Let's Make Robots!

Dynamic measurement of robot's distance from fixed point


I am interested in wirelessly and dynamically/continuously measuring the distance between my slowly moving robot and a fixed point. The robot will act in a space which will never be more than 5ft from the fixed point. Is this possible??

 Thank you very much.


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It is possible.
It is possible.
This actually sounds a bit complicated. You need a way to ping the object or have the object send out a signal. I think the posts above were referring to keeping the bot no father away that 5feet of ANY object, but no farther than 5 feet of a specific object requires overcoming the hurdle of how to know exactly where that object is when you arent looking at it and how it recognizes THAT object and not another.

I'd say, it sounds like preventing robotic vehicle from running away too far from the remote control by accident, when running it in the open space.

I believe the range of all those RF links out there depends on the voltage power supply, so you probably can measure the distance. However, I hardly can see, how you can determine direction where you should go to return to your remote... unless you build some kind of radar?



 Thank you for your comments. The idea isnt to keep the robot from moving too far away from a point or trying to control its range of motion; I just want to be able to visually display how far the object is at any given moment from the fixed point. An operator will be controlling the robots motions and it will only be acting in a small area (appx 5' in diameter) - Im just wondering how this can be accomplished wirelessly and dynamically.

 Thanks again.

The first idea I came up with is to have the object send out some sort of ping signal that is weak enough to only be heard from 5feet or slightly more away. Once the signal gets weak enough the bot moves until it gets strong enough. I'm sure there is a better way, but thats all I got ;)

You could use an audible sound and use a microphone on the bot to detect the volume of the sound (not really accurate if 5 feet needs to be kept exactly). I'm sure others have better ideas.

An overhead camera should do the trick.

Or take a leaf from BaseOverApex's book (which he ripped from bomber wallace): http://letsmakerobots.com/node/1797#comment-5529 and create two or more crossing lightbeams.

Either measure the distance between de projected lightspots (focussed beams) on the wall, or the intensity of the resulting spot where the (soft-focussed) beams collide.

Of course, this will give you only a one dimensional distance reading.


The problem with a camera is how to detect a specific item. I suppose it could be done easily in a white room with 1 black object, but if you have a lot of object and you need to detect a specific one thats a bit tricky. Add in the fact that at various distances and angles the object will look different and you have a big hurdle. Not impossible, but it may require more code that a PIC can handle.

Noone asked about automated interpretation of the produced images. Just show them on your operator console. Let him worry which is which.



I was assuming the robot couldn't move outside of the 5 foot circle (and it made sure of that itself) and the camera was to help it do that. I guess the operator could always see what the camera picks up and determine not to drive it too far away.