Control Of The Differential Drive Assisted Steering System For Electric Vehicle With Electric Motored Wheels

With the deterioration of the environment and the shortage of natural resources, more and more emphasis has been paid on the electric vehicles in recent years at home and abroad. Based on the small electric vehicle with electric motored wheels which is developed by the school of mechanical engineering of Southeast University, a novel power assisted steering system has been introduced in this work, namely the differential drive assisted steering system, which is more suitable for the electric vehicles with electric motored wheels. The main research work includes the following four aspects:(1) Kinematic vehicle models including the three DOFs and five DOFs vehicle dynamic models are established based on Matlab/Simulink for the four wheel independently driven electric vehicle. Becisides the three DOFs and five DOFs vehicle models have been compared in the open-loop simulations to conclude the effects resulting from rolling and pitching on the precision of the vehicle models.(2) The power assisted steering curve of the differential drive assisted steering system is constructed based on the assisted characteristic of the electric power steering system(EPS). Also the steering and aligning control strategies according to the instananeous vehicle speed and steering wheel torque are developed. Besides, a compensatory Fuzzy PID control strategy based on the differential drive of the rear wheels is eatabilited to meet the optimal yaw rate of the current moment.(3) The main models which are constructed in the second chapter are verified by the use of Carsim. A speed conrtrol strategy is designed based on PI controller to simulate the effectiveness and stability of the designed system under different constant speeds.(4) For the understeering characteristics of the vehicle, a rear-wheel differential drive control strategy is designed to assist the steering wheel by the use of the sliding model control theory based on the route planing. Under the extreme circumstance, simulations of such system are conducted to verify the effectiveness of the system.