary gear reduction mechanism 304 is mechanically connected to the worm gear secondary reduction mechanism 305, the worm gear secondary reduction mechanism 305 transmits power to the rack and pinion mechanism 306 through the steering column 312, the rack and pinion mechanism 306 drives the steering trapezoidal arm 311 through the steering tie rod 307, and the steering trapezoidal arm 311 drives the steering knuckle 309 through the steering knuckle arm 310 to drive the wheel 101 to rotate;

[0079] The input of the rollover warning system 105 is the lateral load transfer rate and the center of gravity position change information provided by the central controller 107, and the output is a rollover risk warning signal or an emergency operation instruction, which is fed back to the central controller 107 and transmitted to the power steering device to adjust the steering strategy of the vehicle; the rollover warning system 105 is connected to the central controller 107 through the data bus module 103 and connected to the power steering device 104 through the control signal line, and the emergency anti-rollover measure is started when necessary.

[0080] Specifically, the sensors of the sensor module 102 are connected to the central controller 107 through the data bus module 103 and are responsible for providing real-time vehicle dynamic information, which mainly includes: lateral acceleration sensors 201 located at the front and rear parts of the vehicle for measuring lateral acceleration; longitudinal acceleration sensors 202 located near the center of gravity of the vehicle for measuring longitudinal acceleration; steering wheel angle sensors 205 installed on the steering column for detecting the rotation angle and direction of the steering wheel; steering shaft angle sensors 204 installed on the steering shaft, which are usually composed of multiple sensors to detect the steering angle of the steering shaft; wheel speed sensors 203 installed on the non-rotating part of the wheel assembly for measuring wheel speed; each sensor is connected to the central controller 107 through the data bus module 103; the data bus module 103 supports CAN, LIN, FlexRay and Ethernet protocols to meet different types of data transmission requirements.

[0081] It should be noted that the above examples are only used to illustrate the technical solutions of the present application but not limit the present application. Although the present application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced, without departing from the spirit and scope of the technical solutions of the present application, which should be covered in the scope of the claims of the present application.

Claims

1. A method for anti-rollover motion planning in a steer-by-wire multi-axis system, characterized in that, Includes the following steps: Step 1: Based on the Bézier curve and spline curve methods, construct a trajectory candidate set generation model. First, generate an initial path candidate set. Ensure the smoothness and continuity of the path through curve interpolation technology. And ensure the smoothness and continuity of direction changes by optimizing the path curvature and tangent direction. Step 2: Based on Step 1, vehicle dynamics constraints are further introduced. A nonlinear optimization model is established considering the maximum steering angle, maximum lateral acceleration, and the impact of load forward shift on the vertical load of the front axle during braking under the multi-axle steering system. By optimizing the path curvature and load forward shift effect, the generated path candidate set is ensured to have high stability under emergency braking conditions. Step 3: Based on the accurate modeling of the load forward shift effect in Step 2, a rollover risk assessment model based on roll energy accumulation is proposed. By calculating the roll energy and its cumulative effect, a rollover risk assessment threshold is established, and it is coupled with the path curvature and vehicle speed to optimize the joint strategy of path and speed, so as to reduce rollover risk and improve driving efficiency. Step 4: Based on Step 3, optimize the velocity profile and map the trajectory. Use gradient descent and cooperative control strategies to ensure that the vehicle travels at a smooth speed under different path curvatures. Through the cooperative adjustment of the multi-axis steering system, map the optimized trajectory and speed to the wheel angles of each steering axis to obtain the motion planning results of each wheel angle that can ensure vehicle stability and anti-rollover performance, and realize real-time response and precise control to complex dynamic environments.

2. The anti-rollover motion planning method for a steer-by-wire multi-axis system according to claim 1, characterized in that: Step one specifically includes: 1.1) Initial Path Candidate Set Generation: Using Bézier curves and spline curves, an initial path candidate set is generated based on preset path control points. The path control points are... The generated Bézier curve is represented as: in, For parameters, Here are the path points of the Bézier curve, where n is the order of the Bézier curve and i is the summation index, from 0 to n. 1.2) Based on the path candidate set in 1.1), optimize the smoothness and continuity of the paths: use spline interpolation to smooth the paths generated in 1.1) to ensure path continuity. The spline interpolation function is... Path curvature and tangent direction The optimization objective function is: x: represents the position on the curve; by optimizing the above objective function, the smoothness and continuity of the path are ensured; 1.3) Optimization of smoothness of direction change: Based on 1.2), further optimize the curvature κ(x) and tangent direction of the path. To ensure the smoothness of direction changes, the smoothness of path direction changes can be achieved by minimizing the second derivative of the path curvature: 。 3. The anti-rollover motion planning method for a steer-by-wire multi-axis system according to claim 2, characterized in that: Step two specifically includes: 2.1) Based on the optimized path in 1.3), considering vehicle dynamics constraints: introduce the maximum steering angle of the multi-axle steering system. and maximum lateral acceleration Due to limitations, the path curvature optimization model in 1.3) is adjusted to ensure vehicle stability under dynamic conditions. The optimization formula for path curvature becomes: in, v For vehicle speed; 2.2) Effect of load forward shift during braking on front axle vertical load: Considering the load forward shift effect during braking, adjust the front axle vertical load. Based on Newton's second law, the change in vertical load on the front axle caused by the forward shift of the load. Represented as: in, For the height of the center of mass, Wheelbase For vehicle quality, This refers to the vehicle's longitudinal acceleration; 2.3) Based on the load shifting effect in 2.2), optimize the path curvature and load distribution: Incorporate the load shifting effect into the path optimization model, consider the influence of load distribution on path curvature, and ensure that the generated path candidate set still has high stability under emergency braking conditions. The adjusted optimization model is as follows: ； in, This indicates the vertical load on the rear axle.

4. The anti-rollover motion planning method for a steer-by-wire multi-axis system according to claim 3, characterized in that: Step three specifically includes: 3.1) Based on the load distribution in 2.3), a roll energy accumulation model is proposed: The roll energy is calculated. And its cumulative effect, to assess rollover risk, the roll energy is expressed as: 2) Establishment of rollover risk assessment threshold: Based on the rollover energy accumulation effect in 3.1), a rollover risk assessment threshold is established. The rollover risk threshold is Where γ is the safety factor, the rollover risk condition is: 3) Coupled optimization of path curvature and speed: The rollover risk assessment threshold is combined with the path curvature κ(x) and vehicle speed v(x) to optimize the joint strategy of path and speed, so as to reduce rollover risk and improve driving efficiency. The optimization objective function is: 。 5. The anti-rollover motion planning method for a steer-by-wire multi-axis system according to claim 1, characterized in that: Step four specifically includes: 4.1) Based on the coupling optimization results in 3.3), velocity profile optimization is performed: the gradient descent method is used to optimize the vehicle's velocity profile under different path curvatures. v ( x To ensure the vehicle travels at a stable speed, the objective function for optimizing the velocity profile is: 2) Coordinated Adjustment of Multi-Axle Steering System: Based on the optimized velocity profile and path curvature in 4.1), the coordinated adjustment of the multi-axle steering system is performed, and the optimized velocity profile is adjusted accordingly. Wheel angles mapped to each steering axis The formula is: in, L i The track width of the steering axle. h i The height of the steering shaft; 4.3) Real-time response and precise control: Feedback the wheel angle motion planning results in 4.2) to the central control system to ensure the stability and anti-rollover performance of the vehicle in complex dynamic environments and improve the real-time response capability of the system.

6. The anti-rollover motion planning method for a steer-by-wire multi-axis system according to claim 1, characterized in that: The anti-rollover motion planning method for the steer-by-wire multi-axis system is based on the steer-by-wire multi-axis system and includes: wheels (101), sensor module (102), central controller (107), power steering device (104), active transmission device (108), rollover warning system (105), mechanical transmission device (106), and data bus module. The sensor module (102) receives real-time dynamic data of the vehicle during driving, including lateral acceleration, longitudinal acceleration, vehicle speed, steering wheel angle, steering angle of each axle, and wheel sideslip rate; the output is processed vehicle dynamic parameter data, which is transmitted to the central controller (107). The input to the central controller (107) is vehicle dynamic parameter data from the sensor module (102). The central controller (107) is connected to the power steering unit (104), the active transmission unit (108), and the rollover warning system (105) via control bus or signal line to achieve precise control and information transmission. The output of the central controller is divided into three parts: the steering angle control command of each axle output to the power steering unit is used to adjust the actual steering angle of each wheel (101); the steering adjustment torque control signal output to the active transmission unit (108) is used to ensure that the active transmission unit (108) executes the steering strategy set by the central controller (107); and the lateral load transfer rate and center of gravity position change information output to the rollover warning system (105) is used to assess the rollover risk. The power steering system (104) comprises a steering motor (302), a steering motor controller (301), a steering wheel module (401), a CAN bus (103), a road feel motor (403), and a road feel motor controller (402). The housing of the steering motor (302) and the steering motor controller (301) are integrally cast. The steering motor controller (301) receives the turning angle command from the central controller (107) via the CAN bus (103) and transmits it to the steering motor (302). The steering motor (302) is mechanically connected to the active transmission device (108). The active transmission device (108) is directly connected to the steering shaft of the wheel (101) via a mechanical connection. The road feel motor controller (402) receives the signal from the central controller via the CAN bus (103) and transmits it to the road feel motor (403). The road feel motor (403) is mechanically connected to the steering wheel module (401) to provide feedback on the road feel torque. The input to the active transmission device (108) is the steering angle adjustment torque output by the power steering device (104), and the output is the actual steering angle of each steering shaft; its specific components include: a steering motor controller (301), a steering motor shaft (303), a planetary gear first-stage reduction device (304), a worm gear second-stage reduction device (305), a steering column (312), a gear and rack mechanism (306), a steering tie rod (307), a steering trapezoidal arm (311), a steering knuckle arm (310), a steering knuckle (309), and an active transmission controller (313); its specific connection relationship is that the steering motor controller (301) controls the rotation of the steering motor, and the... The steering motor is connected to the active drive controller (313) via the steering motor shaft. The active drive controller (313) is connected to the planetary gear first-stage reduction device (304). The planetary gear first-stage reduction device (304) is mechanically connected to the worm gear second-stage reduction device (305). The worm gear second-stage reduction device (305) transmits power to the gear and rack mechanism (306) through the steering column (312). The gear and rack mechanism (306) drives the steering trapezoidal arm (311) through the steering tie rod (307). The steering trapezoidal arm (311) is connected to the steering knuckle (309) through the steering knuckle arm (310) to drive the wheel (101) to rotate. The rollover warning system (105) is input to the lateral load transfer rate and center of gravity position change information provided by the central controller (107), and outputs a rollover risk warning signal or emergency operation command, which is fed back to the central controller (107) and transmitted to the power steering device to adjust the vehicle's steering strategy. The rollover warning system (105) is connected to the central controller (107) through a data bus module and to the power steering device (104) through a control signal line, and activates emergency anti-rollover measures when necessary.

7. The anti-rollover motion planning method for a steer-by-wire multi-axis system according to claim 6, characterized in that: The sensor module (102) is connected to the central controller via a data bus module and is responsible for providing real-time vehicle dynamic information. The sensor module (102) includes: a lateral acceleration sensor (201) located at the front and rear of the vehicle for measuring lateral acceleration; a longitudinal acceleration sensor (202) located near the center of gravity of the vehicle for measuring longitudinal acceleration; a steering wheel angle sensor (205) mounted on the steering column for detecting the steering wheel rotation angle and direction; a steering shaft angle sensor (204) mounted on the steering shaft, which is usually composed of multiple sensors to detect the steering shaft angle; and a wheel speed sensor (203) mounted on the non-rotating part of the wheel assembly for measuring wheel speed. Each sensor is connected to the central controller via a data bus module.

8. The anti-rollover motion planning method for a steer-by-wire multi-axis system according to claim 6, characterized in that: The data bus module supports CAN, LIN, FlexRay and Ethernet protocols to meet different types of data transmission needs.

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