An Augmented Kinematic Model for the Cartesian Control of the Hybrid Wheeled-Legged Quadrupedal Robot CENTAURO

This work deals with the kinematic control of Centauro, a highly redundant, hybrid wheeled-legged robot designed at Istituto Italiano di Tecnologia (IIT). Given its full wheeled mobility as allowed by its four independently steerable wheels, the choice of some local frame (in addition to the global world) is required in order to express tasks that are naturally defined in a robot-centric fashion. In this work, we show that trivially selecting such a frame as the robot trunk leads to sub-optimal results in terms of motion capabilities; as main contribution, we therefore propose a comparative analysis among three different choices of local frame, and demonstrate that in order to retain all advantages from the whole-body control domain, the kinematic model of the robot must be augmented with an additional virtual frame, which proves to be a useful choice of local frame, enabling e.g. the automatic adaptation of the trunk posture under constraint activation. The resulting Cartesian controller is finally validated by means of an extensive experimental session on the real hardware.