Study on Roller-Walker (multi-mode steering control and self-contained locomotion)

We have proposed a leg-wheel hybrid mobile robot named "Roller-Walker". Roller-Walker is a vehicle with a special foot mechanism, which changes to a sole in walking mode and a passive wheel in skating mode. On rugged terrain the vehicle walks in leg mode, and on level or comparatively smooth terrain the vehicle makes wheeled locomotion by roller-skating using the passive wheels. The characteristics of Roller-Walker are: (1) it has a hybrid function but is lightweight, (2) it has the potential capability to exhibit high terrain adaptability in skating mode if the control method for roller-walking is fully investigated in the future. In the paper, the 4 leg trajectory of straight roller-walk is optimized in order to achieve maximum constant velocity. Also a steering roller-walk control method is proposed. It is obtained by the expansion of the straight roller-walk trajectory theory adding an offset to the swinging motion. This steering method resembles that of a car. The control system was modified into an untethered system, and control experiments were performed. The realization of the steering motion was verified by them.