Interconnection and Damping Assignment Passivity-Based Impedance Control of a Compliant Assistive Robot for Physical Human–Robot Interactions

Abstract

Interest in series elastic actuators (SEAs) for assistive robots has recently increased due to the unique properties of SEAs compared to those of rigid actuators, such as high force control accuracy, low output impedance, and tolerance to shocks. In this letter, an SEA with a clutch for an assistive robot is designed for accurate torque delivery to provide effective assistance. The mechanical clutch controls the engagement and disengagement of the power transmission during the gait cycle to ensure transparency and user safety. Precise torque control is the main challenge in the control of SEAs. The addition of a clutch in the SEA will result in a new force control challenge with the frequent release and engagement of the clutch aggravating the mechanical vibration and bringing the risk of unsafety to the assistive robot wearer. A new torque control method based on interconnection and damping assignment passivity-based control (IDA-PBC) for SEAs is adopted for the physical human–robot interaction. Experiments are conducted to verify that the IDA-PBC-based SEA torque controller can effectively control actuator timing and allow precise assistive torque control. This letter serves as a stepping stone toward utilizing and designing assistive robots to assist with walking.