Team prepares quarter-scale drone for takeoff.

From the Local Motors blog, a report from the first bench testing of the 1/4 scale prototype of the Airbus Cargo Drone Challenge winner, which will debut at the Commercial UAV Expo in Las Vegas next month. That's me at right (with safety glasses)

Two months ago our co-creation community was drawing sketches on napkins to determine wing taper ratios and materials for what would ultimately become a finished cargo drone. The build has now progressed to the point that Local Motors and Airbus engineers have completed scale models and experimental test flights.

The nose cone, fuselage, tail boom and several other parts of the full-scale Zelator-28 are nearing completion.

Pre-epoxy full-scale build.

The experimental quarter-scale model took flight this past weekend in Henderson, Nev. Local Motors engineers and Jon Daniels of Praxis Aerospace Concepts International (PACI) teamed with Chris Anderson of 3D Robotics (3DR) on the integration and demonstration of his flight control system for vertical take-off and transitional forward flight, known as PX4. Anderson’s flight system served as an interface for the motors, speed controllers and servomechanisms.

The test model completed a hover and touchdown, but a few mechanical issues prevented forward flight. The experiment was very beneficial to the build team, however, as it helped identify potential failure modes before stepping up to the full scale aircraft.

“They are simple fixes for the most part. There was a hardware conflict with the servos and an issue with the motor pods in the quarter-scale model,” said Local Motors engineer Alex Palmer.  “[The quarter-scale model] has a different attachment design than the full scale so that issue will resolve itself.”

The team is now focused on completing two full-scale models of the Zelator-28 that should be ready for flight testing in the next two weeks. Airbus engineers are planning to join the team for the first flights of the prototype. There are still active discussions on the project page for the co-creation community to provide ideas and feedback pertaining to wing design and the landing gear. Make your mark on the present and future of unmanned aerial vehicles by getting in on the discussion.

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Comment by JB on October 16, 2016 at 9:28pm

Geometry is one thing, structural stability and oscillation is quite another. There is no reason to put the quad motors on the wings, where the lever arm and torque moment are largest and requires substantial stiffening of the wings and fuselage. The quad motors are literally trying to "un-screw" themselves from the fuselage. It makes it prone to poor yaw control and vibrations at various harmonics that in turn leads to premature component failure (like 3D printed structural parts ie motor mounts).

There is also no reason to have the motors so far from the fuselage in the first place (lack of roll control is typically a non-issue with QP), a h-quad layout resolves all of this with negligible aerodynamic impact for forward flight, if "designed" correctly. We've tested this to be true, by good ole' fashioned DIY tinkering, no CAD or 3DSMax rendering required. 

Wing and quad motor positioning can also be a bit more "dynamic" depending on the aircraft attitude required in hover or forward flight. Likewise quad motor tilt needs to be explored as well to achieve aerodynamic stability in hover, which is harder to do with the current frame layout shown. Variable payload COG also needs to be addressed somehow as a QP is fairly COG sensitive (read single quad motors can be operating at WOT for extended periods to maintain attitude and overheat).

If forward motor windmilling is "still" an issue that is looking to be resolved, then there is a significant gap in understanding the operations of a quadplane, especially in wind, that needs to be dealt with first. Hint: the forward motor isn't just there to hang around, blowing in the breeze, whilst the quad motors "do their thing". ;-)

The forward motor is essential in operating in wind for position hold, without it no quad plane (that I have seen to date) can maintain position for long without something failing, typically motor/ESC/battery. If one thinks of a QP as a airborne hovercraft with extra altitude then the flying principles are simplified. If done right the problem actually becomes how to get the thing to descend, as low speed quad attitude control with high wing AoA with forward motor make hovering in wind "very efficient", resulting in the QP only wanting to climb in over about 9m/s wind.

Strangely whilst trying to land, the thing that is most likely to cause a crash is a dead battery, because a QP simply doesn't want to land in wind (especially in 20m/s wind tests ;-) ). One can even try it in SITL to see the effect. Maybe also try the Arduplane QP code that has the forward motor position hold feature (amongst many others) to test?

Regards 

Comment by Fnoop on October 17, 2016 at 5:24am

Fascinating juxtaposition with the ardupilot stack, both technically and from a collaborative point of view:

http://discuss.ardupilot.org/t/canberrauav-outback-challenge-2016-d...

It's incredible that they were fixing bugs live in the competition and pushing those fixes out so their competitors could immediately benefit.  This is real collaboration, ingenuity and advancement of human knowledge, not the rendering exercise this post is about.  Shame dronecode is reinventing the wheel from scratch to essentially prevent open collaboration.

Comment by Rob_Lefebvre on October 17, 2016 at 5:41am

Yes, and this is why the performance and features of PX4 are so far behind, because the project does not foster open collaboration, and they aren't getting the same community participation.

Comment by JB on October 17, 2016 at 8:46am

Rob FYI.

We'll be releasing our Arduplane based OBC platform setup as for Christmas if you're interested in trying the "dark side" of VTOL quadplanes! (not being a heli VTOL!) 2.5kg airframe, 100km range, 20m/s cruise, or 15 minute hover, all from a 4S 10Ah pack. Shame I missed the last T3 deadline. Did you finally get your prize yet?  ;-)

Comment by Rob_Lefebvre on October 17, 2016 at 10:19am

Nope, never got the Solo RevB GPS.  I'll be hacking a Drotek M8N on top of it I guess.

Comment by Chris Moore on October 17, 2016 at 5:41pm

JB is right, Rob is right.  But why even give the input, almighty px4 stack can apparently fix poor engineering and overcome the huge ego of the new DroneCode. I honestly dont know how this thing would win a design contest, i dont see how this team could win a prize out of a claw machine. Me thinks that 2nd and 3rd place should have been funded as well. .

Comment by JB on October 17, 2016 at 10:59pm

Hey Rob that's a shame. You opted for a prize, for all you efforts, that will fix a faulty purchase from 3DR??  :-(

We've tried this M8N GPS with good results: http://www.banggood.com/Ublox-NEO-M8N-Flight-Controller-GPS-with-Pr...

-

Chris M

Personally, I think that Digital Prototyping (not rendering) is an expensive, time consuming endeavour, that typically only yields good modelling results after real world prototype testing...

I think the biggest engineering challenge with new systems is finding a viable way to test before production. For that it requires 3 things: 1) The right analytical skill set to design specific test prototypes before "production models" 2) The right test procedures and operational experience for the given platform - "unique" or "revolutionary" simply means it requires more testing to gain more experience, which in turn makes it less unique! 3) And lastly the right tools and principles (like the KISS principle) to engineer solutions for challenges highlighted through testing, in full understanding of the desired, and undesired goals. 

At some point "adding technological solutions" just ends up adding more problems resulting in a death spiral of diminishing returns.

In the extreme one could hypothesise; that in this case, a Quadplane VTOL UAV for parcel freight delivery, that is designed to allow direct, with minimum human labour/intervention, robotised delivery of global corporations "I've been told I need this, me want now" products, by whizzing them above our heads through the air, without public consensus or environmental concern, to our neighbour who "badly needs" delivery of some retail therapeutic mememePhone, so he can Tweet to the world about his latest purchase, which he paid for in worthless convertible debt notes (fiat money) issued by another private corporation called "the Fed", under a fallacy that we require currency to live, which we are taught by media and school from birth, that we must slave for all our lives to accumulate, with impunity, to achieve the "dream",  so that we can be "valued" by society as a success! The problems we have are systemic, and we are perpetuating them with crazy technological ideas to increase the efficiency of making money, which we don't actually need! ;-)

My point is that not all things that are developed by investment funding are good, and not all people are driven to develop technology (as tools to lever our will on the environment), only because they are chasing the money. Sharing is caring, even if you don't get a reward for your efforts. I think that is what "community" is all about.

Comment by Stmpngrnd on October 22, 2016 at 10:30am

maybe they should reverse engineer this..seems to be pretty flight worthy!!!

Comment by Chris Moore on October 22, 2016 at 11:13am

They problem is they looked at several good ideas and said, i like this one the best. What should be done is, lets develop 3 great alternatives, reward the innovation of the teams, and get great options from several areas.

Now theyve committed to one idea and its shown to be obviously deficient in its engineering, but theyre going to push it ahead and right over the cliff. 

If you wanted the community to play, put up the cash for more teams. Right now I see a team kicking an idea that needs a total revamp. If you had 3, or 5, or 10 teams you might have one flying by now.  You might not, but you will have 10 more options available to enhance the final design.

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