urgent need!

[boss_aks]

hello ppl,

i am completely new to this lab view .....the place where i work we often need labview to control our equipment......but we need a bit more than that,,,,we nw need a proper pid to ctrl our readings... being a novice i cant evn thnk of makng one by myself....we had plans of buying a pid module but my boss said that no money n make it urself.....so is der ne1 who cn help me in this...i did found a pid example on the forum posted by sum kind n genious person but i wasnt able to connect it to our existing Current Voltage module....

pls help

[LAVA 1.0 Content]

Hello Boss,

please read the forum Guidelines, and pay attention to 'How to ask questions the smart way'.

Your post misses interpunction in any form. Using full words is a plus.

Ton

[boss_aks]

QUOTE (Ton @ Dec 11 2008, 02:43 PM)

Hello Boss,

please read the forum Guidelines, and pay attention to 'How to ask questions the smart way'.

Your post misses interpunction in any form. Using full words is a plus.

Ton

Oh, my apologies for that.

[LAVA 1.0 Content]

QUOTE (boss_aks @ Dec 11 2008, 06:52 AM)

hello ppl,

i am completely new to this lab view .....the place where i work we often need labview to control our equipment......but we need a bit more than that,,,,we nw need a proper pid to ctrl our readings... being a novice i cant evn thnk of makng one by myself....we had plans of buying a pid module but my boss said that no money n make it urself.....so is der ne1 who cn help me in this...i did found a pid example on the forum posted by sum kind n genious person but i wasnt able to connect it to our existing Current Voltage module....

pls help

Doing a little research (i.e. Googling) you should be able to find enough info online to get a good idea of how to implement the PID algorithm. If you'd look on http://en.wikipedia.org/wiki/PID_algorithm' rel='nofollow' target="_blank">Wikipedia you'd find the following pseudocode. This is a pretty good summary of the basic PID algorithm. So try implementing this in LV. Kp, Ki, and Kd are the gains for each of the three components.

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

[boss_aks]

QUOTE (LV_FPGA_SE @ Dec 11 2008, 04:33 PM)

Doing a little research (i.e. Googling) you should be able to find enough info online to get a good idea of how to implement the PID algorithm. If you'd look on http://en.wikipedia.org/wiki/PID_algorithm' rel='nofollow' target="_blank">Wikipedia you'd find the following pseudocode. This is a pretty good summary of the basic PID algorithm. So try implementing this in LV. Kp, Ki, and Kd are the gains for each of the three components.

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

Thank you so much for your response. I have one more doubt which again might be quite stupid comapred to the standards set by this forum. Where do I put this code?

[Maca]

You don't use the code directly.

You can either rewrite it so it can be used in a formula node (c like code) or implement the code using the standard LV numeric functions.

Shown in the attached picture is the algorithm implemented in standard LV numeric functions.

I have also added some windup (Integral) and output limits.

On a technical note; that there are several different PID algorithms that all behave differently, I.e. not all PID's are alike.

The one shown is just one (see http://en.wikipedia.org/wiki/PID_controlle...ndard_PID_form)

Also a big thanks to Ton, how cool is his code capture tool, well done mate.