Let's Make Robots!

Docking, Beacons and Triangulation (Open Discussion)

I just wanted to open a discussion on getting a robot from A to B using triangulation. Really, I might just be looking for a math class here...

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Do you need to use the follow line at all? If you are using the beacons to position Walter so he can find the line, couldn't you just use them to position him so he can find the dock, say have it mid point between the beacons?

Walter feels hungry, scans the room for beacons. Finds one (or mozies along until he does).
- turns towards the found beacon, facing it head on (angle towards the wall behind beacon is still unknown).
- scans for second beacon, it's on the left or on the right (identifying beacons makes this step unnecessary).
- turns 90 degrees towards second beacon (left or right).
- drives forward, keeping the first beacon at exactly 90 degrees to the (left or right).
- path describes circle segment with first beacon in centre, unknown radius (unless sonar gives distance to wall).
- keep scanning for second beacon, drive until ...

shit, this will not work....


Make one beacon shine 180 degrees around (omni kinda directional) and the second shine a sharp sliver of light perpendicular to wall and black 3' line (uni kinda directional). Place both beacons on the same spot. Continue from "keep scanning"

- keep scanning for second beacon until, well duh, you find it.
- you might not find it, you may have chosen the wrong direction (so when facing the wall at the end of the segment, turn around 180).
- now you've gotta find it.
- turn towards it, drive forward, find black line, do your thing.

Top video is now an explaination of the whole thing.

i should start by saying i may or may not know what is going on...

trig is nice for math problems but using it for angle calculation for something like this would require a high degree of accuracy and precision. if you wanted walter to be within a few centimeters of his calculated position I would think that would be a little hard. again im not sure if im understanding this situation correctly. you could always try a camera or something and have it target a power outlet (which would be awesome)

Why not one docking beam and two detect beams on "Walter"

System would work so.........

One fixed IR detector on Walters left flank ie extream left side , looking straight forward.

One servo Mounted IR Detector on Walters right flank.

(these two give a fixed distance between the two sensors ie this makes up the bottom of a triangle.......

Operation :-

Walter reads his fixed left sensor, then slowly turns (himself) until he detects the beacon and stops (now he has made the left side of his triangle , his left sensor points direct to beacon).(essentialy this is the 90° angle side of the triangle).

Then he rotates his right servo mounted IR sensor until he detects the beacon and stops (now he has made the right side of his triangle). The angle of the servo will give you the extra information needed to work out Walters orientation (in relation to the beacon).

Man that was a mouthfull - i hope you follow what i mean.

If you check this posting it is in the same direction but using lasers (if rik follows the above maybe he would put it in pictures for you.... )

It is just a light house to lure Walter to the beacon and thus across the follow line. This discussion really is just about getting the beam/ sensor/ robot situation accurate enough to not only hit the line, but to hit the line in a position that allows room for walter to turn 90 degrees (from crossing the line to following it) and still leave enough room so it has enough length to follow and be staight and aligned when it gets to the end.

This is a bit embarrasing... It seems I have already done this... Hmmm. Wow, have I really been working on walter for this long? If I ever ask how to build a board to drive big motors, someone please come over, unplug my router and send me to the beach.


I remember that blog very well. I kinda referred to that earlier on. Should I have been more blunt? grin

My question remains though. What are you trying to accomplish woth the beacons? Should Walter "know" where he is in the room and than find his way to the dock? Or is just a little light house luring Walter closer towards the dock? Does Walter keep an internal map at all?