LabVIEW Software Tool to Develop Polynomial from a Data Set

ECET- 462
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Application of Computers in Process Control
Purdue University, Calumet
[LABORATORY 9]
LabVIEW Software Tool to Develop Polynomial from a Data Set
(curve fitting

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LabVIEW Software Tool to Develop Polynomial from a Data Set
(curve fitting
LAB 9
Objective:
To demonstrate the use of Lab View for Polynomial curve fitting.
Software required: Lab View.
Procedure:
Step 1: Open Lab ViewCreate a new viSave it as Polyfit.
Step 2: Go to Block diagram by pressing ‘Cntrl+E’. Go to
FunctionsMathematicsFitting General Polynomial fit.vi
Place it onto block diagram.

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Step 2: Create ‘Control’ from ‘X’, ‘Y’ and ‘Polynomial order’ terminals from the block. And
also create an ‘Indicator’ from the ‘Best Polynomial Fit’ terminal.
Step 3: Go to MathematicsPolynomialPolynomial Evaluation.vi
Again go to Signal Processingsignal generationRamp pattern.vi
Place these two blocks in the block diagram and connect as shown below. Create constants from
the start, end and samples terminals.

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Step 4: Now take two blocks of bundle and a block of Build Array. Connect them as in the figure
below.
Programming Cluster, Class & Variant Bundle.
Programming Array Build Array. Stretch the bundle to make two inputs.

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Step 5: Place one ‘Reverse 1D Array’, one ‘CD construct Transfer function Model’ and one ‘CD
draw Transfer function Equation’ from the destinations shown below and connect them as in
figure. The ‘output’ of reverse 1D array should be connected to the ‘numerator’ terminal of CD
construct Transfer function Model. And the ‘Transfer Function Model’ terminal of CD construct
Transfer function Model should be connected to the ‘Transfer Function Model’ terminal of the
CD draw Transfer function Equation block.
Step 6: Create an Indicator from Equation terminal and a constant from Function Name Terminal
of the CD draw Transfer function Equation block.

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Step 7: Now go to the front Panel and rearrange the items as in figure. In order to increase the
number of rows, stretch the block.
Step 8: From the Controls pallete place a XY graph in the front panel.

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Step 9: Go to block diagram panel. There find the XY graph and connect it to the build array.
Right click on the graph and go to the destination indicated below.
Step 9: Place the XY graph Cursor Position and create an Indiactor

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Step 10: Now right click on the xy graph and select properties. From the Graph Properties select
the indicated properties.

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Step 11: Now go to the Front panel and change the name of x and y axis from their default name
of ‘Time’ and ‘Amplitude’ to some other name. Write down some values in the empty x and y
column and run the program.
Step 12: To do Extrapolation create a control to the ramp generators End terminal (go to block
diagram panel). Go to the front panel and change the value of end block and you will able to see
the predictate values due to extrapolation.

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Step 13: Move your cursor along the curve and you will get the values of x and y for the
corresponding change in cursor position.
Report:
1. Why do we need a ramp generator in this program?
2. Continue to increase polynomial order keeping other terms constant. What does happen?
Why?
3. State some applications of this program.