Transposing a line with known references


by _Bd_
Tags: line, references, transposing
_Bd_
_Bd_ is offline
#1
Feb27-13, 12:12 AM
P: 87
Hi, I have a question for a desing I am working on. I want to model it in excel and I am having a hard time finding out how to transpose some lines:


Let Bar B's position and dimensions be known, and I want bar B to be set in 3 positions, I can however apply joints to anyplace near or at bar B, so that I can get a 4-bar-linkage-system that can move as I desire. so for example point A1(x1,y1) and A2(x2,y2) are the joints that are going to hold on to bar B, how do I calculate the new coordinates of A1 and A2 at position 2 if I only know their relationship to bar B at position 1?

I hope this image helps:
http://img526.imageshack.us/img526/4945/thingoz.png



At position 1 i know everything

At position 2 I only know the coordinates of the bottom bar (the red bar) I know where its two end points are, I know its angle (theta) with the horizontal and I know its lenght.
points A1 and A2 have not changed their position with respect to the bottom bar, but they have moved in the plane, how do I calculate their new position?

thank you!

NOTE: THERE IS ROTATION AND TRANSLATION!! (FROM POS 1 to POS 2)
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SteamKing
SteamKing is offline
#2
Feb27-13, 07:50 AM
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P: 5,599
If you know the coordinates at Position 1, and you know the translation and rotation to Position 2, the coordinates of the bar at Position 2 can be calculated by means of a transfer matrix.

The following link shows the procedure:
http://ugweb.cs.ualberta.ca/~c201/F0...ous_coords.pdf
_Bd_
_Bd_ is offline
#3
Feb27-13, 12:44 PM
P: 87
The thing about that is that I get weird values when I use that matrix, because they are not rotating around the origin so it creates weird

SteamKing
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#4
Feb27-13, 03:57 PM
HW Helper
Thanks
P: 5,599

Transposing a line with known references


Then you need to translate the coordinates of Position 1 to the origin of rotation, then apply the rotation matrix.


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