positioning of BOE bot line follow sensors
We're having trouble with our BOE bot line follow sensors, and I suspect that the physical placement of the sensors is causing the trouble. As part of our competition, we are allowed to use the Basic stamp, servos and wheels that come with the BOE bot, but not the chassis. Our setup has the line follow sensors mounted about· 3.5 inches behind the servos.
The bot will follow a line until it curves slightly, then it will turn and veer itself off the line and is unable to find it again. We know that the sensors are functioning correctly from the debug program. We suspect that the geometry of the setup is to blame. The sensors being 3.5 inches behind the servos essentially makes a "lever arm"· that exxagerates the steering motion of the servos enough to throw the sensors off the line.
Moving the sensors is not a desirable option right now because that would have consequences for other parts of the bot. I think that the problem is in the programming, but I'm not sure what parts of the line follow program must be modified to overcome this problem. Would increasing the sampling rate of the line sensors·or recucing the reactions of the servos help it follow the line better?
The bot will follow a line until it curves slightly, then it will turn and veer itself off the line and is unable to find it again. We know that the sensors are functioning correctly from the debug program. We suspect that the geometry of the setup is to blame. The sensors being 3.5 inches behind the servos essentially makes a "lever arm"· that exxagerates the steering motion of the servos enough to throw the sensors off the line.
Moving the sensors is not a desirable option right now because that would have consequences for other parts of the bot. I think that the problem is in the programming, but I'm not sure what parts of the line follow program must be modified to overcome this problem. Would increasing the sampling rate of the line sensors·or recucing the reactions of the servos help it follow the line better?
Comments
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- Stephen
PDF
http://www.parallax.com/Portals/0/Downloads/docs/prod/robo/FasterQtiSubroutineV1.1.pdf
Zipped source
http://www.parallax.com/Portals/0/Downloads/src/prod/FasterQtiSubroutineSource.zip
It should work pretty well with the sensors about 1/10 of an inch from the surface, and all right next to each other.
Also, it's not hard to write code to make the Boe-Bot realize it has lost the line and search for it. Just figure out what condition indicates no line, and write code to make the Boe-Bot zigzag back and forth (further each time) until it finds the line again.
Andy
P.S. Those links are from the QTI Line Follower product page.
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Andy Lindsay
Education Department
Parallax, Inc.
Post Edited (Andy Lindsay (Parallax)) : 12/10/2007 10:36:54 PM GMT