Modeling and control of a new type of omnidirectional holonomic vehicle

A new type of omnidirectional holonomic vehicle has been proposed. The vehicle has a pair of driving wheel which configuration has a offset distance between a steering axis and a wheel axis. The wheel of this style is known as a nonholonomic system and is usually used for a caster wheel. In the case of proposed vehicle, a wheel of this style is used as a driving wheel by actuating a wheel axle and a steering axle independently. We first present a concept of the offset steered driving wheel", then describe kinematic models of the single driving wheel and a holonomic vehicle with proposed driving wheels. To avoid the nonholonomic characteristics of the wheel, we have introduced a control method in which an orientation of the wheel is neglected to be controlled. Therefore only translational velocities of the steering axle of the wheel are controlled so as to realize reference velocities. By using proposed wheel mechanism and the control method, the wheel can achieve a reproduction of caster motion. The vehicle with a couple of proposed driving wheels achieves omnidirectional and holonomic movements. Finally, proposed control methodology which based on kinematic models of the driving wheel and the vehicle has tested by a prototype vehicle. Experiments of the prototype vehicle have shown successful performances.