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Improve lft functions and lft documentation - #1249
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…tionality and update reference
update iosys_test test_lft docstring
…ter performing lft
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coverage: 94.782% (+0.03%) from 94.757% — tomaantjes:improve-lft-functions into python-control:main |
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Thanks for proposing this. Some tests fail when Slycot is not installed, e.g.,
FAILED control/tests/bdalg_test.py::TestLft::test_lft_tf_inputs[-1--1] - control.exception.ControlMIMONotImplemented: MIMO system conversion not supported without Slycot
FAILED control/tests/bdalg_test.py::TestLft::test_lft_tf_inputs[1-1] - control.exception.ControlMIMONotImplemented: MIMO system conversion not supported without Slycot
Can you fix that? After you do, I will review this pull request.
Of course, I marked it in the newest commit. |
| edition, 2005. | ||
| .. [1] J. Doyle, A. Packard, and K. Zhou, "Review of LFTs, | ||
| LMIs, and mu," Proceedings of the 30th IEEE Conference on | ||
| Decision and Control, Brighton, England, 1991, pp. 1227-1232. |
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| Decision and Control, Brighton, England, 1991, pp. 1227-1232. | |
| Decision and Control, Brighton, England, 1991, pp. 1227-1232. | |
| https://authors.library.caltech.edu/records/8t2hq-w7318 |
Add a URL to help readers find it quickly. (This can also be https://doi.org/10.1109/CDC.1991.261572 or https://doyle.caltech.edu/images/doyle/7/70/CDC1991.pdf, but the Caltech library open access is most helpful, in my opinion.) This is not done universally in the documentation of control, but there are examples with arXiv and DOI URLs.
| def lft(self, other, nu=-1, ny=-1, **kwargs): | ||
| """Return the linear fractional transformation. | ||
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| A definition of the LFT operator can be found in Appendix A.7, |
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I do not have a copy of this book and could not find a reliable free source on the Internet, so I agree that the CDC paper is easier to find.
We should keep a link to the Matlab lft definition because it shows some compatibility between that and this implementation. https://www.mathworks.com/help/control/ref/lft.html is broken. The up-to-date URL seems to be https://www.mathworks.com/help/control/ref/inputoutputmodel.lft.html
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Thanks, I agree adding a link to the Caltech library would be most helpful and I added it in addition to a link to the Matlab documentation.
I also noticed the docstring missed some information regarding the way I currently implemented the fallback with duplicate signal names and added that as well.
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Thanks. I will need another 2 or 3 days to complete my review.
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This PR aims to solve #1156 by updating the current
ss.lftfunction, adding a generallftfunction and adding more documentation.Summary of main changes:
lft(sys1, sys2, [nu, ny], **kwargs)which can be used for anyInputOutputSystemdue to the use ofinterconnectif no statespace conversion is possible.lftfunction.ss.lft()self-contained. Here I added a new reference to a paper as the old one refers to a chapter (A.7) in the second edition of Skogestad which in mine does not discuss LFT's (chapter A.8 is about LFT's but does not contain an explanation of the star product). A reference to the star product does exist in the first edition but I thought this paper was more focused on the topic and also easier to find.lftfunction.lftfunction in appropriate places.AI Disclosure:
Claude was used to proofread and suggest corrections for documentation and verify the documentation and code compliance with the developer standards. Additionally, it was used to assess test coverage and draft some unittests after implementation of the test scaffolding. All suggestions were reviewed, understood and manually tested.