Study On Layered Coordination Control Of Vehicle Semi-active Suspension And Electric Power Steering System Based On Grey Predictive

Suspension and steering system are two important components of the vehicle,and their performance is directly related to vehicle's performances such as ride comfort and handling stability.As the development of the electronic control technology and single chip technology,vehicle's semi-active suspension(SAS) and electric power steering(EPS) have become a research hotspot.SAS can,to a certain extent,improve the handling stability as well as the ride comfort,while EPS can improve the handling stability and steering portability.However,due to the coupling effects between the suspension system and the steering system,when the systems are controlled respectively,only partial performance is improved, while the comprehensive performance of the vehicle is quite hard to be enhanced in large scales.In order to acquire a better comprehensive performance,the two systems should be controlled integratedly.In this paper,aiming at the improvement of vehicle's handling stability and ride comfort,a systematic research on coordination and integrated control of SAS and EPS is undertaken.In view of the mutual restraints and impact between the two systems, the full vehicle dynamic model with integrated system of SAS and EPS is improved.In the tyre model,the effects from changeable vertical load to tyre cornering characteristics is taken into consideration,so is the actual direction of tyre cornering force in the steering model.As a result,the whole model is much closer to the real vehicle.Based on the simulation and analysis of the above models,the coupling relation between the suspension system and steering system is studied.In respect of the two goals of the integrated control:to eliminate the harmful interference and conflicts between the systems and to assign the control inputs of the subsystems reasonably,a layered coordination control method is proposed,and a coordination controller is designed,and a fuzzy controller of SAS and a PID controller of EPS is made respectively.Then aiming at the optimization of the whole vehicle,the coordination strategy of the upper control is established.The results of the simulation show that, the layered coordination control can,improve vehicle's comprehensive performance effectively,and coordinate the ride comfort and handling stability.The layered coordination method is proved to be an effective way in studying integrated control.For the multi input multi output characteristics of SAS and EPS system, and based on grey predictive theory,a multi-variable grey prediction model of SAS and EPS system is established,to predict the performance indexes and their developing trend.Then according to the prediction,the integrated control strategy is in advanced revised,to realize the pre-control of the SAS and EPS system by avoiding a rapid change of the control variables,thus the control is more precise.On the above basis,a layered coordination control method on SAS and EPS integrated system,based on grey predictive theory,is proposed,and a grey predictive coordination control strategy designed.As a result,control imprecision caused by uncertain factors and time delay of the control system is eliminated,and the control performance of the executing agency improved in a large scale.The integrated control effect of the integration system,by adopting grey predictive control,is improved efficiently.As shown in the results of the simulation,this control method can completely meet the need of the integrated control of SAS and EPS integrated system.Integrated system of SAS and EPS controller is explored with ARM2131 single chip computer as microprocessor.The improved semi-active suspension and the integrated controller are installed in the CH7140 to carry on the real vehicle road tests,and the results will be compared with the simulation results.It is showed that the simulation results are coped with the experiments and it is indicated that the established model is right,the control strategy feasible and the technology reliable.In contrast with the passive system,the peak and the standard deviation of the center of mass acceleration is decreased by 28.57%, 27.75%;the yaw rate's peak and standard deviation is decreased by 10.18%, 12.69%;the roll angle's peak and standard deviation is decreased by 15.8%, 8.19%;the lateral acceleration's peak and standard deviation is decreased by 20.8%,18.6%.In human sensitive frequency range,the power spectrum of the center of mass acceleration is reduced obviously.It is showed that the grey predictive layered coordination control can coordinate the contradiction of vehicle ride comfort and handling stability and improve the vehicle performance.