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Originally Posted by wildaburk3160
I'm not sure what you mean by getting 10 times the resolution compared to the accuracy requirements.
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Someone decided that for your system, you needed accuracy of ~+/- 0.75 degrees. Since you have a resolution of almost the same, you need to be perfect. If you're sensor reads that is 1 tick away from where you want to be, you don't know if it's a tiny fraction of a tick off, or almost a full tick off. Since your sensor doesn't know the difference, your software has to respond to them the same. If you're only a tiny bit off, you might overshoot, and if you're almost a full tick off, you might not move far enough. It makes it very hard to tune.
Imagine instead that you're accuracy requirement was 0.75 degrees, but you're sensor measured 0.075 degrees (10 times the resolution compared to the resolution requirements). You would know the difference between a very small bit off, and 0.75 degrees off, and your PID controller could output a different value based on how far off it is.
Quote:
Originally Posted by wildaburk3160
We are using a seven pulse per rotation encoder mounted on a gearbox with a 71:1 reduction, so there are 497 pulses per motor rotation. Since we are only wanting to rotate 90 degrees clockwise or counterclockwise, we divide that number by 4, getting 124.25, or for our purposes, 124, pulses.
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I'm assuming you're using an AM PG71 based on those numbers. Given that the free speed is 75 RPM, You would move 90 degrees in 0.2 seconds. That's very fast and hard to control, especially with your resolution challenges. If you instead added an additional 4:1 gear reduction, you'd do a full motion in 0.8 seconds and you'd have 4 times the resolution at the same time.