We discuss in this section a class of estimators for the nonlinear system (8.1) which we refer to as “certainty-equivalent” worst-case estimators (see also ). The estimator is constructed on the assumption that the asymptotic value of equals x, and the gain matrices are designed so that they are not functions of the state vector x, but of and y only. We begin with the one degree-of-freedom (1-DOF) case, then we discuss the 2-DOF case. Accordingly, we propose the following class of estimators:
where is the estimated output, is the new penalty variable, is the estimated ...