[thunderdork]

Hi,

I'm currently creating a posting on tuning my Gecko g320x Servo Drivers for my site thunderdork.com. My last step is to tune the driver. There are "P", "I", "D" dials. Which I assume means that this adjust the PID as in PID Controller...? There is also a "T", which is for the max amps for the servo (0-20a). I believe this has no affect on the P, I, and D trims.

So if this is exactly like tuning a PID controller (and that CNC servo drivers are pretty much PID controllers), then can anybody give me a layman's explanation of what a PID is and how they are tuned. From what I gather at wikipedia:

PID controller - Wikipedia, the free encyclopedia

Is that P, I and D are all sections to an algorithm that tries to position a motor accurately based on the feedback given in this closed loop and compensating for past, present and future errors. Basically how it gets to where it needs to be and how it stands its ground when it gets there.

P = Proportional = the past
I = Integral = the present
D = Derivative = the future

So if I where to try and explain it like a man steering a boat: "P" is the how alert he is based on weather conditions, "I" is his reaction to events like waves and gales as they come to him based on the weather conditions, and "D" is the back of his mind telling him to put this all in persepctive because the storm will pass...?

If that's anywhere near accurate can anybody give an example on how to tune a servo with these settings? And if its no where near accurate, can somebody lay it out here like you would to a 5 year old

[Al_The_Man]

What you could do is go to the Dr Tal educational Video's on the Galil Motion site, they use Galil products as an example but the scope traces and principle is the same across systems.
http://www.galilmc.com/learning/tutorials.php
Al.

[thunderdork]

It seems I have to register with them to view the tutorials. I'll start doing that. In the meantime I found this:

PID Explained - DIY Drones

They use a great analogy of a car getting to a certain speed.

P = How much you stomp on the gas
I = How much you roll off the pedal when you start getting close
D = Overall friction of the car (engine braking) that influences everything.

Does that sound somewhat more accurate? If so, how does one apply this to servos? Is there a process of tuning or is it a "by ear" thing?

[Al_The_Man]

There are many examples in PDF apart from the video's that you can use as a guide.
http://www.galilmc.com/support/appno...s/note5491.pdf
For a Manual method or 'by ear' in lieu of tuning S/W etc, is to set I =0 P to a low value and bring D up until motor vibrates and back off, then P is increased an following error is noted, then I is increased slightly for zero error.
Other systems have their own method.
Al.