Circle and Popov criteria as tools for nonlinear feedback design.
The authors analyze an earlier circle criterion design, and they show that its feasibility is limited by conditions on the unstable part of the zero dynamics and the relative degree. The restrictions on the zero dynamics are relaxed by using the Popov multiplier, which also reduces the complexity of the circle criterion. The results are illustrated with several design examples.
scientific article; zbMATH DE number 1901004