Matching Design of Assist Characteristic for Electric Hydraulic Power Steering System of Electric Bus

Electric hydraulic power steering system (EHPS) has the characteristics of high energy efficiency and reliability. In this paper, we focus on the design and analysis of assist characteristic for EHPS of electric bus. The relationship of steering assist power, steering wheel torque and steering resisting torque was analyzed; steering system model and vehicle dynamic model were built. By EHPS simulation, the relationship of pump flow rate, steering wheel angular velocity and vehicle speed was deduced and 3-D assist characteristic curve map was plotted, which was suitable for electric bus. In order to apply the assist characteristic curve into practice, we optimized the curve through BP neural network, and then obtained the assist power value under any vehicle speed and steering wheel angular velocity. Finally, EHPS simulation verified the optimized assist characteristic curve having a good performance.