A novel approach for steering wheel synchronization with velocity/acceleration limits and mechanical constraints

Pseudo-omnidirectional robots with independently steerable wheels require a method to synchronize the steering motion of the wheels in order to keep a unique instantaneous center of rotation (ICR). For standard wheels, the instantaneous center of rotation is defined as the intersection point of all wheel axes. We present a novel approach to deal with the problem of continuously shifting the center of rotation of a pseudo-omnidirectional rover from an initial to a demanded position in the Cartesian plane. The main contribution is the consideration of substantial velocity and acceleration limits on the steering units, as well as mechanical constraints and noise affected sensor measurements. We solve this problem by deriving a relationship between the steering accelerations of the single wheels and the acceleration of the center of rotation. We furthermore provide a contribution to the tracking of the ICR in the presence of significant sensor noise. Our results are evaluated by tests on the rover breadboard developed during the activities for the ExoMars mission.