Archived

This topic is now archived and is closed to further replies.

Ellipse

This topic is 5654 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

I''ve come across an engineering problem in the design of a robot I''m working on. I''ve tried searching the internet and I can''t find the data I need. I know from pervious experience that all you gamedevers have a good footing in geometry. My problem is this: I have a tank tread that is 64 inches long. It needs to go over 3 drive cogs that are in the shape of a triangle (two on the ground and one leading slightly above so it can more easily climb obstacles). I want the leading cog to move in a track from 0 to 90 degrees so the angle on the front (and theoretically the ease of climbing objects) can be changed. If I have two fixed points and a known distance to which all the line segments must add up, that''s pretty much the textbook definition of an ellipse. The two fixed cogs become the foci, now I just need to figure out the major and minor axes. Unfortunately, it''s summer, and I''ve forgotten the math I was learning just a few short weeks ago. If someone could give me the formula to get the major and minor axes from the distance between the foci, I''d be thankful. --------------------

You are not a real programmer until you end all your sentences with semicolons; (c) 2000 ROAD Programming
You are unique. Just like everybody else.
"Mechanical engineers design weapons; civil engineers design targets."
"Sensitivity is adjustable, so you can set it to detect elephants and other small creatures." -- Product Description for a vibration sensor

Yanroy@usa.com

Share this post


Link to post
Share on other sites
Well the track runs between the focal points and to a point on the ellipse if I understand you correctly. So if t is the track length and d is the distance between the focal points then the combined distance from the focal points to a point on the ellipse, c, is c=t-d. The minor axis is 2*sqrt(c^2/4-d^2/4) or sqrt(c^2-d^2). Since c=t-d that is the same as sqrt(t^2-2*d*t). The major axis is d+c-d or c or t-d. That is just going to be a rough approximation since you don''t have points. You instead have cogs and the cogs have a radius.

Share this post


Link to post
Share on other sites