Discrete-time reference governors for systems with state and control constraints and disturbance inputs

Reference governors for discrete-time linear systems with state and control constraints are considered. The governors attenuate, but only when necessary, the reference inputs to the linear system so that the constraints are enforced and the system maintains it desirable linear behavior in the presence of nonlinear effects such as actuator saturation. Results of Gilbert and Kolmanovsky (1994) are extended in significant ways. It is possible to treat disturbance inputs and provide flexibility in the choice of the nonlinear function that determines the operation of the reference governor. It is proved that constraint satisfaction is guaranteed for all reference inputs and disturbance inputs. Moreover, under reasonable conditions on the reference input, the eventual action of the reference governor is a unit delay. An example, which illustrates the results of the paper, is given. It shows, among other things, that high sample rates need not increase the complexity of an effective reference governor