2.3.8 Optimal and Adaptive Systems
The basic goal of system design is meeting performance specifications. Performana' specifications are the constraints put on mathematical number of ways. functions The desired describing (or system prescribchared)
acteristics. They may be stated in any system characteristics specify important properties of the system: speed of stability, system accuracy, allowable error, sensitivity, and so on, Satisfactory perfor' mance is determined by the application and the characteristics of the particular system measure of performance is called performance index. In more general The system designs, it is not specified. Instead, the system components, their interconnectiOnS and the parameter values are chosen so that the performance index is maximized minimized. The systems designed in this way are called optimal systems.
In many problems, the performance index is a measure or function of the error bel tween the actual and ideal (or desired) responses. It is formulated in terms of the desigtÿ& parameters chosen, subject to existing physical constraints, to optimize the performan