19 ms·

Underactuated Rotor for Simple Micro Air Vehicles

253 points by command_tab 12y ago

command_tab 12y ago
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"?
- FrankenPC 12y ago
  That's what I was thinking. That would require electrical motor control of the blades. Maybe turbine generator for power source. I would imagine this kind of pulsing would cause severe fatigue on the parts if they scale up too large.
  - TaylorAlexander 12y ago
    The parts will cycle back and forth exactly as much as they would in a traditional helicopter, and there are fewer comparatively small parts. It would likely be stronger and more fatigue resistant than current methods of controlling blade pitch. We can program the motor to change torque as smoothly as we want.
- sliken 12y ago
  So nimble? Looks barely flyable. Compare the video to a quadrotor for instance.
- marvin 12y ago
  Electric motors remove a lot of the complexity in powered-lift flying machines. As soon as your power/endurance requirements demand a combustion engine, you also have to manage the complexity of a piston engine or turbine (jet) engine. This means either including a crankshaft and optionally a system of gears to route the rotational power along the axes you want the rotation in, or ducting the output of a jet turbine in some way that drives the rotors. In addition, there are different limitations with regards to the time required for a given change in RPM as compared to an electrical motor. My impression is that a lot of the complexity in conventional helicopters (and flying machines in general) stems from the limitations of combustion engines. There's a reason that you very rarely see vectored thrust in conventional airplanes, for example. Of course, if batteries and electric motors become sufficiently powerful, this changes the dynamic and it will become possible to design electric aircraft that re-evaluate the traditional design restrictions. This is one of the reasons that the rapid progress of electric cars is so exciting.
  - sebastianavina 12y ago
    or you can generate electricity with a combustion engine a move two electric motors... like the railroads
    - ansible 12y ago
      I don't think a hybrid like what you suggest is practical. Locomotives need lots and lots of torque at zero and low speeds. This would otherwise necessitate a huge transmission. Plus, the weight penalty for a train locomotive isn't nearly as severe as it is for any kind of flying craft. Other commenters have mentioned a hybrid system, with a relatively small electric motor that generates just the instantaneous torque changes needed for the control system, but the majority of the power is supplied via direct mechanical linkage as in today's helicopters. That might be viable, but I'm not sure. The weight and complexity penalty for the old control scheme isn't so bad when scaled up, but is really bad when scaled down. So a hybrid scheme (like in a Prius) might be practical, by my estimation.
- wiredfool 12y ago
  Probably not, for the same reason that a quadcopter doesn't really scale to full size. The inertia effects of larger rotors make changing the speed of the rotors within a rotation much harder. With full sized helis, it takes a long time to spin up the rotors to speed before the pitch is changed to take off.
  - TaylorAlexander 12y ago
    Well the critical difference here is that changing blade speed is not needed or desired. They just need to change blade torque, which would apparently immediately cause a change in blade pitch. I don't see a specific reason why this wouldn't scale. I do wonder what changes in load do to the system though. If it can't handle changing loads without messing up the blade dynamics, it would only work for fixed payload systems like camera platforms.
    - erobbins 12y ago
      It won't scale because of inertia. Rapidly changing the speed/torque of a large combustion engine is nearly impossible. It's a great solution for reducing mechanical complexity in mini/micro sized UAVs, though.
      - prbuckley 12y ago
        I don't think scaling this up is a question of inertia it is more a question of weither a material exists that can be used in those flexural joints with much higher loads. This is a material science question. A material may exist that has the right combination of flex, strength and lets also not forget durability. I am a mechanical engineer and crack propagation and cycle fatigue would be a major concern for a joint like that at large loads. There are all kinds of amazing tricks material scientists know how to play to combat these types of problem. I think this could be scaled up if material to make those flexure joints exist.
        TaylorAlexander 12y ago
        The joints looked like simple pivots, not flex joints. See how the blade is attached at a 45 degree angle? I think it just pivots there.
- ajuc 12y ago
  Big rotor = big moment of inertia = more energy lost on accelerating it and slowing it down each time. At some point it's better to rotate it at constant velocity and change pitch independently.
  - TaylorAlexander 12y ago
    You're not worried about speeding up the blades, just changing the torque on the drive system. The inertia of the blades actually helps you here.
- foobarian 12y ago
  It would probably work but I'm guessing the overhead of the extra actuators is much smaller at full size, so this may not be as helpful as at small sizes.
- prbuckley 12y ago
  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-segway-of-airplanes/?no-ist 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 https://www.youtube.com/watch?v=U-3Ql7G7qRc
  - prbuckley 12y ago
    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 http://www.innovator.mosquito.net.nz/mbbs2/mosquito.asp
- usrusr 12y ago
  The complexity of the conventional helicopter method is not only providing control, but also a considerable amount of safety by enabling autogyro capability. This lack of autogyro is already restricting the quadrocopter setup to "let it crash" dimensions and the same well be true for this admittedly very clever duocopter.
DickingAround 12y ago
I wonder if this will cause some parts of the motor to heat up more; since the blade is 1:1 rotations with the motor then driving more torque (power) during certain phases of the cycle will put more watts on certain coils. It's a cool idea. Human size helicopters would love to avoid all that blade-pitch complexity. :)
- theoh 12y ago
  Couldn't that be addressed (if a large enough effect to be a problem) by just having the body of the vehicle spin at a low rate, like less that 1Hz. With appropriate sensors this wouldn't be a problem[1]. More to the point, there shouldn't be any need for sustained constant "cyclic" input anyway, in normal maneuvering. [1] an axially-symmetric imaging system could compensate easily, e.g. a panoramic system.
alimoeeny 12y ago
The whole thing looks great and all. But I specially liked their last sentence that said "for civilian needs".
zan2434 12y ago
This is so clever! Turning mechanical control problems into informational control problems is critical to the ubiquity of micro air vehicles.
- fasteddie31003 12y ago
  There is a lot of potential in solving mechanical problems with information systems, rather than using complicated mechanical solutions. For instance, hydraulic automatic transmissions and differential.
  - lumpypua 12y ago
    The mechanical solutions are always really interesting and clever, but digital systems are much more flexible. Really cool video on the mechanical ignition timing control in a delorean to control emissions. Explanation of ignition advance at the end: https://www.youtube.com/watch?v=ge1GwepqtK0 https://www.youtube.com/watch?v=ge1GwepqtK0
- swah 12y ago
  I have no idea what you're talking about.
  - Cushman 12y ago
    "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.
    - mrfusion 12y ago
      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?
joosters 12y ago
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?)
- TaylorAlexander 12y ago
  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.
aosmith 12y ago
Now if we could just start printing these parts at home...
- thisjepisje 12y ago
  What's stopping you?
- TaylorAlexander 12y ago
  I did printed helicopter blades three years ago: https://www.youtube.com/watch?v=qXlUSWrVzys https://www.youtube.com/watch?v=qXlUSWrVzys These other components look printable too. Right now I am making 3D printable robots that don't need any non-printed parts aside from motors, bearings, and drive belts (and batteries and electronics). So these definitely should be printable at home.
  - lucaspiller 12y ago
    That sounds cool, do you have any links to your projects?
    - TaylorAlexander 12y ago
      Thanks! Currently I'm working on delivering Flutter Wireless, which is at www.FlutterWireless.com. The 3D printed robots will be for some tutorials we will be launching. Other than that, I've been continually procrastinating about making a website for my personal projects, but I have a lot. If you dig through my youtube account at the original link, I have some other project videos there. Notable ones are: The robot I made when I was in High School: https://www.youtube.com/watch?v=8FJu1eL_dYs&list=UUxTluifYa_E5rO19RnGdtIw https://www.youtube.com/watch?v=8FJu1eL_dYs&list=UUxTluifYa_... An app to interface with some cheap helicopter joysticks (and not shown - I could fly the heli with an app on my phone). https://www.youtube.com/watch?v=gq2x3DVq7gs&list=UUxTluifYa_E5rO19RnGdtIw https://www.youtube.com/watch?v=gq2x3DVq7gs&list=UUxTluifYa_... Lighting a campfire with thermite: https://www.youtube.com/watch?v=7pu-R_IHirE&list=UUxTluifYa_E5rO19RnGdtIw https://www.youtube.com/watch?v=7pu-R_IHirE&list=UUxTluifYa_... A demo sketch I made for 3D printers: https://www.youtube.com/watch?v=KEH7Ji4a3Ss&list=UUxTluifYa_E5rO19RnGdtIw https://www.youtube.com/watch?v=KEH7Ji4a3Ss&list=UUxTluifYa_... The time I was on G4 TechTV: https://www.youtube.com/watch?v=J2R-TlBomnQ&list=UUxTluifYa_E5rO19RnGdtIw https://www.youtube.com/watch?v=J2R-TlBomnQ&list=UUxTluifYa_... My stuff on thingiverse. http://www.thingiverse.com/tlalexander/designs http://www.thingiverse.com/tlalexander/designs Not currently represented online are some of the robots I have made, the Tesla Coil I made when I was in High School, and the gas powered hovercraft I made in 8th grade. :)
aosmith 12y ago
Now if we could just start printing these parts at home...
aosmith 12y ago
Now if we could just start printing these parts at home...
lotsofmangos 12y ago
This is really cool. Would be interesting to see a configuration with two of them front and back, or a conventional tailrotor version.
paulftw 12y ago
Curious to see whether this system is robust enough for unpredictable outdoor breezes.
ww520 12y ago
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.
- vutekst 12y ago
  This always bothered me about Babylon 5 - how/why did the spine of the station remain stationary while the bulk of the station rotated?
mhandley 12y ago
This is such a neat idea, but I wonder if it suffers from vibration problems. Because the blades are mounted on pivots, whenever you've commanding differential pitch, the high angle-of-attack blade will incur more drag and so lag slightly more than the low angle-of-attack blade. Thus the blades won't be exactly opposite each other anymore, creating vibration. Perhaps the blades are spinning so fast this is not a big deal? Probably would be if you scaled up though.
- MadManE 12y ago
  Vibration only becomes a problem when the scales of the drag/lag and rotational frequency are similar. My gut feeling is that this will only happen when your lift-to-drag ratio is close to 1, so not in any meaningful case.
- logfromblammo 12y ago
  I don't think the force on the rotor would change direction fast enough to cause a vibration. It would be more like a constant push relative to the intended tilt, or a slowly spiraling wobble. I'm not a mechanical engineer, though.
emmanueloga_ 12y ago
Reminds me of PWM [1] on old PC speakers. Many old computers (e.g. of the 286 era) had a speaker that was only able to generate square tones. By controlling the start and duration of the pulses, programmers could generate sounds that were a lot more rich than what you would expect from "plain" square waves [2]. In a way this is similar: they start with two actuators that seem very limited in what they can accomplish: you can only speed them up and down. By modulating the speed of both motors in sync, they are able to control that cheap rotor mechanism they came up with, achieving 6DoF [3] 1: http://en.wikipedia.org/wiki/Pulse-width_modulation http://en.wikipedia.org/wiki/Pulse-width_modulation 2: https://www.youtube.com/watch?v=FSe3ysBrXq4 https://www.youtube.com/watch?v=FSe3ysBrXq4 3: http://en.wikipedia.org/wiki/Six_degrees_of_freedom http://en.wikipedia.org/wiki/Six_degrees_of_freedom

253 points by command_tab 12y ago

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"?

FrankenPC 12y ago
That's what I was thinking. That would require electrical motor control of the blades. Maybe turbine generator for power source. I would imagine this kind of pulsing would cause severe fatigue on the parts if they scale up too large.
- TaylorAlexander 12y ago
  The parts will cycle back and forth exactly as much as they would in a traditional helicopter, and there are fewer comparatively small parts. It would likely be stronger and more fatigue resistant than current methods of controlling blade pitch. We can program the motor to change torque as smoothly as we want.
sliken 12y ago
So nimble? Looks barely flyable. Compare the video to a quadrotor for instance.
marvin 12y ago
Electric motors remove a lot of the complexity in powered-lift flying machines. As soon as your power/endurance requirements demand a combustion engine, you also have to manage the complexity of a piston engine or turbine (jet) engine. This means either including a crankshaft and optionally a system of gears to route the rotational power along the axes you want the rotation in, or ducting the output of a jet turbine in some way that drives the rotors. In addition, there are different limitations with regards to the time required for a given change in RPM as compared to an electrical motor. My impression is that a lot of the complexity in conventional helicopters (and flying machines in general) stems from the limitations of combustion engines. There's a reason that you very rarely see vectored thrust in conventional airplanes, for example. Of course, if batteries and electric motors become sufficiently powerful, this changes the dynamic and it will become possible to design electric aircraft that re-evaluate the traditional design restrictions. This is one of the reasons that the rapid progress of electric cars is so exciting.
- sebastianavina 12y ago
  or you can generate electricity with a combustion engine a move two electric motors... like the railroads
  - ansible 12y ago
    I don't think a hybrid like what you suggest is practical. Locomotives need lots and lots of torque at zero and low speeds. This would otherwise necessitate a huge transmission. Plus, the weight penalty for a train locomotive isn't nearly as severe as it is for any kind of flying craft. Other commenters have mentioned a hybrid system, with a relatively small electric motor that generates just the instantaneous torque changes needed for the control system, but the majority of the power is supplied via direct mechanical linkage as in today's helicopters. That might be viable, but I'm not sure. The weight and complexity penalty for the old control scheme isn't so bad when scaled up, but is really bad when scaled down. So a hybrid scheme (like in a Prius) might be practical, by my estimation.
wiredfool 12y ago
Probably not, for the same reason that a quadcopter doesn't really scale to full size. The inertia effects of larger rotors make changing the speed of the rotors within a rotation much harder. With full sized helis, it takes a long time to spin up the rotors to speed before the pitch is changed to take off.
- TaylorAlexander 12y ago
  Well the critical difference here is that changing blade speed is not needed or desired. They just need to change blade torque, which would apparently immediately cause a change in blade pitch. I don't see a specific reason why this wouldn't scale. I do wonder what changes in load do to the system though. If it can't handle changing loads without messing up the blade dynamics, it would only work for fixed payload systems like camera platforms.
  - erobbins 12y ago
    It won't scale because of inertia. Rapidly changing the speed/torque of a large combustion engine is nearly impossible. It's a great solution for reducing mechanical complexity in mini/micro sized UAVs, though.
    - prbuckley 12y ago
      I don't think scaling this up is a question of inertia it is more a question of weither a material exists that can be used in those flexural joints with much higher loads. This is a material science question. A material may exist that has the right combination of flex, strength and lets also not forget durability. I am a mechanical engineer and crack propagation and cycle fatigue would be a major concern for a joint like that at large loads. There are all kinds of amazing tricks material scientists know how to play to combat these types of problem. I think this could be scaled up if material to make those flexure joints exist.
      - TaylorAlexander 12y ago
        The joints looked like simple pivots, not flex joints. See how the blade is attached at a 45 degree angle? I think it just pivots there.
ajuc 12y ago
Big rotor = big moment of inertia = more energy lost on accelerating it and slowing it down each time. At some point it's better to rotate it at constant velocity and change pitch independently.
- TaylorAlexander 12y ago
  You're not worried about speeding up the blades, just changing the torque on the drive system. The inertia of the blades actually helps you here.
foobarian 12y ago
It would probably work but I'm guessing the overhead of the extra actuators is much smaller at full size, so this may not be as helpful as at small sizes.
prbuckley 12y ago
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-segway-of-airplanes/?no-ist 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 https://www.youtube.com/watch?v=U-3Ql7G7qRc
- prbuckley 12y ago
  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 http://www.innovator.mosquito.net.nz/mbbs2/mosquito.asp
usrusr 12y ago
The complexity of the conventional helicopter method is not only providing control, but also a considerable amount of safety by enabling autogyro capability. This lack of autogyro is already restricting the quadrocopter setup to "let it crash" dimensions and the same well be true for this admittedly very clever duocopter.

DickingAround 12y ago

I wonder if this will cause some parts of the motor to heat up more; since the blade is 1:1 rotations with the motor then driving more torque (power) during certain phases of the cycle will put more watts on certain coils. It's a cool idea. Human size helicopters would love to avoid all that blade-pitch complexity. :)

theoh 12y ago
Couldn't that be addressed (if a large enough effect to be a problem) by just having the body of the vehicle spin at a low rate, like less that 1Hz. With appropriate sensors this wouldn't be a problem[1]. More to the point, there shouldn't be any need for sustained constant "cyclic" input anyway, in normal maneuvering. [1] an axially-symmetric imaging system could compensate easily, e.g. a panoramic system.

alimoeeny 12y ago

The whole thing looks great and all. But I specially liked their last sentence that said "for civilian needs".

zan2434 12y ago

This is so clever! Turning mechanical control problems into informational control problems is critical to the ubiquity of micro air vehicles.

fasteddie31003 12y ago
There is a lot of potential in solving mechanical problems with information systems, rather than using complicated mechanical solutions. For instance, hydraulic automatic transmissions and differential.
- lumpypua 12y ago
  The mechanical solutions are always really interesting and clever, but digital systems are much more flexible. Really cool video on the mechanical ignition timing control in a delorean to control emissions. Explanation of ignition advance at the end: https://www.youtube.com/watch?v=ge1GwepqtK0 https://www.youtube.com/watch?v=ge1GwepqtK0
swah 12y ago
I have no idea what you're talking about.
- Cushman 12y ago
  "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.
  - mrfusion 12y ago
    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?

joosters 12y ago

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?)

TaylorAlexander 12y ago
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.

aosmith 12y ago

Now if we could just start printing these parts at home...

thisjepisje 12y ago
What's stopping you?
TaylorAlexander 12y ago
I did printed helicopter blades three years ago: https://www.youtube.com/watch?v=qXlUSWrVzys https://www.youtube.com/watch?v=qXlUSWrVzys These other components look printable too. Right now I am making 3D printable robots that don't need any non-printed parts aside from motors, bearings, and drive belts (and batteries and electronics). So these definitely should be printable at home.
- lucaspiller 12y ago
  That sounds cool, do you have any links to your projects?
  - TaylorAlexander 12y ago
    Thanks! Currently I'm working on delivering Flutter Wireless, which is at www.FlutterWireless.com. The 3D printed robots will be for some tutorials we will be launching. Other than that, I've been continually procrastinating about making a website for my personal projects, but I have a lot. If you dig through my youtube account at the original link, I have some other project videos there. Notable ones are: The robot I made when I was in High School: https://www.youtube.com/watch?v=8FJu1eL_dYs&list=UUxTluifYa_E5rO19RnGdtIw https://www.youtube.com/watch?v=8FJu1eL_dYs&list=UUxTluifYa_... An app to interface with some cheap helicopter joysticks (and not shown - I could fly the heli with an app on my phone). https://www.youtube.com/watch?v=gq2x3DVq7gs&list=UUxTluifYa_E5rO19RnGdtIw https://www.youtube.com/watch?v=gq2x3DVq7gs&list=UUxTluifYa_... Lighting a campfire with thermite: https://www.youtube.com/watch?v=7pu-R_IHirE&list=UUxTluifYa_E5rO19RnGdtIw https://www.youtube.com/watch?v=7pu-R_IHirE&list=UUxTluifYa_... A demo sketch I made for 3D printers: https://www.youtube.com/watch?v=KEH7Ji4a3Ss&list=UUxTluifYa_E5rO19RnGdtIw https://www.youtube.com/watch?v=KEH7Ji4a3Ss&list=UUxTluifYa_... The time I was on G4 TechTV: https://www.youtube.com/watch?v=J2R-TlBomnQ&list=UUxTluifYa_E5rO19RnGdtIw https://www.youtube.com/watch?v=J2R-TlBomnQ&list=UUxTluifYa_... My stuff on thingiverse. http://www.thingiverse.com/tlalexander/designs http://www.thingiverse.com/tlalexander/designs Not currently represented online are some of the robots I have made, the Tesla Coil I made when I was in High School, and the gas powered hovercraft I made in 8th grade. :)

aosmith 12y ago

Now if we could just start printing these parts at home...

aosmith 12y ago

Now if we could just start printing these parts at home...

lotsofmangos 12y ago

This is really cool. Would be interesting to see a configuration with two of them front and back, or a conventional tailrotor version.

paulftw 12y ago

Curious to see whether this system is robust enough for unpredictable outdoor breezes.

ww520 12y ago

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.

vutekst 12y ago
This always bothered me about Babylon 5 - how/why did the spine of the station remain stationary while the bulk of the station rotated?

mhandley 12y ago

This is such a neat idea, but I wonder if it suffers from vibration problems. Because the blades are mounted on pivots, whenever you've commanding differential pitch, the high angle-of-attack blade will incur more drag and so lag slightly more than the low angle-of-attack blade. Thus the blades won't be exactly opposite each other anymore, creating vibration. Perhaps the blades are spinning so fast this is not a big deal? Probably would be if you scaled up though.

MadManE 12y ago
Vibration only becomes a problem when the scales of the drag/lag and rotational frequency are similar. My gut feeling is that this will only happen when your lift-to-drag ratio is close to 1, so not in any meaningful case.
logfromblammo 12y ago
I don't think the force on the rotor would change direction fast enough to cause a vibration. It would be more like a constant push relative to the intended tilt, or a slowly spiraling wobble. I'm not a mechanical engineer, though.

emmanueloga_ 12y ago

Reminds me of PWM [1] on old PC speakers. Many old computers (e.g. of the 286 era) had a speaker that was only able to generate square tones. By controlling the start and duration of the pulses, programmers could generate sounds that were a lot more rich than what you would expect from "plain" square waves [2]. In a way this is similar: they start with two actuators that seem very limited in what they can accomplish: you can only speed them up and down. By modulating the speed of both motors in sync, they are able to control that cheap rotor mechanism they came up with, achieving 6DoF [3] 1: http://en.wikipedia.org/wiki/Pulse-width_modulation http://en.wikipedia.org/wiki/Pulse-width_modulation 2: https://www.youtube.com/watch?v=FSe3ysBrXq4 https://www.youtube.com/watch?v=FSe3ysBrXq4 3: http://en.wikipedia.org/wiki/Six_degrees_of_freedom http://en.wikipedia.org/wiki/Six_degrees_of_freedom