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Slippery Model for a Semi-Passive Mobile Platform Subject to External Wrenches

In this paper we describe a slippery model for a mobile robot with multiple independently steered and passively driven wheels, moving on a slippery surface while being subjected to an external wrench. The model determines the vehicle's instantaneous response to the external wrench given the wheels' configuration. The model is verified and tested in a mobile robot that consists of an upper circular body and three identical semi-passive driving mechanisms. Each mechanism consists of a passive wheel that can freely roll, and a rotation actuator along the radial axes. Kinematic analysis provides tools for designing a motion path that steers the robot to the desired location, and determines the singular configurations. Due to the passive roll, there is no longitudinal slippage, and possible lateral slippage is determined by the dynamic model. This slippage can then be verified from kinematic and odometric models.