Control System Classes

Input/Output System Classes

The classes listed below are used to represent models of input/output systems (both linear time-invariant and nonlinear). They are usually created from factory functions such as tf() and ss(), so the user should normally not need to instantiate these directly.

The following figure illustrates the relationship between the classes:

`InputOutputSystem`	Base class for input/output systems.
`NonlinearIOSystem`	Nonlinear input/output system model.
`LTI`	Parent class for linear time-invariant system objects.
`StateSpace`	State space representation for LTI input/output systems.
`TransferFunction`	Transfer function representation for LTI input/output systems.
`FrequencyResponseData`	Input/output model defined by frequency response data (FRD).
`InterconnectedSystem`	Interconnection of a set of input/output systems.
`LinearICSystem`	Interconnection of a set of linear input/output systems.

The time response of an input/output system is represented using a special NamedSignal class that allows the individual signal elements to be access using signal names in place of integer offsets:

NamedSignal

Named signal with label-based access.

Response and Plotting Classes

These classes are used as the outputs of _response, _map, and _plot functions:

`ControlPlot`	Return class for control platting functions.
`FrequencyResponseData`	Input/output model defined by frequency response data (FRD).
`NyquistResponseData`	Nyquist response data object.
`PoleZeroData`	Pole/zero data object.
`TimeResponseData`	Input/output system time response data.

In addition, the following classes are used to store lists of responses, which can then be plotted using the .plot() method:

`FrequencyResponseList`	List of FrequencyResponseData objects with plotting capability.
`NyquistResponseList`	List of NyquistResponseData objects with plotting capability.
`PoleZeroList`	List of PoleZeroData objects with plotting capability.
`TimeResponseList`	List of TimeResponseData objects with plotting capability.

More information on the functions used to create these classes can be found in the Input/Output Response and Plotting chapter.

Nonlinear System Classes

These classes are used for various nonlinear input/output system operations:

`DescribingFunctionNonlinearity`	Base class for nonlinear systems with a describing function.
`DescribingFunctionResponse`	Results of describing function analysis.
`flatsys.BasisFamily`	Base class for basis functions for flat systems.
`flatsys.BezierFamily`	Bezier curve basis functions.
`flatsys.BSplineFamily`	B-spline basis functions.
`flatsys.FlatSystem`	Base class for representing a differentially flat system.
`flatsys.LinearFlatSystem`	Base class for a linear, differentially flat system.
`flatsys.PolyFamily`	Polynomial basis functions.
`flatsys.SystemTrajectory`	Trajectory for a differentially flat system.
`OperatingPoint`	Operating point of nonlinear I/O system.
`optimal.OptimalControlProblem`	Description of a finite horizon, optimal control problem.
`optimal.OptimalControlResult`	Result from solving an optimal control problem.
`optimal.OptimalEstimationProblem`	Description of a finite horizon, optimal estimation problem.
`optimal.OptimalEstimationResult`	Result from solving an optimal estimation problem.

More information on the functions used to create these classes can be found in the Nonlinear System Modeling, Analysis, and Design chapter.