I sat down and made a sketch after i got the idea of making a full-size Y6 with an APM2.5 and Arducopter firmware :)
A MC like seat and maybe an Samsung Galaxy Tab 2 running AndroPilot or Droidplanner on the dashboard. Or maybe even Mission Planner. Just make a mission and go for a ride :)
This is the frame for the enignes and this will be covered by a Carbon fiber body.
I guess there will be some hard-core calculations for engine dimensions, weight and propellers. But imagine how cool it will be to ride this Air-Scooter in Stabilize or other modes!! Maybe this is an idea for a Kickstarter prosject??? I would love to start the building and testing of this future scooter! :-)
Comments
@Gary McCray: Thank you for your kind words. Poles and zeros, my friend. It's all about transfer function and feedback. Larger inertial moments might seem like stability when in fact they create issues for correction and induce control oscillation potential.
You're right about the messy transition envelope of ground effect. I dare say nobody has seen that like I have with a 27' diameter virtual disk of overlapping rotors 5' high. I did that to get as much lifting area as possible in a compact space in deference to Dr. Leishman's overlapping performance predictions. All the pundits say that ground effect gives you a virtual increase in Cl without raising Cd, but if the resulting correlated AoA is above the stall angle, the blade WILL stall. Put a highly loaded blade within a foot of the ground...and variable pitch is the only answer.
@Brad Hughey, I stand corrected Brad and can appreciate that a muticopter with a centered mass would be relatively neutral in what is essentially a fly by wire system resulting in fastest possible control scenario.
But on reviewing Dr. Paul Pounds paper again, interpreted that he moved it away from the rotor plane because while it was most sensitive it was also most error prone right at that point.
From what I understand moving the COG below the rotor plane decreases sensitivity, increases stability and makes the system response more sluggish (pendulum effect perhaps) while raising the COG above it increases sensitivity, decreases stability and requires faster response input.
For a fully fly by wire system (multicopter), it would seem that system response speed including electronic (sensor and computational) and mechanical (rotor acceleration / thrust change rate) would actually determine the ideal relationship between COG and rotor thrust center for maximum control and responsiveness.
I would also suggest that beyond that, the extremely messy change from ground effect to free flight would be especially awful for the design submitted with it's initial ducted thrust column sitting practically on the ground.
I don't know, maybe my analysis is off, but it did seem to me to be consistent with Paul Pounds paper (which I have also used for inspiration since you first introduced it to me several months ago.)
In any case, Brad I totally defer to you, you understand prop and basic multirotor vehicle dynamics better than anyone else I know.
yea, i think the way of doing these would be with gas and variable pitch and a helicopter type blades, not multirotor ones.
@Gary McCray: I am honored by your words of support, but Dan Wilson is correct. The overhead rotor has everything to do with "packaging" of the disk area, which needs to be large in order to have any hope of a reasonable flight duration. This is especially true for electric power, which is at least 10 times worse than gasoline for energy-to-mass ratio. Having the center of mass substantially away from the lifting plane is actually worse for stability, as is well-documented in the scientific literature. Dr. Paul Pounds (formerly of Yale) has a paper which describes this phenomenon fairly well. His conclusion was that the CG should be slightly above the lifting plane for best control dynamics.
http://eprints.qut.edu.au/33767/1/33767.pdf
@Carles Gelada: Any blade with enough mass to impart gyroscopic stability would be unsuitable for a variable speed control scheme. If you start throwing in the complexities (read: infinitely more failure modes) of variable pitch, you might as well power it with gas.
@Tommy Larson: As mentioned before in my previous screeds, low disk loading is essential for reasonable flight durations, no matter the power source. A scooter-type design with the thrusters near the ground practically prohibits a large lifting area.
I think that the stabilization would be not such a problem as the people was saying. Some one said that the helicopters were so stable because of the pendulum momentum, which is just a minor factor on the stabilitzation.
The main factor is the gyroscopic momentum, the prove is on the rc helicopters, i am sure you have seen them flying perfectly upside down.
( where the pendulum momentum is applying force to turn the helicopter )
So my conclusion is that with a " heavy " blades, these scooter would be pretty stable. And really cool.
what the giroscopic momentum does is a force of mantaining the attitude proportional to the mass and he rotating speed of these.
Sorry for my poor english.
@Gary McCray: Any notion of pendulum like stability in these vehicles is a fallacy. Further, assuming this design is ducted, a higher CG with respect to the CP is actually highly beneficial to avoid ram drag/momentum drag reaction torques.
I really don't think that electric would be the way to go with something like this... For starters, you'd have to build and program a battery monitor with the sole purpose of making sure the batteries discharge evenly so one of them doesn't explode. Then there's the fact that the energy density of a battery is nowhere near the energy density of gas, which is ok for helis, fine for quads, but for anything of this size, it's horrible. Notice the abundance of gas cars, and not electric ones ;P The sheer amount of weight would cause problems with getting enough lift. Plus, for the amount of money you'd spend on electric motor, batteries, etc... you could buy a car engine. I think you'd need a gas engine for this project..... and a parachute system ;P
Also, forgot to mention, you'll need much wider blades to provide any reasonable amount of A) Lift and B) Control and stability. Still, it would look absolutely epic in flight ;)
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