Output-feedback proportional–integral– derivative-type control with simple tuning for the global regulation of robot manipulators with input constraints

An output-feedback proportional-integral-derivative-type control scheme for the global position stabilisation of robot manipulators with bounded inputs is proposed. It guarantees the global regulation objective avoiding input saturation by releasing the feedback not only from the exact knowledge of the system structure and parameter values, but also from velocity measurements. With respect to previous approaches of the kind, the proposed scheme remains simple while increasing design/performance-adjustment flexibility. For instance, it does not impose the use of a specific sigmoidal function to achieve the required boundedness but involves a generalised type of saturation functions. More importantly, it is characterised by a very simple control-gain tuning criterion, the simplest hitherto obtained in the considered analytical context. Experimental tests on a 2-degree-of-freedom direct-drive manipulator corroborate the efficiency of the developed scheme.