Stability Bounds for Nonlinear Systems Designed Via Frequency Domain Stability Criteria

Compensator design results are compared for the circle and Popov criteria, both of which are sufficiency conditions for absolute stability of nonlinear control systems. Analog simulation studies yielded higher compensator gains than either of the two criteria. Nevertheless, the analog results showed the same general trend as the circle and the Popov criteria results. The circle criterion was found to be more conservative than the Popov criterion in the numerical examples presented here.