.. currentmodule:: control

.. _version-0.9.0:

Version 0.9.0 Release Notes
----------------------------

* Released: 21 Mar 2021
* `GitHub release page
  <https://github.com/python-control/python-control/releases/tag/0.9.0>`_

Version 0.9.0 of the Python Control Toolbox (python-control) contains
a number of enhanced features and changes to functions. Some of these
changes may require modifications to existing user code and, in
addition, some default settings have changed that may affect the
appearance of plots or operation of certain functions.

Significant new additions including improvements in the I/O systems
modules that allow automatic interconnection of signals having the
same name (via the `interconnect` function), generation and plotting
of describing functions for closed loop systems with static
nonlinearities, and a new :ref:`optimal control module
<optimal-module>` that allows basic computation of optimal controls
(including model predictive controllers). Some of the changes that may
break use code include the deprecation of the NumPy `~numpy.matrix`
type (2D NumPy arrays are used instead), changes in the return value
for Nyquist plots (now returns number of encirclements rather than the
frequency response), switching the default timebase of systems to be 0
rather than None (no timebase), and changes in the processing of
return values for time and frequency responses (to make them more
consistent). In many cases, the earlier behavior can be restored by
calling ``use_legacy_defaults('0.8.4')``.

New features
............

* Optimal control module, including rudimentary MPC control
* Describing functions plots
* MIMO impulse and step response
* I/O system improvements:

  - `linearize` retains signal names plus new `interconnect` function
  - Add summing junction + implicit signal interconnection

* Implementation of initial_phase, wrap_phase keywords for bode_plot
* Added IPython LaTeX representation method for StateSpace objects
* New `~StateSpace.dynamics` and `~StateSpace.output` methods in `StateSpace`
* `FRD` systems can now be created from a discrete time LTI system
* Cost and constraints are now allowed for `flatsys.point_to_point`


Interface changes
.................

* Switch default state space matrix type to 'array' (instead of 'matrix')
* Use `~LTI.__call__` instead of `~LTI.evalfr` in LTI system classes
* Default dt is now 0 instead of None
* Change default value of `StateSpace.remove_useless_states` to False
* Standardize time response return values, `return_x`/`squeeze`
  keyword processing
* Standardize `squeeze` processing in frequency response functions
* Nyquist plot now returns number of encirclements
* Switch `LTI` class and subclasses to use ninputs, noutputs, nstates
* Use standard time series convention for `markov` input data
* TransferFunction array priority plus system type conversion checking
* Generate error for `tf2ss` of non-proper transfer function
* Updated return values for frequency response evaluated at poles


Improvements, bug fixes
.......................

* Nyquist plot improvements: better arrows, handle poles on imaginary axis
* Sisotool small visual cleanup, new feature to show step response of
  different input-output than loop
* Add `bdschur` and fox modal form with repeated eigenvalues
* Fix rlocus timeout due to inefficient _default_wn calculation
* Fix `stability_margins`: finding z for ``|H(z)| = 1`` computed the wrong
  polynomials
* Freqplot improvements
* Fix rlocus plotting problem in Jupyter notebooks
* Handle empty pole vector for timevector calculation
* Fix `lqe` docstring and input array type
* Updated `markov` to add tranpose keyword + default warning
* Fix impulse size for discrete-time impulse response
* Extend `returnScipySignalLTI` to handle discrete-time systems
* Bug fixes and extensions for `step_info`