feed back signal is not been adding to the summation block

[GerdW]

Hi prasad,

what is the expected result of this (very Rube-Goldberg-style) code part:

More Rube-Goldberg:

b := MAX(X, MIN(X, Y))
Y > X -> b := X
Y < X -> b := X
Y = X -> b := X
->
a := X * 0.48672

So the whole code snippet can be replaced by a simple multiplication of X with 0.486726…

[prasad145]

I have attached the pic of MATLAB simulation and expected result at point (a) of your previous pic. Expected result is as per Screenshot (34) and the point (a) is described as  (voltage required to drive the FAP in Screenshot 33). and I have used only one loop here as per Screenshot(35)  

[GerdW]

Hi prasad,

I have attached the pic of MATLAB simulation

All I see are images of some SIMULINK sheets…

and expected result at point (a) of your previous pic.

The code snippet in my image does NOT output a waveform, it outputs a scalar value.

I don't know how you want to compare the SIMULINK waveform with the code snippet from my previous message…

[prasad145]

I replaced the constants as per your suggestion but i am getting of square wave now i have attached the VI. The expected result should be sinusoidal wave for this VI. 

[prasad145]

Dear Friends,

I Have designed a model in LabVIEW. The LabVIEW program is giving some error(giving a step signal)  after i add my feedback (shift register) signal to the summation (compound arithmetic) block. i tired with inverting the summation (compound arithmetic) block at the feed back signal input, which was also not working. Please help in getting a sinusoidal waveform as the output signal. 

[GerdW]

Hi prasad,

is there any reason to start a new thread for the very same problem???

The LabVIEW program is giving some error(giving a step signal) after i add my feedback (shift register) signal to the summation (compound arithmetic) block.

I still cannot follow your problem description:

Why don't you move constants out of the loop? Why do I have to show the same code improvements again and again?

[prasad145]

Dear Sir,

            I respect your suggestions and you are spending time on this. But my concern is the code is  actually not doing any operation (subtraction)  from the summation block.(which might be true) I have recreated the code as per the suggestions by you. Here what i found is  the amplitude of the waveform before entering the feedback ( which is the result point) is at approximately -350( I attached VI).  The amplitude of the waveform after the multiplication and before subtracting from the summation block is approximately -500. and after subtracting the result is still -350 where as in Matlab i get +1000 as the amplitude of the waveform. I checked the constants which are fine in both MATLAB as well as LabVIEW. I apologise for creating a new topic since i was concern about the amplitude and the signal operation. 

Thank You 

[GerdW · Accepted solution]

Hi prasad,

I just moved the reciprocal and negate function to a different (but IMHO more logical) place:

[RavensFan]

If you have a compound arithmetic node set for addition, and you want to subtract one of the inputs, then right click on that input and pick invert.  (If you want to negate the output, then select the output and pick invert.)

If you have a compound arithmetic node set for multiplication, and you want to divide one of the inputs, then right click on that input and pick invert.  (If you want to take the reciprocal of the output, then select the output and pick invert.)

If you have a compound arithmetic node set for a boolean operation (AND,OR, XOR) and you want to NOT one of the inputs, then right click on that input and pick invert.  (If you want to NOT the output, then select the output and pick invert.)

[Kevin_Price]

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@RavensFan wrote:

If you have a compound arithmetic node...

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Good tips!  I've switched over almost entirely to using the compound arithmetic node in place of the dedicated primitives.  The ability to invert individual inputs or the output as a whole can save a lot of diagram clutter.  If the value I want to subtract comes from a wire up higher in my diagram, no problem.  I can invert that particular input and avoid the possible ambiguity of crossed wires!

Another big advantage is that it's expandable to support more than 2 inputs.  It's even nice as a more compact version of a boolean NOT when shrunk to single-input size.  Same for the arithmetic (1/x) and (-x) operations.

-Kevin P