Decentralized Control of Harmonic Drive Based Modular Robot Manipulator using only Position Measurements: Theory and Experimental Verification

This paper presents a decentralized control approach of harmonic drive (HD) based modular robot manipulator (MRM) using only position measurements. Unlike known methods that rely on joint torque and velocity sensing, this paper addresses the problem of controlling HD based MRM using only position measurements on the motor and link sides of each module. The dynamic model of HD based MRM is formulated by employing a high-fidelity HD model and the velocity of each robot joint is estimated based on a novel nonlinear velocity estimator. With only local information on each module, a decentralized integral sliding mode controller (ISMC) is designed based on variable gain super-twisting algorithm (VGSTA) to compensate the model uncertainty and to reduce the chattering effect of the controller. The asymptotic stability of the closed-loop system is proved using the Lyapunov theory. Finally, experiments are performed for a 3-DOF MRM to verify the advantage of the proposed method.