Power assist system for sinusoidal motion by passive element and impedance control

In this paper, we propose a power assist system that amplifies sinusoidal human´s torque and attains minimization of control input requirement using an impedance control and resonance. This impedance control is designed to realize the following features: 1) sinusoidal torque amplification. 2) Minimization of control input requirement by adjusting stiffness. 3) No requirement for the knowledge of amplitude, frequency and phase of human´s torque. 4) No requirement for myoelectric signals. 5) Satisfaction of causality. Convergence of the proposed controller is proven theoretically. Simulation results verify the validity of the control scheme including some conditions not discussed in the theory. Experimental results show the validity of the control system including real human´s complex dynamics and feedback loops