Analysis And Control Of The Network Induced Delays Of The Distributed Drive Electric Vehicle

Distributed drive EV(electric vehicle),with the adoption of independent drive system which is set nearby wheels,has many advantages compared with traditional centralized drive EV.Especially,this pattern of driving has become one of the most important development trends of EV due to its advantages in dynamic control to the vehicle by the implement of the direct yaw-moment control.However,due to the adoption of network layout,discreteness of sampling and network delays existing in the real situation,if the research results from continuous model are directly applied in the EV,they will always cause problems of delayed instability in the dynamic control.Based upon the research on the direct yaw-moment control of current distributed drive EV,the problems of insufficient study on the instability in vehicle dynamics caused by network induced time delays and problems of handling stability of controlling from distributed drive EV with the adoption of CAN bus,this paper will give detailed descriptions as follows:(1)Based on Matlab/Simulink,the “human---vehicle” closed loop simulation platform has been established,which is composed of eight-freedom vehicle model,motor and drive system model,the wheel and tire model and driver model.(2)Study on vehicle's handling stability has been conducted under the continuous control circumstance,which has adopted hierarchical structure,using two-freedom linear vehicle model as the reference model to have designed feed-forward + LQR feedback upper movement controller of continuous control and to have adopted lower torque distribution controller of torque average distribution.(3)The NCS model of CAN bus is established based on the NCS theory and the analysis of the time delay in the process of network transmission is made.The NCS delay model is added to the distributed drive EV closed loop model.Analysis of discrete control and network delay influence exerted on the vehicle handing stability is made via simulation experiments in the conditions of the step-angle input,double lane change and slalomtest respectively.(4)Based on the fuzzy theory,the variable period scheduling is designed to suppress the network delay and improve the effectiveness of network control.The experiment results indicate that after adopting the variable sampling period,the performance of the NCS control of CAN bus,the existing the problem of network delay,has improved significantly.