From: Ed McBride <firstname.lastname@example.org> Date: 09 Mar 2000 10:41:45 -0800 Organization: Wybron, Inc. Followups: 1 2 3 4 5 6 7 8 9 10 11 12 13
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Please note that my areas of expertise are mechanical engineering, engineering mechanics, and some classical physics. I have essentially no background in aeronautical, electrical and a bunch of other stuff. I am a consulting engineer in Colorado Springs with a client who wants to track a few objects using on-board accelerometers and gyroscopes that communicate with a central processor. The objects are confined to an area of roughly 25 meters square, and a height of no more than 5 meters above ground. It is necessary to know the location of each object within about 0.1 m, over a time period of a half hour or so. The objects can move at speeds up to 10 m/s, and can experience accelerations up to 2-3 g (20-30 m/s^2). The objects can also rotate at angular velocieies up to a few rev/s. (10-15 rad/s). The cost of the system cannot exceed something like $2,000 per object. My investigations indicate that there at least two major problems: 1. Accelerometers have output errors that will, through random walk, lead to large position errors in a relatively short time. 2. In order to track using accelerometers, it is necessary to know orientation very accurately. I can't find anything that even comes close. But I keep hearing that people take off in an airplane, fly across country, and know where they are within a foot or so. The only explanation I can come up with is that these airplanes must be "re-zeroing" rather often. I obviously have about a zillion questions. Can anyone please either explain to me what's going on, or point me to a reference that will help me figure things out? TIA, Ed McBride, P.E.