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Underactuated Rotor for Simple Micro Air Vehicles

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Re: Underactuated Rotor for Simple Micro Air Vehicles

#41

Post by TaylorAlexander »

joosters wrote: post #6

Very clever! I hadn't fully understood the mechanical complexities involved in a standard single-rotor helicopter. I just thought that they were hard to fly manually (which made me very confused to see all the computer-controlled quadrocopters - why didn't they use just one rotor?)

Well the issue isn't just that they're hard to fly or that they're mechanically complex - the issue is that they're both. So you crash often (when flying models) and crashes are expensive. This makes it a very expensive hobby.

The issue when flying is that they balance as if they are on a ball. You need to constantly adjust the controls to stop from "falling off the ball". Go the wrong direction and you speed up the rate at which it falls. When it is facing away from you, that's not very hard. When it is facing towards you everything is backwards. When you are turning, the correct direction to stay balanced is constantly changing.

Automated systems can do this automatically for you though, so a drone-like autopilot in a standard helicopter could make them as easy to fly as quadcopters. Traditional helicopters are still mechanically complex though. This system looks to fix that. And this would be more efficient than a multirotor.

Re: Underactuated Rotor for Simple Micro Air Vehicles

#42

Post by woah »

TaylorAlexander wrote: post #37
brk wrote: post #26

Earlier quoted context omitted.

Seriously, why? Injection molding has far lower cost, higher quality, and you're talking about things that are very cheap and easy to ship. What does 3D printing bring to this?

Injection molding is on the order of 10,000x more expensive if you only need a single part. I'm currently on a quest to design highly functional robots that can be made with just a 3D printer and a minimum of external parts - so far only bearings, motors, drive belts, batteries and electronics are the non-printed parts needed. I make everything so that it fits together by interlocking or with minimal use of some coar…

Seems to me that the worst part of 3d printed stuff is "the grain" is there any way to fix that?

Re: Underactuated Rotor for Simple Micro Air Vehicles

#43

Post by durkie »

woah wrote: post #42
TaylorAlexander wrote: post #37

Earlier quoted context omitted.

Injection molding is on the order of 10,000x more expensive if you only need a single part. I'm currently on a quest to design highly functional robots that can be made with just a 3D printer and a minimum of external parts - so far only bearings, motors, drive belts, batteries and electronics are the non-printed parts needed. I make everything so that it fits together by interlocking or with minimal use of some coar…

Seems to me that the worst part of 3d printed stuff is "the grain" is there any way to fix that?

i was about to propose some sort of annealing process like they do with metals, and it seems like someone has already beaten me to it: http://3dprint.com/3388/study-how-to-make-3d-prints-stronger...

as a side note, this looks like kind of a cool way to smooth pla prints, for which up till now there wasn't really a great option.

Re: Underactuated Rotor for Simple Micro Air Vehicles

#44

Post by prbuckley »

command_tab wrote: post #2

This thing is so nimble in the air yet has a fraction of the complexity of a regular helicopter. I wonder if this method will scale up to "full size"?

Depending on what you mean by scaling up. There have been single man vertical take off and landing (VTOL) vehicles that have two rotors and require no variable pitch for directional control so they are even simpler then the system in this video since the 1950's! The first such vehicle was the Hiller VZ-1, dubbed the "Flying Platform". If you are in the bay area you can go check a real one out at the Hiller Aviation museum next to the san carlos airbort (30 minutes south of sf). Or enjoy watching this video...

http://www.smithsonianmag.com/videos/category/history/the-se...

Directional control is achieved by leaning, the gyroscopic forces from the dual rotating blades creates inherent stability without any feedback system. They are like segways of the sky. Reports say it only took 20 minutes for a non pilot to learn how to fly it. These machines are incrdible and I don't understand why more hasn't been done with them.

A late 1970's version called the williams x jet WASP added a cruise missle turbojet for more horsepower, and was coined the "flying pulpit".

https://www.youtube.com/watch?v=U-3Ql7G7qRc

Re: Underactuated Rotor for Simple Micro Air Vehicles

#45

Post by prbuckley »

prbuckley wrote: post #44
command_tab wrote: post #2

This thing is so nimble in the air yet has a fraction of the complexity of a regular helicopter. I wonder if this method will scale up to "full size"?

Depending on what you mean by scaling up. There have been single man vertical take off and landing (VTOL) vehicles that have two rotors and require no variable pitch for directional control so they are even simpler then the system in this video since the 1950's! The first such vehicle was the Hiller VZ-1, dubbed the "Flying Platform". If you are in the bay area you can go check a real one out at the Hiller Aviation m…

As an aside I think a vehicle like this could be developed today and fall under the FAA ultralight powered vehicle classification (weighing less then 254 pounds and carrying less then 5 gallons of fuel). This classification doesn't require you to have a pilots license!

People here might also be interested in the Mosquito Air helicopter as well. It falls into this ultralight classification and is a kit you can build in 200-300 hours. It costs about $30,000...

http://www.innovator.mosquito.net.nz/mbbs2/mosquito.asp

Re: Underactuated Rotor for Simple Micro Air Vehicles

#46

Post by mrfusion »

Cushman wrote: post #24
swah wrote: post #22

Earlier quoted context omitted.

I have no idea what you're talking about.

"The linkage to change the pitch of this rotating blade is way too complex! Can we simplify it somehow?" "How about we just add a simple device that associates the pitch of the blade with the torque, and let a computer figure out how to spin the motor to get the pitch we want? No linkage!" Yeah, that is dang clever.

I'm still not getting it. Wouldn't the pitch of the two sides be the same so how would that be useful? How do you control the pitch of two blades with a single motor?

Re: Underactuated Rotor for Simple Micro Air Vehicles

#47

Post by ww520 »

At first viewing of the video I didn't understand why the body doesn't spin around with one rotor and a pair of blades. That was some magic! Then looked at the picture again and saw another rotor underneath. Pretty neat to have two rotors counteracting each other.

Re: Underactuated Rotor for Simple Micro Air Vehicles

#48

Post by vutekst »

ww520 wrote: post #47

At first viewing of the video I didn't understand why the body doesn't spin around with one rotor and a pair of blades. That was some magic! Then looked at the picture again and saw another rotor underneath. Pretty neat to have two rotors counteracting each other.

This always bothered me about Babylon 5 - how/why did the spine of the station remain stationary while the bulk of the station rotated?

Re: Underactuated Rotor for Simple Micro Air Vehicles

#49

Post by lnanek2 »

mrfusion wrote: post #46
Cushman wrote: post #24

Earlier quoted context omitted.

"The linkage to change the pitch of this rotating blade is way too complex! Can we simplify it somehow?" "How about we just add a simple device that associates the pitch of the blade with the torque, and let a computer figure out how to spin the motor to get the pitch we want? No linkage!" Yeah, that is dang clever.

I'm still not getting it. Wouldn't the pitch of the two sides be the same so how would that be useful? How do you control the pitch of two blades with a single motor?

Didn't you read the article and watch the video? There is a sinusoidal signal added (i.e. up and down) that matches the rotation of the blades and controls the hinges on the blades. So the signal can be high when the blade is on one side of the vehicle then low when the blade is on the other side. Or vice-a-versa if the control system wants to go the other way. Both blades tilt the desired direction when they are on the desired side of the vehicle. The video is quite good and shows the blades hinging different directions on different sides when the signal is applied.

Re: Underactuated Rotor for Simple Micro Air Vehicles

#50

Post by mhb »

mrfusion wrote: post #46
Cushman wrote: post #24

Earlier quoted context omitted.

"The linkage to change the pitch of this rotating blade is way too complex! Can we simplify it somehow?" "How about we just add a simple device that associates the pitch of the blade with the torque, and let a computer figure out how to spin the motor to get the pitch we want? No linkage!" Yeah, that is dang clever.

I'm still not getting it. Wouldn't the pitch of the two sides be the same so how would that be useful? How do you control the pitch of two blades with a single motor?

There are two motors.
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