Poloidal Drive: Direct-Drive Transmission Mechanism for Active Omni-Wheels With Spoke Interference Avoidance

Wheels require extra space for steering. Omnidirectional wheels are ideal for confined spaces as they can move in all directions: forward/backward and left/right. Conventional omnidirectional wheels with passive rollers achieve this movement by combining multiple wheels. However, if even one wheel loses contact with the ground, the vehicle becomes inoperable. To overcome this limitation, omnidirectional wheels with actively driven rollers have been proposed. These designs, however, require additional components, which increase weight. This is because multi-step intermediate transmission mechanisms are needed to convert spindle rotation into roller rotation. Eliminating the intermediate transmission mechanism reduces the number of components and provides more space to enhance wheel strength. This study proposed a mechanism without intermediate transmission, clarified its design framework, and experimentally demonstrated its feasibility as an active omnidirectional wheel. The proposed design framework defines conditions to maximize both power transmission efficiency and strength. Experimental results showed that the transmission efficiency of the proposed mechanism is comparable to that of conventional mechanisms.