High-order sliding control of mechanical systems: Theory and experiments

In this paper, the control of a class of mechanical systems via output feedback is considered. The proposed control strategy is based on a second-order sliding manifold MIMO approach, that is used to design a robust multivariable linear controller. A trajectory tracking problem is faced and a suitable time-varying sliding surface is defined in order to deal with the so-called peaking phenomenon resulting from possible unmatched initial conditions of the reference trajectory. Experimental results are carried out on a 6-dof Comau SMART-3 S robot manipulator. As confirmed by experiments, the proposed control strategy exhibits high tracking accuracy and strong robustness properties against plant uncertainties and external disturbances.