High Fidelity Impedance Control of Series Elastic Actuator for Physical Human-machine Interaction

This paper proposes a novel control system using a Series Elastic Actuator (SEA) for human-machine interactive applications. SEA allows high torque transparency between a forward and a backward torque transmission with the geared motor and the closed-loop controller and it so enables that human-friendly interaction is achieved. Even though the torque-controlled SEA system plays important roles in human-machine interactive applications, there is performance limitation to implement pure interactive behavior due to the imperfection of torque source such as torque ripple of the electric motor. The limitation of SEA causes the uncomfortable feeling to the human in the application such as steer-by-wire system which is the target system in this paper. This paper focuses on the minimization of the influence that is caused by the torque ripple of the electric motor in the SEA system. The proposed controller based on the principle of Disturbance Observer (DOB) is designed to realize the desired human-machine interactive behavior. Experiments have been conducted to explore the characteristics of SEA system and to verify the performance of the proposed controller.