A frequency-domain stability chart for nonlinear feedback systems

A modification of the Popov criterion for absolute stability is presented. A new chart, designed to facilitate the application in practice of the new criterion, is introduced and its use is discussed. The range of use of the chart is then extended to encompass a previously published generalization of the Popov criterion. Then a procedure for use of the chart in conjunction with a Nichols chart in a simple and straightforward engineering procedure for designing absolutely stable single-loop nonlinear feedback systems is presented. An example is included to illustrate the procedure described.