Experiments in Second Order Sliding Mode Control of a CPG based Spherical Robot

Abstract

A novel caterpillar inspired rolling gait generation in a spherical robot and its control mechanism is presented in this paper. A rhythmic rolling pattern mimicking Pleurotya caterpillar is produced for the spherical robot locomotion. The pattern is represented by central pattern generators (CPGs)in combination with nonlinear robot dynamics. These rhythmic patterns are controlled by a non-linear high (second) order sliding mode (HOSMC) feedback method, to maintain robot stability and robustness in the presence of matched parameter uncertainties and bounded external disturbances. Design and experimental evaluation of the proposed control strategy for the spherical robot is done on both smooth and rough ground surfaces. Control performance of the robot is measured by virtue of roll angle stability its convergence and wheel velocities. Experimental results validate that proposed second-order HOSMC strategy is more efficient in robust rolling gait control of a spherical robot compared to a first-order SMC on two different types of ground surfaces.