Mechanical design of an active-caster robotic drive with dual-wheel and differential mechanism

A new type of the active-caster robotic drive with dual-wheels and differential mechanism (ACRO-DD) is presented in this paper. The active-casters have been used for the driving devices for wheeled mobile robots, wheelchairs, etc. The new active-caster equips dual-wheels which are driven by a wheel motor via a differential gear mechanism. The dual-wheel configuration contributes to reduce frictions in turning, which enables smooth caster motions. For maintaining the two-wheel-contact to the ground even on the irregular surface, an individual suspension is installed on each wheel. The dual-wheel-design enables the mechanism to equip large wheels compared with the single wheel design, which realizes high step climbing capability. Moreover, to realize a mechanism with compact size and light weight, we install a novel sensor system for detecting the absolute orientation of the wheel using two smallpotentiometers. The mechanical design and the sensing system are embodied by a prototype which shows expected caster motions with high mobility.