Experimental Performance of Adaptive Fast Terminal Sliding Mode Control on a Suspended Cable Robot

Fast-tracking of reference trajectory and performance improvement in the presence of dynamic and kinematic uncertainties is of paramount importance in all robotic applications. This matter is even more important in the case of cable-driven parallel robots due to the flexibility of the cables. Furthermore, cables are limited in the sense that they can only apply tensile forces, for this reason, feedback control of such robots becomes more challenging than conventional parallel robots. To address these requirements for a suspended cable-driven parallel robot, in this paper a novel adaptive fast terminal sliding mode controller is proposed and then the stability of the closed-loop system is proven. In the proposed controller, a nonlinear term as a fractional power term is used to guarantee the convergent response at a finite time. At last, to show the effectiveness of the proposed controller in tracking the reference trajectory, simulations and the required experimental implementation is performed on a suspended cable-driven robot. This robot, named ARASCAM, has three degrees of transmission freedom. The obtained results confirm the suitable performance of this method for cable robots.