"An optimal control problem for linear regulators with external disturbances is formulated. it is shown that, if some a priori knowledge of the disturbance is incorporated into the design procedure, the optimal control is not an explicit function of the disturbance and can be implemented as a linear function of the state of the system."

Some recent developments in the area of sensitivity in optimal control systems are summarized. The several sensitivity, definitions, analysis methods, and design techiniques are placed in perspective. A selected list of references is included.

"The sensitivity of a control system is usually taken to be the normalized variation of plant or controller parametes. Rather than the usual absolute sensitivity described above, a new definition of relativy sensitivity is introduce for optimal control problem, wherein teh system performace is always compared with its optimum under the given circunstances. The implications of the relative sensitivity and its relevance to optimal system design are discussed in detail. Moreover, a theorical approach to the problem of system optimization when plant parameters are subject to change or are incompletely specified is presented."

In a recent paper the syntesis technique proposeby Guillermin for linear stationary systems was extended for nonstationary feedback systems. It is to be expected, however, that stability problems may arise when applying the method for unstable or nonminimum phase plants, as it does in the time-invariant case.