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Speed and Altitude of Aircraft

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saeed_pk

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Hi all,
I have to make a module that can measure the speed and altitude of an RC aircraft where from i should start .
And tell what mechanisms aeroplanes do use to get these.

I have an idea that if i use laser and hit it on ground while plane is flying it will reflect back to the plane then i use doppler's effect to fine the distance(altitude) and relative speed of the aircraft.
 

Mr.MEB

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Isaw lots of projects like that on the net. Mainly students and hobbyist. But there are serious researchers on this topic too (for drones).
Most of the used sensors are accelerometers (you should use several to make 3D - 6Dof of the aircraft ) then gyros, magnetic compass and pressure differential altimeters. Depends on the complexity you want.
I think laser and doppler are not bad ideas but how will you process then the signal? Have you got the required hardware and algorithm?
 

saeed_pk

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@ Mr.Meb
I will use signal processing and will measure the difference in frequecny of reflected wave that will give me speed and altitude
but you told me some other mechanisms like
"Most of the used sensors are accelerometers (you should use several to make 3D - 6Dof of the aircraft ) then gyros, magnetic compass and pressure differential altimeters"

@alzomor
Can we find speed on GPS ok if so, then do a GPS describes altitude too.
Please advise
 

Mr.MEB

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"signal processing and will measure the difference in frequecny of reflected wave"
That's what i was wondering. How?
 

saeed_pk

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@ Mr.MEB
Dear when a wave is reflected back it has changed its frequency due to relative velocity we know the speed of wave so in Signal Processing we just have to find change in freq .... i think it should work ... i want to make it concise and versatile
 

Mr.MEB

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If you said that for ultrasonic wave there will be no problem. Lot's of easy circuits around for ultrasonic telemeters (like sonar). But your talking about making a "radar".
I don't know if Doppler effect would be involved since at constant altitude there won't be change of distance between earth and the aircraft. (Maybe you could use an integration.)
Anyway, what would the hardware be for detecting the change of the frequency of the light (timer of MCU or DSP won't be of great help) ? And what will be the precision?
GPS is a reasonable solution, depending on your module you can log your position accurately (-/+ 10 m to +/- 2 m , or even more???)

In fact you can embedded a Doppler radar:
http://www.fpga-guru.com/files/wxradar.pdf
 

wiztronix

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i think GPS is the best way because using laser and measuring reflection will have a serious problem when the aircraft is flying over various types of terrain.. for instance, various kinds of soil will definitely have different reflectivities when compared to water... so i think that'd be a tough task...

regards,
wiztronix
 

viveklengade

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Hi,

I think so if u use the GPS for all it is going to better option, Normally using GPS we can able to find position, Course, speed and if we using 3D GPS then it will also give the altitude information. As the information about sopped and course are not so accurate but as you are using this on RC aircraft is ok. Visit following link it will help you to choose and implement any one of them


H**p://www.sparkfun.com/commerce/categories.php?cPath=4_17
 

royal_stalin

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U can use gps reciver for ur purpose.
u can avail a utracker 02 if want it to connect to a seperate kit
insted u can use tp-051 if use a pc to observe the data
 

kender

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I would do it the old-fashioned way: pressure altimeter and Pitot tube. There lots of cheap and light MEMS pressure sensors that are fit for this job.

Yes, GPS will give you altitude. But small cheap GPS receive will have a big error (5m easily).

Pitot tubes give the speed w.r.t. (with respect to) to air. If there's wind, the speed w.r.t. air can be different than the speed w.r.t. ground. This raises another question is: what do you need to know the speed for? Is it for mid-air flight control or for landing? :?:
 

watermelon

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Oh, the reflected wave kind of a thing is called FMCW radar and works like sending a continuously increasing or decreasing frequency CW. Read more about the FMCW radar at http://emlab.kyunghee.ac.kr/docs/Combined_Vehicle_detector.doc

I guess, of the lot of solutions suggested, the GPS based altimeter will work out the best : reliable, economical, repeatable (requires intelligent decision making system) and engineerable.

Radar kind of stuff is difficult to design and engineer.

Of course, check out if the GPS receiver supports speeds of your machine.

And let us all know about your project's success :)
 

netfirms

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how to process if an aeroplane fly in other action ?
 

watermelon

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netfirms,
Your question is not understood. Can you please explain?
Did you mean to measure the speed and direction?
 

netfirms

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watermelon said:
netfirms,
Your question is not understood. Can you please explain?
Did you mean to measure the speed and direction?
yes
 

watermelon

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Use 4 FMCW radars : two on the edges of left and right wings, one near the nose and one near the tail. All should be looking at the ground outwards for example, the nose radar should look slightly ahead of the ground below the nose.

The doppler and change in total travel of energy of each path will cause unequal differences in the received frequency. The difference in the received frequency of the four FMCW radars can then be used to calculate speed, direction and height of the aircraft(?), (as far as I can recall).

Please read some book on Radars for more explanation.
 

alvarorahul

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well as some ppl hv already said, i think gps would b a very gud option here

i was part of a research project where we have used gps for tracking an underwater autonomous robot. It was very reliable.

You can use d GPS for knowin the exact position on d earth, location as well as height above sea level.
 

watermelon

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I guess, the best option is GPS with accelerometers. And of course, some very innovative algorithms to carry out information processing.

Definition of best :

(a) Economically viable.
(b) Easily available technology.
(c) Easily engineered solution.
(d) Meets requirements to a great extent.
(e) Repeatable.
(f) Can be enhanced easily.
(g) Easily repairable.
(h) Large knowledge base available.
 

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