Predictive control of fast unstable and nonminimumphase nonlinear systems

The problem of controlling fast, unstable, and nonminimum-phase systems is considered. With stan-dard predictive control, the time required for optimiza-tion is typically larger than the sampling interval that is needed for stabilization of the fast dynamics. On the other hand, due to the nonminimum-phase behav-ior, control based on input-output feedback linearisa-tion leads to unstable internal dynamics. In this paper, a cascade structure is proposed, with control based on input-output feedback linearisation forming the inner loop and predictive control the outer loop. Assuming high-gain feedback for the inner loop, a stability anal-ysis of the global scheme is provided based on singular perturbation theory. The approach is illustrated via the simulation of an inverted pendulum system