Study On Control Strategy For Electric Power Steering System Of All Terrain Vehicle

All terrain vehicle (ATV) has been widely used in agriculture, forestry, military andmany other fields because of its passing topography capacity and transportation capacity.Because of its bad driving environment, the steering ability has been one of main factorswhich influence its performance. This paper aims to build the simulation model of ATV,and then design assist curve of EPS according to the characteristics of ATV, andimprove the control strategy through simulation, thus provide the theory basement forproduct development in future.The characteristic parameters of ideal assist curve of ATV has been determinedaccording to the research results of EPS at home and abroad and the characteristics ofmechanical steering system of ATV. The mechanical steering model, three freedom carmodel, tire model and motor model were built in Simulink. The straight-line type assistcurve was built through the simulation analysis, and the effect of the assist curve wasproved by simulation.In order to meet the request of steering maneuverability and steering feeling, thestraight-line type assist curve was modified by fuzzy control. The compensation controlstrategy, return control strategy and damping control strategy were built and proved bythe simulation model. The fuzzy PID controller of EPS was built according to thecharacteristics of nonlinear and time varying of ATV，the simulation result proved thatthe robustness of the system can be improved by using the fuzzy PID controller. Theswitch condition of four control strategies was designed to build the combinationcontrol strategy according to the steering characteristics of ATV.The3D model of ATV in CATIA was imported into ADAMS by SimDesigner, andthe multi-body dynamics model of ATV was built. The human body model and roadmodel were built according to the national standards. The accuracy of the model wasverified by steady static circular test, and the result indicated that the model can be usedto analyze the controllability and stability of ATV.Finally, the co-simulation model was built by using the ATV model in ADAMS andcontrol strategy model in Simulink. The steering effort test and the steering transientresponse test were done according to the national standards, the simulation resultsproved that the control strategy of EPS which was designed in this paper, can makeATV have better performance in steering maneuverability, and the transient response of ATV can be improved.