PID Tuning Process?

[plnyyanks]

Really, the best way to tune PID constants in Guess and Check - after a little practice, you get pretty good at guessing the correct constants. This is pretty much the method we use on 1124, and we haven't really found the need to migrate away from it.

Originally Posted by Wikipedia

If the system must remain online, one tuning method is to first set Ki and Kd values to zero. Increase the Kp until the output of the loop oscillates, then the Kp should be set to approximately half of that value for a "quarter amplitude decay" type response. Then increase Ki until any offset is corrected in sufficient time for the process. However, too much Ki will cause instability. Finally, increase Kd, if required, until the loop is acceptably quick to reach its reference after a load disturbance. However, too much Kd will cause excessive response and overshoot. A fast PID loop tuning usually overshoots slightly to reach the setpoint more quickly; however, some systems cannot accept overshoot, in which case an over-damped closed-loop system is required, which will require a Kp setting significantly less than half that of the Kp setting causing oscillation.

In our robots, we've found that an I parameter is rarely needed - we usually get what we want with only PD (or sometimes just P) controllers. It's really dependant on your application and the type of feedback you want. There's no really easy way to say it: it's a long, time consuming process.

Some more links to read into

To do this in LabVIEW, you have your PID VI, and one of its inputs is a cluster of three doubles, which are the P,I, and D constants that you tune to your liking. The best way to tune quickly is to probably run your code through a computer (using the Run button on Robot Main.vi - not building/running as startup) and modify that parameter cluster until you get satisfactory results. Just remember to reinitialize your PID VI (it's another control - wire that input to a button on your front panel or something like that) to "apply" your changes. NI also has a good whitepaper about working with PID in LV. It's a good read - check it out.