Variable structure controller design for flexible-link robots under gravity

This paper presents an approach for the design of a nonlinear variable structure controller (VSC) for the joint regulation and vibration control of flexible-link robots under gravity. We propose a linear state-variable transformation for the system dynamics. The system dynamics expressed in the new state variables enables one to consider VSC design and vibration suppression separately. A modified sliding surface is introduced to damp out vibration in the flexible-link robot. Stability of the closed-loop system is proved. Simulation results show that the VSC can provide good joint angle regulation and can effectively damp our vibration in flexible-link robots