Use nonlinear model identification when a linear model does not completely capture your system dynamics. You can identify nonlinear models in the System Identification app or at the command line. System Identification Toolbox™ enables creation and estimation of three nonlinear model structures:
Nonlinear ARX models — Represent nonlinearities in your system using dynamic nonlinearity estimators such as wavelet networks, tree-partitioning, and sigmoid networks.
Hammerstein-Wiener models — Estimate static nonlinearities in an otherwise linear system.
Nonlinear grey-box models — Represent your nonlinear system using ordinary differential or difference equations (ODEs) with unknown parameters.
Nonlinear model identification requires uniformly sampled time-domain data. Your data can have one or more input and output channels. You can also model time series data using nonlinear ARX and nonlinear grey-box models. For more information, see About Identified Nonlinear Models.
You can use the identified models to simulate and predict model output at the command line, in the app, or in Simulink®. If you have Control System Toolbox™, you can also linearize your model and use it for control-system design. For more information, see Linear Approximation of Nonlinear Black-Box Models.