Nonlinear control: the joys of having an extra sensor

Concerns the measurement feedback nonlinear control problem and a practical aspect of extending H^∞ control to it. In the linear and nonlinear H^∞ situations the commonly analyzed regular case precludes many common situations; for example state feedback control does not fall into this category. More generally, cases where the number of (independent) sensors, Sens, is bigger than the number of command signals plus substantial disturbances, Dis, in the problem is a singular as opposed to regular situation. We call this the cheap sensor case. In this paper we extend the information state approach to nonlinear control from the regular case to the cheap sensor case