Link Motion Feedback based Force/Torque Servo Control of Robot Joint with Series Elasticity

This paper presents an effective method to generate desired force/torque from an actuator with intrinsic compliance. Instead of direct spring deflection feedback control method, we utilize link motion information with precise actuator-side motion control to compensate undesirable effect in generation of spring force/torque. We show that the structure of proposed controller gives spring-stiffness-independent actuation bandwidth, which was conventionally known to be dependent. Comparison experimental results with conventional controller shows better force/torque tracking performance of compliant joint in both time domain and frequency domain.