Abstract: Electric power steering system provides assistant torque with motor. The tracking performance of control system is an important factor that affects the assistance of electric power steering system. Bad tracking performance will cause assistant delay, and make road feel to be bad. The tracking performance is directly influenced by the deviation of assistant torque. Input steering torque and the measuring noise of steering torque are factors that affect the deviation of assistant torque. Cutting down the deviation of assistant torque is an effective method to enhancing the tracking performance. H-infinity control theory is applied in the development of tracking performance. A mathematic model of electric power steering system is set up. H-infinity controller is designed with LMI. Simulation using Matalab and computer program based on H-infinity controller are developed. A bench test is finished. The results prove that electric power steering has a good tracking performance.

Key words: controller, Electric power steering, Tracking performance