Composite Controller for Antagonistic Tendon Driven Joints With Elastic Tendons and Its Experimental Verification

In this paper, we present the dynamic modeling and controller design of a tendon-driven system that is antagonistically driven by elastic tendons. In the dynamic modeling, the tendons are approximated as linear axial springs, neglecting their masses. An overall equation for motion is established by following the Euler-Lagrange formalism of dynamics, combined with rigid-body rotation and vibration. The controller is designed using the singular perturbation approach, which leads to a composite controller (i.e., consisting of a fast sub-controller and a slow sub-controller). An appropriate internal force is superposed to the control action to ensure the tendons to be in tension for all configurations. Experimental results are provided to demonstrate the validity and effectiveness of the proposed controller for the antagonistic tendon-driven system.