Sliding Mode Control of an Underactuated Two‐Link Manipulator

Abstract

We consider a horizontally mounted two-link manipulator of which only the first joint is actuated and the friction in the second joint is neglected. As a consequence, predefined equilibrium points are difficult to reach and point-to-point control is a challenging task. Starting from a partially feedback linearized model, a transformation to Byrnes-Isidori normal form is presented. Based on this decomposition, the projection into a two-dimensional subspace reveals certain similarities to a double integrator. Modifying an existing sliding mode approach for that system, a control law which steers the manipulator to an equilibrium point can be deduced.

A Review on the Control of Second Order Underactuated Mechanical Systems

“…ACRObat robot [12,28,29] and the Pendubot [30][31][32] shown in Figures 1(a) and 1(b), respectively, are 2-link planar robots with a single actuator. They graphically seem to be very similar; however, the difference resides in the location of their single actuator that causes a major difference in their standard representation.…”