The use of correlation techniques in the study of servomechanisms

Methods of analysis and synthesis of linear servomechanisms in the past have largely been based upon the frequency-response approach. Analogue computer techniques have also been widely used, particularly for transient-input tests. Random inputs which statistically resemble the expected inputs may be more valuable than sine-wave or simple transient inputs for the testing of many servomechanisms. With such input functions the use of correlation functions and of devices for measuring auto- and cross-correlation becomes important. Random input functions and correlator measurement used together with analogue computer techniques are shown to be most valuable in the study of non-linear servomechanisms and other non-linear devices.