Control system performance measures: Past, present, and future

An increased amount of emphasis on the mathematical formulation of control system performance can be found in recent literature on automatic control. There are two areas of control system theory in which the application of performance measures is of interest: 1) the evaluation of control system designs in general, and 2) the design of adaptive control systems. In the former case, the performance measure is becoming an increasingly important aid to the control system designer. In the latter case, the performance measure takes on even greater significance, since adaptive systems include, by definition, a performance measure as an essential function which permits correction of system dynamic response during actual operation. Furthermore, the over-all evaluation of the adaptive loop itself presents new problems in the choice and use of performance criteria. In the past, emphasis has been placed on various types of integrals, such as integral of error-squared and integral of the product of time and absolute error (ITAE); present emphasis is being placed on forms of integrals of a more general type; the trend for future emphasis appears to be in applications of statistical concepts and in attacking the problem of choice of the error measure in the adaptive system.