Caster drive mechanisms for holonomic and omnidirectional mobile platforms with no over constraint

A new type of mobile platform with a novel wheel mechanism for holonomic and omnidirectional robots is presented. The drive mechanism equips with a couple of standard wheels in a differential-drive manner driven by two independent motors. A steering joint, driven by the third motor, is mounted on the differential drive mechanism at a location off-centered from a mid-point of the two wheels. Thus, the drive mechanism has a dual-wheel-caster configuration. First, the concept of the original caster drive is reviewed briefly followed by kinematic analysis of the dual-wheel-caster mechanism. A prototype vehicle is designed, built and its mobility tested. Other possible variation for the future vehicle design with a traditional synchro-drive mechanism is proposed. The kinematics and statics of the drive mechanism are also analyzed. All wheel driving without over constraint decoupled control and efficient driving can be achieved with the proposed synchro-drive.