topic Iterative solution to nonlinear equation? in LabVIEW

Iterative solution to nonlinear equation?

testingHotAir — Fri, 06 Feb 2009 14:49:15 GMT

Hi all,

I"m trying to put together a VI that will solve an equation of the form:

A = B*x^b+C*x^c

for the variable x (all others are numbers). Does Labview have a block that will do the iterative solution or do I need to make my own. I'm using Labview 8.6 Pro.

Thanks

Re: Iterative solution to nonlinear equation?

DSPGuy — Fri, 06 Feb 2009 14:53:38 GMT

This is a polynomial, so you could use the "Polynomial Roots.vi".

-Jim

Re: Iterative solution to nonlinear equation?

DSPGuy — Fri, 06 Feb 2009 14:59:20 GMT

Well, a polynomial if b and c are integers. If b and/or c are real numbers then you will need a zero finder. There are two available, named "Newton Raphson Zero Finder.vi" and "Ridders Zero Finder.vi".

-Jim

Re: Iterative solution to nonlinear equation?

testingHotAir — Fri, 06 Feb 2009 15:36:59 GMT

Thanks Jim!

I'm trying to get the Newton Raphson solver going right now, but it keeps giving me a syntax error. I'm feeding it a string that looks like:

50.00=0.019231*(2*a)^0.15+675*(2*a)^0.5

I've built this string programatically. Is there something I'm missing here?

Re: Iterative solution to nonlinear equation?

DSPGuy — Fri, 06 Feb 2009 16:04:04 GMT

Newton Raphson is expecting something like "expression=0", but the =0 is implied. Try this.

0.019231*(2*a)^0.15+675*(2*a)^0.5-50

-Jim

Re: Iterative solution to nonlinear equation?

testingHotAir — Fri, 06 Feb 2009 16:21:10 GMT

Ah. Now it's working. Thanks again!