Loosely Coupled Joint Driven by SMA Coil Actuators

We introduce a robotic prototype of an arm with a loosely coupled joint, modeled on the human joint. A viscoelastic object functions as cartilage and soft actuators as muscles. First, we show that although viscoelastic object affords smooth movement owing to shift in the center of rotation, the repeat accuracy of the joint is poor under open-loop control. The repeat accuracy was much improved by visual feedback. Under P control, the prototype was shown to be highly robust against mechanical disturbance owing to its good mechanical compliance.