Robust Control Of Electric Power Steering System

Compared with hydraulic power steering system ,electric power steering system has many advantages which was the hot topic for scholars and producers home and abroad. Currently, EPS fixed in high-class cars were from abroad, only a small amount of micro-car with the domestic EPS.There was a long way for EPS to industrialization and to occupy most of the domestic auto market,it needed a lot of research, especially in EPS control strategy, assistance characteristics.Modeled EPS with Lagrange Equation , in order to achieve steering light and a good'road feel',assistance curve was designed for the electric power steering system.Stability influence caused by assistance coefficient was discussed. For the uncertainty of the established EPS model, EPS was studied with H∞loop shaping method.The results show that: angle input of EPS, overshoot of step response of the rack displacement increased as the assistance coefficient ,the vibration intensified,but the system remained stable.Torque input of EPS, the system was stable when assistance coefficient must be less than a certain value.Road impulse input of EPS, the moment of torque the pulse response along with assistance coefficient increased, system's vibration was fiercer, steering comfort became worse(especially in the high-frequency), indicating that the damping reduced for high-frequency inpact.EPS controller based H∞loop shaping was designed which reduced the influence of disturbance and sensor noise.Simulation of EPS when it may occur on the structural perturbation (perturbation) and non-structural perturbation (non-parameter perturbation),results show that the designed controller had strong robust stability in parameter perturbations and non-parameter perturbation.