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3D Printed Ornithopter - Micro UAV Drone

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In the past couple years there has been quite a bit of activity into r&d of tiny insect/drone/ornithopter type vehicles. Two intriguing designs I've been following are Harvard's RoboBee and Cornell's Ornithopter. While some designs, like Harvard's, are out of reach of the average DIYer (check out their white paper, it's awesome) the Cornell 3D printed ornithopter is attainable and I took it as a challenge to make my own. Cornell's use of 3D printing techniques makes it easy to try out and make modifications. Unfortunately they don't give out their files and they built theirs on a 3D printer that cost 100k. My work has been to model my own design off of their work, but make it using commonly available 3D printers. You can see the results below.


 
Quickly I would like to discuss how amazing desktop 3D printers are. So far I have been able to make two versions: the first is blue and printed by my schools 3D printer (6.07 grams), the second is clear plastic and made by a Makerbot Replicator 2 (4.729 grams). For a reference point Cornell's weighed 3.89 grams. Between my first and second designs the weight of the wings has gone from 4 grams to 2.6 grams because the wing thickness went from 0.02 inches to 0.008 inches (200 microns). After receiving comments about more flexible wings, I have made a new version with a total wing weight of 1.968 grams making my ornithopter a total of 4.10 grams (the total weight of 4.729 grams minus the difference in the wings (2.6 - 1.968) grams) making it only 0.21 grams off of Cornell's weight! I am not done with this project yet and would really love to get a design that flies, so please give me your comments and ideas!
 
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Ben Finio1 year ago
Cool! I worked on the RoboBee as a graduate student at Harvard (that's my "Steerable RoboBee" video you linked to at the beginning) and coincidentally am in the Creative Machines Lab at Cornell now, although to the best of my knowledge no one here is working on the ornithopter project anymore.

FYI I just posted directions to make a simple paper RoboBee model - this isn't an actual flying version, and really better suited as a craft project for kids, but lets you see how the mechanism works: http://www.instructables.com/id/Build-a-Paper-Robobee-Model/. In case you haven't seen it they recently got the real RoboBee to hover.

Also, not sure if you're interested in walking robots at all - but the Biomimetic Millisystems Lab at U.C. Berkeley has a bunch of really cool hexapod-inspired robots made from laser-cut cardstock. So if you're into DIY versions of robots that started in academia, that might be worth checking out - I think they have some of the drawing files on their website. For the record the RoboBee project actually has its roots in the "Berkeley Micromechanical Flying Insect" project from the early 2000s.
0.o I need to gets me some piezo actuators, those tiny robots are boss!
Mizchief100 (author)  Ben Finio1 year ago
Thank you for commenting! I had actually read your paper RoboBee when it came out and saw you said you worked on the real one, that is TOO cool! I'm going into undergrad as an ME next year and hope to be able to do something like that for grad work.

That is awesome, I had seen the RoboBee hover but I haven't heard anything about that lab at U.C. Berkeley I will definitely read into it! I've actually been wanting to look into bipedal or hexapods recently so that is too neat. Keep me posted on your future work!
Wow, that's great that you're getting started with this stuff so early. I didn't get started with robotics until grad school. I'm not working on the RoboBee anymore, the best place to check for updates will always be the Microrobotics Lab's publications page. They also tend to put the latest/best YouTube video on their homepage. I'm happy to answer any questions you have in the meantime, or can try to point you to the right publications.
Tomdf1 year ago
Very Awesome! That is a really good idea trying to print onto the wing material, I would be very interested in hearing how that goes.
I've also attempted to design a 3D printed ornithopter but ran into the same snag that you have, the wings. I'm fairly certain that getting flex on the wings is crucial. I did have some luck with mylar before shelving the project. 

Here is some nice technical info on wing design if yer interested:
http://www.ornithopter.de/english/principle.htm
Mizchief100 (author)  Tomdf1 year ago
Thanks! Yeah I actually read yours while I was doing this 'ible and although we take different approaches it seems some stuff is in common. The printing onto the wing material unfortunately hasn't gone too well, I'm going to try increasing the extruder temp a bit more to see if that'll melt the wing material and the plastic together. Usually the plastic pops right off. I checked out that site you linked, good stuff.
Don't the bottoms of each wing need to be flexible?
is any lift generated
Similar to a lot of other suggestions, I say that you should need to remove the lower part of the wing frame completely, and stick on Mylar wing surfaces. I believe wings gets a lift by making a sweeping action, which pushes the air down each time with a backward and forward action. It has nothing to do with an aerofoil section whatsoever.
There is a French company that makes a flying bird called Tim. It operates with a wind up rubber band, and flies very successfully. This has a stiff leading edge and the free-floating Mylar wing. A downward curve on the leading edge should prevent the wing surface from flapping horizontally, which would obviously produce no lift.
the ultimate problem with this little miniature flyer is the power supply. I doubt it will ever be able to lift a battery.
Mizchief100 (author)  kitemancake1 year ago
Interesting, I had never heard of Tim! But yeah I will definitely be redesigning the wing.
found out that it's called the Timmy Bird. please see:
http://www.youtube.com/watch?v=JQWb7uLzW9Y and
http://www.youtube.com/watch?v=j_fJVjWS-hU

cheers!
Mizchief100 (author)  zenTaurus1 year ago
Haha I really enjoyed the music in those vids.
and a TEDtalk -- A robot that flies like a bird:

http://www.youtube.com/watch?v=Fg_JcKSHUtQ
Ben Finio1 year ago
Also - some random advice after reading some of the comments below and looking at the videos: fine-tuning the wing flexibility is actually a big challenge for any flapping-wing MAV, and can definitely have a huge impact on lift generation. Long story short there are generally two approaches: you have a rigid wing with a hinge at the top that lets the angle of attack change throughout the stroke (RoboBee approach), or you have a flexible wing that bends along the chord as it flaps (Cornell ornithopter approach). It's hard to tell without high-speed video but judging by your video, you'd get more lift if the trailing edge of your wing was more flexible, which you can probably accomplish by tapering the outline to be thinner at the trailing edge (depending on the resolution of your printer).

If that doesn't make sense in writing I can try to find an appropriate figure from my thesis or one of the RoboBee papers.
Mizchief100 (author)  Ben Finio1 year ago
Interesting stuff, yeah the tapering of the wing structure is a great idea. I'll draw up a new one with a thinner bottom and side edge but maintain the stronger axle to mount it. I looked back at Cornell's videos and can definitely see a lot more bend when theirs flaps versus mine.
You also might want to try wings with veins made out of carbon fiber rods with a thin plastic film (search for Mylar or Kapton) as a membrane. 3D printing the whole thing is kind of a cool novelty, but carbon fiber is much stronger and lighter than the plastic from consumer 3D printers. At a minimum, I would just print the veins and then stretch a membrane across them. You might be able to try Saran wrap if you don't want to order Mylar or Kapton - might require a couple layers so it doesn't tear.
Mizchief100 (author)  Ben Finio1 year ago
Yeah a film would make printing much easier for sure as well. I'll look into it. So just print the veins onto the plastic film? Sounds do-able, I'll draw some stuff up and look into it.
Not sure if you'll be able to print directly onto the plastic film - that will depend on the printer (e.g. could you stretch film over the print platform then expect the extruded plastic to stick? not sure). If not, you can always print the membrane first then stretch the film over it, using a SMALL amount of glue or adhesive to bond around the perimeter (don't want to add too much weight to the wing).
Mizchief100 (author)  Ben Finio1 year ago
I'll test both. I think I'm also going to try printing the frame onto the stretched out saran wrap, perhaps the hot plastic would bond more easily than with glue. Should be interesting.
You could try use some light tissue to infill the wing and to increase it's strength, soak the tissue in ABS juice so when it dissolves, it'll reinforce the tissue nicely and bond it to the wing. That could cut the weight even more for you.
Kiteman1 year ago
To test the lift capability, attach the bottom of the thread toa weight sitting on a scale - the lift will show as a drop in weight.

I would also be tempted to remove the bottom part of the frame around the wing. This would let the skin of the wing flex more, changing the angle of attack, and (hopefully) generating more lift.
Mizchief100 (author)  Kiteman1 year ago
Good ideas for testing thanks! Yeah I'm drawing up some more wings right now, hopefully I'll be able to make them soon and let you guys know how it goes.

Any other weight reduction ideas?
I would try tapering the thickness of thd frameas well, make it thinner near the bottom. That might need careful sanding if you are near the limit of printing thinly.

Not only would that be lighter, but it would allow thd lower part of the wing to flex more as well.

Otherwise, look to nature for lighter wings - bird bones have an air-filled structure. Try printing with gaps in the structure, or CNC milling from a foamed material.
While I haven't had a chance to attempt this build yet, from watching your video my first suggestion would be to shorten the stroke of your wings. They seemed to be colliding with each other, in which case your losing a lot of energy and stability that could be directed towards lift instead. Secondly, you might try tapering your wings, thickest at the top, thin at the bottom. This should allow for a little more flexibility as they flap and generate more upward force rather than side to side. Just my thoughts from my experiences. Good luck with the project, hope to see it flying soon.
Mizchief100 (author)  tschnizlein1 year ago
Yeah the clicking noise made me think they touched too but I tried putting paper between the wings and there wasn't any contact with it. I think it might be rubbing the frame a bit though... But thanks, good ideas!
he3r01 year ago
that is what i was wondering too... IMHO pointless instructable if it aint working (good material for blog), though interesting design.
Mizchief100 (author)  he3r01 year ago
It get's people thinking and they can give me new ideas.
eng_Andy1 year ago
If you want to upload STEP files of your designs here, I think you can try putting them in a .Zip or .RAR archive, as I've seen compressed archive files on some other instructables.
Mizchief100 (author)  eng_Andy1 year ago
Cool I'll give it a try.
I only see flopping and no flying. Am I missing something?
That's what I saw too. Is there an explanation?
Mizchief100 (author)  dgateley1 year ago
Yep, this project so far is my first two test trail versions. I have designs for a third version that will be much closer to the weight of Cornell's robot but I'm not sure when I will be able to print it so I thought I would get some ideas while I waited.
Got it. Following along to see how it goes. I don't think passive control has a prayer of working but I'd love to be wrong.
farabide1 year ago
Great idea:
CanI suggest a hanging balance for testing (like a wide baby's mobile) and removing most of the bottom of the wing section, leaving the outer curve and a point for more of an analogue sweep (made up term but i like it) and greater downdraft.
I love the vertical crank - very elegant :)
Mizchief100 (author)  farabide1 year ago
Cool stuff, the baby's mobile might work! I'll see if it has enough tension but thanks for the ideas.
nomasfilms1 year ago
Your work is wonderful! If I could offer a suggestion, I would ditch the 3D printing of the wing surface, and use a thin plastic film which I would glue to your frame. The lightest RC models in the world do just that. See here: http://www.indoorduration.com/indoordurationlinks.htm

Also, varying the wings frame thickness might get you a little more flex in your trailing edge, as mentioned before. Great work though... Any chance this device would fly for a few seconds on a supercapacitor? :-)
after observation i am presuming that the way this model acheives air flow from the flapping is from the wings flexing as they flap to create the air flow, the issue with your design is there is far to much rigidity in the wing, you should make a wing where the root is thick and it constantly gets thinner as it gets to the other end, this would allow rotational flexing but stop warping from the movement.
sitearm1 year ago
@Mizchief100; Fascinating! I had no idea this kind of work was being done. I've watched your video and looked up your Cornell link. Sharing with my friends now. Cheers! Site
Mizchief100 (author)  sitearm1 year ago
Thanks! Yeah the stuff Cornell and Harvard have been doing were just so cool I thought I'd give it a go! Fun stuff.
rimar20001 year ago
Great work!

Seeing the video I think you could make thinner the lower part of the wings's frame. So it would be a little more flexible, and will create greater air flow down.
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