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PostPosted: Thu Jan 03, 2008 3:57 pm 
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Hello,

I was trying to find a good starting point, and was hoping anyone here could help. I was looking for a sensor setup that would allow me to track an object, without using a visual camera (like the color tracking or CMU camera systems out there).

I need a good amount of range, maybe 20' - 50'. Ultimately, I would like to be able to achieve the same sort of tracking that the CMUCam demonstration video's, just without the usage of a camera itself. Video: http://www.youtube.com/watch?v=GDOC9yZ7IHc

Could this be done with some sort of IR technology, RFID, Bluetooth, transceivers, sonor, etc? GPS cannot be used in this application.

Thoughts?

Thanks.


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PostPosted: Thu Jan 03, 2008 5:10 pm 
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Hello!

I 'm sorry, to have object tracking you need vission which requires a camera.

IR detection can provide object avoidance but not tracking.

RFID will not do either because RFID stands for Radio Frequency IDentification, like the one use for toll road tags. In Texas, they are called EZ-Tags.

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PostPosted: Thu Jan 03, 2008 5:15 pm 
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I'm sure you can track a object using IR range sensors, though I think it only works on the horizontal plane.

Some bit down on this page you can see how that is done: http://www.societyofrobots.com/robot_iRobot_Create_mod.shtml

I think you'll need to move the object pretty slowly for this to work. However, you could use two IR sensors and check which one saw the object the last time. Then you'll just have to pan the servo in that direction until both sensors sees it again.

You could probably solve the vertical plane by applying a matrix of IR sensors, but I'm absolutely not sure.


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PostPosted: Thu Jan 03, 2008 5:25 pm 
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The link to that page discusses edge detection and navigation. Tracking requires real time monitoring in bothe the X and y planes simultaneously. I'm not going to say that it is impossible to use IR in a clever manor to get some sort of tracking but its not practical. If it sees an object one second and then it moves somewhere else the sensor has to rescan for it.

Cameras are best for this application.

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PostPosted: Thu Jan 03, 2008 5:32 pm 
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Sorry, the link was pretty inconvenient. Later down there is a video of it tracking an object:

http://www.youtube.com/watch?v=f_VOQNXp ... _mod.shtml

Although it's actually edge detection, I don't see why it can't be called object tracking as well.

And, yes, cameras are best for it, but Red-Rx7 asked for non-visual object tracking :wink:


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PostPosted: Fri Jan 04, 2008 8:25 am 
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For a project at school I had to make a "tracking" system that would allow a motorized cart to follow a person around.

I decided to use an infrared emitter which had to be buckled to the person's belt, so the device had a source to track.

Although this isn't exactly what you're looking for, it would provide a simple tracking system, provided you're willing to attach an emitter to the item you want to track.

Other than that, i'm out of ideas :)

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PostPosted: Fri Jan 04, 2008 10:48 am 
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Fredrik Andersson wrote:
Sorry, the link was pretty inconvenient. Later down there is a video of it tracking an object:

http://www.youtube.com/watch?v=f_VOQNXp ... _mod.shtml

Although it's actually edge detection, I don't see why it can't be called object tracking as well.

It can't be called object tracking because it isn't object tracking. It's edge detection and only works in the plane horizontal to the robot. If the object is above or below the robot, it will not be seen.

Object tracking works in 3D, not just 2D.

Not using the correct terms to describe a process causes confusion, which is not good.

8-Dale

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PostPosted: Fri Jan 04, 2008 11:09 am 
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Fredrik Andersson wrote:
Sorry, the link was pretty inconvenient. Later down there is a video of it tracking an object:

http://www.youtube.com/watch?v=f_VOQNXp ... _mod.shtml

Although it's actually edge detection, I don't see why it can't be called object tracking as well.

And, yes, cameras are best for it, but Red-Rx7 asked for non-visual object tracking :wink:


I must admit that video was impressive. I have not seen tracking using edge detection and I was surprised at the speed at which it was able to do it. I would like to see the code to that.

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PostPosted: Fri Jan 04, 2008 11:38 am 
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Thanks for all the replies!

To further clarify:

- I am able to put an emmiter source on the object, for tracking.
- The tracking would need to be both on a horizontal and vertical planes.

Based on most of the suggestions, it seems like a visual camera source is not only the ideal solution, but quite possibly the most practical one as well?

I originally did not want to use a visual device due to some of the costs and room we have to work with, but sometimes there is no viable alternative. With that in mind, is the CMU Cam the suggested item for such application? Anyone know what the range capability of the CMU Cam would be off the top of their head?

Thanks for all the feedback once again!


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PostPosted: Fri Jan 04, 2008 1:16 pm 
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Well scud's Idea wuld work no?

you just attach the emiter and you can make it follow without a camera.

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PostPosted: Fri Jan 04, 2008 1:39 pm 
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How you track an object depends on the properties of the object being tracked, and the surrounding environment. If the object is capable of having some sort of beacon on it, then there are numerous approaches. A siimple one would be to use an IR object detection setup where the IR emitter is used as the beacon on the object being tracked, and the IR receiver is used as the object detector. The detector field of vision could be physically limited such that a servo can pan/tilt the detector until the beacon is detected and its location established.


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PostPosted: Fri Jan 04, 2008 1:56 pm 
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if you can have an emitter on the tracked object then you could use an IR beacon and a iris + pin-diode array similar in concept to how heat seeker missles work. the pin-diodes are arranged in a geometric pattern with a lens and iris above them. the basic concept, the iris is wide open until it sees enough signal to track on one or more of the pin-diodes. it uses the strongest signal to "steer" the nose in an attempt to center the signal as it closes the iris to narrow the window and increase accuracy. if it looses the signal the iris opens and the logic attempts to re-acquire. wet hair, lather, rinse, repeat. In this case I would think the signal would be a modulated IR beam, say 38 to 40KHz and the pin-diodes would have a programmable gain amplifier and a real sharp bandpass filter, followed by a rectifier stage so you can read the signal in on an A/D converter. this way you could reject other "noise" and allow you to follow only the strongest source. You could use a TV remote as your "beacon" to track. you would need a lens, IR filter, and auto-iris (and its driver circuit) of course but those can be had from places like supercircuits in a standard C or CS mount. You could even use the cheapest B&W camera that will mount the lens/filter/iris as your platform to develop with and then replace the CCD with your diode array.


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PostPosted: Fri Jan 04, 2008 2:04 pm 
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Fredrik Andersson wrote:
... Later down there is a video of it tracking an object:
http://www.youtube.com/watch?v=f_VOQNXp ... _mod.shtml

I think this would seriously freak the dog out... persistently follow it around, then stay a certain distance away, backing up if he charges... oh my head. If you could couple the IR range detector with a PIR sensor you could determine a warm target from the general environment. :)


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PostPosted: Fri Jan 04, 2008 5:10 pm 
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Red-Rx7 wrote:
I need a good amount of range, maybe 20' - 50'. .


I was planning to use a thermal sensor array for a similar application, but I was hoping for maybe a 5' range. The range you are describing seems crazy far unless the trackee is going to be broadcasting its position.


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PostPosted: Sat Jan 05, 2008 3:53 pm 
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SN96 wrote:
I must admit that video was impressive. I have not seen tracking using edge detection and I was surprised at the speed at which it was able to do it. I would like to see the code to that.


This is pretty much the same thing.

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