Convergent systems constitute a practically important class of nonlinear systems that extends the class of asymptotically stable linear time-invariant systems. In this note, we extend frequency response functions defined for linear systems to nonlinear convergent systems. Such nonlinear frequency response functions for convergent systems give rise to nonlinear Bode plots, which serve as a graphical tool for performance analysis of nonlinear convergent systems in the frequency domain. The results are illustrated with an example.
Pavlov, A. V., Wouw, van de, N., & Nijmeijer, H. (2007). Frequency response functions for nonlinear convergent systems. IEEE Transactions on Automatic Control, 52(6), 1159-1165. https://doi.org/10.1109/TAC.2007.899020