Instability in a nonlinear conditionally stable system subjected to a sinusoidal input

This paper considers the response of a saturating conditionally stable system to a sinusoidal input. When the input signal is sufficiently large, the system becomes unstable and it is found that the resultant oscillation depends to a marked extent on the frequency of the input signal. An extension to the previously developed describing-function technique is presented, which gives a unified explanation for all the observed phenomena. Experimental work agrees with theoretical predictions for a particular system.