Research On Vehicle Stability Control Based On Time Delay Compensation

With the increase of vehicle ownership and frequent traffic accidents,vehicle safety has become an increasingly serious social problem.Active safety is mainly used to avoid accidents and also helps to improve vehicle stability.The vehicle is a coupled system with parameter uncertainty,highly nonlinear dynamic characteristics,and time delay.The existence of the time delay of the actuator will affect the stability of the vehicle system and even cause the vehicle to be unstable.Therefore,the research on the stability of the vehicle system must inevitably consider the effect of the time delay of the actuator.Especially when the system is driving on a high speed or low adhesion road,the active safety system needs extremely fast response time,at which time the time delay has a greater impact on system stability.In addition,the current drive-by-wire technology of the entire vehicle is rapidly developing,and the signal transmission delay is particularly obvious.In order to improve vehicle stability,this paper analyzes the influence of time delay on vehicle stability,and designs an extended stability controller based on time delay compensation.First,we research the vehicle stability and stochastic algorithm theory based on phase plane,establish a vehicle model without time delay,and design an ideal stability controller based on model prediction(MPC).Then research the possible position of time delay in the model.Through the joint simulation experiments of ve DYNA and Matlab / Simulink,give the analysis of the influence of the time delay at different positions on the vehicle dynamic characteristics.By analyzing the causes of vehicle instability,the vehicle motion is divided into regions,and then the time-delay boundary is identified.The obtained value space is divided into stable,transition,and unstable regions,and the transition region boundary is used as the stability of subsequent vehicle stability research theoretical basis of the boundary ceiling.Then,under normal operating conditions,a linear vehicle model with time delayis established based on the time delay boundary identified by a random algorithm for the time delay of the actuator.Analyze the effect of time delay in an unconstrained system,and design an unconstrained linear MPC stabilizing controller to track the expected yaw rate and sideslip angle;and then consider the saturation effect of the actuator in the system and the state constraints,and propose constrained linear MPC expansion stability controller.Under the MPC control framework,considering the influence of multi-channel control input time delay,the multi-channel and multi-scale time delay can be compensated at the same time.Considering the identified sideslip angle constraint,the control requirements are converted into an objective function.By optimizing the front wheel steering angle and the additional yaw moment online,the vehicle yaw rate and the sideslip angle can accurately track the expected value.The results of joint simulation experiments verify the effectiveness of the time-delay compensation extended stability controller.Finally,on the basis of the aforementioned control strategy,when the vehicle is in the extreme conditions of high speed and low adhesion,the lateral force is saturated and the tire works in the non-linear region.The time-delay-compensated nonlinear MPC extended stability controller considers three constraint schemes: fixed constraint,phase-plane stability boundary constraint,and penalty function.Through joint simulation experiments,compare the performances of the controllers with and without lateral force saturation,as well as under different constraints.It can be known from the simulation analysis that on a low adhesion road surface,the non-linear expansion stability controller can better guarantee the vehicle's handling stability and better trajectory tracking performance.