Model-based compensation of wire elongation for tendon-driven rotary actuator

Tendon-driven rotary actuators are utilized for bilateral control. However, tendon-driven systems have a problem. When force is applied to wires, polyethylene lines are extended. In this paper, a model-based compensation method of the wire elongation for tendon-driven rotary actuators is proposed. In proposed method, the wires are modeled based on Voigt model which is composed of an elastic spring and a viscous damper. Coefficients of elasticity and viscosity are identified by offline experiment using constant force command. Then, wire elongations are estimated by the wire model using identified values. The proposed method was applied to angle control and bilateral control of tendon-driven rotary actuators. Then the performances of wire elongation compensation were compared. The validity of the proposed method was confirmed by experiments. Angle error caused wire elongation was reduced by proposed method.