RoboTrikke: A Novel Undulatory Locomotion System

The TRIKKE is a three-wheeled, human-powered scooter that can be propelled by a combination of cyclic motion of its handlebar and swaying motion of the rider. This paper addresses the modeling, dynamics and control of the TRIKKE and the development of a robotic platform called the ROBOTRIKKE that is derived from similar principles. The TRIKKE can be modeled as a modified roller-racer with an unstable steering arrangement. The model of the TRIKKE reduces to the roller-racer [8] in the absence of this steering arrangement. We prove that under certain conditions on the geometric parameters of the system, the TRIKKE and roller-racer systems cannot be stopped after motion starting from rest using the steering control as the sole input. As a consequence, the ideal model is severely limited from the point of view of controllability. We demonstrate the validity of our model through comparison with experimental measurements on a small-scale robotic prototype of the TRIKKE. We present closed-loop control results for tracking (on average) a straight line trajectory using visual feedback from an overhead camera.