Generalized servomechanism evaluation

In the course of staking general evaluations of servo systems utilizing magnetic amplifiers, the inadequacy of classical methods becomes immediately evident. Statistical treatment of the signal and the system error is neccessary criteria of performance other than the quadratic are essential; and it is possible that accurate evaluation can result only from including the effects of the inherent non-linearities of the system. Progress to date has resulted in three separate approaches to the problem: a) A computer which includes a system analog, and an error criterion and integrating circuit, and which accepts statistically typical signals from a signal storage or generating device. There results a single number describing the performance of the system. b) An analytical method applicable only to linear systems, which makes use of the atrtocorrelation function of the signal and noise inputs, and also of the higher moment correlation fkutions of the two. c) An analytical method applicable in instanrces when the signal spectrum changesabruptly. The anaysis is applicable only to linear systems and considers a quadratic criterion.