Less Conservative Robust Reference Governors and Their Applications

The applications of reference governors to systems with unmeasuredset-bounded disturbances can lead to conservative solutions. This conservatismcan be reduced by estimating the disturbance from output measurements andcanceling it in the nominal control law. In this paper, a reference governorbased on such an approach is considered and time-varying, disturbance and stateestimation errors bounding sets are derived. Consequently, the traditionalimplementation of a reference governor, which exploits a constraint admissiblepositively-invariant set of constant commands and initial states, is replacedby one which utilizes a time-dependent sequence of similar sets (which are notnecessary nested). Examples are reported which include two applications tolongitudinal control of aircraft that illustrate handling of elevatoruncertainty and wing icing.