Any ideas for a homemade outdoor Local Positioning System
April 7, 2012
I've been thinking about designing an autonomous lawnmower for a while now. I've pretty much got it all figured out in my head except for how to maintain accurate positioning. I'm figuring I need to have somewhere around 1ft (.3m) error in accuracy. I know how to do kalman filters using odometry, IMU, LIDAR scan matching, etc, but I need something to correct for drift and GPS won't give me accurate enough data, (plus my yard has massive trees covering it). I've started reading about Local Positioning Systems and was wondering if anyone here has any experience with them?
There seems to be a bunch of different ways of doing it, but the way I think sounds the best is using RF transmit/receivers as beacons, and have a transmitter/receiver on my robot as well, pretty much setting up a miniature GPS network in my back yard. One difference between this and GPS would be that I would measure the round-trip time from robot to beacon, instead of the one-way flight time that GPS does, this way I wouldn't have to worry about time synchronization.
It would work like this:
-robot sends out a signal and starts a clock
-beacon sees this signal and sends back its unique ID code back
-robot sees this ID code, and then stops the clock. I can calculate distance based on the time it took, and with three or more beacons in range of the robot I can do trilateration to get a pretty good estimate of where I am.
I haven't figured out if the robot should send one signal for all beacons to respond to, or do them one at a time, that will depend on the speed of my logic device I guess. I'm still in the early stages.
Anyone have any thoughts...specifically, does this sound feasible? Got any links to related projects? Specifically, I'm only interested in methods that can be used outdoors in noisy environments (IR is definitely out, ultrasonic may not work since it'll be on a lawnmower).
reference: "GPS-less Low Cost Outdoor Localization For Very Small Devices" by Nirupama Bulusu et al. It gives a great overview of LPS systems, but the system they propose in the paper doesn't sound very good to me. Seems like it would take too many beacons to get decent accuracy.