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Posted by on May 11, 2006, 11:41 am
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I have a RC model airplane capable of carrying max 800grams payload (after
all my onboard electronics, batteries, GPS, video camera). I want to try
auto takeoff and landing. Especially for the auto landing, it important to
be able to determine the slop of the final landing approach. For this
intended application, I need to accuratelly determine the height of the
airplane. (The static pressure sensor alone is not accurate for this).
So, the obvious question;
1. Do you know any range/distance/height/altitude sensor with the following
features;
* LIGHT WEIGHT
* Low power (and hopefully low cost)
* Measurement range 25m-25cm
* Measurement resolution (better than) 10cm
* Measurement rate 10 Hz
And also
2. Would you suggest any method that helps to line-up the airplane with the
landing field (runway). (Currently I'm planing to use the GPS data but it
seems to be not very accurate.)se
Cheers,
Falco
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Posted by Shawn B. on May 11, 2006, 1:50 pm
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Falco wrote:
> I have a RC model airplane capable of carrying max 800grams payload (after
> all my onboard electronics, batteries, GPS, video camera). I want to try
> auto takeoff and landing. Especially for the auto landing, it important to
> be able to determine the slop of the final landing approach. For this
> intended application, I need to accuratelly determine the height of the
> airplane. (The static pressure sensor alone is not accurate for this).
>
> So, the obvious question;
> 1. Do you know any range/distance/height/altitude sensor with the following
> features;
> * LIGHT WEIGHT
> * Low power (and hopefully low cost)
> * Measurement range 25m-25cm
> * Measurement resolution (better than) 10cm
> * Measurement rate 10 Hz
>
> And also
> 2. Would you suggest any method that helps to line-up the airplane with the
> landing field (runway). (Currently I'm planing to use the GPS data but it
> seems to be not very accurate.)se
>
> Cheers,
>
> Falco
>
>
There are a couple of good methods for detecting the ground. Aircraft
use a few methods, but a Radar altimeter is the most widely used. See
http://www.roke.co.uk/aviation/miniature_radar_altimeter.asp This will
most likely be out of your budget and weight range though.
If the weather is clear, you're not too high, and the ground is fairly
reflective, a laser range finder with RS232 output will work rather
nicely. See:
http://laseroptronix.se/dispu/ilm400el.html
You might also try hacking one of these cheaper consumer products:
http://www.professionalequipment.com/xq/ASP/ProductID.4231/id.15/subID.125/qx/default.htm
As for lining up with the centerline and glide slop of the runway,
aircraft use multiple technologies for that including ILS, MLS, and DGPS
(see http://www.edu-observatory.org/gps/dgps.html).
The resolution, price and weight of ILS and MLS will not make sense for
a small model though, plus you need to have multi-million dollar
ground-based transmission equipment for each, plus very expensive
receivers on board. Although the receiver is relatively inexpensive,
DGPS has a resolution of 3-6 meters. The last time I flew RC, our
runway was 25 feet wide with tall grass on either side. Not wide enough
to overcome the DGPS error. I suppose if you had a wide enough runway
you could at least line up with it. With laser distance detection, you
could over come the error of the DGPS and control your low-level
altitude. I would rely on a digital barometric pressure sensor or the
DGPS altitude for descending to pattern altitude and follow the DGPS
altitude down until the laser picks up the ground.
You might also consider using Ultra Wide Band Radar for ground
detection, see http://www.uniroma2.it/fismed/faculty/Stadero/papers/osee.pdf
Have fun,
Shawn
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Posted by on May 12, 2006, 9:37 pm
Please log in for more thread options >2. Would you suggest any method that helps to line-up the airplane
>with the landing field (runway
Don't airplanes have a visual method available for the pilots using
lights on or near the runway. I am talking about the system that they
use for the glide slope.
Is your video good enough for a computer to process this image?
A different idea is to use two ground based cameras to view the
approach area. A computer would calculate the angles and generate the
3-d location of the plane. Superbright LED's on the front of the plane
may provide a bright enough light source to help the process.
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Posted by Shawn B. on May 15, 2006, 12:05 pm
Please log in for more thread options cadcoke3@yahoo.com wrote:
>> 2. Would you suggest any method that helps to line-up the airplane
>> with the landing field (runway
>
> Don't airplanes have a visual method available for the pilots using
> lights on or near the runway. I am talking about the system that they
> use for the glide slope.
>
> Is your video good enough for a computer to process this image?
>
> A different idea is to use two ground based cameras to view the
> approach area. A computer would calculate the angles and generate the
> 3-d location of the plane. Superbright LED's on the front of the plane
> may provide a bright enough light source to help the process.
>
They have different types of visual glide slope indicators using
directed multi-colored lights, but you would not want to use them as
part of an auto land system. Plus, this is a model airplane landing at
what I presume is a non airport.
Shawn
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Posted by Tim Auton on May 16, 2006, 2:54 pm
Please log in for more thread options <Falco> wrote:
>I have a RC model airplane capable of carrying max 800grams payload (after
>all my onboard electronics, batteries, GPS, video camera). I want to try
>auto takeoff and landing. Especially for the auto landing, it important to
>be able to determine the slop of the final landing approach. For this
>intended application, I need to accuratelly determine the height of the
>airplane. (The static pressure sensor alone is not accurate for this).
>
>So, the obvious question;
>1. Do you know any range/distance/height/altitude sensor with the following
>features;
> * LIGHT WEIGHT
> * Low power (and hopefully low cost)
> * Measurement range 25m-25cm
> * Measurement resolution (better than) 10cm
> * Measurement rate 10 Hz
The other answers you've had haven't been especially encouraging. I
think that's because no off-the-shelf solution exists which meets your
specs. Laser rangefinding gets the closest, but isn't very
light-weight (in a model aircraft context) or low-cost.
What *is* light-weight and low-cost is sonar. A few tens of dollars
and a few grammes gets you a sensor which will read out to 5-10m. I
don't know how well sonar fares against moving (relative to the
sensor), soft (the vegetation around most flying fields) targets
though. It wouldn't be a very difficult or expensive experiment to
find out if sonar could do the job, if you already have an
instrumented aircraft (which you do).
Tim
--
Did I really still have that sig?
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> all my onboard electronics, batteries, GPS, video camera). I want to try
> auto takeoff and landing. Especially for the auto landing, it important to
> be able to determine the slop of the final landing approach. For this
> intended application, I need to accuratelly determine the height of the
> airplane. (The static pressure sensor alone is not accurate for this).
>
> So, the obvious question;
> 1. Do you know any range/distance/height/altitude sensor with the following
> features;
> * LIGHT WEIGHT
> * Low power (and hopefully low cost)
> * Measurement range 25m-25cm
> * Measurement resolution (better than) 10cm
> * Measurement rate 10 Hz
>
> And also
> 2. Would you suggest any method that helps to line-up the airplane with the
> landing field (runway). (Currently I'm planing to use the GPS data but it
> seems to be not very accurate.)se
>
> Cheers,
>
> Falco
>
>