Nonlinear control of input-constrained systems

This paper presents an optimization-based method for deriving model-based controllers that are applicable to input-constrained, multi-input multi-output, nonlinear processes described by a discrete-time mathematical model. By this method, nonlinear model-based control laws that inherently include optimal directionality and windup compensators are derived. The control laws can minimize the mismatch between constrained and unconstrained process responses, are input-output linearizing in the absence of input constraints, and allow one to adjust the rate of decay of the mismatch between constrained and unconstrained process responses when the constraints are no longer active. The connections between (a) the derived control laws and (b) model state feedback control and modified internal model control are established. The application and performance of the derived control laws are demonstrated by three examples.