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Posted by Adam Chapman on March 19, 2008, 2:34 pm
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Hi,
For a student project Im designing an autonomous air-to-air refuelling
system.
Im thinking that it would be cool to put IR LEDs in a ring around the
tanker's drogue (http://www.jdwetterling.com/6-refueling.jpg) and use
rangefinding sensors on the airfract being refuelled to find the
drouge.
I think that basic IR rangefinders use a special lense that reflects
ir light to a certain part of something similar to a CCD sensor, and
the point where the beam hits that sensor is used to determine a
range.
Now I know that the beams used on products like the sharp rangefinder
are pretty thin.
I want to use them to line up an aircraft's refuelling probe with the
beam emmitted from the tanker's drogue so I need a wider angle beam to
be emitted.
My question is: If I have a wider beam emmitted from the drogue, would
I need bigger lenses and sensors on the aircraft that is to be
refuelled?
Thanks for any help offered.
Adam
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Posted by cadcoke4 on March 19, 2008, 11:25 pm
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You are diving into the deep end. I imagine that controling an
aircraft with this sort of precision is an extremely big challenge.
But, regarding your question;
First, I am not certain you understand how the Sharp distance sensors
work. They emit a beam of IR light that is seen as a dot on the
object being measured (well, you would see it if you could see IR).
Then, a lens focuses the image of that dot onto a linear sensor (sort
of like a camera, but with only one dimension, not two). How far left
or right that focused dot falls on the sensor is what determines the
distance.
Other, cheaper, IR sensors work by simply emitting an IR light (fairly
broadly) and then a sensor simply detects any reflected IR light. The
brighter the reflected IR light, the closer it is presumed to be. So,
it doesn't really detect distance. Rather, it is detecting if
something is close.
Neither of the above are good methods for distance measurements if you
are tracking a small point.
Ultrasonic range finding is another option, by perhaps having the
drogue emit a pulse of light and an ultrasonic "ping" at the same
time. Your airplane would then look for the light, and listen for the
ping and measure the time difference between the two to determine the
distance. But, I suspect that there will be too much noise in the
environment for this to work.
This leaves using two cameras to see your infrared beacon on the
drogue. The difference in the postion on the image on the two cameras
is the method of determining distance. It would also tell you the
direction of the drogue in relation to the airplane. The CMUcam has
the ability to automatically track colored objects, and communitate
the coordinates to your CPU over a serial connection. Perhaps simply
provding a red surface on the drogue is enough to target it.
Joe Dunfee
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Posted by Adam Chapman on March 20, 2008, 6:21 am
Please log in for more thread options > You are diving into the deep end. =A0I imagine that controling an
> aircraft with this sort of precision is an extremely big challenge.
> But, regarding your question;
>
> First, I am not certain you understand how the Sharp distance sensors
> work. =A0They emit a beam of IR light that is seen as a dot on the
> object being measured (well, you would see it if you could see IR).
> Then, a lens focuses the image of that dot onto a linear sensor (sort
> of like a camera, but with only one dimension, not two). =A0How far left
> or right that focused dot falls on the sensor is what determines the
> distance.
>
> Other, cheaper, IR sensors work by simply emitting an IR light (fairly
> broadly) and then a sensor simply detects any reflected IR light. =A0The
> brighter the reflected IR light, the closer it is presumed to be. =A0So,
> it doesn't really detect distance. Rather, it is detecting if
> something is close.
>
> Neither of the above are good methods for distance measurements if you
> are tracking a small point.
>
> Ultrasonic range finding is another option, by perhaps having the
> drogue emit a pulse of light and an ultrasonic "ping" at the same
> time. Your airplane would then look for the light, and listen for the
> ping and measure the time difference between the two to determine the
> distance. =A0But, I suspect that there will be too much noise in the
> environment for this to work.
>
> This leaves using two cameras to see your infrared beacon on the
> drogue. The difference in the postion on the image on the two cameras
> is the method of determining distance. =A0It would also tell you the
> direction of the drogue in relation to the airplane. =A0The CMUcam has
> the ability to automatically track colored objects, and communitate
> the coordinates to your CPU over a serial connection. =A0Perhaps simply
> provding a red surface on the drogue is enough to target it.
>
> Joe Dunfee
Thanks, I was of similar mind about sonar. Last night I was thinking
about using maybe some webcam type sensors dotted around the aircraft
needing fuel and finding the 3D location of a bright beaon like the
drogue and you confirmed this morning that it would probably work.
Thanks again
Adam
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Posted by John Nagle on March 20, 2008, 4:55 pm
Please log in for more thread options Adam Chapman wrote:
> Hi,
>
> For a student project Im designing an autonomous air-to-air refuelling
> system.
>
> Im thinking that it would be cool to put IR LEDs in a ring around the
> tanker's drogue (http://www.jdwetterling.com/6-refueling.jpg) and use
> rangefinding sensors on the airfract being refuelled to find the
> drouge.
Neat idea. Not easy to do. How large an aircraft is this for?
I'd suggest using a vision system with an IR emitter on the target
and a camera with an narrow IR filter on the detection end. Range
should come from a time of flight system, either laser or RF.
NASA Dryden demonstrated this in 1992, so you should read their
papers:
http://www.dfrc.nasa.gov/Gallery/Movie/AAR/HTML/EM-0053-01.html
John Nagle
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Posted by Adam Chapman on March 23, 2008, 2:46 pm
Please log in for more thread options > Adam Chapman wrote:
> > Hi,
>
> > For a student project Im designing an autonomous air-to-air refuelling
> > system.
>
> > Im thinking that it would be cool to put IR LEDs in a ring around the
> > tanker's drogue (http://www.jdwetterling.com/6-refueling.jpg) and use
> > rangefinding sensors on the airfract being refuelled to find the
> > drouge.
>
> =A0 =A0 Neat idea. =A0Not easy to do. =A0How large an aircraft is this for=
?
>
> =A0 =A0 I'd suggest using a vision system with an IR emitter on the target=
> and a camera with an narrow IR filter on the detection end. =A0Range
> should come from a time of flight system, either laser or RF.
>
> =A0 =A0 NASA Dryden demonstrated this in 1992, so you should read their
> papers:
>
> =A0 =A0 =A0 =A0http://www.dfrc.nasa.gov/Gallery/Movie/AAR/HTML/EM-0053-01.=
html
>
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 John Nagle
Thanks John, very interesting
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> aircraft with this sort of precision is an extremely big challenge.
> But, regarding your question;
>
> First, I am not certain you understand how the Sharp distance sensors
> work. =A0They emit a beam of IR light that is seen as a dot on the
> object being measured (well, you would see it if you could see IR).
> Then, a lens focuses the image of that dot onto a linear sensor (sort
> of like a camera, but with only one dimension, not two). =A0How far left
> or right that focused dot falls on the sensor is what determines the
> distance.
>
> Other, cheaper, IR sensors work by simply emitting an IR light (fairly
> broadly) and then a sensor simply detects any reflected IR light. =A0The
> brighter the reflected IR light, the closer it is presumed to be. =A0So,
> it doesn't really detect distance. Rather, it is detecting if
> something is close.
>
> Neither of the above are good methods for distance measurements if you
> are tracking a small point.
>
> Ultrasonic range finding is another option, by perhaps having the
> drogue emit a pulse of light and an ultrasonic "ping" at the same
> time. Your airplane would then look for the light, and listen for the
> ping and measure the time difference between the two to determine the
> distance. =A0But, I suspect that there will be too much noise in the
> environment for this to work.
>
> This leaves using two cameras to see your infrared beacon on the
> drogue. The difference in the postion on the image on the two cameras
> is the method of determining distance. =A0It would also tell you the
> direction of the drogue in relation to the airplane. =A0The CMUcam has
> the ability to automatically track colored objects, and communitate
> the coordinates to your CPU over a serial connection. =A0Perhaps simply
> provding a red surface on the drogue is enough to target it.
>
> Joe Dunfee