03-07-2010 04:38 AM
Hello,
I'm trying to make a PI control model with Control and Design in labview 2009. I'm tyring to create the following transferfunction:
D(z)=Kp+((Kp*Ki)/(1-z^-1))
But labview adds by itself an extra z^-1 in the Numerator
See the attachment what I have tried. I first want to create 1+(1/(1-z^-1)). What I'm I doing wrong ?
Greetz,
Jeroen
03-07-2010 11:11 AM
Jeroen,
The two expressions "1+(1/(1-z^-1))" and "(2-z^-1)/(1-z^-1)" are equivalent to one another. They just have the terms rearranged. Since LabVIEW expresses a transfer function as a numerator and denominator, it is drawing the function as "(2-z^-1)/(1-z^-1)". You aren't doing anything wrong.
Chris M
03-07-2010 01:13 PM - edited 03-07-2010 01:14 PM
Ah, stupid off me. Matlab gives the same awnser.
Another question, how do I implant in control and design a Saturation block ? In Simulation there is a standard block but nog for control and design.
I'm trying to determine de P an I values for an embedded PI motor controller.
03-07-2010 06:09 PM
Jeroen,
The Control Design VIs create transfer functions, state-space, and zero-pole-gain models, which are all linear, time invariant (LTI). Since saturation is nonlinear, it cannot be represented by an LTI model. I suggest using a saturation block in a simulation loop.
Chris M
03-08-2010 12:35 AM
03-09-2010 03:37 PM
You can use CD Convert Control Design to Simulation VI to convert from Control Design to Simulation