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Gravity shouldn't be a filter state variable #5

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badicsalex opened this issue Jan 14, 2023 · 1 comment · May be fixed by #14
Open

Gravity shouldn't be a filter state variable #5

badicsalex opened this issue Jan 14, 2023 · 1 comment · May be fixed by #14

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@badicsalex
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I have found that gravity estimation interferes with finding accelerometer bias, and makes the filter stability way worse. In my opionion it should instead be a builder parameter and supplied by the user based on geographic information. (Or simply left as a constant, as the error of that is not that much compared to other error sources)

I do have a patchset that removes gravity from the state, which reduces the size of the covariance matrix (and thus makes the calculations faster), and also made convergence much faster for my use-cases. I've ran tests and compared carla plots, and this doesn't seem to affect performance.

Do you have any opinion about this?

@badicsalex
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BTW, I've re-read the paper, and this is actually mentioned at the bottom of section 5.3.1

We do so to improve linearity: indeed, equation (235b) is now linear in g, which carries all the uncertainty, and the initial orientation q0 is known without uncertainty, so that q starts with no uncertainty.

For what it's worth, in my experience it's not better at all.

@avsaase avsaase linked a pull request Sep 29, 2024 that will close this issue
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