Step ascension of a two-wheeled robot using feedback linearisation

Abstract

This paper investigates the modelling and control of step traversal using a two-wheeled robot (TWR). The traversal of TWRs over steps and other uneven terrain requires large platform tilt angles to adjust the centre of mass. This process is highly nonlinear, which complicates the controller design process. An auxiliary reaction wheel actuator is used in a novel way to facilitate step traversal. A mathematical model of step ascent is derived and used to create a feedback linearisation controller. The performance of the controller is assessed in simulation against a baseline controller from literature. The feedback linearisation controller yields significant improvements in tracking performance, with a decrease in tracking error of up to 86% when climbing a step in 1 second. Furthermore, the effects of varying the ascent conditions on performance are assessed. The controller is shown to operate over a large range of ascent times and reference tilt angles.