Developer

Just a normal day in the park

I just came across this one.

Disregarding all the usual concerns involved with manned flights of this type etc. I like the technical solution of using many self contained units, each with it's own battery, ESC, motor and propeller. Keeps it simple and adds redundancy at the same time.

• lots of mathematics involved, but for the doubting ones about multirotors manned flight check

http://www.e-volo.com/

• Here is a link to Dr. Pounds' excellent paper on the subject:

http://eprints.qut.edu.au/33767/1/33767.pdf

Based on rather rigorous mathematical analysis of quadrotor dynamics, his conclusion is "...the system exhibits an unstable oscillation when the CG is below the rotor, pure divergence when it is above the rotor, and neutral stability when coincident with the rotor." The only way conventional helicopters get away having such a pronounced under-slung mass is that they mechanically decouple the disk (tetering/flapping) and use variable pitch.

http://eprints.qut.edu.au/33767/1/33767.pdf
• Developer

I'm more impressed by this guy with his hoverboard, which is by design very instable, but looks well tuned :

Actually having the trust below and making it top heavy makes it more stable. It's a well known principle, and a big factor in what makes for example rockets work.

1955 - Hiller VZ-1 Pawnee - https://www.youtube.com/watch?v=7XzDMlhk4Sw

Hiller VZ-1 Pawnee
The Hiller VZ-1 Pawnee (U.S. Army designation; earlier Army designation: HO-1) was a unique direct-lift rotor aircraft, using contra-rotating ducted…
• Just for the record, I am convinced that commercialized manned electric multicopter flight isn't just possible - it is inevitable. I too applaud the intrepid souls who are pioneering this area. They are heralding the future. However, if you study the control dynamics, i.e. examine the various academic papers on the subject (Dr. Pounds, et al.) and plot the transfer function poles and zeros, you'll find that the getting the disk loading low enough for practical flight times is directly at odds with increasing blade radius and having thrust response fast enough to maintain stability. My conclusion is that practical manned-scale electric multicopters cannot be done without variable pitch blades.

• it is very interesting to see such dedicated individuals. so much of labour and money. I would suggest that you put dummy load in place of live human being and trim/tune the aircraft with RC. also suggested is that toy tether the aircraft with ropes so it doesn't strays beyond a safety envelope until it is finely tuned.

• What I'm surprized is the location chosen, so close to trees...

Also this type of testing should require a special firmware that will put an altitude limit (like 1 meter, it's just for testing). And just a 80 kg dummy onboard, not a human pilot.

There's a point in the video where he looks scared to jump too high. It made me think of the guy who wanted to show the world his proof of concept parachute by jumping from the Eiffel tower, and fell at free fall speed...

I'm more impressed by this guy with his hoverboard, which is by design very instable, but looks well tuned :

http://www.grindtv.com/random/man-sets-guinness-world-record-for-fa...

• Developer

Nice demonstration and congrats to the designers/builders.  It's definitely less scary to watch than that Y6 video a few months ago.

It's not ardupilot that's being used here but just for the record, obviously ardupilot is not meant for manned vehicles and we strongly discourage that.  For manned vehicles when designing failsafes, you obviously have to put some priority on saving the vehicle & pilot while for unmanned you're thinking about making sure the vehicle doesn't fall hard on someone.

• Brad: to me it looks like a typical hover in acro mode.  I bet the yaw performance is poor but overall it looks totally controllable.  I agree of course there's more to a manned multicopter than thrust but this seems like a pretty clever mechanical setup (and a less clever electric setup)

• Developer

I also suspect at that altitude he was in and out of ground effect, or at least still in turbulent air.

• Here's another example of the fact that there's more to a large-scale electric multicopter design than merely having enough thrust vectors to add together. The basic problem is rotational inertia, of both the propellers and the airframe. As Mr. Renteria was saying, having all that weight distributed so far from the control axes means that the control system cannot respond fast enough to keep the craft oriented. He got off the ground, but he appears to be floating at the whim of the local aerodynamic environment.