For questions regarding the control of nonlinear dynamical systems with known or unknown nonlinearities.
Nonlinear control is the tool used to force certain desired behaviors directly into nonlinear plants which in general provide an enhanced and more accurate description of the physical dynamic processes. Nonlinearities can be considered known, unknown or even approximated through certain mathematical tools such as neural networks, basis functions etc. The designer should take into consideration these knowledge regarding the system in order to design a proper nonlinear controller. More information can be found under this link: Nonlinear Control.