Exploiting the natural dynamics of compliant joint robots for cyclic motions

Abstract

Due to the significant flexibility arising as a result of the incorporation of passive compliance into traditional rigid actuators, that enables the excitation of sizeable resonance movements, the generation of highly dynamic motions using such systems has been studied in the literature; however, a majority of these methods are limited to single actuators. This work presents a novel scheme employing the natural dynamics of compliant joint robots in order to perform cyclic motions. The use of the system's natural dynamics can therefore result in the execution of robot movements that consume a slight amount of energy as compared to the energy they generate, provided that the motion trajectory is on the limit cycle manifold. The energy efficiency advantages during such cyclic motions, which have rarely been studied in the literature, are also discussed. The proposed scheme, which is based on modal decoupling of the system's natural dynamics, is finally evaluated in simulation in order to investigate the energy-efficiency of different modal motions, as well as the effect of various joint stiffness levels.