Algorithm For Vehicle Stability Control Based On Model Decomposition

In recent years, the automobile-related technology is rapidly developing, and the vehicle electronic control is the main direction. Vehicle stability control is part of the automotive electronic control, and it has received a lot of attention because of its active role in the protection of vehicle stability. Vehicle stability control system is an active safety system, which can effectively improve the stability of the vehicle to prevent rollover, skidding, understeer, oversteer and other dangerous situations, so as to ensure personal safety.The main research of this paper is to maintain the stable operation of the vehicle. This thesis is mainly divided into two parts: the design of the upper stable controller and the solution of the lower level distribution controller. The purpose of upper layer stability controller design is to ensure the running state of the vehicle to track the desired longitudinal velocity, lateral velocity, yaw rate and velocity, under the premise, the vehicle’s lateral force, longitudinal force and yaw moment are determined. Although the stable operation of the vehicle is ensured at this time, the force(moment) on the vehicle cannot be directly controlled, so the lower level allocation controller is designed, the lateral force, the vertical resultant force and the yaw moment are distributed, and the longitudinal force and lateral force on each wheel are obtained, then the wheel torque which can provide the longitudinal force and lateral force can be obtained, and the stability of the vehicle can be realized.In this paper, the vehicle stability control process of the system is actually the reverse process of the above analysis, through the control of the wheel torque, the force of each wheel is obtained, and indirectly the vehicle’s lateral force, longitudinal force and yaw moment control are achieved, and ultimately the longitudinal velocity, lateral velocity, yaw rate, lateral inclination angle and speed of the vehicle are controlled to ensure the stability of the vehicle.The main contents and contributions of this paper are as follows:(1) For four freedom degrees of vehicle model, we propose a model decomposition method, the original vehicle model is decomposed into the yaw rate model and the roll model. In this way, each part of the model contains less control than the whole vehicle model, which is easy to design the controller for each part. At the same time, there is no change in the overall control, this not only reduces the difficulty of the vehicle model analysis, but also ensures the accuracy of control.(2) Process the two sub models to achieve two goals: 1) to remove the nonlinear part of the model, 2) to make the control process more rigorous. Specific methods are: 1) removing the nonlinear factors of roll model by approximating, 2) removing the nonlinear factors of speed horizontal pendulum model through feedback linearization, Model uncertainty is added to the linear model because removing the nonlinear part is a kind of ideal state by means of feedback,the residual amount exists in the linear model,in addition, the four degree of freedom model is not accurate, and the actual controlled vehicle is more complex.(3) Two sub models of the vehicle controllers are designed: 1) for the speed yaw model, linear quadratic suboptimal controller is designed considering the parameter uncertainty; 2) for the roll model, a linear quadratic optimal controller is designed. By keeping the stability of the vehicle, the input of the controller is obtained: longitudinal force, lateral force and yaw moment.(4) The resultant force(moment) of the controller is assigned to the actuator of each wheel, by introducing the pseudo inverse method the stable operation of the vehicle wheel longitudinal force and lateral force are ensured, on this basis, by the vehicle dynamics equation the moment of each wheel is further determined, and ultimately to achieve the directly controlled wheel moment to maintain the stable operation of the vehicle.(5) Vehicle stability control system designed in this paper is verified in the four degree freedom of vehicle model and 15 freedom degrees of vehicle model of AMESim, Results verify that the vehicle stability control system has good control performance for the above two vehicle models, the good control effect on the high degree freedom of vehicle model proofs that the vehicle stability control system is of positive significance in engineering practice.The proposed method and the data conclusion can provide a reference for the vehicle stability control research.