Integration

[ptc-2083886]

Hi.

I hope this the right place to post this. If not, I crave forgiveness.

I do consulting in capacitive sensing, mostly electronics engineering. But sometimes I get stuck on a math problem.

For instance, see attached (simplified, don't worry about trying to solve it yet), I'd like to get a symbolic solution but MathCAD won't do it.

So I can use the numeric solution, but then I've got a three-dimensional lookup table (too big) or a mess of polynomial approximations (too confusing). My math skills are at the college freshman level.

I could use a MathCAD expert who could tell me if a symbolic solution is possible, and if not, help with the polynomials.

Anybody want to do a little consulting?

...L

Larry Baxter

lb@capsense.com

www.capsense.com

[Werner_E]

Not sure what you mean with the numeric aolution you tried. If you provide values for R, r and d (and maybe K), Mathcad will be happy to numerically calculate the integral.

BTW, are you sure about the way you have set up the intgral over the degree range? I think you would rather need I3 (you may replace the ° by typing deg) or I2.

[ptc-2083886]

Hi, Werner,

I'm not so much as looking for an answer as looking for a consultant. Are you available? Where do you live?

Please contact me at lb@@capsense.com

...L

[Werner_E]

I'm not so much as looking for an answer as looking for a consultant. Are you available?

Sorry, no.

Where do you live?

Europe, Austria (no - no kangaroos here) 😉

[AlanStevens]

Larry Baxter wrote:

... I'd like to get a symbolic solution but MathCAD won't do it.

I don't think you've a cat in hell's chance of getting a symbolic solution (more so if this is only a simplified version!).

The fact that you are thinking in terms of a lookup table or polynomial fits suggest that you want to implement the results in something other than Mathcad. (If you stay within Mathcad then you only ever need to use a numerical form of the integral, as in Werner's reply).

If this is the case there might be other ways of generating what you want. However, we can't tell without seeing more detail (e.g. data values and desired integrals).

Alan

[RichardJ]

If you can substitute y=cos(phi) I can give you a solution to the integral in terms of y. I don't know what your end goal is though, so I don't know if it would be acceptable to work in the cosine of the angle rather than the angle itself. The expression is really big and ugly looking too.

So I can use the numeric solution, but then I've got a three-dimensional lookup table (too big) or a mess of polynomial approximations (too confusing).

That depends on what the required accuracy is. If the required accuracy is not too great then an approximation in terms of chebyshev polynomials might not mook too bad.

Anybody want to do a little consulting?

Consulting is what I do for a living, but I am swamped right now.