Abstract
A new vehicle assembly for holonomic and omnidirectional mobile robots is presented. A caster-drive mechanism is one of the feasible solutions to allow a holonomic omnidirectional vehicle to equip standard wheels for its driving wheels. A traditional synchro-drive transmission is applied to the caster-drive system. Multiple drive-caster wheels are mechanically coupled and simultaneously driven and steered by respective motors. A rotational stage, orienting a vehicle frame, is attached on the center top of the mobile base. Position and translational velocities of the mobile base are controlled by the synchronized drive-casters. The orientation of the vehicle frame is controlled by the rotational stage completely decoupled from the translational motion of the mobile base. The synchro-drive transmission brings enormous advantages to the holonomic vehicle; three motor driven, all wheel drive, decoupling control, and simpler mechanism. In addition, an offset gear drive is also applied to the drive-caster wheel. This gear transmission enables a decoupling control of the drive shaft from the steering shaft on each wheel. By applying those mechanisms, the vehicle kinematics becomes very simple. Kinematics and statics of the proposed omnidirectional vehicle are analyzed and verification of the mechanism is shown by computer simulations.
