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0 pointschuckadams9mo ago0 comments

> (consider gimbal lock: "fixing" that requires understanding quaternions or some other orthogonal orientation space, and that's hard!)

Or just avoiding gimbal lock by other means. We went to the moon using Euler angles, but I don't suppose there's much of a choice when you're using real mechanical gimbals.

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ajross9mo ago

That is the "tuning" solution. And mostly it works by limiting scope of execution ("just don't do that") and if that doesn't work by having some kind of recovery method ("push this button to reset", probably along with "use this backup to recalibrate"). And it... works. But the bug is still a bug. In software we prefer more robust techniques.

FWIW, my memory is that this was exactly what happened with Apollo 13. It lost its gyro calibration after the accident (it did the thing that was the "just don't do that") and they had to do a bunch of iterative contortions to recover it from things like the sun position (because they couldn't see stars out the iced-over windows).

NASA would have strongly preferred IEEE doubles and quaternions, in hindsight.

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0 pointschuckadams9mo ago0 comments

> (consider gimbal lock: "fixing" that requires understanding quaternions or some other orthogonal orientation space, and that's hard!)

Or just avoiding gimbal lock by other means. We went to the moon using Euler angles, but I don't suppose there's much of a choice when you're using real mechanical gimbals.

0 comments

ajross9mo ago

NASA would have strongly preferred IEEE doubles and quaternions, in hindsight.

j / k navigate · click thread line to collapse