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Unread 14-01-2004, 10:46
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Programming & Electrical
FRC #0342 (Burning Magnetos)
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Re: What to do with autonomous

Hi,
This is my first year in the FIRST compo as a mentor. I must say that the first "15 seconds" seems to me to be the most interesting and challenging aspect after reading so many posts.

I was an Inertial Navigation tech on US Missile subs during the 80 and early 90's. We would leave port with accurate position information. Our inertial navigators (dead-reckoning) would use 3 accelerometers mounted on a gyro stabilized platform. Acceleration was integrated once to yield velocity north, west and vertical. Acceleration was integrated a second time to yield displacement (distance) changes north and west. These were good systems. After several days we would obtain a position "fix" from the old NavSat system (single satelite pass in a polar orbit), land based radio triangulation (LORAN) or underwater topography. We were generally only a few hundred yards off at the very most...pretty neat.

We could NOT use the three sources of position fix information all the time because the info was not available. NavSats a few times a day, LORAN only if close to land and topography every hundred miles or so.

Real-time constant triangulation with two IR beacons is pretty cool. If you can determine their directions then you can triangulate positions very easily given know distances between them. I don't see a need for line-following or dead-reckoning in this case if your system is accurate.

Dead-reckoning with time, encoders or distance traveled estimates should maintain some relative accuracy for 15 seconds. No need for triangulation or line following.

Line following from previous postings can be slow. In fact time could be lost trying to follow the line. However, it was shown in last year's competition that line-following works and has a lot of potential for improvement.

All in all there are many possibilities for that first 15 seconds of autonomous operations.

We are experimenting with 4 Banner sensors arranged in a diamond pattern. The current goal is not to follow the line exactly but to stay near it. This is much like a ship at sea following the coastline. If you are heading north on the East coast and you lose site of land, you gently steer to port (left) until land is visibile. We believe it is possible for the robot to travel much faster using this approach then typical line following techniques.

For those of you learning to drive, you know that when you are traveling 50 mph and your right side car wheels slip off of the road that the correct action is to let off of the accelerator (no brakes) and to gently steer back onto the road...then resume your speed and direction.

We'll keep you posted of any new results or ideas.

Regards,
Chuck
 


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