A vehicle motion control system based on corner module dynamics

Abstract

The present application belongs to the field of vehicle control technology, and relates to a kind of automobile motion control system based on angle module dynamics.System construction contains two degrees of freedom driver control system of steering wheel input and vehicle body posture lever input, for respectively representing path curvature tracking demand and vehicle body posture adjustment demand;Based on driver control input, ideal yaw rate control target and ideal mass side slip angle control target are constructed, and four-wheel steering angle feedforward control amount is determined through pure yaw motion and pure lateral motion vehicle kinematics;Through feedback optimization control, additional yaw torque and four-wheel steering angle control amount are carried out compound working condition coordinated control, based on working condition self-adaptive adjustment control weight and constraint, four-wheel drive / braking torque and four-wheel steering angle distribution control are realized.The present application realizes the decoupling control of vehicle yaw motion and lateral motion by constructing two degrees of freedom driver control system and combining feedforward kinematics and feedback dynamics control.

Description

Technical Field

[0001] This invention relates to the field of vehicle control technology, and in particular to a vehicle motion control system based on angular module dynamics. Background Technology

[0002] The corner modular vehicle is equipped with an independent corner module at each wheel. This module integrates a drive-by-wire system, a braking-by-wire system, a steering-by-wire system, and an active suspension system, eliminating the traditional steering trapezoidal mechanism and mechanical connections between wheels. This achieves physical decoupling of the four wheels at the structural level, improving the freedom and flexibility of vehicle motion control. Existing vehicle motion control methods based on traditional structures are insufficient to fully adapt to the dynamic characteristics of the corner modular vehicle's distributed actuator architecture. Furthermore, current technologies for analyzing driver intentions often rely on single-dimensional modeling based on steering wheel input, lacking effective representation of multi-degree-of-freedom maneuvering behaviors such as vehicle posture adjustment intentions. This hinders the full exploitation of the corner modular vehicle's potential in multi-degree-of-freedom maneuvering and complex operating condition control. Therefore, given the novel dynamic characteristics of corner modular vehicles, there is an urgent need for a vehicle motion control method that can accurately represent the driver's multi-degree-of-freedom maneuvering intentions and fully leverage the advantages of the distributed actuator collaborative control in corner modular vehicles. This method aims to achieve coordinated control and decoupled adjustment of vehicle motion in all directions under complex operating conditions. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a vehicle motion control system based on angular module dynamics, comprising:

[0004] A two-degree-of-freedom driver control system is constructed, which includes driver steering wheel input and vehicle posture lever input, to separately analyze the driver's driving intentions for path curvature tracking and vehicle posture adjustment;

[0005] Based on the two-degree-of-freedom driver control system, an ideal yaw rate control target corresponding to path curvature tracking and an ideal center of mass sideslip angle control target corresponding to vehicle attitude adjustment are respectively constructed.

[0006] Based on the vehicle kinematics feedforward control method for pure yaw motion and pure lateral motion, four-wheel steering angle feedforward control quantities are designed corresponding to the ideal yaw rate control target and the ideal center of mass sideslip angle control target, respectively.

[0007] Based on the feedforward control of the four-wheel steering angle as the basic control variable, feedback optimization control is introduced to jointly adjust the additional yaw moment based on distributed drive / braking and the four-wheel steering angle control based on independent four-wheel steering, thereby achieving decoupled control of vehicle yaw motion and lateral motion.

[0008] Based on the vehicle's operating conditions, an adaptive adjustment strategy is designed for the control target weights, control variable penalty weights, and constraint conditions to determine the vehicle motion control parameters based on angular module dynamics.

[0009] Based on the feedforward-feedback coordinated control strategy, the additional yaw moment is distributed to obtain four-wheel drive / braking moment, and four-wheel steering angle control quantities are generated and applied to the four-wheel angle modules to achieve vehicle motion control.

[0010] Furthermore, the two-degree-of-freedom driver control system includes a steering wheel and a vehicle attitude lever;

[0011] The steering wheel communicates with the vehicle control unit via steer-by-wire. The driver inputs their intention to track the curvature of the path through the steering wheel input. The vehicle control unit calculates and distributes the actuator momentum to the four-wheel corner module system based on the steering wheel input, and simultaneously provides the driver with vehicle driving status information through the road feel simulation unit. The four-wheel corner module system has the same actuators and physical structure, and includes independent steer-by-wire systems, drive-by-wire systems, brake-by-wire systems, and active or semi-active suspension systems.

[0012] The vehicle attitude lever communicates with the vehicle control unit via a drive-by-wire method. The driver can input the vehicle attitude adjustment intention by moving the vehicle attitude lever left and right, combined with the mapping relationship between the opening of the vehicle attitude lever and the center of gravity sideslip angle at different vehicle speeds. This is used to represent the driver's independent control needs for vehicle attitude adjustment in addition to path curvature tracking.

[0013] By combining the steering wheel and the vehicle posture lever to form a two-degree-of-freedom driver control system, a comprehensive representation of the driver's yaw motion adjustment needs and lateral motion adjustment needs can be achieved, providing decoupled control input for subsequent control strategies.

[0014] Furthermore, in the design of the ideal yaw rate control target and the ideal center-of-gravity sideslip angle control target based on the two-degree-of-freedom driver control system, the ideal yaw rate control target is constructed based on the mapping relationship between the driver's steering wheel angle and the path curvature, as follows:

[0015] The driver's input to the steering wheel represents their intention to track the road ahead, based on the steering wheel angle. The relationship between the path curvature and the desired path curvature is used to determine the desired path curvature. It satisfies the following relationship:

[0016]

[0017] In the formula, Based on the steering sensitivity coefficient, For the longitudinal speed of the vehicle, Characteristic velocity parameters;

[0018] when At that time, steering sensitivity It will drop to half of its zero speed. The path curvature is used; under neutral steering conditions, steering sensitivity is independent of speed; by introducing understeer, steering sensitivity decreases with increasing speed.

[0019] Based on the geometric relationship between path curvature and the rate of change of heading angle, an initial reference value for the ideal yaw rate based on path curvature tracking is constructed:

[0020]

[0021] in, The initial reference value for the ideal yaw rate. The ideal rate of change of heading angle;

[0022] To achieve yaw rate and centroid side slip angle The decoupling control will set the initial reference value of the ideal yaw rate to... Defined as a reference value based on the curvature of the center of mass trajectory, and eliminating the effect of the center of mass sideslip angle on the heading angle, that is, introducing a compensation term for the change in the center of mass sideslip angle into the initial reference value of the ideal yaw rate to obtain the final ideal yaw rate control target:

[0023]

[0024] in, To achieve the ideal yaw rate control target, Let be the rate of change of the centroid sideslip angle.

[0025] Furthermore, in the design of the ideal yaw rate control target and the ideal center-of-gravity sideslip angle control target based on the two-degree-of-freedom driver control system, the ideal center-of-gravity sideslip angle control target is constructed based on the vehicle attitude lever input, as follows:

[0026] The driver's input to the vehicle attitude lever represents the driving intention to adjust the vehicle attitude. Combined with the Vehicle Attitude Control Lever Interpretation (ALI) model, the driver's input to the vehicle attitude lever is mapped to the ideal centroid sideslip angle control target representing changes in vehicle attitude in vehicle lateral motion control. ;

[0027] In the analytical model of the vehicle attitude lever, the opening degree of the vehicle attitude lever is defined. Adjusting the angle of the vehicle attitude lever Limit angle of the lever The ratio of satisfies:

[0028]

[0029] The positive or negative sign of the opening of the vehicle attitude lever is used to represent the direction of vehicle attitude adjustment, and the absolute value of the opening of the vehicle attitude lever is used to represent the intensity of vehicle attitude adjustment.

[0030] Setting the vehicle longitudinal velocity threshold in the vehicle attitude lever analytical model The vehicle longitudinal speed threshold is obtained through calibration based on road surface adhesion conditions, vehicle dynamics characteristics, or dynamic control requirements, and is set when the vehicle longitudinal speed meets the requirements. As the opening of the vehicle attitude lever increases, the vehicle changes from straight driving to diagonal driving at different angles. The angle of diagonal driving increases with the increase of the lever opening. The vehicle motion mode corresponding to the maximum opening of the vehicle attitude lever is defined as the lateral translation mode.

[0031] The vehicle's longitudinal speed satisfies As the vehicle speed increases, a speed attenuation factor is introduced to suppress the lateral translation trend, and a mapping relationship is constructed between the limiting centroid sideslip angle corresponding to the maximum opening of the vehicle attitude lever and the vehicle speed:

[0032]

[0033] in, This indicates that the longitudinal speed of the vehicle satisfies The corresponding limiting centroid sideslip angle at that time This indicates that the longitudinal speed of the vehicle satisfies The corresponding limiting centroid sideslip angle at that time This is the vehicle speed attenuation factor;

[0034] Based on the mapping relationship between the vehicle attitude lever opening and the limit center of gravity sideslip angle, the ideal center of gravity sideslip angle control target is constructed as follows:

[0035]

[0036] in, The target is to control the sideslip angle of the ideal center of mass.

[0037] Furthermore, in the aforementioned vehicle kinematics feedforward control method based on pure yaw motion and pure lateral motion, the feedforward control method based on pure yaw motion includes:

[0038] In pure yaw motion control mode, an ideal yaw rate control target based on path curvature tracking is constructed according to the driver's steering wheel angle input. Combined with the steady-state yaw rate gain inverse model of the two-degree-of-freedom vehicle dynamics model, the nominal vehicle steering angle that satisfies the ideal yaw rate control target is calculated. The formula is as follows:

[0039]

[0040] in, To be related to the longitudinal speed of the vehicle Inverse processing of the relevant steady-state yaw rate gain, The target is to achieve the ideal yaw rate control.

[0041] Based on the Ackermann steering geometry, the nominal vehicle steering angle is distributed to each wheel on the front and rear axles to obtain the yaw motion feedforward control quantity based on the ideal path tracking requirements. ;Setting the vehicle longitudinal speed threshold in the feedforward control method based on pure yaw motion It can be obtained through calibration based on road surface adhesion conditions, vehicle dynamics characteristics, or dynamic control requirements, provided that the vehicle's longitudinal speed meets the requirements. At that time, a front-to-rear wheel steering distribution mode is adopted; when the vehicle's longitudinal speed meets the requirements... At the same time, the rear axle steering angle distribution weight is adjusted according to the vehicle's longitudinal speed, so that the rear axle steering angle distribution weight decreases as the vehicle's longitudinal speed increases, in order to balance vehicle maneuverability and driving stability.

[0042] Feedforward control methods based on pure lateral motion include:

[0043] In pure lateral motion control mode, an ideal center of gravity sideslip angle control target is constructed based on the mapping relationship between the vehicle attitude lever opening and the ideal center of gravity sideslip angle under different vehicle speed conditions. Pure lateral motion control tracks the ideal center of gravity sideslip angle control target under the condition that the change in yaw rate does not exceed a preset threshold. The preset threshold for the change in yaw rate is a proportional threshold relative to the steady-state value of yaw rate. In some embodiments, the proportional threshold can be taken as ±3% to ±10% of the steady-state value of yaw rate, preferably ±5%.

[0044] The steering angle of the four wheels is distributed based on the principle of front and rear wheels steering in the same direction to support extended driving modes, including lateral translation and diagonal driving;

[0045] By combining the ideal center-of-gravity sideslip angle control target with the driver posture adjustment mapping curve, the four-wheel steering angle distribution relationship under different steering modes is obtained. The driver posture adjustment mapping curve is obtained by data fitting based on vehicle state and road conditions. Its objective is to construct the desired mapping relationship between the center-of-gravity sideslip angle and the four-wheel steering angle while minimizing the impact on yaw rate, satisfying the following optimization relationship:

[0046]

[0047] in, For the four-wheel steering angle, They are the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. The yaw rate is angular velocity. The sideslip angle is the angle of the center of mass. Indicates constraints;

[0048] This yields the lateral motion feedforward control variable based on the driver's posture adjustment intention. This provides the basic input for subsequent angular module dynamic feedback control.

[0049] Furthermore, the feedback optimization control method includes:

[0050] The four-wheel steering angle feedforward control quantity obtained by the vehicle kinematics feedforward control method based on pure yaw motion and pure lateral motion As the basic control variable for feedback optimization control, among which ; This is the feedforward control variable for yaw motion. This is the lateral motion feedforward control quantity;

[0051] Based on the basic control variables, feedback optimization control is introduced to achieve an ideal yaw rate control objective based on a two-degree-of-freedom driver control system that includes steering wheel angle and vehicle attitude lever opening. And the target of the ideal center of mass sideslip angle control As a feedback control objective;

[0052] Additional yaw moment generated by vehicle distributed drive / braking The four-wheel steering angle control quantity of four-wheel independent steering is jointly optimized to compensate for the impact of vehicle nonlinear dynamic characteristics and changes in driving conditions on control accuracy.

[0053] By utilizing the overdrive characteristics of the corner module automotive actuator, decoupled control of the vehicle's yaw and lateral motion under combined operating conditions can be achieved.

[0054] Furthermore, in the adaptive adjustment strategy for the control target weights, the adaptive adjustment methods for the weights of the ideal yaw rate control target include:

[0055] When the vehicle attitude lever is open At this time, the vehicle control system controls solely based on the driver's steering wheel input and employs a primarily feedforward control method; in feedback control, the weight corresponding to the ideal yaw rate control target... Represented as:

[0056]

[0057] Among them, the function For lateral acceleration A monotonically increasing function;

[0058] When the vehicle attitude lever is open At that time, the driver operating system is a two-degree-of-freedom driver control system including a steering wheel and vehicle attitude levers; in feedback control, the weight corresponding to the ideal yaw rate control target is... Represented as:

[0059]

[0060] Among them, the function For lateral acceleration Vehicle attitude lever opening A monotonically increasing function;

[0061] Furthermore, the weights corresponding to the ideal center-of-mass sideslip angle control target are determined based on the lateral acceleration. Vehicle attitude lever opening Perform adaptive adjustment, when When within the preset low lateral acceleration range, the weights follow... It increases with the increase of; when When within the preset high lateral acceleration range, the weights follow... The lateral acceleration decreases as the lateral acceleration increases. The low lateral acceleration range and the high lateral acceleration range are divided based on the vehicle yaw stability boundary or tire adhesion characteristics, and are determined through calibration.

[0062] Furthermore, the method for adaptively adjusting the penalty weights of the control variables is as follows:

[0063] Penalty weights are set for the additional yaw moment based on distributed drive / braking and the four-wheel steering angle control quantity based on four-wheel independent steering, respectively;

[0064] The control variable penalty weight Lateral acceleration With vehicle attitude lever opening The function is represented as:

[0065]

[0066] Among them, the function satisfy:

[0067] When the vehicle's lateral acceleration Within the preset low lateral acceleration range, and with the vehicle attitude lever open... When the control variable is within a preset small opening range, the penalty weight of the control variable is set to a larger value. The preset small opening range of the vehicle posture lever opening is a preset proportional range relative to the maximum opening of the lever. In some embodiments, the preset small opening range is 0% to 30% of the maximum opening of the lever, preferably 0% to 20%. Setting the penalty weight of the control variable to a larger value means that the penalty weight of the control variable is set to a larger value relative to its value range. In some embodiments, the value range is determined by calibration as the range from the minimum weight value to the maximum weight value. Larger values ​​correspond to values ​​close to The value of .

[0068] When lateral acceleration Or vehicle attitude lever opening When the lateral acceleration or the vehicle attitude lever opening increases, the penalty weight of the control variable decreases.

[0069] Furthermore, methods for adaptive adjustment strategies of constraints include:

[0070] Vehicle state constraints, including yaw rate stability limits determined based on ultimate tire forces. The stability limit value of the centroid sideslip angle determined based on the front and rear axle saturation sideslip angles And based on the road surface adhesion coefficient longitudinal speed of vehicles And the four-wheel steering angle dynamically updates the stability limit value, and the vehicle's yaw rate. and centroid side slip angle The constraints are satisfied:

[0071]

[0072] in, For the four-wheel steering angle, They are the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively.

[0073] The tire working point constraint includes the four-wheel tire saturation slip angle constraint. The saturation slip angle is obtained by fitting tire data based on different road adhesion coefficients and vertical tire force conditions. The tire working point constraint is dynamically updated according to the real-time road adhesion coefficient and vertical load to avoid the tire working point from entering the saturation region of the tire slip characteristic curve.

[0074] Furthermore, the feedforward-feedback coordinated control strategy distributes the additional yaw moment to obtain four-wheel drive / braking torque and generates four-wheel steering angle control quantities, which are then applied to the four-wheel angle modules to achieve vehicle motion control. The method is as follows:

[0075] Based on the additional yaw moment obtained from feedback optimization control, under the constraints of the tire force feasible domain, combined with the lateral control objective and the longitudinal vehicle speed tracking control objective, the additional yaw moment is optimized and allocated in multiple objectives to determine the four-wheel drive / braking torque, and then applied to the vehicle's distributed drive / braking system.

[0076] A wheel load utilization rate index is introduced to characterize the relationship between the tire force of each wheel and the corresponding vertical load under the action of four-wheel drive / braking force and four-wheel steering angle. A control target cost function is constructed based on the wheel load utilization rate index, and the distribution of the load utilization rate of each wheel is adjusted by adaptively adjusting the weight of the cost function.

[0077] The lateral forces and longitudinal forces of the four wheels are combined to obtain the resultant force of each wheel, and the resultant force of each wheel is constrained within the feasible range of tire forces determined by the road adhesion coefficient and the vertical load of the wheel.

[0078] The four-wheel steering angle feedback control quantity obtained from the feedback control is superimposed with the four-wheel steering angle feedforward control quantity determined based on pure yaw motion and pure lateral motion to obtain the four-wheel steering angle control quantity, which is then input into the four-wheel angle module steering system.

[0079] The beneficial effects of this invention are:

[0080] 1) This invention introduces a two-degree-of-freedom driver control system consisting of a steering wheel and a vehicle posture lever, which enables collaborative analysis of the driver's path tracking intention and the vehicle posture adjustment intention. This overcomes the problem that traditional vehicles only rely on a single steering wheel input, which limits the dimension of driver intention expression and improves the completeness and accuracy of driver control intention modeling.

[0081] 2) Based on the dynamic characteristics of the two-degree-of-freedom driver control system and the angular module vehicle distributed actuator, this invention decouples the ideal yaw rate control target and the ideal center of mass sideslip angle control target, and constructs a composite control architecture that integrates feedforward control and feedback optimization control. By jointly adjusting the steering angle of the four wheels and the additional yaw moment, the coordinated adjustment and effective decoupling of the vehicle's yaw motion and lateral motion are achieved, thereby improving the accuracy and stability of vehicle motion control under complex working conditions.

[0082] 3) This invention designs feedforward control strategies for pure yaw and pure lateral conditions respectively, and combines them with a vehicle speed adaptive adjustment mechanism to achieve a smooth transition between lateral movement mode, diagonal movement mode and conventional steering mode. While ensuring vehicle driving stability, it expands the vehicle's lateral translation, diagonal movement and other driving modes, and improves the continuity and adaptability of vehicle control functions. Attached Figure Description

[0083] Figure 1 This is an overall flowchart of the vehicle motion control system based on angular module dynamics of the present invention.

[0084] Figure 2 This is a flowchart illustrating the ideal control target of the two-degree-of-freedom driver control system of this invention.

[0085] Figure 3 This is a flowchart of the vehicle kinematics feedforward control method based on pure yaw motion and pure lateral motion according to the present invention. Detailed Implementation

[0086] See Figure 1 As shown, this embodiment provides a vehicle motion control system based on angular module dynamics, comprising:

[0087] Input layer: The inputs are the driver's steering wheel, the vehicle attitude lever, and the vehicle status;

[0088] Control layer:

[0089] Ideal target design based on a two-degree-of-freedom driver control system:

[0090] A two-degree-of-freedom driver control system is constructed, which includes driver steering wheel input and vehicle posture lever input, to separately analyze the driver's driving intentions for path curvature tracking and vehicle posture adjustment;

[0091] Based on the two-degree-of-freedom driver control system, an ideal yaw rate control target corresponding to path curvature tracking and an ideal center of mass sideslip angle control target corresponding to vehicle attitude adjustment are respectively constructed.

[0092] Vehicle kinematics feedforward control method based on a single operating condition:

[0093] Based on the vehicle kinematics feedforward control method for pure yaw motion and pure lateral motion, four-wheel steering angle feedforward control quantities are designed corresponding to the ideal yaw rate control target and the ideal center of mass sideslip angle control target, respectively.

[0094] Dynamic decoupling optimization control method based on combined working conditions:

[0095] Based on the feedforward control of the four-wheel steering angle as the basic control variable, feedback optimization control is introduced to jointly adjust the additional yaw moment based on distributed drive / braking and the four-wheel steering angle control based on independent four-wheel steering, thereby achieving decoupled control of vehicle yaw motion and lateral motion.

[0096] Based on the vehicle's operating conditions, an adaptive adjustment strategy is designed for the control target weights, control variable penalty weights, and constraint conditions to determine the vehicle motion control parameters based on angular module dynamics.

[0097] Execution layer:

[0098] Based on the feedforward-feedback coordinated control strategy, the additional yaw moment is distributed to obtain four-wheel drive / braking moment, and four-wheel steering angle control quantities are generated and applied to the four-wheel angle modules to achieve vehicle motion control.

[0099] In this embodiment, the two-degree-of-freedom driver control system includes a steering wheel and a vehicle attitude lever;

[0100] The steering wheel adopts a traditional steering wheel structure and eliminates the mechanical connection between it and the four-wheel steering system. It communicates with the vehicle control unit via steer-by-wire. The driver inputs the intention to track the curvature of the path through the steering wheel input. The vehicle control unit calculates and distributes the actuator momentum to the four-wheel corner module system based on the steering wheel input. At the same time, the road feel simulation unit provides feedback on the vehicle's driving status to the driver. The four-wheel corner module system has the same actuators and physical structure, and includes independent steer-by-wire systems, drive-by-wire systems, brake-by-wire systems, and active or semi-active suspension systems.

[0101] The vehicle attitude lever is a newly added driver operation unit that communicates with the vehicle control unit via a drive-by-wire method. The driver can input the vehicle attitude adjustment intention by moving the vehicle attitude lever left and right, combined with the mapping relationship between the opening of the vehicle attitude lever and the center of gravity sideslip angle at different vehicle speeds. This is used to represent the driver's independent control needs for vehicle attitude adjustment in addition to path curvature tracking.

[0102] By combining the steering wheel and the vehicle attitude lever to form a two-degree-of-freedom driver control system, the system can comprehensively represent the driver's yaw and lateral movement adjustment needs, providing decoupled control inputs for subsequent control strategies. This enables the vehicle to achieve various driving modes such as lane change obstacle avoidance, attitude adjustment obstacle avoidance, lateral translation, diagonal driving, and stationary turning, and supports smooth transitions between different driving modes.

[0103] In this embodiment, the ideal control target design based on the two-degree-of-freedom driver control system is as follows: Figure 2As shown, the ideal yaw rate control target is constructed based on the mapping relationship between the driver's steering wheel angle and the path curvature, as follows:

[0104] The driver's input to the steering wheel represents their intention to track the road ahead, based on the steering wheel angle. The relationship between the path curvature and the desired path curvature is used to determine the desired path curvature. It satisfies the following relationship:

[0105]

[0106] In the formula, Based on the steering sensitivity coefficient, For the longitudinal speed of the vehicle, Characteristic velocity parameters;

[0107] when At that time, steering sensitivity It will drop to half of its zero speed. The path curvature is used; under neutral steering conditions, steering sensitivity is independent of speed; by introducing a certain degree of understeer, the steering sensitivity decreases as speed increases, thus achieving direct determination of the curvature by the steering wheel at low speeds, and improving high-speed stability by avoiding oversteering at high speeds.

[0108] Based on the geometric relationship between path curvature and the rate of change of heading angle, an initial reference value for the ideal yaw rate based on path curvature tracking is constructed:

[0109]

[0110] in, The initial reference value for the ideal yaw rate. The ideal rate of change of heading angle;

[0111] To achieve yaw rate and centroid side slip angle The decoupling control will set the initial reference value of the ideal yaw rate to... Defined as a reference value based on the curvature of the center of mass trajectory, and introducing a compensation term for the change in the sideslip angle of the center of mass into the initial reference value of the ideal yaw rate, the final ideal yaw rate control target is obtained:

[0112]

[0113] in, To achieve the ideal yaw rate control target, Let be the rate of change of the centroid sideslip angle.

[0114] In this embodiment, the ideal centroid sideslip angle control target is constructed based on the vehicle attitude lever input and the vehicle speed, as follows:

[0115] The driver's input to the vehicle attitude lever represents the driving intention to adjust the vehicle attitude. This invention constructs an analytical model for the vehicle attitude lever (Vehicle-Attitude Control Lever Interpretation, ALI) to map the driver's input to the vehicle attitude lever into an ideal centroid sideslip angle control target that represents changes in vehicle attitude during lateral motion control. ;

[0116] In the analytical model of the vehicle attitude lever, the opening degree of the vehicle attitude lever is defined. Adjusting the angle of the vehicle attitude lever Limit angle of the lever The ratio of satisfies:

[0117]

[0118] The positive or negative sign of the opening of the vehicle attitude lever is used to represent the direction of vehicle attitude adjustment, and the absolute value of the opening of the vehicle attitude lever is used to represent the intensity of vehicle attitude adjustment.

[0119] Setting the vehicle longitudinal velocity threshold in the vehicle attitude lever analytical model When the vehicle's longitudinal speed satisfies As the vehicle attitude lever opening increases, the vehicle transitions from straight-line driving to diagonal driving at different angles. The angle of diagonal driving increases with the lever opening. The vehicle motion mode corresponding to the maximum opening of the vehicle attitude lever is defined as the lateral translation mode. When the vehicle's longitudinal speed satisfies... As the vehicle speed increases, a speed attenuation factor is introduced to suppress the lateral translation trend, and a mapping relationship is constructed between the limiting centroid sideslip angle corresponding to the maximum opening of the vehicle attitude lever and the vehicle speed:

[0120]

[0121] in, This indicates that the longitudinal speed of the vehicle satisfies The corresponding limiting centroid sideslip angle at that time This indicates that the longitudinal speed of the vehicle satisfies The corresponding limiting centroid sideslip angle at that time This is the vehicle speed attenuation factor;

[0122] Based on the mapping relationship between the vehicle attitude lever opening and the limit center of gravity sideslip angle, the ideal center of gravity sideslip angle control target is constructed as follows:

[0123]

[0124] in, The target is to control the sideslip angle of the ideal center of mass.

[0125] In this embodiment, the vehicle kinematics feedforward control method based on pure yaw motion and pure lateral motion obtains four-wheel steering angle feedforward control quantities corresponding to the ideal yaw rate control target and the ideal center-of-gravity sideslip angle control target. These quantities are used to convert the driver's input intention into an executable four-wheel steering control target, such as... Figure 3 As shown;

[0126] Among them, the feedforward control method based on pure yaw motion includes:

[0127] In pure yaw motion control mode, an ideal yaw rate control target based on path curvature tracking is constructed according to the driver's steering wheel angle input. Combined with the steady-state yaw rate gain inverse model of the two-degree-of-freedom vehicle dynamics model, the nominal vehicle steering angle that satisfies the ideal yaw rate control target is calculated. The formula is as follows:

[0128]

[0129] in, To be related to the longitudinal speed of the vehicle Inverse processing of the relevant steady-state yaw rate gain, The target is to achieve the ideal yaw rate control.

[0130] Based on the Ackermann steering geometry, the nominal vehicle steering angle is distributed to each wheel on the front and rear axles to obtain the yaw motion feedforward control quantity based on the ideal path tracking requirements. ;Setting the vehicle longitudinal speed threshold in the feedforward control method based on pure yaw motion When the vehicle's longitudinal speed satisfies At that time, a front-to-rear wheel steering distribution mode is adopted; when the vehicle's longitudinal speed meets the requirements... At the same time, the rear axle steering angle distribution weight is adjusted according to the vehicle's longitudinal speed, so that the rear axle steering angle distribution weight decreases as the vehicle's longitudinal speed increases, in order to balance vehicle maneuverability and stability.

[0131] Feedforward control methods based on pure lateral motion include:

[0132] In pure lateral motion control mode, the ideal center of gravity sideslip angle control target is constructed based on the mapping relationship between the opening of the vehicle attitude lever and the ideal center of gravity sideslip angle under different vehicle speed conditions; pure lateral motion control achieves tracking of the ideal center of gravity sideslip angle control target under the condition that the change in yaw rate does not exceed a preset threshold.

[0133] The steering angle of the four wheels is distributed based on the principle of front and rear wheels steering in the same direction to support extended driving modes, including lateral translation and diagonal driving;

[0134] By combining the ideal center-of-gravity sideslip angle control target with the driver posture adjustment mapping curve, the four-wheel steering angle distribution relationship under different steering modes is obtained. The driver posture adjustment mapping curve is obtained by data fitting based on vehicle state and road conditions. Its objective is to construct the desired mapping relationship between the center-of-gravity sideslip angle and the four-wheel steering angle while minimizing the impact on yaw rate, satisfying the following optimization relationship:

[0135]

[0136] in, For the four-wheel steering angle, They are the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. The target for controlling the sideslip angle of the ideal center of mass; The yaw rate is angular velocity. The sideslip angle is the angle of the center of mass. Indicates constraints;

[0137] This yields the lateral motion feedforward control variable based on the driver's posture adjustment intention. This provides the basic input for subsequent angular module dynamic feedback control.

[0138] In this embodiment, the feedback optimization control method includes:

[0139] The four-wheel steering angle feedforward control quantity obtained by the vehicle kinematics feedforward control method based on pure yaw motion and pure lateral motion As the basic control variable for feedback optimization control, among which ; This is the feedforward control variable for yaw motion. This is the lateral motion feedforward control quantity;

[0140] Based on the basic control variables, feedback optimization control is introduced to achieve an ideal yaw rate control objective based on a two-degree-of-freedom driver control system that includes steering wheel angle and vehicle attitude lever opening. And the target of the ideal center of mass sideslip angle control As a feedback control objective;

[0141] Additional yaw moment generated by vehicle distributed drive / braking The four-wheel steering angle control quantity of four-wheel independent steering is jointly optimized to compensate for the impact of vehicle nonlinear dynamic characteristics and changes in driving conditions on control accuracy.

[0142] By utilizing the overdrive characteristics of the corner module automotive actuator, decoupled control of the vehicle's yaw and lateral motion under combined operating conditions can be achieved.

[0143] In this embodiment, the method of adaptive adjustment strategy for control target weight is as follows: an adaptive adjustment strategy for control target weight based on vehicle state and driver operation is designed for the ideal yaw rate control target and the ideal centroid sideslip angle control target, respectively, in order to match the differences in vehicle dynamics decoupling capability under different working conditions.

[0144] The adaptive adjustment methods for the weights of the ideal yaw rate control target include:

[0145] When the vehicle attitude lever is open hour,

[0146] The vehicle control system operates solely based on driver steering wheel input and employs a primarily feedforward control approach. In feedback control, the weight corresponding to the ideal yaw rate control target is... Represented as:

[0147]

[0148] Among them, the function For lateral acceleration A monotonically increasing function;

[0149] To maintain the original vehicle's basic handling characteristics under low lateral acceleration conditions, and to enhance the feedback control's ability to compensate for nonlinear vehicle dynamics under high lateral acceleration conditions;

[0150] When the vehicle attitude lever is open At that time, the driver operating system is a two-degree-of-freedom driver control system including a steering wheel and vehicle attitude levers; in feedback control, the weight corresponding to the ideal yaw rate control target is... Represented as:

[0151]

[0152] Among them, the function For lateral acceleration Vehicle attitude lever opening A monotonically increasing function;

[0153] The adaptive adjustment methods for weights of the ideal centroid sideslip angle control target include:

[0154] The weight corresponding to the ideal centroid sideslip angle control target is based on the lateral acceleration. With vehicle attitude lever opening Perform adaptive adjustment, when When within the preset low lateral acceleration range, the weights follow... It increases with the increase of; when When within the preset high lateral acceleration range, the weights follow... The lateral acceleration decreases as the lateral acceleration increases. The low lateral acceleration range and the high lateral acceleration range are divided based on the vehicle yaw stability boundary or tire adhesion characteristics, and are determined through calibration.

[0155] In this embodiment, the method for adaptively adjusting the penalty weight of the control variable is as follows:

[0156] Penalty weights are set for the additional yaw moment based on distributed drive / braking and the four-wheel steering angle control quantity based on four-wheel independent steering, respectively;

[0157] The control variable penalty weight Lateral acceleration With vehicle attitude lever opening The function is represented as:

[0158]

[0159] Among them, the function satisfy:

[0160] When the vehicle's lateral acceleration Within the preset low lateral acceleration range, and with the vehicle attitude lever open... When the lever is within a preset small opening range, the penalty weight of the control variable is taken as close to its maximum value; the preset small opening range is 0% to 30% of the maximum opening of the lever, preferably 0% to 20%. Taking a large value for the penalty weight of the control variable means that the penalty weight of the control variable is taken as a larger value relative to its value range. In some embodiments, the value range is determined by calibration as the range from the minimum weight value to the maximum weight value. Larger values ​​correspond to values ​​close to The value of .

[0161] When lateral acceleration Or vehicle attitude lever opening When the lateral acceleration or the vehicle attitude lever opening increases, the penalty weight of the control variable decreases.

[0162] In this embodiment, the method for adaptive adjustment of constraints includes:

[0163] Vehicle state constraints, including yaw rate stability limits determined based on ultimate tire forces. The stability limit value of the centroid sideslip angle determined based on the front and rear axle saturation sideslip angles And based on the road surface adhesion coefficient longitudinal speed of vehicles And the four-wheel steering angle dynamically updates the stability limit value, and the vehicle's yaw rate. and centroid side slip angle The constraints are satisfied:

[0164]

[0165] in, For the four-wheel steering angle, They are the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively.

[0166] The tire working point constraint includes the four-wheel tire saturation slip angle constraint. The saturation slip angle is obtained by fitting tire data based on different road adhesion coefficients and vertical tire force conditions. The tire working point constraint is dynamically updated according to the real-time road adhesion coefficient and vertical load to avoid the tire working point from entering the saturation region of the tire slip characteristic curve.

[0167] The adaptive adjustment strategy of control target weight is combined with the adaptive adjustment strategy of control variable penalty weight, vehicle state constraint and tire working point constraint to form a weight and constraint collaborative adaptive adjustment mechanism suitable for complex working conditions.

[0168] In this embodiment,

[0169] The feedforward-feedback coordinated control strategy distributes the additional yaw moment to obtain four-wheel drive / braking torque and generates four-wheel steering angle control quantities, which are then applied to the four-wheel angle modules to achieve vehicle motion control. The method is as follows:

[0170] Based on the additional yaw moment obtained from feedback optimization control, under the constraints of the tire force feasible domain, combined with the lateral control objective and the longitudinal vehicle speed tracking control objective, the additional yaw moment is optimized and allocated in multiple objectives to determine the four-wheel drive / braking torque, and then applied to the vehicle's distributed drive / braking system.

[0171] A wheel load utilization rate index is introduced to characterize the relationship between the tire force of each wheel and the corresponding vertical load under the action of four-wheel drive / braking force and four-wheel steering angle. A control target cost function is constructed based on the wheel load utilization rate index, and the distribution of the load utilization rate of each wheel is adjusted by adaptively adjusting the weight of the cost function.

[0172] The lateral forces and longitudinal forces of the four wheels are combined to obtain the resultant force of each wheel, and the resultant force of each wheel is constrained within the feasible range of tire forces determined by the road adhesion coefficient and the vertical load of the wheel.

[0173] The four-wheel steering angle feedback control quantity obtained from the feedback control is superimposed with the four-wheel steering angle feedforward control quantity determined based on pure yaw motion and pure lateral motion to obtain the four-wheel steering angle control quantity, which is then input into the four-wheel angle module steering system.

Claims

1. A vehicle motion control system based on angular module dynamics, characterized in that, include: A two-degree-of-freedom driver control system was constructed, which includes driver steering wheel input and vehicle posture lever input, to separately analyze the driver's driving intentions for path curvature tracking and vehicle posture adjustment; Based on the two-degree-of-freedom driver control system, an ideal yaw rate control target corresponding to path curvature tracking and an ideal center of mass sideslip angle control target corresponding to vehicle attitude adjustment are respectively constructed. Based on the vehicle kinematics feedforward control method for pure yaw motion and pure lateral motion, four-wheel steering angle feedforward control quantities are designed corresponding to the ideal yaw rate control target and the ideal center of mass sideslip angle control target, respectively. Based on the feedforward control of the four-wheel steering angle as the basic control variable, feedback optimization control is introduced to jointly adjust the additional yaw moment based on distributed drive / braking and the four-wheel steering angle control based on independent four-wheel steering, thereby achieving decoupled control of vehicle yaw motion and lateral motion. Based on the vehicle's operating conditions, an adaptive adjustment strategy is designed for the control target weights, control variable penalty weights, and constraint conditions to determine the vehicle motion control parameters based on angular module dynamics. Based on the feedforward-feedback coordinated control strategy, the additional yaw moment is distributed to obtain four-wheel drive / braking moment, and four-wheel steering angle control quantities are generated and applied to the four-wheel angle modules to achieve vehicle motion control. The two-degree-of-freedom driver control system includes a steering wheel and vehicle attitude control levers: The steering wheel communicates with the vehicle control unit via steer-by-wire. The driver inputs their intention to track the curvature of the path through the steering wheel input. The vehicle control unit calculates and distributes the actuator momentum to the four-wheel corner module system based on the steering wheel input, and simultaneously provides the driver with vehicle driving status information through the road feel simulation unit. The four-wheel corner module system has the same actuators and physical structure, and includes independent steer-by-wire systems, drive-by-wire systems, brake-by-wire systems, and active or semi-active suspension systems. The vehicle attitude lever communicates with the vehicle control unit via a drive-by-wire method. The driver can input the vehicle attitude adjustment intention by moving the vehicle attitude lever left and right, combined with the mapping relationship between the opening of the vehicle attitude lever and the center of gravity sideslip angle at different vehicle speeds. This is used to represent the driver's independent control needs for vehicle attitude adjustment in addition to path curvature tracking. By combining the steering wheel and the vehicle posture lever to form a two-degree-of-freedom driver control system, a comprehensive representation of the driver's yaw motion adjustment needs and lateral motion adjustment needs can be achieved, providing decoupled control input for subsequent control strategies.

2. The vehicle motion control system based on angular module dynamics according to claim 1, characterized in that: In the design of the ideal yaw rate control target and the ideal center-of-gravity sideslip angle control target based on a two-degree-of-freedom driver control system, the ideal yaw rate control target is constructed based on the mapping relationship between the driver's steering wheel angle and the path curvature, as follows: The driver's input to the steering wheel represents their intention to track the road ahead, based on the steering wheel angle. The relationship between the path curvature and the desired path curvature is used to determine the desired path curvature. It satisfies the following relationship: In the formula, Based on the steering sensitivity coefficient, For the longitudinal speed of the vehicle, Characteristic velocity parameters; when At that time, steering sensitivity It will drop to half of its zero speed. The path curvature; under neutral steering conditions, steering sensitivity is independent of speed; By introducing understeer, the steering sensitivity decreases as speed increases; Based on the geometric relationship between path curvature and the rate of change of heading angle, an initial reference value for the ideal yaw rate is constructed for path curvature tracking: in, The initial reference value for the ideal yaw rate. The ideal rate of change of heading angle; To achieve yaw rate and centroid side slip angle The decoupling control will set the initial reference value of the ideal yaw rate. Defined as a reference value based on the curvature of the center of mass trajectory, and eliminating the effect of the center of mass sideslip angle on the heading angle, that is, introducing a compensation term for the change in the center of mass sideslip angle into the initial reference value of the ideal yaw rate to obtain the final ideal yaw rate control target: in, To achieve the ideal yaw rate control target, Let be the rate of change of the centroid sideslip angle.

3. The vehicle motion control system based on angular module dynamics according to claim 1, characterized in that: In the design of the ideal yaw rate control target and the ideal center-of-gravity sideslip angle control target based on the two-degree-of-freedom driver control system, the ideal center-of-gravity sideslip angle control target is constructed based on the vehicle attitude lever input, as follows: The driver's input to the vehicle attitude control lever represents the driver's intention to adjust the vehicle attitude. Combined with the analytical model of the vehicle attitude control lever, the driver's input to the vehicle attitude control lever is mapped to the ideal centroid sideslip angle control target, which represents the change in vehicle attitude, in the lateral motion control of the vehicle. ; In the analytical model of the vehicle attitude lever, the opening degree of the vehicle attitude lever is defined. Adjusting the angle of the vehicle attitude lever Limit angle of the lever The ratio of satisfies: The positive or negative sign of the opening of the vehicle attitude lever is used to represent the direction of vehicle attitude adjustment, and the absolute value of the opening of the vehicle attitude lever is used to represent the intensity of vehicle attitude adjustment. Set the vehicle longitudinal velocity threshold in the analytical model of the vehicle attitude lever. When the vehicle's longitudinal speed satisfies As the opening of the vehicle attitude lever increases, the vehicle changes from straight driving to diagonal driving at different angles. The angle of diagonal driving increases with the increase of the lever opening. The vehicle motion mode corresponding to the maximum opening of the vehicle attitude lever is defined as the lateral translation mode. The vehicle's longitudinal speed satisfies As the vehicle speed increases, a speed attenuation factor is introduced to suppress the lateral translation trend, and a mapping relationship is constructed between the limiting centroid sideslip angle corresponding to the maximum opening of the vehicle attitude lever and the vehicle speed: in, This indicates that the longitudinal speed of the vehicle satisfies The corresponding limiting centroid sideslip angle at that time This indicates that the longitudinal speed of the vehicle satisfies The corresponding limiting centroid sideslip angle at that time This is the vehicle speed attenuation factor; Based on the mapping relationship between the vehicle attitude lever opening and the limit center of gravity sideslip angle, the ideal center of gravity sideslip angle control target is constructed as follows: in, The target is to control the sideslip angle of the ideal center of mass.

4. The vehicle motion control system based on angular module dynamics according to claim 1, characterized in that: The aforementioned vehicle kinematics feedforward control method based on pure yaw motion and pure lateral motion includes a feedforward control method based on pure yaw motion, which comprises: In pure yaw motion control mode, an ideal yaw rate control target based on path curvature tracking is constructed according to the driver's steering wheel angle input. Combined with the steady-state yaw rate gain inverse model of the two-degree-of-freedom vehicle dynamics model, the nominal vehicle steering angle that satisfies the ideal yaw rate control target is calculated. The formula is as follows: in, To be related to the longitudinal speed of the vehicle Inverse processing of the relevant steady-state yaw rate gain, The target is to achieve the ideal yaw rate control. Based on the Ackermann steering geometry, the nominal vehicle steering angle is distributed to each wheel on the front and rear axles to obtain the yaw motion feedforward control quantity based on the ideal path tracking requirements. ;Setting the vehicle longitudinal speed threshold in the feedforward control method based on pure yaw motion When the vehicle's longitudinal speed satisfies At that time, a front-to-rear wheel steering distribution mode is adopted; when the vehicle's longitudinal speed meets the requirements... At the same time, the rear axle steering angle distribution weight is adjusted according to the vehicle's longitudinal speed, so that the rear axle steering angle distribution weight decreases as the vehicle's longitudinal speed increases, in order to balance vehicle maneuverability and stability. Feedforward control methods based on pure lateral motion include: In pure lateral motion control mode, the ideal center of gravity sideslip angle control target is constructed based on the mapping relationship between the opening of the vehicle attitude lever and the ideal center of gravity sideslip angle under different vehicle speed conditions; pure lateral motion control achieves tracking of the ideal center of gravity sideslip angle control target under the condition that the change in yaw rate does not exceed a preset threshold. The steering angle of the four wheels is distributed based on the principle of front and rear wheels steering in the same direction to support extended driving modes, including lateral translation and diagonal driving; By combining the ideal center-of-gravity sideslip angle control target with the driver posture adjustment mapping curve, the four-wheel steering angle distribution relationship under different steering modes is obtained. The driver posture adjustment mapping curve is obtained by data fitting based on vehicle state and road conditions. Its objective is to construct the desired mapping relationship between the center-of-gravity sideslip angle and the four-wheel steering angle while minimizing the impact on yaw rate, satisfying the following optimization relationship: in, For four-wheel steering angle, They are the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. The target for controlling the sideslip angle of the ideal center of mass; The yaw rate is angular velocity. The sideslip angle is the angle of the centroid. Indicates constraints; This yields the lateral motion feedforward control quantity based on the driver's attitude adjustment intention. This provides the basic input for subsequent angular module dynamic feedback control.

5. A vehicle motion control system based on angular module dynamics according to claim 1, characterized in that: The feedback optimization control method includes: The four-wheel steering angle feedforward control quantity obtained by the vehicle kinematics feedforward control method based on pure yaw motion and pure lateral motion As the basic control variable for feedback optimization control, among which ; This is the feedforward control variable for yaw motion. This is the lateral motion feedforward control quantity; Based on the basic control variables, feedback optimization control is introduced to achieve an ideal yaw rate control objective based on a two-degree-of-freedom driver control system that includes steering wheel angle and vehicle attitude lever opening. And the target of the ideal center of mass sideslip angle control As a feedback control objective; Additional yaw moment generated by vehicle distributed drive / braking The control parameters of the four-wheel steering angle of the four-wheel independent steering system are jointly optimized to compensate for the impact of the vehicle's nonlinear dynamic characteristics and changes in driving conditions on the control accuracy. By utilizing the overdrive characteristics of the corner module automotive actuator, decoupled control of the vehicle's yaw and lateral motion under combined operating conditions can be achieved.

6. A vehicle motion control system based on angular module dynamics according to claim 1, characterized in that: In the adaptive adjustment strategy for control target weights, the adaptive adjustment methods for the weights of the ideal yaw rate control target include: When the vehicle attitude lever is open At this time, the vehicle control system controls solely based on the driver's steering wheel input and employs a primarily feedforward control method; in feedback control, the weight corresponding to the ideal yaw rate control target... Represented as: Among them, the function For lateral acceleration A monotonically increasing function; When the vehicle attitude lever is open At that time, the driver operating system is a two-degree-of-freedom driver control system including a steering wheel and vehicle attitude levers; in feedback control, the weight corresponding to the ideal yaw rate control target... Represented as: Among them, the function For lateral acceleration Vehicle attitude lever opening A monotonically increasing function; The weight corresponding to the ideal centroid sideslip angle control target is based on the lateral acceleration. Vehicle attitude lever opening Perform adaptive adjustment, when When within the preset low lateral acceleration range, the weights follow... It increases with the increase of; when When within the preset high lateral acceleration range, the weights follow... It decreases as it increases.

7. A vehicle motion control system based on angular module dynamics according to claim 1, characterized in that: The adaptive adjustment strategy for the penalty weight of the control variable is as follows: Penalty weights are set for the additional yaw moment based on distributed drive / braking and the four-wheel steering angle control quantity based on four-wheel independent steering, respectively; The control variable penalty weight Lateral acceleration Vehicle attitude lever opening The function is represented as: Among them, the function satisfy: When the vehicle's lateral acceleration Within the preset low lateral acceleration range, and with the vehicle attitude lever open... When the opening is within a preset small range, the penalty weight of the control variable takes a large value; When lateral acceleration Or vehicle attitude lever opening When the lateral acceleration or the vehicle attitude lever opening increases, the penalty weight of the control variable decreases.

8. A vehicle motion control system based on angular module dynamics according to claim 1, characterized in that: Methods for adaptive adjustment strategies of constraints include: Vehicle state constraints, including yaw rate stability limits determined based on ultimate tire forces. The stability limit value of the centroid sideslip angle determined based on the front and rear axle saturation sideslip angles And based on the road surface adhesion coefficient longitudinal speed of vehicles And the four-wheel steering angle dynamically updates the stability limit value, and the vehicle's yaw rate. and centroid side slip angle The constraints are satisfied: in, For four-wheel steering angle, They are the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. The tire working point constraint includes the four-wheel tire saturation slip angle constraint. The saturation slip angle is obtained by fitting tire data based on different road adhesion coefficients and vertical tire force conditions. The tire working point constraint is dynamically updated according to the real-time road adhesion coefficient and vertical load to avoid the tire working point from entering the saturation region of the tire slip characteristic curve.

9. A vehicle motion control system based on angular module dynamics according to claim 1, characterized in that: The feedforward-feedback coordinated control strategy distributes the additional yaw moment to obtain four-wheel drive / braking torque and generates four-wheel steering angle control quantities, which are then applied to the four-wheel angle modules to achieve vehicle motion control. The method is as follows: Based on the additional yaw moment obtained from feedback optimization control, under the constraints of the tire force feasible domain, combined with the lateral control objective and the longitudinal vehicle speed tracking control objective, the additional yaw moment is optimized and allocated in multiple objectives to determine the four-wheel drive / braking torque, and then applied to the vehicle's distributed drive / braking system. A wheel load utilization rate index is introduced to characterize the relationship between the tire force of each wheel and the corresponding vertical load under the action of four-wheel drive / braking force and four-wheel steering angle. Based on the wheel load utilization rate index, a control target cost function is constructed, and the distribution of the load utilization rate of each wheel is adjusted by adaptively adjusting the weight of the cost function. The lateral forces and longitudinal forces of the four wheels are combined to obtain the resultant force of each wheel, and the resultant force of each wheel is constrained within the feasible range of tire forces determined by the road adhesion coefficient and the vertical load of the wheel. The four-wheel steering angle feedback control quantity obtained from the feedback control is superimposed with the four-wheel steering angle feedforward control quantity determined based on pure yaw motion and pure lateral motion to obtain the four-wheel steering angle control quantity, which is then input into the four-wheel angle module steering system.

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