Gain-scheduling-based control structure for steering of lateral-pendulum unicycle robot — Part 1: Combined form

Unicycle robot stabilized by a lateral pendulum is an underactuated unstable system which is very challenging from control perspective. Its control challenge arises from difficulty in lateral stabilization, absence of direct control input for the control of turning motion and couplings among the longitudinal, lateral and turning dynamics. Research on this robot is mainly based on linear dynamic model which is developed by initially assuming that the longitudinal and lateral dynamics are completely decoupled. Such method results in the absence of turning dynamic model and, therefore, accurate control of turning motion is not possible. However, as a type of mobile robots, lateral-pendulum unicycle robot must have turning-motion-control capability, so that navigational control tasks such as path following can be achieved. In this paper, we present a control structure based on gain scheduling which can steer the robot and maintain its lateral stability at the same time. This control structure consists of two controllers namely (1) thrust controller and (2) steering controller. Thrust controller is responsible for the generation of forward motion according a pre-set reference by means of wheel actuation. Taking into account the robot´s forward speed, steering controller actuates the pendulum to generate turning motion according to its given reference. The performance of this control structure is investigated through numerical simulation.