Semi-degeneracy in stiffness generation of an anthropomorphic robot

This paper presents the analysis of an anthropomorphic robot as an active variable stiffness generator, with emphasis on the degeneracy in stiffness generation. First, the attachment of mono-/bi-articular muscles are optimized to maximize the dynamic ranges of the self and the coupling joint stiffness. Based on the geometric interpretation of the joint stiffness, a simple and effective way of determining the optimal muscle attachment is presented. Next, the cause of the semi-degeneracy in stiffness generation is identified as the sign inconsistency of the actual and the desired coupling joint stiffness. Using the configurational dependency of the actual coupling joint stiffness, the semi-degeneracy map over the entire joint space is obtained. Simulation results are also given