Driving-power Steering Theory And VDC Research Of Motorized Wheels Driving Vehicle

For the situation of environment and pollution, automobile industry should increase the efficiency of energy using and decrease the outlet of contamination-stuff. However, it's hard to solve the problem by improving the performance of popular vehicle. The application and popularization of electric vehicle become the necessary demand of sustainable development.EV has a lot of advantage relative to traditional vehicle such as high efficiency, trivial pollution, various energy using and small noise. The application of motorized wheels take more supremacy to E.V through realizing the performance which traditional vehicle can't realize and decreasing the cost of ordinary EV, so motorized wheel auto become a new hot study topic. Motorized wheel car's key technology includes the size choice and control strategy, the differential between driving wheels, the traction force control and the dynamics control. The application of electronic and electric make steering system changing a lot, EHPS, EPS and steering by wire came out as the popular technology. VDC is a new initiative safety system designed to prevent the response of vehicle from rapid change, it can reduce the negative influence resulted by all kinds of facts as far as possible. For example, on the road with small attachment coefficient, deviant should be as small as possible, and the load, the situation of road and the change of crosswind should not be unsafe factor to vehicle. VDC take advantage of optimizing control theory to make the driver's action to be the best, and it can adjust the driving force and the braking force of each wheel, and angel of steering wheel to modify the unstable condition and avoid the disadvantage influence of running stability resulted by mistake of driver.According to the trait that each turning wheel of motorized wheel auto can produce different driving force, the theory of driving force power steering is raised and proved by building simulation model. During the process of model building, deflation idea is used to simplify the power steering system to a physical model which contains three parts as steering wheel-column part, gear-rack part and front turning wheel part. Then dynamics equation is constructed by the physical model. The returning torque is worked out.The dynamics model with 18 freedoms for electric vehicle with motorized wheels is made, inclusive of the six freedoms of the vehicle body. Based on the model, the simulation desktop of the electric vehicle with motorized wheels is build using matlab/simulink. With high precision and less parameters, the desktop can simulate many kinds driving mode of vehicle. It is the foundation for the research in this paper。VDC is a new initiative safe system which can control vehicle movement condition under state of emergency through modifying the steering angel, accelerator pedal and pressure of brake to make the target parameter to reach expected value. The main function of VDC is to decrease the differential of response trait between normal working conditions and limit working condition so that the driver's ability to control vehicle is enhanced. The point of VDC of motorized wheel vehicle is to pay attention to that torque produced by driving motor can be adjusted in time. According to the real time state of the vehicle, controller adjusts the torque produced by each driving wheel so that modify the running condition of the vehicle. The physical concept of the vehicle dynamics control is expounded and the literatures about VDC research of EV with motorized wheels are reviewed. The estimation method of the vehicle motion parameter by four wheel speeds is bought out. It expresses the motion parameter on mass center of vehicle using four wheel speeds by geometry. With a view to the merit of the motorized wheel, the dynamics control of the EV with motorized wheels using optimal PD control strategy is studied and the controller model is made by matlab/simulink。On the highμroad and lowμroad, the performance of the controller with step input is researched by simulation on the fore-mentioned desktop. It is indicated by simulation result that the VDC controller of EV with motorized wheels using optimal PD control can hold linear response and stability of vehicle at limiting condition, and the handling stability and safety of the vehicle is improved greatly。...