Thread: Swerve Gear Box
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Unread 27-08-2011, 20:43
davidthefat davidthefat is offline
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Re: Swerve Gear Box
Quote:
Originally Posted by apalrd View Post
It makes a big difference.

Say I have a mechanism, and want to go to 50 units. I am currently at 30 units. The formula you gave would output error as (50-30)/50 = 20/50 = 0.4

Now say I want to go back to 30 units, from the 50 units I was just at. The formula you gave would now give me (30-50)/30 = -20/30 = -0.6667. Not the inverse of what we just saw, this is very different.


As for versatility, the P, I and D parameters should be expected to be tuned to fit a particular system. Thinking that scaling the input will make these magically work for everything is just wrong.

As for input of rate vs distance, an input of rate requires integrating the output of the PID controller so that the output drives the change in motor power. The alternative is to use the I term as the P term (with other terms changing positions and such) or use a feed-forward plus a PID (with the I term still doing a lot of work). Thus, any sort of interchangeability between inputs of rate and distance goes out the window.
I also did not realize the fact that if the desired output is smaller than current position. I am at 150 and I want 50. 100/50 = 2... Okay, I see...
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