Bang Bang Control of an Overhead Cartesian Crane

A motion controller for a 3-D Cartesian crane is designed under the constraint that the control action belong to a discrete set of assigned values. The design procedure rests upon a two step approach. First, one determines a constraint-free motion controller satisfying the required specifications. In a second step, this controller is replaced with an equivalent controller satisfying the discrete constraint. The first step is implemented by adopting a heuristic 3-D ext ension of a wellproven 2-D controller; the second, by applying recent sliding mode results.