future development of the control package

[Lukas Reichlin]

Hi Thomas,
dear Octave community,

On Friday morning, I have published control-3.0.0, the first major release 
after control-2.0.0 in early 2011. I’m very pleased with the outcome [1] and 
hope that it finds general approval. However, its development process during 
October 2015 was freelancing/a solo run and I did not include you in the 
decision process. For future releases, I would like to improve this and involve 
especially you (as co-author), but also other contributors (therefore CC’ing 
maintainers list), more into decision making. Appreciation and an attempt to 
increase the bus factor are two of the reasons for this step.

Regarding control-3.0.1, I propose the following changes:
- Your work on tf2ss conversion
- Accepting only finite values as inputs, see bug #46330.  
<http://savannah.gnu.org/bugs/?46330>
- Fix problems with "algebraic loops» (as Matlab calls this) as outlined in [2].

Regarding the third point, I wonder whether it’s possible to apply some kind of 
state transformation if matrice A is not invertible in the equation below. 
(such that C A^-1 B can be computed)

y = [D - C A^-1 B] u


For the mercurial repository, I propose the creation of a second branch 
(besides default), named stable, similar to Octave.
I have tried to merge control-3.0.0 into your control-time-delay repo, but I 
had to give up. There were simply too many conflicts. Maybe it’s better when I 
create a «delay» branch in the control repo and you copy-paste your changes 
there? I could start by integrating your oct-files into a single 
__control_delay_functions__.oct.
Shall we create this delay branch before or after realizing the array feature? 
(see bug #45314, <http://savannah.gnu.org/bugs/?45314>). Please don’t feel 
pressed for an answer, we could discuss such topics in meeting, see the next 
paragraph.


Finally, I would like to propose a meeting in real life. Since you’re still 
working at ETH Zurich and we haven’t met for quite a while, what do you think 
about a meeting in one of its cafeterias (in November)? Fellow Swiss residents 
(JuanPi, Reza) are welcome as well!

Best regards,
Lukas

[1]
http://sourceforge.net/p/octave/control/ci/default/tree/NEWS

[2]
http://sourceforge.net/p/octave/control/ci/default/tree/devel/algebraic_loops.m