Design of second order sliding mode controller for balancing of unicycle

Abstract

A Unicycle robot based on a dynamic model is under study for balance and velocity control. Unicycle robot motion consists of roll and pitch axis control, roll axis motion is controlled by a reaction wheel and pitch axis motion is controlled by an in-wheel motor. There is no actuator for yaw axis control to make the dynamics simple. Dynamic equations are derived for the unicycle using the Euler-Lagrange equation to balance the unicycle and to obtain the dynamic speed control. Two separate sliding-mode controllers (SMC) are utilized to obtain roll axis balance along with pitch axis balance and velocity control respectively, their behaviour is studied and to avoid the chattering seen, a second order SMC (SOSMC) is proposed and implemented.