A development of the model based torque feedback control with disturbance observer for electric power steering system 2019-01-1233
Electric Power Steering (EPS) control algorithm needs to meet both functional requirements and stability, because a driver interacts with the vehicle using steering system. First, it should make natural steering feeling. Second, it should ensure stability against deterioration of hardware. In order to meet these requirements, conventional control algorithms are designed with a stabilizing compensator and an assist torque map which is a one-to-one map between driver torque and assist motor torque. However, It is hard to tune parameters for satisfy both steering feel and stability because these things interact with each other. So, this paper supposes a torque feedback control algorithm to get independence between steering feel and stability. This paper presents a torque feedback control algorithm to improve steering feel and robustness against deterioration of hardware for EPS system. The proposed control algorithm consists of two main components : target torque generator, target torque tracking controller. To make natural steering feel, the steering feel should reflect information about the vehicle condition. So, the proposed control algorithm estimate the rack force which has information about the vehicle condition from EPS system model and use the estimated rack force for generating target torque. Lead-lag compensator and disturbance observer are applied for tracking target torque and stability. Disturbance observer is designed from EPS system model so that control algorithm can improve robustness against deterioration of hardware. The performance of the proposed control algorithm is evaluated through vehicle experiments, which show that the control algorithm is effective in improving steering feel and robustness.
Deukpyo Lee, Yun Gab Lo, Minwoo Han, Kyuwon Kim, Chulhee Kim