Research On Return-to-center Control Based On Angle Estimation Of DC

With the steps of steering system development, Electric Power Steering System is the stage beyond the mechanical steering system, hydraulic power steering system and electric hydraulic power steering system. It not only provides steering effects of comfort and flexibility steering, but has the advantages of compact structure, low energy consumption and easy assembly. It is one of hotspots in automotive electronics and would have wide application in the future. And the EPS without steering-wheel angle sensor is a new trying. The new method of position estimation proposed in this paper allows estimating the angular position of the steering wheel by the motor angle. Then the return to center control designed in this paper base on the estimation angle of steering wheel.Firstly, two DC controlling methods are introduced in detail. And then the angle estimation principle of DC is discussed base on DC controlling approaches. And the hardware and software of DC angle estimation model is designed and experiment on test bench, and it shows the effectiveness of the estimation. That affords supporting for the controlling strategy, software and hardware design of EPS.Secondly, an appropriate trigger rule for return control and a kind of return control strategy based on the angle estimation of DC are made. The controller model, whole vehicle model and driver model are established in Carsim and Simulink. And Co-simulation results verify the effectiveness of the return control strategy.Thirdly, hardware structure of EPS controller is introduced at first, and the minimum system, power module, ignition signal collection circuit, current sensor circuit and motor driving circuit are designed which use MC9S12XS128as controller’s CPU. Then angle estimation module of DC is integrated in the EPS controllerFourthly, the software designed by using Code Warrior. The software includes steering wheel angle estimation program, return trigger program, PID controlling and return to center program, etc. and software parts cooperated in it.Finally, the real car experiment of EPS is implemented to verify the effectiveness of the return to center control base on angle estimation. The test results show that this strategy does correct decision in judging return situation, and makes improvement in the returning speed and the residual angle. And it improves the return performance.