Dynamic Analysis Of Electric Power Steering System Based On Virtual Prototype Technology

An Electric Power Steering System (EPS) is a dynamic steering control system which can real time supply assist torque according to the status of the automobile movements and driver's requirements. Automobile equipped with EPS can meet the requirements of the higher maneuverability for low speed driving and the stability for high speed driving. Electric Power Steering Systems offer improvements over conventional mechanical steering systems or hydraulic assist systems by improving fault-tolerant, disturbance rejection, fuel economy, start-up on low temperature, safety and environmental friendliness, which makes the EPS the main steam of future power steering systems and an intense target of current technology innovation.Virtual prototype Technology (VP) is based on kinematics, dynamics and theory of control. Three-dimension computer graphical technology, net-work technology, informatics and other modern technologies are used to make VP more advantageous and easier for modeling and simulation of mechanical systems. It's the future trends of modeling and simulating full vehicle system with VP.In this paper, ADAMS (Automatic Dynamic Analysis of Mechanism System) is used to establish the multi-body dynamics model of vehicle system, including mechanical systems of EPS, front and rear suspensions, tires and road, etc, which aims at the dynamic analysis of one EPS used on mini-sized vehicles.Co-simulation technology is also used in this paper to link the control model established in MATLAB to the mechanical model established in ADAMS. Assist torque is the input of mechanical model, and it is also used as the output of control model. The outputs of mechanical model, wheel input torque and signal of vehicle speed, are used as the inputs of control model. A control strategy including phase compensation, feedforward and feedback control, PID, etc. In order to decrease the control current dissipation caused by friction torque, inertia torque and damping torque in motor, methods of damping compensation control and returnability compensation control should be added to. The state variables are set up in order to communicate the mechanism with control model. Co-simulation can be reliable from building closed loop data communicating cannels.The method of co-simulation provides a different way to research the kinematicsand dynamics of EPS. It also can be an example for analysis of full vehicle and other mechanism which would be used co-simulation.The exchange of three-dimension model built by CAD software into ADAMS using Mech\Pro is also introduced in this paper.