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formulas of curve

Question asked by Selcuk Bolukbasi on Aug 4, 2008
Latest reply on Oct 14, 2008 by 1-8MMYCK

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when we draw any compound curve such as two or three circle that are tangency coincident we obtain any curve,

i wanna learn that new compund curve formulas;

my first message in this forums so may be i cant explain exactly but if any body help me i will be soo happppy,

No one else has this question

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Roland Schwarz Aug 4, 2008 12:27 PM
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A series of tangent arcs can not be described with a single formula due to discontinuities. It would require a set of discontinuous formulae.
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Ricky Gutierrez @ Roland Schwarz on Aug 4, 2008 12:42 PM
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i have seen a friend of mine take points off a series of discontinuous arcs from "MATLAB" and create an array.

Once those points are found you can easily import them to solidworks via a design table creating points then use Spline to connect them.

It is not exact but the standard deviation is minimal depending on how accurate you need the curve to be. It is lots of work to do especially if your curve doesn't need to be exact.

Im sure someone else can provide easier alternatives.
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Selcuk Bolukbasi Aug 4, 2008 2:48 PM
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Roland Schwarz and Ricky Gutierrez thanks for interest,

i will wait another ideas,

and that compound curve is continuous curve (not discontinuous)
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Mahir Abrahim Aug 4, 2008 3:28 PM
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I've written macros to go from formula to curve, but curve to formula is more complicated. Like Roland pointed out, you can't describe a series of tangent arcs with only one equation. It is indeed discontinuous in that your curve is given by a series of separate circular equations that share continuous slope (1st derivative), but discontinuous 2nd derivative. However, you can use one formula to describe a spline that approximates those arcs. After forming your arcs, try going over it with a spline that is close to the same shape. After that, extract the XY coordinates of the spline's control points. You might be able to find or write a macro that does this automatically. Using the coordinates of the control points and the TREND() function in Excel (or whatever other software you have available) you can calculate a regression for those known coordinates. If you use Excel, you will have to fit to a function of the form y = m1*x1 + m2*x2 + ... + b, where m1, m2, m3 correspond to x, x^2, x^3 as used in a spline's polynomial equation.
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Jerry Steiger @ Selcuk Bolukbasi on Aug 5, 2008 4:08 AM
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Selcuk,

I'm not sure if this is of any help to you, but SW has a function called a "Fit Spline" that fits a single spline to a any geometry that you choose. You can control the accuracy of the fit spline. It's in Tools/Spline Tools.
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Mahir Abrahim Aug 5, 2008 5:45 AM
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Hmm... didn't know about that one, Jerry. Thanks.
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Selcuk Bolukbasi Aug 5, 2008 7:39 AM
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dear friends thanks all of you i wanna give more information about that question;

but i cant send any file;

can anybody help me to send a file to explain what i want;
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Jerry Steiger @ Selcuk Bolukbasi on Aug 6, 2008 9:27 PM
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Selcuk,

You have to zip the file before you can attach it. The process to attach a file is tedious. It seems like you have to click a number of buttons to get it done. As I recall, you have to upload the file and then you have to attach it.
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Christopher Thompson @ Jerry Steiger on Aug 7, 2008 12:21 AM
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I would like to see SolidWorks provide a curve-driven equation feature as it already exists in Pro-E, and it would be helpful if SW added this to SW 2009. I believe other SW users have been requesting this feature for a few years.

In Pro-E, datum points from excel can be imported, than a curve can be routed through these points in the X, Y, and Z directions. I assume SolidWorks can do this as well, but I have not tested it. Perhaps the 3D Curve allows the creation of a spline through 3D datum points.
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Mahir Abrahim @ Christopher Thompson on Aug 7, 2008 3:10 AM
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Chris, SW is taking baby steps towards the equation driven curve feature. SW2009 has the ability to create 2D splines of the form y=f(x). It's nowhere near as flexible as Pro-E's equation driven curves, but at least it's getting there. If you're looking for similar 3D curve functionality now, you can try this thread.
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Selcuk Bolukbasi Aug 7, 2008 8:04 AM
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Jerry can you tell me how can i send a zip file as a reply please. i m new user of this forums so please write step one step please if you want to help me;

thanks for everything to everyone

sorry may be this isnt related our question but i have to learn to give more clue in our question and answer
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Mahir Abrahim @ Selcuk Bolukbasi on Aug 7, 2008 2:45 PM
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1. Click the Attach File(s) button at the bottom of the Reply window.
2. In the Attach File(s) window that comes up, click the Choose button and select the file you want to upload (zip, png, jpg).
3. Click Upload File.
4. Now select that file in the file listing and click the green Attach File link.
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Selcuk Bolukbasi Aug 8, 2008 5:01 AM
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thanks Mahir Abrahim i understood that i use quick reply so i dont see attach button thanks for interest
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Charles Culp @ Selcuk Bolukbasi on Oct 1, 2008 6:28 PM
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You can email me the file, if you wish, and I will post it for you.
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Selcuk Bolukbasi Oct 1, 2008 6:37 PM
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thanks for interest charles, now we are in ramadan holiday so i dont have that curve we will start 0n monday. i can send on monday.
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Eddie Cyganik @ Christopher Thompson on Oct 2, 2008 5:25 PM
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Chris,

You're referring to "TrajPar" (Trajectory Parameters?)

Yes I have asked and I have complained and I have touted the fact that Pro/E had this capability from Day-One, so what's the problem?

Got Me!!!
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Selcuk Bolukbasi @ Eddie Cyganik on Oct 9, 2008 6:55 AM
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Charles, i send file (you want to obtain formulas or equation)

thanks for interest
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- formulas_of_curve.zip22.4 KB
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1-8MMYCK Oct 9, 2008 2:22 PM
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as others said, you cant get mathematical formulas out of the software, automatically. for the case you have posted, it's easy to obtain the equation manually. if you need the equation of this curve only, i can help.
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Selcuk Bolukbasi Oct 10, 2008 6:56 AM
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tim, i only need that compound curve equation (formulas) such as y= ax4+bx3+cx2+dx+e . sure starting point is 0,0 it means that e=0

thanks for interest
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Selcuk Bolukbasi Oct 10, 2008 6:58 AM
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tim and also can you explain how can i obtain that formulas;
i will be soo happy thanks
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1-8MMYCK @ Selcuk Bolukbasi on Oct 10, 2008 1:01 PM
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as the curve is compound, the equation is compound too. see below. is this what you are looking for?
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- fml.jpg26.2 KB
- eqt.jpg34.9 KB
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Mahir Abrahim Oct 10, 2008 5:39 PM
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Tim, you go above and beyond. I like being helpful, but I don't think I'd go as far as doing someone's algebra homework for them
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Mahir Abrahim Oct 10, 2008 5:40 PM
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Tim,
By the way, what is your avatar? It looks like some Persian flag.
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1-8MMYCK Oct 10, 2008 7:14 PM
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yeah thats a persian symbol called Farvahar, which dates back to thousands of years ago. i've seen that in bistoon, http://i16.tinypic.com/4q51pvr.jpg http://www.izadmehr.com/bistoon.katibe.jpg the symbol is carved on a mountain 70m above ground (700 BC) and in persepolis,takht jamshid (515 BC). http://www.bestirantravel.com/...s/shiraz/p_symbol.jpg
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Phil Marra @ 1-8MMYCK on Oct 11, 2008 10:16 AM
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Does anyone know if its possible to create a curve from an aspheric equation?
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