Research On Yaw Stability Control Method Of In-wheel Motor Electric Vehicle

With the decreasing of oil resources and rising of air pollution,electric vehicles as zero pollution motors are increasingly concerned.Among them,the hub motor electric vehicle is a new type of car.Because of its drive motor which mounted directly on the drive motor inside the tire,the hub motor electric vehicles has undergone great changes compared with conventional cars on chassis structure.Then its vehicle yaw stability is certain has big difference with the traditional internal combustion engine cars,so for this new structure control method for vehicle yaw stability study is of important significance.Firstly,according to this study,selected the seven degrees of freedom model which including the car's longitudinal,lateral,yaw,and four wheels vehicle dynamics model.And the "magic formula" tire models is selected,paving the way for the following research on control strategy.The establishment of two-degree-freedom ideal reference model has a very good analysis of factors influencing vehicle yaw stability,selected two variables of yaw stability: yaw velocity and side slip.Compared the difference of vehicle yaw stability control on the executive bodies between hub motor with a traditional internal combustion engine,concluded that hub motor has the advantage of quick response and independently controllable.Based on the analysis of effect of yaw stability causes a yaw stability control strategy: using a two-tier structure,in the upper controller information as input steering angle and vehicle speed,fuzzy control theory by quasi-steady-state vehicle required under the additional yaw moment.In down-level controller based on longitudinal force of car usage to minimize the objective function,constraints on the implementation of the motor capacity,using weighted least squares algorithms will optimize the distribution between the turn.The designed controllers and models are connected at MATLAB/Simulink to make the offline simulation under four conditions: high speed,low speed,high speed,low speed.The simulation results compared with the average allocation method,proved that the optimal allocation method can increase vehicle yaw stability.The simulation results of making an analysis on high speed vehicles under low and high conditions in control of large deviations in the process analysis or instability.Due to the restrictions relating to the capacity,the motor do not meet requirements incertain conditions.Therefore joined the hydraulic brake assist systems and off-line simulation is obtained after the addition of the hydraulic system can further enhance the vehicle's yaw stability.In order to verify the effectiveness of the controller,the rapid control prototyping tests are made under the dSPACE platform.Experimental results are consistent with the simulation results,further evidence of the effectiveness and feasibility of the controller.