Moderator Comment by Chris Anderson on May 29, 2008 at 3:58pm

This is great! Too bad the code object in is Propeller Spin, and not C, but the write-up is refreshingly clear. My takehome: I've been using "P"s already, could easily add "I"s, and maybe don't need "D"s ;-)

Moderator Comment by wayne garris on May 29, 2008 at 5:50pm

PID 1.1.zip
here is a easy to read PID loop from the BasicX web site

Comment by mmprestine on May 30, 2008 at 10:53am

Here is probably the best written explanation of PID loops. It is in C.

Comment by mmprestine on May 30, 2008 at 10:54am

Strange that the hyper link didnt function.

http://www.embedded.com/2000/0010/0010feat3.htm

Moderator Comment by Chris Anderson on May 30, 2008 at 11:21am

Brilliant. Many thanks!

Moderator Comment by James Ross on May 30, 2008 at 11:27am

mmprestine
A hyperlink takes two parts: the URL and a text description (what you click on). You're not the first one to miss the second part.
<a href="http://www.embedded.com/2000/0010/0010feat3.htm">need text description here</a>

Here's the C code from the article: ftp://ftp.embedded.com/pub/2000/wescott

Moderator Comment by wayne garris on May 30, 2008 at 4:25pm

tunning a PID loop can be hard here is a good link with a few furmulas

3D Robotics Comment by Jordi Muñoz on June 1, 2008 at 11:22am

This is a very good and simple example:

previous_error = 0
start:
error = setpoint - actual_position
P = Kp * error
I = I + Ki * error * dt
D = (Kd / dt) * (error - previous_error)
output = P + I + D
previous_error = error
wait(dt)
goto start

You just need to adjust the values Kp, Ki, Kd between .01 to 20, depending you model, the only way is the method better know as "Trial and Error", till you get it... There is a professional way too (but was in german and i don't remember anything).. if you search in torrents you going to find very interesting things.. =)

3D Robotics Comment by Jordi Muñoz on June 1, 2008 at 11:30am

This is the difference between a normal way, and the PID system =)...

Comment by faskunji on June 16, 2008 at 9:18am

some of my examples:
roll of aircraft in X-Plane flight sim:
only P control, you can see oscillations here. You can calibrate P gain so that you do not have such oscillation, but this is possible only for one target value, for example I calibrated for 20 degree roll, but when I tried 30 degree roll I still had problems.
and here: PID control. This gave same results on 10,20 or 30 degree rolls.

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