The Virtual Wheel Concept for the Singularity-Free Kinematics and Dynamics Modeling and Control of Pseudo-Omnidirectional Vehicles

Pseudo-omnidirectional vehicles (POV) are equipped with several center steered and driven standard wheels, and exhibit high maneuverability and positioning accuracy. Yet this class of mobile systems is rarely considered. Despite their simple setup, the mathematical modeling is challenging. Moreover all models presented so far suffer from artificial singularities (due to a particular parameterization), which is often tackled with switching strategies. This is a critical issue as the model is the basis for simulation, motion planning, control, and design. In this letter, a novel modeling concept is introduced which is singularity-free and does not rely on a switching strategy. Its application to kinematics and dynamics modeling of general POV is presented. Closed form solutions for the traction forces and drive torques are presented. These solutions account for the practically relevant situation of non-exactly aligned wheels. This model serves as basis for optimal path planning and model-based control. Simulations are reported showing the robustness and applicability of the concept.