On the Kinematics of Wheeled Motion Control of a Hybrid Wheeled-Legged CENTAURO robot

Legged-wheeled robots combine the advantages of efficient wheeled mobility with the adaptability to real-world terrains through the legged locomotion. Due to this hybrid mobility skill, they can excel in many application scenarios where other mobile platforms are not suitable for. However, their versatile mobility increases the number of constraints in their motion control where both the properties of legged and wheeled systems need to be considered. Relevant schemes for legged-wheeled platforms so far have been developed exploiting separate motion control of the wheeled and legged functionalities. This paper discusses the legged-wheeled motion kinematics without constraining the camber angles of the wheels, and it proposes a first-order inverse kinematics scheme that stabilizes the legged-wheeled system in the wheeled motion. Furthermore, the work adopts a floating base model that allows to easily incorporate the legged motion to the scheme. The developed controller is tested in simulation and experiments on a legged-wheeled centaur-like robot - CENTAURO.