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Andrew

RADAR Altimeter

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One of the difficulties with telemetry or altitude hold for a UAV(especially helicopter) is accurate altitude readings. Has anyone experimented with using RADAR altitude detection or is this something that is beyond the hobbyist?

The Mk IV unit in this link is accurate to 12.5cm.

http://www.roke.co.uk/aviation/miniature_r...r_altimeter.asp

Cool stuff no?

Edited by Andrew

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My guess is that it's definitely expensive. They make you request a price quote and don't have any pricing info on their website. Do you think it's possible to make a device to measure altitude using radar? Maybe adapt a radar gun sensor from measuring doppler shift(speed) to measuring distance?

Maybe hack one of these devices?

http://www.hobbytron.net/r-sg7.html

Edited by Andrew

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I was also thinking a radar gun would be a possible donor for the project. But I believe they all rely on the doppler effect (which does not readily offer distance measurements on static objects). We would want pulse echo ranging in order to get that sort of data.

The big issue is that you would have to rewrite the firmware. Perhaps dropping in a new microcontroller is all that is required, but I would expect some circuitry remodeling would be needed. The good news is that some of the hardware in the gun should be salvageable.

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The acoustical method (ultrasound) might not work well in many R/C aircraft applications. It often will not work if there is excessive vibration or noise. Also, even under ideal situations, ranging is limited to a few dozen feet.

However, for quiet settings that need a few feet of ranging, ultrasound is king. It is very popular in robotics. It all depends on the exact application; I would imagine that in a nitro powered model, the radar method might be a better choice.

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Yes, max range is usually 15-20m... only useful as an automatic landing aid...

I've also come across some laser devices which can range up to 150m, but inside of course.. with the ambient light they surely won't work...

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I'll let everyone know how much $$$ the unit costs when I find out.

Probably the "$$$" will be more like $,$$$. ;)

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$8,241.27 ouch. That's not including the taxes and required export license. Might be a cool project to try to make one on your own, but unfortunately I lack the technical savvy that would require.

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Check autonomous landing video of neural robotics chopper:

http://www.neural-robotics.com/videopage.htm

I wonder if there is a reason they land on pavement? It's possible they use ultrasonic finder which (my guess) is much better in reading distance to hard surfaces.

Regards,

Val.

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