.. currentmodule:: control

.. _version-0.9.3:

Version 0.9.3 Release Notes
----------------------------

* Released: date of release
* `GitHub release page
  <https://github.com/python-control/python-control/releases/tag/0.9.3>`_

This release adds support for collocation in finding optimal
trajectories, adds the ability to compute optimal trajectories for
flat systems, adds support for passivity indices and passivity tests
for discrete time systems, and includes support for gain scheduling
(in `create_statefbk_iosystem`.  Setup is now done using setuptools
(`pip install .` instead of `python setup.py install`).

This release requires Python 3.8 or higher.


New classes, functions, and methods
...................................

The following new classes, functions, and methods have been added in
this release:

* `ispassive`: check to see if an LTI system is passive (requires
  `cvxopt`).

* `get_output_fb_index`, `get_input_ff_index`: compute passivity indices.

* `flatsys.BSplineFamily`: new family of basis functions for flat
  systems.

* `flatsys.solve_flat_ocp`: allows solution of optimal control
  problems for differentially flat systems with trajectory and
  terminal costs and constraints, mirroring the functionality of
  `optimal.solve_ocp`.

* `zpk`: create a transfer funtion from a zero, pole, gain
  representation.

* `find_eqpts` (now `find_operating_system`) now works for
  discrete-time systems.

Bug fixes
.........

The following bugs have been fixed in this release:

* Fixed `timebase` bug in `InterconnectedSystem` that gave errors for
  discrete-time systems.

* Fixed incorect dimension check in `matlab.lsim` for discrete-time
  systems.

* Fixed a bug in the computation of derivatives for the Bezier family
  of basis functions with rescaled final time, and implemented a final
  time rescaling for the polynomial family of basis functions.

* Fixed bug in the processing of the `params` keyword for systems
  without states.

* Fixed a problem that was identified in PR #785, where
  interconnecting a LinearIOSystem with a StateSpace system via the
  interconnect function did not work correctly.

* Fixed an issued regarding the way that `StateSpace._isstatic` was
  defining a static system. New version requires nstates == 0.

* Fixed a bug in which system and system name were not being handled
  correctly when a `TransferFunction` system was combined with other
  linear systems using interconnect.

* Fixed a bug in `find_eqpt` where when y0 is None, dy in the root
  function could not be calculated (since it tries to subtract
  None).


Improvements
............

The following additional improvements and changes in functionality
were implemented in this release:

* Handle `t_eval` for static systems in `input_output_response`.

* Added support for discrete-time passive systems.

* Added a more descriptive `__repr__` for basis functions (show the
  family + information on attributes).

* `StateSpace.sample` and `TransferFunction.sample` return a system
  with the same input and output labels, which is convenient when
  constructing interconnected systems using `interconnect`.

* `optimal.solve_ocp`: add collocation method for solving optimal
  control problems.  Use `trajectory_method` parameter that be set to
  either 'shooting' (default for discrete time systems) or
  'collocation' (default for continuous time systems). When
  collocation is used, the `initial_guess` parameter can either be an
  input trajectory (as before) or a tuple consisting of a state
  trajectory and an input trajectory.

* `StateSpace` objects can now be divided by a scalar.

* `rlocus`, `sisotool`: Allow `initial_gain` to be a scalar (instead
  of requiring and array).

* `create_statefbk_iosystem` now supports gain scheduling.

* `create_estimator_iosystem` now supports continous time systems.


Deprecations
............

The following functions have been newly deprecated in this release and
generate a warning message when used:

* In the :ref:`optimal module <optimal-module>`, constraints are
  specified in the form ``LinearConstraint(A, lb, ub)`` or
  ``NonlinearConstraint(fun, lb, ub)`` instead of the previous forms
  ``(LinearConstraint, A, lb, ub)`` and ``(NonlinearConstraint, fun,
  lb, ub)``.

The listed items are slated to be removed in future releases (usually
the next major or minor version update).