Predictive PI-control of linear plants under positional and incremental input saturations

A predictive control strategy is developed for set-point tracking of LTI plants in the presence of joint positional and incremental (rate) input saturation constraints. The resulting control algorithm is built so as to provide an integral action capable to asymptotically reject arbitrary constant disturbances. This task is achieved by possibly modifying on-line the set-point in the case this becomes incompatible with constraints and disturbances. When applied to asymptotically null controllable with bounded inputs (ANCBI) plants, viz. all stabilizable linear systems with eigenvalues in the closed unit circle, the control law is shown to globally provide set-point tracking in the presence of arbitrary constant disturbances and initial state. For non-ANCBI plants, viz. systems with exponentially unstable modes, the control law features the mentioned properties locally, viz. in bounded regions of initial states and disturbances. (C) 2000 Elsevier Science Ltd. All rights reserved.