TUBE-BASED ROBUST NONLINEAR MODEL PREDICTIVE CONTROL1

A successful method for model predictive control of constrained linear systems uses a local linear control law that, in the presence of disturbances, maintains the disturbed trajectory of the controlled system in a tube whose centre is the nominal trajectory (generated ignoring the disturbance) and whose ‘cross-section’ is a robust, positively invariant set; robust exponential stability of an invariant set centred on the origin may be established. The purpose of this paper is to show how this successful procedure may be extended to provide robust model predictive control of constrained nonlinear systems. An ancillary problem is proposed, the solution of which provides a local nonlinear control law. The disturbed trajectories lie in a tube and this provides the means for constructing a tube-based robust nonlinear model predictive controller.