|Aug 09, 2005, 04:02 PM|
MAV (Micro Air Vehicle) Resources and Links
John (Fly...Please) has recently increased the interest in MAV's on the forum. He and I have talked about maybe starting some threads for MAV's. I'll start them and let John and others contribute the content. And, I'll clean up certain threads, like this one, which are intended to be resource threads.
I'll also be starting two other threas.
"Working MAV's (Micro Air Vehicles)"
"MAV (Micro Air Vehicle) Discussion.
Ok, post away with those links and resources. Periodically I will take links and format them in a couple of posts at the top of the thread to keep it all easy to find. If these threads generate sufficient interest I will add them to the "Micro Threads Index".
|Aug 09, 2005, 04:09 PM|
Compilation of Links Posted later on in this thread (this post is a work in process, bear with me). As people post links below I'll gradually review them and categorize them in these two posts for a quick reference.
Articles and Sites about International MAV Competitions
Barron Johnson's article about the 2005 MAV competiton in Seol Korea.
1st european-US MAV demonstration and assessment, to take place in Germany September 19th 2005.
The University of Notre Dame site summarizes MAV competitons from 1997 throgh 2001.
University MAV Sites
University of Arizona
|Aug 09, 2005, 07:11 PM|
University of Arizona MAV program
The University of Arizona is one of the leaders in the development of MAV's.
Please see the link to read various related stories:
|Aug 09, 2005, 07:34 PM|
I'm not sure if the 42$ sample option is still going on, but here's a 0.3g CMOS camera. It might be interesting to buy up broken camera phones off ebay and play around with different CMOS cams.
This tx is supposed to be 1.8g 'including wires and connector', I wonder how light it could be made with a lighter antenna and wires/connector?
|Aug 09, 2005, 07:57 PM|
Joined Jun 2004
Some links related to MAVs:
1) biomimetic vision using optic flow for autonomous navigation
2) 1st european-US MAV demonstration and assessment
3) There are MAV competitions since 1997
|Aug 09, 2005, 08:23 PM|
Wow, some small cameras and TXs! The camera phone technology should really help bring down the costs of small cameras. I read somewhere (probably AP forum) that its a good idea to have a separate battery for your video/TX in order to avoid interference in the video signal. RFI filtering of all the power lines, motor power too.
Would love to see actual TX'ed video from one of these 3.3V microcamera.com setups. Wonder what kind of range you get with 50mW TX power? Their color wireless cam w/RX combo says it has 500ft LOS range, but it doesn't say what TX output power it has.
Anybody know the pros/cons of pinhole vs lensed micro cams for MAV use? I wonder if low light capability is important (considering that one might fly around dusk for calm air).
I'm impressed that such light wireless video gear is not really that expensive. I just wonder about the quality of the video and range.
|Aug 09, 2005, 08:50 PM|
I don't rally think that the 0.3g camera from a video phone is what you want to use in a MAV. It does not give that good of resolution and might not be that compatible with 2.4 Ghz transmitters.
I really like the cameras from microcameras.com. They are great and lightweight. That is what I use in my surveillance MAVs. In fact, I do have an aerial video from the camera that was taken in my MAV. I could try to post the video if you would like, but I don't know how to do that. My video is really bad, but is getting better. UF has excellent video with the same camera.
If you have a good 50 mW Tx you might be able to get 400m range. If you have a 80 mW Tx then you should get a range exceeding 600m if you don't have allot of interference. Their Tx has an output power of 20mW (just a guess).
Lensed cameras are bigger/heavier. Probably better quality. However pinholes are quite a bit smaller. Usually everyone uses pinhole cameras (I think). Low light capability is not nearly as important as high light capability. The cameras work allot better indoors than outdoors. When I (and UF) flies that camera outdoor a neutral density light filter is used in addition to an IR filter. I think that that helps quite a bit.
The video quality from most all of these micro cameras is about the same (except from the video phones I think)
However, you have to pay allot for range. It costs $500 for a 80 mW Tx! That is what I have to use to get the 600m range.
As for using a separate battery for the camera/Tx, it is a really good approach. It cuts out most of the motor noise, etc. Power lines are still problematic though. One of the problems that I have been experiencing (and other universities) is that when you place the camera directly behind the prop you get allot of little lines through you're image. You can live with these if you want... or you can try to get rid of them. You're choice really.
I hope this helps,
|Aug 09, 2005, 10:02 PM|
I think you are right about the camera phone video components -- the emphasis there is not on quality (yet), and interfacing to a TX might be problematic.
Good to hear from an actual user of the microcameras.com gear. Its hard to tell if something is OK just from a website. I'd be interested in seeing some of your video if its not too much of a hassle.
Is your MAV flight smooth enough for not-too-jerky video? I would think image stabilization would be needed -- although that's costly in dollars and weight. Good to know about the ND and IR filter tip. Do you just cut some sheet filter material down to the size needed for your camera?
When you mention the lines in the video -- do you mean the strobing of the prop? Hmmm... seems like it would be hard to eliminate that (sync video rate to prop RPM or something?).
Are 900Mhz TXs also suitable for MAVs or is 2,4Ghz prefered? I would imagine you have to use a directional antenna for your RX and that the RX antenna is pretty critical for best range (?).
Thanks for the info. All this is very cool.
|Aug 10, 2005, 12:10 AM|
I wouldn't quite call MAV flight or video smooth by any means. However, it works for the competition. All you need for the competition is to be able to get to and video a target 600m away. The target just has to be legible, and to qualify it only takes 1 frame. So in the i-MAV competition stability is not sought after too much.
However, for practical application it would be really nice to have stable video. I don't think that video stabilization on the MAV scale has been investigated at all (maybe by AV) so it is yet another aspect of MAV flight that can be pursued.
For the ND and IR filter I just take a hammer and a flat head screwdriver to it and hope for the best. I don't have anything to cut glass, otherwise I would go the more "civilized" route. The filters themselves are just square sheets or round sheets that fit on the end of a regular camera lens.
What do you mean by "strobing from the prop"? I don't know what the actual term for the lines is caused but I do know what cause of it. The refresh rate for different cameras differs a bit but it cannot usually adjust to the RPM of the prop. The prop turns around at something like 350 Revs/sec and this means that sometimes when a frame is capured with the camera the prop is in front of the camera and sometimes it is not. Somehow this causes horizontal lines to run across the image.
There aren't many ways that I know of to get rid of those lines except for the one that I am currently using. I now mount my camera in the very tip of my vertical stab so that it completley misses the prop. This combined with the filters and the seperate batteries greatly improve image quality. I suppose that you could do allot of messing around with the camera itself and programming some type of filter or something to tune out the frequency of the prop. I think that would be rather hard and time consuming though.
As for the Tx frequency, all MAVs that I know of operate off of 2.4 GHz. That is not to say that 900 MHz wouldn't work, I just don't know.
It might not be best to use a highly directional (parabolic) antenna for the video. Then again, I may be wrong. I know that you don't want to use a non-directional antenna... those are horrible. Just about all the MAV teams use patch antennas with either a 14 or 18 dBi gain. These are "semi-directional". The problem with highly directional antennas is that you have to have someone constantly pointing the antenna at the MAV if the MAV is flying in close proximity to yourself.
|Aug 10, 2005, 03:36 PM|
Joined May 2005
I actually have a very similar phone-cam (salvaged) and read up on them. Unlike most of the cams we've been playing with, these have a digitial interface. They do not product analog composit video. What this means is that you won't be able to watch them on a TV set without quite a bit of electronics in between. But the good news from a MAV perspective is that if you do have a digital downlink from the plane for telemetry, you can insert the video as well into the datastream.
Has anyone produced code in a PIC that will interface to these cameras ?
|Aug 11, 2005, 03:24 PM|
MAV Research Papers
MAV Research Papers:
- Excellent MAV paper from AeroVironment. Explains Surveillance System, MDO, flight performance, etc.
- Another excellent paper describing the University of Florida's MAV development over the past few years. Great wind tunnel results with a novel aeroelastic wing that adapts to gusts and improves max Cl. Also lots of practical component specifications, etc.
- A good UF paper describing a method for horizon detection and methods of roll stabilization using the horizon as a reference.
- A masters thesis by a very accomplished UF student on MAVs and morphing wing capabilities.
- Great paper on the effects of tip vorticies on MAVs. Discusses the effects of endplates, etc.
http://www.cnel.ufl.edu/files/1018377332.pdf- An interesting PowerPoint presentation describing initial research by the University of Florida that lead them to their current configuration. Very informative.
http://techreports.larc.nasa.gov/ltr...46spie-gaf.pdf - - A good paper by Martin Wazack at NASA about elastic membrane wings. Discusses wind tunnel optical results, etc.
- Another good paper by Martin Wazack at NASA. This is a follow-up to the previous paper
- A MAV paper from the University of Colorado. Interesting design and CFD approach.
- Development of the University of Arizona's Autonomous MAV.
http://techreports.larc.nasa.gov/ltr...-2003-5345.pdf- A good paper by NASA on the theory and testing of MAV biologically-inspired ornithopter designs.
- A paper that describes Lehigh U's MAV development efforts. Foam design.
http://techreports.larc.nasa.gov/ltr...4-cr213271.pdf- A paper describing in-flight variations of the MAV wing geometry. Wind tunnel results.
- A MAV design paper by the MBL company describing the development of a 6" ICB-powered MAV.
I have attached a research paper that I wrote about the development, testing, and hopefull "optimization" of my MAV. Edit: Nevermind, I can't upload the file... it is too big (500 kb). If anyone wants it I can email it to them.
There are Many more research papers/design reports on MAVs, and some of them have really interesting results/info. However, they are not available online. I have ".pdf" copies of them that were obtained from the AIAA website, but I don't think that I am allowed to post them here. If anyone is interested I could post the titles of the informative ones from AIAA. They can be purchased from the online library at a price of $25/piece... Ouch!
|Aug 11, 2005, 04:12 PM|
Thanks for posting these. I was pretty sure you had such a list. Now this thread starts to be a resource with a lot of good sources for anyone interested in MAVs.
BTW, did you travel to Korea for the MAV competition. Or, did just your MAV travel there. The article on that competition is very nice as it has lots of pictures and some details on MAV's. It's interesting that most of the MAV's use the U80 prop. What seemed surprising to me is some that I saw that were cut down shorter didn't have the blades reprofiled to be nice and smooth. They looked like they might have just been hacked off with a knife and left that way. It's a small thing but re-profiling is pretty easy and might be worth it in a competition. Maybe others did do this but I didn't see it in the pictures.
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