[Ether]

Originally Posted by Tom Line

I wanted to sum this information up for some of the team members (since a couple of the kids on my team didn't understand a lot of things in this post).

First - the getrate implementation (at least in labview) oscillates because it has a very short time period. To obtain a more stable rate, you canput the calculation function in periodic tasks and run it at its own loop speed.

...or you could set the encoder to 1x, if you haven't done so already

This function should be:

(current encoder count - past encoder count) / loop time = count rate

To smooth this rate further, you can average the samples over several loops, or you can extend the time (calculate the count over 2 or three loops and the time over 2 or three loops). Both may give you somewhat delayed results, depending on your loop rate.

I think taking readings every execution cycle and filtering them would be a better solution than taking readings only every n^th cycle. Can anyone comment on that?

a speed PID varies mainly in that you need to send the setpoint from the last speed loop into the new loop and modify THAT value...The derivation from Jared on team 341 can be found here:

http://www.chiefdelphi.com/forums/sh...7&postcount=13

I believe what Jared showed was that you need to accumulate the output of the PID.