Locomotion and Control of a Friction-Driven Tripedal Robot

This paper presents a novel omnidirectional gait design and feedback control of a radially symmetric tripedal friction-driven robot. The robot features 3 servo motors mounted on a 3-D printed chassis 7 cm from the center of mass and separated 120 degrees. These motors drive limbs, which impart frictional reactive forces on the body. We first introduce a mathematical model for the robot motion, then show experimental observations performed on a uniform friction surface, which validated the accuracy of the model. This model was then used to create an omnidirectional gait that allows the robot to translate in any direction. Based on this gait, we also introduce a Proportional-Integral (PI) feedback control framework that enables the robot to closely follow a desired path. Contrasting with feedforward motion generation, the proposed feedback controller reduced the tracking error by approximately 46%. We have successfully demonstrated the approach in our robot hardware for the problem of line following using live feedback from an overhead tracking camera. Our controller is also able to correct for aerodynamic disturbances generated by a high-volume industrial fan with a mean flow speed of 5.5ms⁻¹, reducing path error by 65% relative to the basic position update procedure.