A Novel Kinematic Model for Rough Terrain Robots

We describe in detail a novel kinematic simulation of a three-wheeled mobile robot moving on extremely uneven terrain. The purpose of this simulation is to test a new concept, called Passive Variable Camber (PVC), for reducing undesirable wheel slip. PVC adds an extra degree of freedom at each wheel/platform joint, thereby allowing the wheel to tilt laterally. This extra motion allows the vehicle to better adapt to uneven terrain and reduces wheel slip, which is harmful to vehicle efficiency and performance. In order to precisely model the way that three dimensional wheels roll over uneven ground, we adapt concepts developed for modeling dextrous robot manipulators. The resulting equations can tell us the instantaneous mobility (number of degrees of freedom) of the robot/ground system. We also showed a way of specifying joint velocity inputs which are compatible with system constraints. Our modeling technique is adaptable to vehicles of arbitrary number of wheels and joints. Based on our simulation results, PVC has the potential to greatly improve the motion performance of wheeled mobile robots or any wheeled vehicle which moves outdoors on rough terrain by reducing wheel slip.