Dynamic modeling and characteristics analysis of lateral-pendulum unicycle robot

Lateral-pendulum unicycle robot is a type of single-wheeled mobile robot which utilizes an inverted pendulum mounted laterally for its stabilization and control. Even though this concept was first mentioned in the 1980s, it has not been sufficiently explored especially from the theoretical point of view. Therefore, this robot represents a niche which is still open for more thorough research. This paper presents four contributions to the research of this particular robot. First, the complete model of the robot dynamics is derived and this model can facilitate more accurate study of the robot's static and dynamic behaviors. Secondly, two important constants namely (1) lateral-statics boundary and (2) lateral-statics constant, which are useful for the lateral stabilization, are derived and analyzed. Thirdly, turning constant, required for the control of the turning motion, is derived and used to study the achievable path curvature in maneuvering control. Lastly, dynamics couplings during steady linear motion and steady circular motion are studied and the necessity of integral action in the lateral controller for circular motion is shown and explained. Throughout this paper, numerical simulation is used intensively and two case studies are presented to illustrate the concepts.