Effect of delay on the robustness of feedback systems: The gap metric

The objective of this paper is to highlight the drawbacks inherent in modeling unit feedback systems in the presence of wideband output disturbances without allowing for delay in the feedback path. The results are obtained using the properties of the gap metric introduced by Zames and El-Sakkary[1] and El-Sakkary.[2] The effect of delay in the feedback path on robustness and performance of the closed loop is highlighted. Possible configurations that improve robustness are suggested. Computational examples are included to illustrate the concepts introduced.