Study on Roller-Walker — Improvement of Locomotive Efficiency of Quadruped Robots by Passive Wheels

Abstract

Abstract Roller-Walker is a leg–wheel hybrid mobile robot using a passive wheel equipped on the tip of each leg. The passive wheel can be transformed into sole mode by rotating the ankle roll joint when Roller-Walker walks on a rough terrain. This paper discusses the energy efficiency of locomotion in wheeled mode. We define a leg trajectory to produce forward straight propulsion, and discuss the relationships between the parameters of the leg trajectory and energy efficiency of the propulsion using a dynamics simulator. We find optimum parameter sets where optimization criterion is specific resistance. The results indicate that faster locomotion achieves higher energy efficiency. We then carry out hardware experiments and empirically derive the experimental specific resistance. We show that wheeled locomotion has an 8-times higher energy efficiency than the ordinary crawl gait. Finally, we compare the specific resistance of Roller-Walker with other walking robots described in the literature.