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Reachability using the parallelotope method #93
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@mforets Do you have an implementation of parallelotopes? |
Hi David, Depending on the application that you have in mind, you can use zonotopes, which are a generalization of parallelotopes of order greter than one. As explained in the notes, there are different approaches for the parallelotope, either in constraint form (as in #1632) on in generator form. Again, depending on the use case, one representation may be preferable than the other. |
OK great, thanks. I was asking in terms of implementing the algorithms in this and related papers by Goldsztejn. |
Alright, I had a look to that paper again, and to get started we would need Theorem 3.1 in page 7, which gives a parallelotopic enclosure of the image set of a parallelotope through a (differentiable) function. I have to think about it, but perhaps i can add it as an extension in RangeEnclosures.jl. |
To mimic the notation in the paper, one can use a Parallelotope(A, 𝐮, x̃) = AffineMap(A, 𝐮, x̃) or equivalently Parallelotope(A, 𝐮, x̃) = x̃ ⊕ A*𝐮 After looking with some detail Section 3.2, I think there are typos. Since |
With such considerations, I tried implementing Theorem 3.1 and the result can be found in this notebook. The final result is at the very end. I'm under the impression that i did something wrong, because the parallelotopic overapproximation is much bigger than the box overapproximation, which can be found in the plot in |
That's a really fantastic notebook, thanks! It illustrates very well a lot of the concepts that you've implemented so nicely in I'll try to think about what's going on. |
I agree that there is an error as you point out in the paper, and I think your interpretation is correct. |
See:
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