.. currentmodule:: control

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

.. autosummary::
   :toctree: generated/
   :template: custom-class-template.rst

   TransferFunction
   StateSpace
   FrequencyResponseData
   TimeResponseData

Input/output systems are accessed primarily via a set of subclasses that allow for linear, nonlinear, and interconnected elements:

.. autosummary::
   :template: custom-class-template.rst
   :nosignatures:

   InputOutputSystem
   InterconnectedSystem
   LinearICSystem
   LinearIOSystem
   NonlinearIOSystem

.. autosummary::
   :template: custom-class-template.rst
   :nosignatures:

   DescribingFunctionNonlinearity
   flatsys.BasisFamily
   flatsys.FlatSystem
   flatsys.LinearFlatSystem
   flatsys.PolyFamily
   flatsys.SystemTrajectory
   optimal.OptimalControlProblem
   optimal.OptimalControlResult