Study on Roller-Walker - Energy efficiency of Roller-Walk -

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 ankle roll joint when Roller-Walker walks on rough terrain. This paper discusses 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 numerical simulator. We find optimum parameter sets where optimization criteria is specific resistance. Then we carried out hardware experiments and empirically derived experimental specific resistance. We show that wheeled locomotion has 8 times higher energy efficiency than ordinary crawl gait. Finally we compare the specific resistance of Roller-Walker with other walking robots described in the literatures.