Generating Locomotion with Effective Wheel Radius Manipulation

Travel over sloped terrain is difficult as an incline changes the interaction between each wheel and the ground resulting in an unbalanced load distribution which can lead to loss of traction and instability. This paper presents a novel approach to generating wheel rotation for primary locomotion by only changing its centre of rotation, or as a complimentary locomotion source to increase versatility of a plain centre hub drive. This is done using linear actuators within a wheel to control the position of the centre hub and induce a moment on the wheel from gravity. In doing so our platform allows for active ride height selection and individual wheel pose control. We present the system with calculations outlining the theoretical properties and perform experiments to validate the concept under loading via multiple gaits to show motion on slopes, and sustained motion over extended distance. We envision applications in conjunction to assist current motor drives and increasing slope traversability by allowing body pose and centre of gravity manipulation, or as a primary locomotion system.