Trajectory-tracking control of an input delayed omnidirectional mobile robot

This article describes the design of a linear observer-linear controller-based robust output feedback scheme for output reference trajectory tracking tasks in an input delayed omnidirectional mobile robot. The unknown, possibly state-dependent, additive nonlinearity influencing the tracking error dynamics, is modeled as an absolutely uniformly bounded, additive unknown “time-varying disturbance” input signal. This procedure simplifies the system tracking error description to that of three independent chains of second order integrators with, known, position-dependent control input gain matrix, while additively being perturbed by the unknown, smooth, time-varying signal. A GPI observer is the basis of a suitable perturbation prediction scheme, aimed at perturbation cancellation in the forward system, which allows to reduce the nonlinear delayed input control problem to that of a weakly perturbed linear delayed system. The approximate cancellation of the perturbation input facilitates the use of the classical Smith Predictor Compensator in the resulting dominantly linear problem. The results are implemented on a laboratory prototype.