Abstract
The viscoelastic elements of muscle play an important role in control and stability of human movement. The viscoelasticity is not constant but changes its magnitude depending on the muscle tension, length and contracting velocity. The aim of the present investigation was to develop a torque actuator with viscoelasticity simulating the mechanical property of human muscle. The viscoelastic torque was produced by adjusting the magnitude of torque generated by an induction motor through an electromagnetic powder clutch. The powder clutch possesses intrinsically hysteresis, nonlinearity and a limit to quick response. After examining a current drive, which provided large hysteresis and higher response, and a voltage drive, which had reciprocal characteristics to the current drive, a pulse width modulation with their intermediate characteristics was used for driving the powder clutch. Furthermore, torque feedback and push-pull operation of two powder clutches with different direction led to greater correction in hysteresis, linearity and response. Viscoelastic torque to 150kg·cm was produced stably by feeding angle and angular velocity back. Electromyographic activities of biceps brachii muscle in elbow joint flexion with external viscoelastic load generated by this equipment were discussed.
