Offset-free Receding Horizon Control of Constrained Linear Systems

This paper addresses the design of a dynamic state feedback receding horizon controller, which guarantees robust constraint satisfaction, robust stability and offset-free control of constrained linear systems in the presence of time-varying setpoints and unmeasured disturbances. This objective is obtained by first designing a dynamic linear offset-free controller and computing an appropriate domain of attraction for this controller. The linear (unconstrained) controller is then modified by adding a perturbation term, which is computed by a (constrained) robust receding horizon controller. The receding horizon controller has the property that its domain of attraction contains that of the linear controller. In order to ensure robust constraint satisfaction, in addition to offset-free control, the transient as well as the limiting behavior of the disturbance and setpoint need to be taken into account in the design of the receding horizon controller. The fundamental difference between the results in this paper and the existing literature on receding horizon control is that, in this paper, the transient effect of the disturbance and setpoint sequences on the so-called “target calculator” is explicitly incorporated in the formulation of the receding horizon controller. An example of the control of a continuous stirred tank reactor is presented. Topical Heading: Process system engineering