Proto4, PID, worm gears

So we’ve redesigned the lift mechanism a couple of times.  The lift you see here has about six worm gears (inside of a gear housing) that drive four gears around four rack gears.  This corresponds to one gear on each corner of the lift rod.  There are differentials between each set of gears and the central driving gear (three differential gears).  This is an improvement over some of our last models, which had dozens of gears – our theory is that at this small scale, the more plastic LEGO gears you introduce, the more possibility of error.  So less is more.

We’ve also been visually logging our degree variance in the Processing sketch I’m writing.  It’s pretty primitive, but gives you a good idea of how close we are to a target rotation count.  At the moment, using a pseudo PID (with multiple levels of bi-directional adjustment once the degree count is within certain thresholds, as well as fail-safe conditions, in case of run away motors), we get an average of about 5 degrees of variance.   That’s not bad when we’ve got gear factors of 1,728 and 576 (track & lift).  To the left you can see the screen grab of what that visual graph looks like.

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