Anti-rollover motion planning method for drive-by-wire multi-axis steering system

Abstract

The invention discloses an anti-rollover motion planning method for a drive-by-wire multi-axis steering system, and the method comprises the following steps: 1, constructing a trajectory candidate set generation model based on a Bezier curve and spline curve method; secondly, vehicle dynamics constraint conditions are further introduced, and a nonlinear optimization model is established by considering the maximum steering angle and the maximum lateral acceleration under a multi-axle steering system and the influence of forward load in the braking process on the vertical load of a front axle; 3, proposing a rollover risk assessment model based on rollover energy accumulation based on the accurate modeling of the load forward effect in the step 2; and 4, on the basis of the step 3, speed profile optimization and trajectory mapping are carried out, it is ensured that the vehicle runs at a stable speed under different path curvatures through a gradient descent method and a cooperative control strategy, and real-time response and accurate control over the complex dynamic environment are achieved. According to the method, smooth transition of direction change is realized, and the accuracy and adaptability of path generation are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of motion planning of intelligent electric trucks, and in particular to an anti-rollover motion planning method for a wire-controlled multi-axis steering system. Background Art

[0002] With the popularization of intelligent trucks, trajectory planning and motion planning technologies, as core technologies for the safe and precise execution of intelligent truck tasks, directly affect their application and transformative role in the global economy. The current trajectory planning methods are mainly divided into two directions: fast planning based on geometric paths and optimization planning based on dynamic models. 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 risks, which restricts the development of autonomous driving truck technology. In the existing research on anti-rollover motion planning methods, for example: the Chinese invention patent application number is CN202011641346.1, and the name is "Path Tracking Optimization Control Method for Distributed Drive Unmanned Vehicles". The invention first determines the relevant parameters of the longitudinal vehicle speed constraint according to the vehicle rollover and sideslip conditions, and then designs the active speed limit activation conditions based on the vehicle speed distribution range, so as to obtain the vehicle's expected longitudinal force in different speed distribution ranges; then determines the optimal objective function of multiple constraints, and proposes a weight coefficient adjustment method for different motor failures and failure forms, and obtains the driving and braking torques of each motor through the effective set algorithm. Then, according to the vehicle dynamics model, the objective function of vehicle trajectory tracking is proposed to realize trajectory tracking; the Chinese invention patent application number is CN202211564129.6, and the name is "A safe trajectory planning method for multi-axis special vehicles considering obstacle avoidance stability". This invention establishes a five-axis special vehicle dynamics model, refers to the relative motion state of surrounding vehicles and special vehicles, and establishes a five-axis special vehicle dynamics constraint model based on the vehicle's yaw stability and roll safety, thereby designing an MPC trajectory planner and generating a safe driving trajectory. This method can generate a vehicle driving trajectory that achieves stable obstacle avoidance and realize safe, stable and high-speed driving of multi-axis special vehicles.

[0003] However, the above existing anti-rollover motion planning methods have the following two potential problems: 1. Existing anti-rollover motion planning methods are limited 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 vehicles", have achieved certain results on two-axle vehicles, these methods often ignore the smoothness and continuity of the path generation process, especially under the complex steering requirements of multi-axle vehicles. These methods fail to make full use of appropriate path planning technology, resulting in inaccurate path generation in practical applications and inability to adapt to changing road conditions and vehicle dynamics. 2. Existing anti-rollover motion planning for multi-axle vehicles does not fully integrate vehicle dynamic constraints and load forward effects: Existing anti-rollover motion planning methods for multi-axle vehicles, such as the Chinese invention patent application number CN202211564129.6: "A safe trajectory planning method for multi-axle special vehicles considering obstacle avoidance stability", although they have begun to consider the special needs of multi-axle vehicles, they often fail to fully integrate vehicle dynamic constraints, especially the impact of load forward on vehicle stability under extreme conditions such as sudden braking. These methods fail to establish a nonlinear optimization model that comprehensively considers the maximum steering angle, maximum lateral acceleration, and the impact of load forward during braking, resulting in insufficient path following ability and driving safety of vehicles under complex dynamic conditions in practical applications.

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

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

[0006] In view of the above-mentioned problems existing in the existing anti-rollover motion planning method for a wire-controlled multi-axis 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 wire-controlled multi-axis steering system, which solves the problem in the prior art that, when performing rollover risk assessment and motion planning, the dynamic characteristics of the vehicle's center of gravity transfer and the synergistic relationship between trajectory planning and motion planning are not fully considered, resulting in an overly conservative anti-rollover control strategy and failure to effectively ensure vehicle stability under complex road conditions.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions: a rollover prevention motion planning method for a wire-controlled multi-axis steering system, comprising the following steps: Step 1: 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 by using curve interpolation technology, and the smoothness and continuity of the direction change are ensured by optimizing the path curvature and tangent direction. Step 2: Based on step 1, vehicle dynamics constraints are further introduced to establish a nonlinear optimization model by considering the maximum steering angle, maximum lateral acceleration and the influence of load forward shift on the vertical load of the front axle during braking under the multi-axis 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 forward load effect in step 2, a rollover risk assessment model based on rollover energy accumulation is proposed. The rollover risk assessment threshold is established by calculating the rollover 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 to reduce the rollover risk and improve driving efficiency. Step 4: Based on step 3, the speed profile is optimized and the trajectory is mapped. The gradient descent method and collaborative control strategy are used to ensure that the vehicle travels at a steady speed under different path curvatures. Through the coordinated adjustment of the multi-axis steering system, the optimized trajectory and speed are mapped to the wheel angles of each steering axle, and the motion planning results of each wheel angle that can ensure vehicle stability and anti-rollover performance are obtained, realizing real-time response and precise control of complex dynamic environments.

[0009] As a preferred solution of the anti-rollover motion planning method for a wire-controlled multi-axis steering system of the present invention, the step 1 specifically includes: 1.1) Preliminary path candidate set generation: Using Bezier curve and spline curve methods, a preliminary path candidate set is generated according to the preset path control points. Assume that the path control points are , then the generated Bezier curve is expressed as: ,in, As parameters, is the path point of the Bezier curve; 1.2) Based on the candidate path set in 1.1), the smoothness and continuity of the path are optimized: the path generated in 1.1) is smoothed using spline interpolation technology to ensure the continuity of the path. Assume 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; 1.3) Optimization of smoothness of direction change: Based on 1.2), further optimize the curvature κ(x) and tangent direction of the path , ensuring the smoothness of direction changes, the smoothness of path direction changes can be achieved by minimizing the second-order derivative of the path curvature: .

[0010] As a preferred solution of the anti-rollover motion planning method for a wire-controlled multi-axis steering system of the present invention, the step 2 specifically includes: 2.1) Based on the optimization path in 1.3), consider the vehicle dynamics constraints: introduce the maximum steering angle of the multi-axis steering system and maximum lateral acceleration The path curvature optimization model in 1.3) is adjusted to ensure the stability of the vehicle under dynamic conditions. The optimization formula of the path curvature becomes: , where v is the vehicle speed; 2.2) Impact of load forward movement on the vertical load on the front axle during braking: Consider the effect of load forward movement during braking and adjust the vertical load on the front axle ; Based on Newton's second law, the vertical load change on the front axle caused by the forward movement of the load It is expressed as: ,in, is the centroid height, is the wheelbase, is the vehicle mass, is the longitudinal acceleration of the vehicle; 2.3) Based on the load forward effect in 2.2), optimize the path curvature and load distribution: Incorporate the load forward effect into the path optimization model, consider the impact 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: .

[0011] As a preferred solution of the anti-rollover motion planning method for a wire-controlled multi-axis steering system of the present invention, the step three specifically includes: 3.1) Based on the load distribution in 2.3), a roll energy accumulation model is proposed: Calculate the roll energy and its cumulative effect to assess the rollover risk, the rollover energy is expressed as: ; 3.2) Establishment of rollover risk assessment threshold: Based on the rollover energy accumulation effect in 3.1), establish a rollover risk assessment threshold Assume that the rollover risk threshold is (where γ is the safety factor), then the rollover risk condition is: ; 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) to optimize the joint strategy of path and speed to reduce the rollover risk and improve driving efficiency. The optimization objective function is: .

[0012] As a preferred solution of the anti-rollover motion planning method for a wire-controlled multi-axis steering system of the present invention, the step 4 specifically includes: 4.1) Based on the coupled optimization results in 3.3), the speed profile is optimized: 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 stable speed. The optimization objective function of the speed profile is:

[0013] 4.2) Coordinated adjustment of multi-axis steering system: Based on the optimized speed profile and path curvature in 4.1), the coordinated adjustment of the multi-axis steering system is carried out. Wheel angles mapped to each steering axis , the formula is: , where L i is the wheelbase of the steering axle, h i is the height of the steering axis; 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 improve the real-time response capability of the system.

[0014] As a preferred solution of the anti-rollover motion planning method for a wire-controlled multi-axis steering system of the present invention, wherein: the anti-rollover motion planning method for a wire-controlled multi-axis steering system is based on a wire-controlled multi-axis steering system, including: wheels, a sensor module, a central controller, a power steering device, an active transmission device, a rollover warning system, a mechanical transmission device, and a data bus module; 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 the processed vehicle dynamic parameter data, which is transmitted to the central controller; The input of the central controller is the vehicle dynamic parameter data from the sensor module. The central controller is connected to the power steering device, the active transmission device and the rollover warning system through the 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 device is used to adjust the actual steering angle of each wheel; the steering adjustment torque control signal output to the active transmission device to ensure that the active transmission device executes the steering strategy set by the central controller; the lateral load transfer rate and center of gravity position change information output to the rollover warning system is used for rollover risk assessment; The power steering device comprises a steering motor, a steering motor controller, a steering wheel module, a CAN bus, a road sense motor, and a road sense motor controller; the housing of the steering motor and the steering motor controller are integrally cast, the steering motor controller receives a steering angle command from a central controller through the CAN bus and transmits it to the steering motor, the steering motor is mechanically connected to an active transmission device, the active transmission device is directly connected to a wheel steering shaft through a mechanical connection, the road sense motor controller receives a signal from a central controller through the CAN bus and transmits it to the road sense motor, and the road sense motor is connected to the steering wheel module through a mechanical device to feedback a road sense torque; The input of the active transmission device is the steering angle adjustment torque output by the power steering device, and the output is the actual steering angle of each steering shaft; its specific components include: a steering motor controller, a steering motor 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 transmission controller; its specific connection relationship is that the steering motor controller controls the steering motor to rotate, the steering motor is connected to the active transmission controller through the steering motor shaft, the active transmission controller is connected to the planetary gear primary reduction device, the primary planetary gear reduction mechanism is mechanically connected to 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 to the steering knuckle through the steering knuckle arm to drive the wheel to rotate; The input of the rollover warning system is the lateral load transfer rate and center of gravity position change information provided by the central controller, and the output is a rollover risk 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 vehicle's steering strategy; the rollover warning system is connected to the central controller through a data bus module, and is connected to the power steering device through a control signal line, and emergency anti-rollover measures are initiated when necessary.

[0015] As a preferred solution of the anti-rollover motion planning method for a wire-controlled multi-axis steering system described in the present invention, wherein: each sensor of the sensor module is connected to the central controller through a data bus module, and is responsible for providing it with real-time vehicle dynamic information. The module mainly includes: lateral acceleration sensors located at the front and rear parts of the vehicle, for measuring lateral acceleration; a longitudinal acceleration sensor located near the center of gravity of the vehicle for measuring longitudinal acceleration; a steering wheel angle sensor installed on the steering column for detecting the turning angle and direction of the steering wheel; a steering shaft angle sensor installed on the steering shaft, which usually uses multiple sensors to detect the steering angle of the steering shaft; a wheel speed sensor installed on the non-rotating part of the wheel assembly for measuring the wheel speed; each sensor is connected to the central controller through the data bus module.

[0016] As a preferred solution of the anti-rollover motion planning method for a wire-controlled multi-axis steering system described in the present invention, the data bus module supports CAN, LIN, FlexRay and Ethernet protocols to meet different types of data transmission requirements.

[0017] Beneficial effects of the present invention: 1. The present invention not only constructs a trajectory candidate set generation model based on Bezier curves and spline curves to ensure the smoothness and continuity of the path, but also realizes a smooth transition of direction changes on the basis of optimizing the path curvature and tangent direction, effectively improving the accuracy and adaptability of path generation; 2. The present invention further introduces vehicle dynamics constraints, comprehensively considers the maximum steering angle of the multi-axis steering system, the maximum lateral acceleration, and the influence of load forward displacement on the vertical load of the front axle during braking, and establishes a nonlinear optimization model. By optimizing the path curvature and load distribution, the generated path candidate set is ensured to be highly stable under extreme conditions such as sudden braking, and the path following ability and driving safety of the vehicle under complex dynamic conditions are improved; 3. The present invention proposes a rollover risk assessment model based on rollover energy accumulation by accurately modeling the load forward effect. By establishing a rollover risk assessment threshold and coupling it with the path curvature and vehicle speed, the combined strategy of path and speed is optimized, effectively reducing the rollover risk and improving driving efficiency, so that the system can maintain high stability and safety under complex road conditions; 4. Based on the assessment of rollover risk, the present invention further optimizes the speed profile and trajectory mapping, and ensures that the vehicle travels at a stable speed under different path curvatures through the gradient descent method and the coordinated control strategy of the multi-axis steering system. Finally, through precise wheel angle motion planning and real-time response control, the stability and anti-rollover performance of the vehicle in a complex dynamic environment are achieved, greatly improving the dynamic response capability and overall control performance of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them: Figure 1 It is the principle diagram of the method of the present invention; Figure 2 This is a schematic diagram of the multi-axis steering-by-wire system of the present invention; Figure 3 is a position diagram of the sensor module of the present invention; Figure 4 This is a structural diagram of the active transmission module of the present invention; Figure 5 This is a structural diagram of the power steering module of the present invention. DETAILED DESCRIPTION

[0019] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0020] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0021] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0022] Secondly, the present invention is described in detail with reference to the schematic diagram. When describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0023] Reference Figure 1-Figure 4 , provides an anti-rollover motion planning method for a wire-controlled multi-axis steering system, comprising the following steps: Step 1: 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 by using curve interpolation technology, and the smoothness and continuity of the direction change are ensured by optimizing the path curvature and tangent direction. Step 2: Based on step 1, vehicle dynamics constraints are further introduced to establish a nonlinear optimization model by considering the maximum steering angle, maximum lateral acceleration and the influence of load forward shift on the vertical load of the front axle during braking under the multi-axis 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 forward load effect in step 2, a rollover risk assessment model based on rollover energy accumulation is proposed. The rollover risk assessment threshold is established by calculating the rollover 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 to reduce the rollover risk and improve driving efficiency. Step 4: Based on step 3, the speed profile is optimized and the trajectory is mapped. The gradient descent method and collaborative control strategy are used to ensure that the vehicle travels at a steady speed under different path curvatures. Through the coordinated adjustment of the multi-axis steering system, the optimized trajectory and speed are mapped to the wheel angles of each steering axle, and the motion planning results of each wheel angle that can ensure vehicle stability and anti-rollover performance are obtained, realizing real-time response and precise control of complex dynamic environments.

[0024] Among them, step one specifically includes: 1.1) Preliminary path candidate set generation: Using Bezier curve and spline curve methods, a preliminary path candidate set is generated according to the preset path control points. Assume that the path control points are , then the generated Bezier curve is expressed as: ,in, As parameters, is the path point of the Bezier curve; 1.2) Based on the candidate path set in 1.1), the smoothness and continuity of the path are optimized: the path generated in 1.1) is smoothed using spline interpolation technology to ensure the continuity of the path. Assume 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; 1.3) Optimization of smoothness of direction change: Based on 1.2), further optimize the curvature κ(x) and tangent direction of the path , ensuring the smoothness of direction changes, the smoothness of path direction changes can be achieved by minimizing the second-order derivative of the path curvature: .

[0025] Furthermore, step 2 specifically includes: 2.1) Based on the optimization path in 1.3), consider the vehicle dynamics constraints: introduce the maximum steering angle of the multi-axis steering system and maximum lateral acceleration The path curvature optimization model in 1.3) is adjusted to ensure the stability of the vehicle under dynamic conditions. The optimization formula of the path curvature becomes: , where v is the vehicle speed; 2.2) Impact of load forward movement on the vertical load on the front axle during braking: Consider the effect of load forward movement during braking and adjust the vertical load on the front axle ; Based on Newton's second law, the vertical load change on the front axle caused by the forward movement of the load It is expressed as: ,in, is the centroid height, is the wheelbase, is the vehicle mass, is the longitudinal acceleration of the vehicle; 2.3) Based on the load forward effect in 2.2), optimize the path curvature and load distribution: Incorporate the load forward effect into the path optimization model, consider the impact 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: .

[0026] Furthermore, step three specifically includes: 3.1) Based on the load distribution in 2.3), a roll energy accumulation model is proposed: Calculate the roll energy and its cumulative effect to assess the rollover risk, the rollover energy is expressed as: ; 3.2) Establishment of rollover risk assessment threshold: Based on the rollover energy accumulation effect in 3.1), establish a rollover risk assessment threshold Assume that the rollover risk threshold is (where γ is the safety factor), then the rollover risk condition is: ; 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) to optimize the joint strategy of path and speed to reduce the rollover risk and improve driving efficiency. The optimization objective function is: .

[0027] Specifically, step four includes: 4.1) Based on the coupled optimization results in 3.3), the speed profile is optimized: 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 stable speed. The optimization objective function of the speed profile is: ; 4.2) Coordinated adjustment of multi-axis steering system: Based on the optimized speed profile and path curvature in 4.1), the coordinated adjustment of the multi-axis steering system is carried out. Wheel angles mapped to each steering axis , the formula is: , where L i is the wheelbase of the steering axle, h i is the height of the steering axis; 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 improve the real-time response capability of the system.

[0028] The anti-rollover motion planning method for a wire-controlled multi-axis steering system is based on a wire-controlled multi-axis steering system, including: a wheel 101, a sensor module 102, a central controller 107, a power steering device 104, an active transmission device 108, a rollover warning system 105, a mechanical transmission device 106, and a data bus module 103; 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 axis and side slip rate of the wheel; the output is the processed vehicle dynamic parameter data, which is transmitted to the central controller 107; The input of the central controller 107 is the vehicle dynamic parameter data from the sensor module 102. The central controller 107 is connected to the power steering device 104, the active transmission device 108 and the rollover warning system 105 through the 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 instructions of each axle output to the power steering device are used to adjust 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 center of gravity position change information output to the rollover warning system 105 are used for rollover risk assessment; 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 sense motor 403, and a road sense 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 a steering angle command from the central controller 107 through 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 through a mechanical connection, the road sense motor controller 402 receives a signal from the central controller through the CAN bus 103 and transmits it to the road sense motor 403, and the road sense motor 403 is connected to the steering wheel module 401 through a mechanical device to feedback the road sense torque; The input of 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 motor shaft 303, a planetary gear primary reduction device 304, a worm gear secondary reduction device 305, a steering column 312, a gear rack 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; its specific connection relationship is that the steering motor controller 301 controls the steering The motor 302 rotates, 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 gear rack mechanism 306 through the steering column 312, the gear rack mechanism 306 drives the steering trapezoidal arm 311 through the steering tie rod 307, and 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 input of the rollover warning system 105 is the lateral load transfer rate and 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 vehicle's steering strategy; the rollover warning system 105 is connected to the central controller 107 through the data bus module 103, and is connected to the power steering device 104 through the control signal line, and emergency anti-rollover measures are initiated when necessary.

[0029] Specifically, each sensor of the sensor module 102 is connected to the central controller 107 through the data bus module 103, which is responsible for providing it with real-time vehicle dynamic information. The module mainly includes: a lateral acceleration sensor 201 located at the front and rear parts of the vehicle, used to measure 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 installed on the steering column for detecting the turning angle and direction of the steering wheel; a steering shaft angle sensor 204 installed on the steering shaft, which usually uses multiple sensors to detect the steering angle of the steering shaft; a wheel speed sensor 203 installed on the non-rotating part of the wheel assembly for measuring the 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.

[0030] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A rollover prevention motion planning method for a wire-controlled multi-axis steering system, characterized in that: The following steps are involved: Step 1: 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 by using curve interpolation technology, and the smoothness and continuity of the direction change are ensured by optimizing the path curvature and tangent direction. Step 2: Based on step 1, vehicle dynamics constraints are further introduced to establish a nonlinear optimization model by considering the maximum steering angle, maximum lateral acceleration and the influence of load forward shift on the vertical load of the front axle during braking under the multi-axis 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 forward load effect in step 2, a rollover risk assessment model based on rollover energy accumulation is proposed. The rollover risk assessment threshold is established by calculating the rollover 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 to reduce the rollover risk and improve driving efficiency. Step 4: Based on step 3, the speed profile is optimized and the trajectory is mapped. The gradient descent method and collaborative control strategy are used to ensure that the vehicle travels at a steady speed under different path curvatures. Through the coordinated adjustment of the multi-axis steering system, the optimized trajectory and speed are mapped to the wheel angles of each steering axle, and the motion planning results of each wheel angle that can ensure vehicle stability and anti-rollover performance are obtained, realizing real-time response and precise control of complex dynamic environments.

2. The anti-rollover motion planning method for a wire-controlled multi-axis steering system according to claim 1, characterized in that: The step 1 specifically includes: 1.1) Preliminary path candidate set generation: Using Bezier curve and spline curve methods, a preliminary path candidate set is generated according to the preset path control points. Assume that the path control points are , then the generated Bezier curve is expressed as: ,in, As parameters, is the path point of the Bezier curve; 1.2) Based on the candidate path set in 1.1), the smoothness and continuity of the path are optimized: the path generated in 1.1) is smoothed using spline interpolation technology to ensure the continuity of the path. Assume 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; 1.3) Optimization of smoothness of direction change: Based on 1.2), further optimize the curvature κ(x) and tangent direction of the path , ensuring the smoothness of direction changes, the smoothness of path direction changes can be achieved by minimizing the second-order derivative of the path curvature: .

3. The anti-rollover motion planning method for a wire-controlled multi-axis steering system according to claim 2, characterized in that: The step 2 specifically includes: 2.1) Based on the optimization path in 1.3), consider the vehicle dynamics constraints: introduce the maximum steering angle of the multi-axis steering system and maximum lateral acceleration The path curvature optimization model in 1.3) is adjusted to ensure the stability of the vehicle under dynamic conditions. The optimization formula of the path curvature becomes: , where v is the vehicle speed; 2.2) Impact of load forward movement on the vertical load on the front axle during braking: Consider the effect of load forward movement during braking and adjust the vertical load on the front axle ; Based on Newton's second law, the vertical load change on the front axle caused by the forward movement of the load It is expressed as: ,in, is the centroid height, is the wheelbase, is the vehicle mass, is the longitudinal acceleration of the vehicle; 2.3) Based on the load forward effect in 2.2), optimize the path curvature and load distribution: Incorporate the load forward effect into the path optimization model, consider the impact 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: .

4. The anti-rollover motion planning method for a wire-controlled multi-axis steering system according to claim 3, characterized in that: The step three specifically includes: 3.1) Based on the load distribution in 2.3), a roll energy accumulation model is proposed: Calculate the roll energy and its cumulative effect to assess the rollover risk, the rollover energy is expressed as: ; 3.2) Establishment of rollover risk assessment threshold: Based on the rollover energy accumulation effect in 3.1), establish a rollover risk assessment threshold Assume that the rollover risk threshold is (where γ is the safety factor), then the rollover risk condition is: ; 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) to optimize the joint strategy of path and speed to reduce the rollover risk and improve driving efficiency. The optimization objective function is: .

5. The anti-rollover motion planning method for a wire-controlled multi-axis steering system according to claim 1, characterized in that: The step 4 specifically includes: 4.1) Based on the coupled optimization results in 3.3), the speed profile is optimized: 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 stable speed. The optimization objective function of the speed profile is: ; 4.2) Coordinated adjustment of multi-axis steering system: Based on the optimized speed profile and path curvature in 4.1), the coordinated adjustment of the multi-axis steering system is carried out. Wheel angles mapped to each steering axis , the formula is: , where L i is the wheelbase of the steering axle, h i is the height of the steering axis; 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 improve the real-time response capability of the system.

6. The anti-rollover motion planning method for a wire-controlled multi-axis steering system according to claim 1, characterized in that: The anti-rollover motion planning method for a wire-controlled multi-axis steering system is based on the wire-controlled multi-axis steering system, comprising: a wheel (101), a sensor module (102), a central controller (107), a power steering device (104), an active transmission device (108), a rollover warning system (105), a mechanical transmission device (106), and a data bus module (103); The input of the sensor module (102) is real-time dynamic data of the vehicle during driving, including lateral acceleration, longitudinal acceleration, vehicle speed, steering wheel angle, steering angle of each axis and side slip rate of the wheel; the output is processed vehicle dynamic parameter data, which is transmitted to the central controller (107); The input of the central controller (107) is vehicle dynamic parameter data from the sensor module (102). The central controller (107) is connected to the power steering device (104), the active transmission device (108) and the rollover warning system (105) through a control bus or a signal line to achieve precise control and information transmission. The output of the central controller is divided into three parts: a steering angle control command of each axle output to the power steering device, which is used to adjust the actual steering angle of each wheel (101); a 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); and lateral load transfer rate and center of gravity position change information output to the rollover warning system (105) for rollover risk assessment. The power steering device (104) comprises a steering motor (302), a steering motor controller (301), a steering wheel module (401), a CAN bus (103), a road sense motor (403), and a road sense motor controller (402); the housing of the steering motor (302) and the steering motor controller (403) are integrally cast; the steering motor controller (301) receives a steering angle instruction from a central controller (107) through the CAN bus (103) and transmits the instruction to the steering motor (302); the steering motor (302) is mechanically connected to an active transmission device (108); the active transmission device (108) is directly connected to a steering shaft of a wheel (101) through a mechanical connection; the road sense motor controller (402) receives a signal from the central controller through the CAN bus (103) and transmits the signal to the road sense motor (403); the road sense motor (403) is connected to the steering wheel module (401) through a mechanical device to feedback a road sense torque; The input of 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 motor shaft (303), a planetary gear primary reduction device (304), a worm gear secondary reduction device (305), a steering column (312), a gear 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 steering The motor is connected to an active transmission controller (313) via a steering motor shaft (302); the active transmission controller (313) is connected to a planetary gear primary reduction device (304); the primary planetary gear reduction mechanism (304) is mechanically connected to a worm gear secondary reduction mechanism (305); the worm gear secondary reduction mechanism (305) transmits power to a gear rack mechanism (306) via the steering column (312); the gear rack mechanism (306) drives a steering trapezoidal arm (311) via a steering tie rod (307); the steering trapezoidal arm (311) is connected to a steering knuckle (309) via a steering knuckle arm (310) to drive the wheel (101) to rotate; The input of the rollover warning system (105) is the lateral load transfer rate and 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 is connected to the power steering device (104) through the control signal line, and emergency anti-rollover measures are initiated when necessary.

7. The anti-rollover motion planning method for a wire-controlled multi-axis steering system according to claim 6, characterized in that: Each sensor of the sensor module (102) is connected to the central controller via a data bus module (103) and is responsible for providing the central controller with real-time vehicle dynamic information. The module mainly includes: a lateral acceleration sensor (201) located at the front and rear parts of the vehicle and used to measure lateral acceleration; a longitudinal acceleration sensor (202) located near the center of gravity of the vehicle and used to measure longitudinal acceleration; a steering wheel angle sensor (205) installed on the steering column and used to detect the rotation angle and direction of the steering wheel; a steering shaft angle sensor (204) installed on the steering shaft and usually composed of multiple sensors to detect the steering angle of the steering shaft; and a wheel speed sensor (203) installed on the non-rotating part of the wheel assembly and used to measure the wheel speed. Each sensor is connected to the central controller via a data bus module (107).

8. The anti-rollover motion planning method for a wire-controlled multi-axis steering system according to claim 6, characterized in that: The data bus module (103) supports CAN, LIN, FlexRay and Ethernet protocols to meet different types of data transmission requirements.

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