Flight tests with the UAV DevBoard

After my last UAV project went up in flames (literally!) I’ve shifted gears and designed a dedicated autopilot (AP) test vehicle. She is a tailless plane with removable wings for transportation and has plenty of room in the fuselage with easy access.

For the autopilot, I’m using Bill’s UAV DevBoard with a modified AileronAssist code for handling the elevons. This modification is a work in progress by Ben Levitt and he is including a lot of great features. You can check out the latest versions of the code here. The tailless had her first autonomous flights this weekend and I’ll be posting all of the flight logs on this blog. So far, I’m really pleased with the AP’s performance. Not only does the DevBoard and software perform well, but Bill also provides a wealth of information on the theory of his methods as well as the “how to” to get the hardware and software installed and running. I know this is beginning to sound like a commercial for Bill’s stuff but if you do a search on this website, you’ll find nothing but praise for Bill and his accomplishments. And to top it all off, he’s always willing to immediately chime in and help whoever asks for assistance.

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  • Hi Bryan ,
    I am having trouble with setting up UDB in my wing.. Can you please shed some light ,,THe details are below..
    I have setup UDB on my new platform (Wing)..It’s a 36” tail less foam wing. I am facing below issue. Anyone who has already ventured into this setup. I know Bryan has done a lot in this and I hope this email reaches him too. I have attached my option.h file to review. I am using old R141..Below are other details.

    Tx-Rx :- Futaba 9Cap + R129 DP Rx.

    Ch1 Rx as aileron goes to ch 1 input to UDB

    Ch2 Rx as Elevator.. goes to ch 2 input to UDB

    Ch3 is direct to ESC…

    Ch6 Rx goes to CH4 input to UDB

    Tx programmed as Elevons.. All controls works perfect..

    Manual flight is ok with the UDB setup, everything trimmed and ok..

    If I put the UDB in stab mode (after a GPS lock and a WAG) on the ground.. and if I do the test by tilting the aircraft , the controls behaves as it should.. Nose down , both the control surfaces go up , nose up they goes down.. If I tilt the aircraft on left (viewing from the cockpit) right aileron goes up-left goes down and if I tilt the aircraft on right the left aileron goes up-right goes down..

    SO I think the config and connections are proper.

    Now the issue is , after I takeoff in manual mode , I put the aircraft in stab mode (after doing some circles to achieve a yaw lock) the aircraft suddenly banks either on the left or right.. It’s uncertain. and eventually enters in to a roll and then dive..I tried initializing the same keeping the aircraft on a perfect level-motion less couple of times.. Reduced gains a lot but it still happens..

    I also tried putting the aircraft in stab mode with motor off just to eliminate the possibility of vibrations causing this but it’s the same.

    Just a note , I am using EM406 on this one since I have only one Ublox.

    Anyone who can flash something am I missing ? or doing wrong..
    My option.h file is attached..

    SID options.h
  • Cool! Thanks UFO_MAN.
  • Hi, I have posted my PWM "code" and the "schematic" for a wire cutter PWM controller i banged together under my blog in case anyone is interested in duplicating it. Basically its an Arduino with a FET. The FET is controlled by a PWM output. It will give you precise control of power with an analog input (e.g. a potmeter to control the power). It can also be modded to accept RS232 commands.

  • I work for a small, high tech, R&D company that develops mainly USV's. You got me on the power I use. I've never measured it, but go by how easily the wire cuts through a scrap piece of foam. That way, it's independent of wire length, wire gauge and material. If you hear a sizzle and the wire cuts like a hot knife through butter without even having to apply force, it's too hot. If it cuts (with force applied) slower than about 0.5 in/sec, it’s too cold. Sorry about the qualitative answer.
  • Bryan, back to the hot-wire, what voltage/current are you running for a 30 inch wing panel?
  • No problem. What is your day job, if I may ask?
  • Andy,
    We may end up using my blended wing design for a work project so I'd rather not give out CAD models or drawings. I will post pictures though when I make more progress.
    Let me know how your fuselage construction technique works out.
  • More great tips. I might try hot wiring yet... I use SolidWorks as well, and have been trying to get used to Alibre as a lower cost alternative, along with the CAM software. Are you interested in sharing any of your SW models so I can leverage them for my design? If not, I understand. We should keep in touch - maybe I can help you out with some CNC work.
  • Andy, I wish I had access to a CNC machine but all I have is the old school hot wire bow and variometer. I prefer 18 gauge stainless steel fishing leader to nichrome wire and I use either plastic laminate or 1mm thick Aluminum for templates. I would love to use carbon fiber in the fuselage and wings but I'm leery about the conductive effects on my transciever, Rx---. What I'm doing for my current fuse is designing in SolidWorks, shaping dense, extruded, blue foam with band saw, hot wire/templates and 50 grit sanding paper. Covered with a few layers of epoxy, waxed and used this male mold for fiberglass lay up. It sounds like your approach is easier.
    I've never dealt with flyingfoam.com but it's not hard to cut your own. Like anything else, just takes a little experimentation. You want to get the wire hot enough and the force on the bow set right so you end up with a cutting speed around two seconds/inch and angel hairs are produced. Sagging shouldn't be a problem with the span you want to cut. I like your idea of modularity: one fuselage with interchangeable wings.
  • Thanks for all the great feedback Bryan. I'm rethinking the battery location - it should probably be in front from a impact point of view too. That way, when I it crashes, the battery doesn't take out all the electronics. I'm also planning on an EPP nose cone...
    For the fuselage, I'm planning on CNCing the foam shape (after modeling to match the wings in CAD), cover with either glass or carbon (need to read about using antennas properly with carbon), bagging it, and melting out the foam.
    Is your foam cutting set-up using two templates or 4-axis CNC? I'm considering using flyingfoam.com for wings - any advice? I have a nice variable power supply and nichrome wire - so I've considered DIY wings, but for the sake of progress I should probably outsource the wings. I'm just wondering how tricky it is to get the wire temperature set right and cut without sagging. Also, with the EPP wings, I hope to only use the carbon tubes for spars and skip the need to glass the wings. I'm thinking a strong fuselage shell is key, and the wings can be replaceable/swappable as I experiment. I really like the modularity this whole approach brings, and the simplicity of just a wing.
    1984 hosting
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