Inertial Navigation System: Difference between revisions

However, they do have their disadvantages. One is reliability -- the spinning gyros and gimbals all move, so you have wear and tear and they can fail or lose their accuracy. However, a more prominant issue is with "gimbal lock."[http://history.nasa.gov/alsj/gimbals.html] This is when two of those three gimbals align. Since they both function about one axis, and the other only does one axis too, you only have two axes -- any rotation about the last axis cannot occur, so the platform is swung and misaligned with rotation about that axis. There are two main solutions: navigate around it or a fourth gimbal. On Apollo 11 there were only three gimbals, so they planned their maneuvers around gimbal lock. Their computers told them where not to go to keep two gimbals from aligning. The second, but more complex, solution is a fourth gimbal. This gimbal is motorized to keep it always oriented away from the other gimbals, so you keep three independent axes at all times. However, this is mechanically more complex. The fourth-gimbal system is used more in more recent gimballed inertial navigation systems.

==References==

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