Jet-Scheduling Control for SpiderCrane: Experimental Results

SpiderCrane is a three-dimensional crane, whose main particularity lies in the absence of large inertial moving parts. This paper presents experimental results obtained with the novel jet-scheduling control methodology that is based on differential flatness. Jet scheduling consists essentially in using measurements to regenerate the derivatives associated with a reference trajectory. Through this regeneration, the feedforward control law, which is computed from the reference trajectory using the flatness property, is transformed into a feedback control law. Jet-scheduling control takes full advantage of the dynamic possibilities of SpiderCrane as it allows operation far away from the quasi-static mode of operation. In contrast to proportional-like compensators, the proposed control scheme does not over-react whenever the load is displaced in a persistent way, mainly because only higher derivatives are scheduled. Furthermore, the position of the upper pulley can be adapted without requiring a change in the load position, that is, without over-pulling the main cable. This general compliance makes the control methodology ``user friendly'' without cutting down on dynamic performance. Both point stabilization and trajectory tracking can be implemented.