Variable impedance magnetorheological Clutch Actuator and telerobotic implementation

Variable impedance actuation is characterized by the ability to independently set output force and output impedance for a robotic device. Adjusting the output impedance in real-time allows a device to better adapt to a variety of tasks, operate in human-like fashion, and support human safety. This paper focuses on a series clutch actuator based on magnetorheological fluid which allows a fast, electrical change of the impedance while maintaining good force tracking. In particular the mechanical clutch can alter the high-frequency impedance, decoupling the motor inertia and thus reducing impact forces. We present the mechanical clutch design and a control system architecture to automatically adjust the fluid magnetization level and leverage the clutch benefits. Experiments verify torque tracking and impact force reduction both in autonomous and telerobotic operation. The actuator was designed and manufactured in collaboration with the Materials Design Institute at Los Alamos National Laboratory, and is tested in a single degree of freedom demonstration.