how to connect prbs to nonliner model(using formula node)

[kathyct]

hi..

i have a set of state equation and by using the formula nodes, its work and get the response if the input which is D and W i give a constant value.. it is mimo model in which 2 inputs and 4 outputs. these 2 inputs i've to excite by using prbs signal. the problem is, i don't know how to connect the prbs with the model? i try to connect directly to D and W but its have an error. in this model D and W are input(prbs).

see attachment.

the response that i get from the figure is when D and W are constant

tq

[Gak]

hi kathyct,

sorry I did not understand, Can you tell me what is prbs?

[kathyct]

PRBS is pseudo random binary signal and it is all called MLS.

[kathyct]

or in labview Maximum length sequences(MLS)

[Gak]

Hi kathyct,

First of all, try to avoid abbreviations, like mimo...I guess it is multiple inputs multiple outputs.

Now about your question, if it is a sequence then I guess you will be having array for D and W..Right?

Can you post what error you are getting?

[Barp]

To excite your system using the VIs from Signal Processing you just need to place the VI outside the Control and Simulation Loop and use the "Indexer" function (inside the Simulation Palette under "Utility"). This will convert the vector into points that are fed correctly to the solver.

In addition, the PRBS signal generator is available in the System Identification Toolkit, under the utility folder.

Let me know if you have more questions

[kathyct]

i've already done connect the prbs to D and W, and thanks for the solution. now i want to design the ouput of the responses  follow the PRBS signal(input of D and. W). so output have two waveforms one is prbs and another one is the system output. how i'm gonna do that? hope u will give an idea, or steps to do that.

tq 

[kathyct]

when i test the signal, if i used the indexer i didnt get the waveform axactly same as signal that i want(waveform prbs2). i dont know how to setting the indexer so that the waveform is not a straight line. how u will guide me to setting that. 

tq

see attachment

[Barp]

Hello,

This is interesting problem. Because you need the 'sharp transitions' for your code, then the indexer can not be used for this case since it uses linear interpolation for it.

Then, I decided to use the 'Lookup Table" with 'Above' Option. This would give the correct signal applied to the system.

[kathyct]

hii..

my model have to connect with prbs, and i got a result.. but based on the result, it seems like it have a noise..my question is how to remove the noise? i hv to makesure that i get the steady state response. so in my response for eg dissolve oxygen i have get a straight line example starting from 6 and after a few sec/min it goes to 4 sec/min and steady.

another question , it is the polynomial and  seed in prbs will contribute the diff result? if yes how i have to setting this? i've already put 0 seed, but it just try and error. actually i dont know what value i have to put.