CN-120003464-B - Distributed driving vehicle chassis cooperative control method based on variable steering characteristics

CN120003464BCN 120003464 BCN120003464 BCN 120003464BCN-120003464-B

Abstract

The invention relates to a distributed driving vehicle chassis cooperative control method based on variable steering characteristics, which belongs to the technical field of vehicle dynamics control and comprises the following steps of S1, generating a reference vehicle state based on target steering characteristics and a two-degree-of-freedom two-wheel vehicle transverse dynamics model, and S2, generating an AFS front wheel steering angle and a DYC additional yaw moment based on MPC control. And S3, distributing wheel driving or braking torque based on the tire utilization minimization and the target additional yaw moment. The invention can adjust the steering characteristic of the controlled vehicle on the premise of not changing the hardware characteristic, is beneficial to setting constraint and improving control precision, and improves the transverse stability of the vehicle by minimizing the utilization rate of tires.

Inventors

HU XIAOSONG
WU KUNHAO
LI JIACHENG
LIU CONGZHI
KANG ZHE
CUI HANGHANG
YANG BIN

Assignees

重庆大学

Dates

Publication Date: 20260505
Application Date: 20250325

Claims (8)

1. A distributed driving vehicle chassis cooperative control method based on variable steering characteristics is characterized by comprising the following steps: S1, generating a reference vehicle state based on target steering characteristics and a two-degree-of-freedom two-wheeled vehicle transverse dynamics model; s2, generating an AFS front wheel steering angle and a DYC additional yaw moment based on MPC control; S3, distributing wheel driving or braking torque based on the tire utilization minimization and the target additional yaw moment; The step S1 of generating a reference vehicle state through a two-degree-of-freedom two-wheeled vehicle lateral dynamics model based on the target steering characteristic specifically includes: s11, establishing a differential equation of a two-degree-of-freedom two-wheeled vehicle transverse dynamics model according to Newton' S second law; S12, replacing and expressing the tire transverse force as the product of cornering stiffness and cornering angle on the differential equation established in the step S11, and substituting the product into a calculation formula of the cornering angle; s13, in the differential equation modified in the step S12, the transverse speed of the vehicle is set And yaw rate of vehicle The derivative of (2) is 0, and the steady state response of the two-degree-of-freedom model is obtained; s14, understeer gradient representing steering characteristics of vehicle Expressing as a function of cornering stiffness of the front and rear tires, obtaining an explicit relation between cornering stiffness and steering characteristics; the differential equation in step S11 is: Wherein, the For the mass of the vehicle it is, For the mass of the vehicle it is, For the distance of the front axle of the vehicle to the centroid, For the distance of the rear axle of the vehicle to the centre of mass, For the longitudinal speed of the vehicle, For the transverse velocity of the vehicle, For the yaw rate of the vehicle, Is the rotation angle of the front wheel of the vehicle, (I=f, r) is the front-rear tire lateral force; In step S12, the tire lateral force is written as cornering stiffness Angle with the side deviation Is a product of (1), and has: Slip angle The calculation formula of (2) is as follows: the original differential equation is rewritten as: The steady state response of the two-degree-of-freedom model in step S13 is:
2. The method for cooperative control of a vehicle chassis based on variable steering characteristics according to claim 1, wherein the generating of the AFS front wheel steering angle and the DYC additional yaw moment based on MPC control in step S2 specifically comprises the steps of: s21, establishing a controlled object state space according to a differential equation of a two-degree-of-freedom four-wheel vehicle dynamics model; S22, predicting the state quantity and the output quantity of the system based on the current state quantity and the future control input quantity of the system; S23, minimizing a weighted quadratic cost function of tracking error and control input, and expanding the weighted quadratic cost function into a matrix form; s24, defining constraint conditions of input, output or state quantity, and explicitly embedding the constraint conditions into an optimization problem; S25, solving an optimization problem through a quadratic programming method to obtain a control input sequence; S26, after the control input is applied, the system advances to the next moment, the time domain is scrolled, the step S21 is returned, and the steps S21-S25 are re-executed.
3. The method for cooperative control of a chassis of a vehicle driven by a variable steering characteristic according to claim 2, wherein the controlled object state space in step S21 is established as follows: Assuming lateral velocity based on a two-degree-of-freedom four-wheel vehicle lateral dynamics model And yaw rate It can be seen that the following state space is established: Wherein the state vector Control input vector Output vector , In the form of a system matrix, In order to control the matrix, The expression of each matrix is as follows: Wherein the method comprises the steps of
4. The method for cooperative control of a vehicle chassis based on a variable steering characteristic according to claim 2, wherein the step S22 is based on a current state of the system And future control sequences Predicting system future Status and output of steps: Wherein the method comprises the steps of In order to predict the time domain of the signal, To control time domain% ); The weighted quadratic cost function that minimizes tracking error and control input in step S23 is: Spread into a matrix form: Wherein the method comprises the steps of In order to predict the output sequence of the signal, And As a matrix of weights, the weight matrix, For reference from two-degree-of-freedom transverse dynamics model of vehicle A track.
5. The method for cooperative control of a vehicle chassis based on variable steering characteristics according to claim 2, wherein the constraint condition is defined in step S24 as follows: explicitly embedding input, output or state constraints into the optimization problem: the input constraints are determined by the actuator limits: output or state constraints: the solving the optimization problem in step S25, to obtain a control input, includes: Substituting the predictive model into the objective function to construct To optimize the quadratic programming problem of variables: Wherein the second order sensitivity matrix of the control input to the objective function And a linear drive vector of the deviation amount of the reference vector and the current state prediction versus the objective function Generated by a system model and a weight matrix, and a constraint matrix Constraint vector Constructed from constraints, the specific following are: hessian matrix And a linear term vector : Wherein, the For the lower triangular matrix, the elements are (When ); ; Constraint matrix Constraint vector : Wherein, the 、 And Respectively control quantity, control quantity change rate and output quantity constraint matrix, 、、 Control amount, control amount change rate, and output amount constraint vector, respectively: Wherein, the Is that Is a matrix of units of (a); Represents the Kronecker product of the equation, Is of length of Is the full 1 vector of (2); is of the same kind ; Wherein, the Is that Is a differential matrix of (a);
6. The method for cooperative control of a vehicle chassis based on a distributed drive of a variable steering characteristic according to claim 1, wherein the step S3 of distributing the wheel driving or braking torque based on the tire utilization minimization and the target additional yaw moment comprises the steps of: S31, introducing the tire utilization rate, rewriting the tire utilization rate into the torque expression of the wheel, and simultaneously introducing the tire vertical force considering load transfer; S32, determining an optimization variable as wheel torque, and constructing an objective function as a square sum of tire utilization rate; s33, defining constraint conditions by the total driving requirement and the additional yaw moment calculated in the step S25; and S34, solving the optimization problem through a quadratic programming method to obtain the optimal wheel torque.
7. The method for cooperative control of a vehicle chassis based on a variable steering characteristic according to claim 6, wherein in step S31, the definition of the introduced tire utilization is: Wherein the method comprises the steps of For the longitudinal force of the tire, For the lateral force of the tyre, In the event of a tire vertical force, The variable characterizes the utilization condition of the current friction force of the tire, namely, the closer the utilization ratio of the tire is to 1, the closer the tire is to the friction limit, namely, the tire is in a slipping state; The above expression is rewritten as a calculation expression expressed by the wheel torque: Wherein the method comprises the steps of In order to achieve the wheel torque, An effective rolling radius for the wheel; the tire vertical load expression considering load transfer is: Wherein the method comprises the steps of The acceleration of the gravity is that, Is one-half of the wheel track, As the height of the center of mass of the vehicle, For the longitudinal acceleration of the vehicle, Is the vehicle lateral acceleration.
8. The method for cooperative control of a vehicle chassis based on a variable steering characteristic according to claim 6, wherein in step S32, an objective function is defined: let the optimization variable be the additional torque : Wherein the subscript , , , Respectively representing left front, right front, left rear and right rear wheels; building an objective function as the sum of squares of tire utilization: defining constraint conditions in step S33 includes: the total drive requirement constraint is: wherein the total required driving torque Determined by driver demand; the additional yaw moment constraint is: Wherein the method comprises the steps of , , , The expression of the moment generated around the mass center for each wheel is as follows: the solution to the optimization problem in step S34 is calculated in real time to obtain the optimal wheel torque: converting the optimization problem into a standard QP problem form: wherein the constraint matrix Constraint vector Constructed from constraints.

Description

Distributed driving vehicle chassis cooperative control method based on variable steering characteristics Technical Field The invention belongs to the technical field of vehicle dynamics control, and relates to a distributed driving vehicle chassis cooperative control method based on variable steering characteristics. Background With the rapid development of the automobile industry and the continuous improvement of the socioeconomic level, the demands of people on automobiles exceed basic displacement functions, the personalized driving feeling of the automobiles is increasingly emphasized, and an electric Control system of the automobile chassis domain provides possibility for meeting such further demands, namely an active front wheel steering system (Active Front Steering, AFS) and a direct yaw moment Control system (DIRECT YAW Control, DYC) are used as main stream technologies in the field of automobile dynamics Control, and are widely applied to improving the operability and safety of the automobiles: AFS aims to compensate for the understeer or oversteer tendency of a vehicle by dynamically adjusting the front wheel steering angle. However, the control efficacy of AFS is limited by the mechanical limitations of the tire, especially in low adhesion coefficient road surfaces or extreme driving conditions, where tire lateral forces tend to saturate, resulting in failure of AFS control. The DYC generates an additional yaw moment by distributing the wheel driving force or braking force, thereby effectively suppressing the vehicle sideslip and improving the track following accuracy. However, on vehicles employing a centralized drive architecture, a DYC strategy that is overly dependent on braking intervention may induce longitudinal dynamic oscillations, reducing ride. In contrast, the distributed drive system (each wheel is independently driven by an in-wheel motor or a wheel-side motor) can accurately decouple the wheel drive force, providing a higher degree of freedom for the DYC control strategy. Currently, AFS and DYC systems are mostly used for controlling vehicle stability, and control strategies for personalized driving of automobiles are relatively lacking. Disclosure of Invention In view of the above, the present invention aims to provide a chassis cooperative control method based on variable steering characteristics, which generates a reference vehicle state through a target steering characteristic, incorporates AFS rotation angle compensation and DYC torque allocation into a unified constraint solution based on a multi-target optimization framework of model predictive control (Model Predictive Control, MPC), and introduces a tire force utilization ratio to perform wheel driving/braking force allocation, and finally realizes tracking of the reference vehicle state, so that a controlled vehicle exhibits the target steering characteristic, thereby realizing personalized driving feeling. In order to achieve the above purpose, the present invention provides the following technical solutions: a distributed driving vehicle chassis cooperative control method based on variable steering characteristics comprises the following steps: S1, generating a reference vehicle state based on target steering characteristics and a two-degree-of-freedom two-wheeled vehicle transverse dynamics model; and S2, generating an AFS front wheel steering angle and a DYC additional yaw moment based on MPC control. And S3, distributing wheel driving or braking torque based on the tire utilization minimization and the target additional yaw moment. Further, the step S1 of generating the reference vehicle state by the two-degree-of-freedom two-wheeled vehicle lateral dynamics model based on the target steering characteristic specifically includes: s11, establishing a differential equation of a two-degree-of-freedom two-wheeled vehicle transverse dynamics model according to Newton' S second law; S12, replacing and expressing the tire transverse force as the product of cornering stiffness and cornering angle on the differential equation established in the step S11, and substituting the product into a calculation formula of the cornering angle; s13, in the differential equation modified in the step S12, enabling the derivatives of the transverse speed v u and the transverse angular speed r of the vehicle to be 0, and obtaining the steady-state response of the two-degree-of-freedom model; And S14, expressing an understeer gradient K representing the steering characteristics of the vehicle as a function of the cornering stiffness of the front and rear tires, and obtaining an explicit relation between the cornering stiffness and the steering characteristics. Further, the differential equation in step S11 is: Where m is the vehicle mass, I z is the vehicle mass, l f is the distance from the front axle to the centroid, l r is the distance from the rear axle to the centroid, v x is the vehicle longitudinal speed, v y is the vehicle lateral s