Transfer Function Problem

[tebu]

Hi,
 
I created this transfer function in Labview. But I realised that a small input value (in my case I used 0.0014) will produce a different result compare to the one in Matlab. I couldnt figure out what is the problem. Could you help me in this?

Attached are the LabVIEW and Matlab files that I created.

FYI, I used LabVIEW 2009 and Matlab R2007b.

 
Thanks

[LeManu]

Hi,

I am no a develloper, just user by I know both softwares.

You have a different configuration of simulation.

In Labview:

You (or Labview), define an Initial Step Size, Minimum and Maximum Step size, and Relative&Absolute Tolerance.

In Matlab:

Almos all these parameters are defined like "Auto", in the Variable Step Type Option. (ctrl + E)

If you define this parameters with those on Labview, you will have "the same" graphics.

Now.... wich graphic is the good one.... you know...

(This doesn't mean that a software is wrong.... but the step size and tolerance (and the ODE Solver method!) must be choice carefully when you work with small values, and parameters are setting manually)

Good luck (Y)

Manuel SANCHEZ BURGOS

[Barp · Accepted solution]

The initial parameters used by the Control and Simulation Module does not solve the problem you have. This value that 'walks' down and oscilating is incorrect since you only have a first order model, and as you know, you should expect a first order response, similar to a capacitor been charged from a step response. If you change the maximum step size to 0.01, you should get the expected response that converge to 0.0014.

This shows us how simulation can be misleading if you do not have an idea to what to expect from it and, most importantly, no simulation can substitute the knowledge or intuition of expert developer. You should always validate the results of your simulation and convince yourself that you are obtaining good results, doesn't matter which package or vendor you have.

[tebu]

thanks. this solve my problem! 🙂