
#1
Feb2713, 12:12 AM

P: 85

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 4barlinkagesystem 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) 



#2
Feb2713, 07:50 AM

HW Helper
Thanks
P: 5,549

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 



#3
Feb2713, 12:44 PM

P: 85

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




#4
Feb2713, 03:57 PM

HW Helper
Thanks
P: 5,549

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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