Can any expert check on my LabView Code? The questions are inside

[ian_fung]

Missing VIs from niTClk.llb?

[maymaythar]

Yes, This VI need simulation toolkit and control tool box and system ID tool box.

Our group used those toolkit and we are not quite familiar with those toolbox.
What we did is we try to simulate one transfer function using different methods (using control tool box and simulation tool box) and the simulation tool box give different answer. And I think in our program (question.vi) we did something wrong which we can’t figure it out.

Message Edited by nayisoe on 05-31-2005 02:19 PM

[Ricardo_SR]

Hello,

I checked the VI and basically the reason why you are not getting the same response is because you are doing two different analyses. When you are using the Control Design, you are creating the transfer function and then getting the bode plot or magnitude and phase plots for your transfer function. When using the simulation toolkit, you are analyzing the chirp signal that goes into a plant (that originally in your VI it is not the same transfer function as the one described in the Control Design section).
You are mixing two different tools that are supposed to be used for different things. The Control Design is exactly for what you are doing, creating your Control. The Simulation toolkit will allow you to simulate a whole plant.
Hope this helps

Ricardo S.
National Instruments

[maymaythar]

Yes, that is what we want to know. We have a system and we use a simulation tool kit to get the bode plot of that system. But what we found is if we use the simulation loop, the plot is different. Thats what we trying to find out (so we compare the control design result with simulation result and we found that they are different)

[Ricardo_SR]

Hello

I don't think I understand your question. Before going any further, if you check your VI, in the Transfer Function VI for the Simulation toolkit, you have a 1/s+1 as a transfer function. You need to right click on it and change it to be the same as the one used with the Control Design Toolkit.
Now, what I said before, the reason why you are getting different results is because with the Control Design you are getting the bode plot for the transfer function of the plant by itself. On the Simulation toolkit, you are adding a chirp signal to a transfer function (that by default is the 1/s+1). And then you are getting the bode plot of that but with an external signal.
If you change the Chirp signal to be something else or even change the frequency, you will see that the plot changes. That means that you are not taking the bode plot for the plant itself.



Ricardo S.
National Instruments.