9 ms·
Should Quadrotors All Look Like This?
- speeq 13y ago"The researchers explained that the standard "control" quadrotor had an optimized design, while the triquad was not optimized at all (because its design was constrained to keep it as similar as possible to the control quadrotor). This gave the control aircraft an advantage in power of about 9 percent." I wonder what the optimized "triquad" would have looked like?
- brianbreslin 13y agoIs there a video of this thing in action? I didn't see a link in the article (skimmed it quickly though)
- BrandonMarc 13y agoI can't find one, but these links may help: Dr Paul Pounds, the project leader: http://www.itee.uq.edu.au/bme/pounds http://www.itee.uq.edu.au/bme/pounds http://www.eng.yale.edu/pep5/ http://www.eng.yale.edu/pep5/ Scott Driessens, his student: http://www.youtube.com/user/sdriessens http://www.youtube.com/user/sdriessens
- kybernetyk 13y agoI always wondered why there are no "real life" sized quadcopters in use for manned flight. From what I understand the design is simpler and requires less maintenance compared to "normal" helicopters. Are there any reasons why we're not flying quadcopters around instead?
- kabouseng 13y agoI wouldn't say less maintenance, you've got 4 times as much motors running than a conventional helicopter.
- jamesaguilar 13y agoFor the hobby sized quads, it's simple enough to swap a motor. It is definitely easier to maintain since a spare is only 20 bucks and attaches in minutes with zip ties.
- kybernetyk 13y agoI'm by no way an expert on this topic. I just skimmed over the wikipedia article[1] where I read the following: > First, quadcopters do not require mechanical linkages to vary the rotor blade pitch angle as they spin. This simplifies the design and maintenance of the vehicle. As already mentioned I'm blatantly ignorant about this topic so it would be nice if someone who knows this stuff could chime in :) [1] http://en.wikipedia.org/wiki/Quadcopter http://en.wikipedia.org/wiki/Quadcopter
- lytfyre 13y agoThe advantage doesn't scale up well. small quadcopters basically speed up and slow down the motor itself to control how much lift is generated. As the size and weight of the blade increase, inertia makes that impractical, so you have to go to variable pitch for control.
- 2bluesc 13y agoLady Gaga flies with a hexacopter @ http://www.dailymail.co.uk/sciencetech/article-2499954/How-Lady-Gagas-flying-dress-works.html http://www.dailymail.co.uk/sciencetech/article-2499954/How-L... ... what the world is coming to?
- pygy_ 13y agoMorning coffee, this put a big smile on my face. She (or, probably, her team) has been hacking the entertainment scene for a while. Dubbing "a dress" what would otherwise be considered a nerd toy is genius. What's not a dress for her?
- sanoli 13y agoShe will also fly with Virgin Galactic: http://www.vanityfair.com/online/oscars/2013/11/lady-gaga-first-to-sing-space http://www.vanityfair.com/online/oscars/2013/11/lady-gaga-fi...
- exDM69 13y ago> I always wondered why there are no "real life" sized quadcopters in use for manned flight. The explanation is simple: quadrotor physics do not scale up. The rotational inertia of the rotors is proportional to the length of the rotor blade to the fifth power. Double the rotor blade length and the inertia of that rotor goes up by a factor of 32. High inertia rotors are not suitable for quadrocopter because fast changes in the rotation of the rotors required for maneuvering them. Having one big rotor for lift and three (or more) small ones for control is a very good idea. Another idea that is being researched is having multiple quadrotor copters flying in co-operation.
- rpenm 13y agoThe moment of inertia for a uniform rod pivoting on end is (1/3)ML^2 where M is mass and L is length. Assuming mass scales with length, inertia should be proportional to the third power. Where am I wrong?
- exDM69 13y agoMass is not linearly proportional to length, because a longer rotor needs to be a lot heavier to be structurally sound. A uniform rod is not a good analog for a rotor blade. It's not a far fetched idea to think that the mass is cubically or at least quadratically proportional to the length of the rotor. Unfortunately I can't remember the source where I saw the 5th power figure. In addition, the aerodynamics of a rotor don't scale up linearly either.
- barrkel 13y agoYour assumption is way too simple. Mass increases with the cube of the scale, while cross section area increases with the square of the scale. The cross section will need to increase to cope with the extra mass, and that in turn will increase the mass itself, and this mass is specifically the rotating mass.
- kashkhan 13y agothere are :) human powered at least: http://www.youtube.com/watch?v=syJq10EQkog http://www.youtube.com/watch?v=syJq10EQkog
- Zigurd 13y agoThere was some crazy man/scammer building a manned flying thing with six snowmobile engines powering six rotors. I remember this because I was working for Ray Ozzie at the time and he was telling people in the office about it because he had invested in it.
- rsl7 13y agoMoller?
- Zigurd 13y agoYeah! That's the guy! HOly moley moller.com still exists. EDIT: Wow, this has been going on since the '70s: http://www.downside.com/scams/moller/ http://www.downside.com/scams/moller/ The name "Discojet" is way more badass name than "Skycar." Just another sign of lowered expectations.
- Pxtl 13y agoYeah, the Moller Skycar has been an impressively long-running scam. It felt like he got his own article in Popular Mechanics on an annual basis. I wonder how much damage he does to the nascent industry if personal flying vehicles by sucking all the oxygen out of the room.
- bambax 13y agoIt takes (at least) six months to learn to fly a helicopter (or, in the case of the linked video from the article, probably a lifetime). It takes ten minutes to learn to fly a quadcopter.
- nakedrobot2 13y agoNo. Try a cheap quadcopter without any auto stabilization. it takes more than 10 minutes. Maybe 8-12 hours of flying time to become proficient enough to, say, risk mounting something breakable (like a camera) onto it. Less time than a normal helicopter though, so I get your point.
- bambax 13y agoI have two quadcopters -- that both have auto stabilization: Parrot AR Drone and DJI Phantom, and it did take around 10 minutes to learn to fly them. Is it even possible to fly quadcopters without stabilization? Would they not start spinning out of control as soon as they take off?
- Sae5waip 13y agoHe probably means "stabilized using gyro and accelerometer" (ie, release sticks = evens itself out) as opposed to "just stabilized by gyros" (ie, release sticks, copter stops any rotation but keeps pitched/rolled position). Sure, learning to hover in one general spot is doable in 10 minutes. I wouldn't call that "learning to fly". What about very basic maneuvers like landings (no bouncing around, no dropping from too high, and at the spot where you wanted to land) or circles/eights, dealing with ambiguous orientations when your copter is high enough (~ 6m ?), nose-in flying / dealing with control reversal and recovering from orientation loss?
- krasin 13y agoWhat software should I use to verify their claims? aerodynamics simulators or how they are called?
- shitlord 13y agoDid anyone else watch the linked video of the RC helicopter? It was amazing! I had no idea that those things were so powerful. The only ones I've ever seen are the ones at the mall.
- kabouseng 13y agoIs the helicopter in the video under manual control, or some kind of control system preprogrammed manuever?
- jamesaguilar 13y agoIt's under manual control. The tricks are performed by adjusting the trim on the blades to invert lift.
- kabouseng 13y agoThanks.
- BrandonMarc 13y agoAgreed. I was impressed by the RC pilot's skill, and noted the craft's behavior was, at times, very insect-like. Or hummingbird. ... and I couldn't help but think, if a life-size helicopter were even capable of such maneuvers, its human occupants would likely die from the G forces. Clearly such maneuvers seem only possible in an unmanned craft.
- h4rrison 13y agoA cursory glance around the internet suggests that these things are capable of 20G manoeuvres (!), far in excess of the human maximum of 5-10G (depending on axis of acceleration). http://en.wikipedia.org/wiki/G-force#Human_tolerance_of_g-force http://en.wikipedia.org/wiki/G-force#Human_tolerance_of_g-fo...
- Zimahl 13y ago
- zobzu 13y agoThat's kinda stupid garage-scienticism to be honest. - TFA does not mention the stability issue. Guess why people and drones fly tri, quads, etc and not regular helis. Yeah. (a simplification: stand on one leg. Now stand on 2, and use your 2 hands as well. 4 legs. Stable heh?) - Yes single large prop is more efficient than many tiny props. But put many large props and the difference isn't so big. Let's take a $1000 ultra efficient quad: www.youtube.com/watch?v=t0SR5bzuFq4 yeah thats 100min of flight time for something smaller than the Align Trex of the video. And it's cheaper too.. The trex flies 5 to 10minutes (6S 5000mah). At equivalent batteries, the trex flies 25min (hint: the trex is not made for efficiency, it's made for 3D). An average camera-less quad flies 10 to 15min (3S 3000mah). - TFA compares a $5000 Align Trex 700 with a bunch of expensive upgrades - the top of the top - with one very good pilot with decades of training... to a $200 toy. - $200 toys made of wood and plastic flown by random people are actually pretty good at acro. Why? Because being more stable they're much easier to fly. Ex: http://www.youtube.com/watch?v=qzu5eSZqKpY http://www.youtube.com/watch?v=qzu5eSZqKpY http://www.youtube.com/watch?v=8QP0QjIsTTM http://www.youtube.com/watch?v=8QP0QjIsTTM So yeah. Not exactly impressed when that's coming from a university. I expected much better.
- h4rrison 13y agoAgreed, though the one leg analogy would more accurately be hanging from one arm, since the lift is provided from above.
- jlgreco 13y agoEhhh... that sounds like an example of the rocket pendulum fallacy: http://en.wikipedia.org/wiki/Pendulum_rocket_fallacy http://en.wikipedia.org/wiki/Pendulum_rocket_fallacy Maybe there is something more complicated going on with helicopters that I am not aware of, but a helicopter would not be an inherently stable system due to it "hanging" from the rotor because the direction the rotors are providing thrust changes (all other things being equal), when the helicopter starts to tip one direction.
- h4rrison 13y ago
- marvin 13y agoThis is really cool, and probably a better solution than quadcopters for many applications. However, what we would ideally want in the end, would be a tilt-rotor of some sort which incorporates wings. Fixed wings are a lot more efficient than active lift, and is necessary if you want to squeeze more speed and range out of your UAV.
- Pxtl 13y agoSo, like, a remote-controlled Osprey?
- neya 13y agoWow, readers, please do yourselves a favor and watch the linked video in that article! [https://www.youtube.com/watch?v=p8t41avFuCc https://www.youtube.com/watch?v=p8t41avFuCc] though it's slightly WTf-y, it's definitely cool. I'm just wondering - Are heli's better at carrying my Canon DSLR or would the triquad work better for this?? Anyone with experience, please suggest, as I am SO gonna build this tri quad (and integrate it with my Raspberry Pi) :D
- fijter 13y agoA heli carrying a DSLR is big, expensive, hard to fly, dangerous and maintenance intensive. It's good for lifting a DSLR but I would go with a multicopter, the more blades the better. A hexacopter or even an octocopter are very stable, easier to fly, possibly cheaper to build and have a fail-safe, if a motor fails you can land it safely because the other motors take over. You can find a nice video about the subject here: http://flitetest.com/articles/T_Rex_800E_DSLR_Camera_Gimbal http://flitetest.com/articles/T_Rex_800E_DSLR_Camera_Gimbal It demo's a Heli carying a DSLR and afterwards (after the first 7 minutes of video) they talk about this compared to multi-rotors. For the best video results you should probably pick the stable octocopter, you can fly FPV as well with a multicopter, great for live previewing your video.
- neya 13y agoThanks! That's pretty informative! :)
- Dave_Rosenthal 13y agoFor any interested HN'ers: Though quads are much more trendy in the tech world today, as you can see from that video, plain-old RC helicopters are pretty amazing today. The biggest advance in the hobby IMHO has been the development of very small (~1oz) RC helicopters (e.g. [http://www.bladehelis.com/Products/Default.aspx?ProdID=BLH3300] http://www.bladehelis.com/Products/Default.aspx?ProdID=BLH33...) that include the same fundamental control system (called collective-pitch) that enables these large (~10 lbs) helicopters to be so acrobatic. The size shrink brings huge benefits: Small helis basically don't get damaged in most crashes, they mostly can't hurt you, and they are cheap. Today's super-stabilized and gps-locked quads are like a modern AAA game: you press "A" over and over and watch them go, and say "Wow!". A micro collective-pitch heli is like an old-school game--you're going to need a lot of restarts, but is great fun and will provide many hours/months of challenge.
- CraigJPerry 13y agoHow does this perform cross wind compared to a traditional micro quad? That main rotor will act like an umbrella does in a gust of wind. The micro quads don't suffer the same problem. I'm not sure of the physics involved (and if anyone knows i'd love to learn more!) but just from hands-on piloting both micro quads and larger helis, the micro quads are some of the least susceptible to cross winds i've ever flown.
- loup-vaillant 13y agoAccelerometers are bound to detect such adverse effects. Correcting roll and pitch automatically shouldn't be hard. Also, I would guess that the higher the main rotor (compared to the centre of mass), the more susceptible the device. So, if you build the main rotor as close to possible as the centre of mass, you should have a more neutral design. While we're at it, I've flown a little toy with two main rotors, rotating in opposite directions, controlling power and yaw, while the tail rotor controlled pitch (the whole thing was auto-stable, so there was no need for roll control). It worked like a charm. So, if we're willing to suffer the complexity of an actual swashplate[1], we could try a design with 2 main rotors, one above, and one below, hereby getting a neutral, manoeuvrable, and (hopefully) efficient design. [1]: https://en.wikipedia.org/wiki/Swashplate_%28helicopter%29 https://en.wikipedia.org/wiki/Swashplate_%28helicopter%29
- CraigJPerry 13y agoAIUI there's all sorts of considerations & trade-offs. E.g. the motors have a limit to how quickly they can change output (up to around 400Hz today). Because there's no swashplate on the upper rotor of those wee co-axial rotor designs, they're really ineffective in cross wind. You can't apply the required corrective input when the top rotor gets blown off axis.
- loup-vaillant 13y agoThe design I was thinking about puts the lowest rotor below the gravity centre. First, it would lower the highest rotor, and second, crosswind would have the opposite effect on the low rotor. I really expect such a design to be neutral.
- rplst8 13y agoI for one welcome our new...
- deleted 13y ago[deleted]
- jwr 13y agoI really like this, because it shows that quadrotor (and flying vessel in general) research is far from "done". Most people would tell you that you'd be insane to try to design new types of aircraft, because we already know how to do that. This research proves otherwise.
- Gravityloss 13y agoOne might almost say that anybody knowing basics of Newtonian mechanics would say maximizing your blade swept area reduces power needed to stay aloft. Then there's stuff like tip vortices etc. So just one big rotor is great. The problem becomes control. With many small rotors you don't need to control blade pitch, as the electric motors have high torque and the blades are light, so you can control with quick engine thrust changes. And it's that what makes the quad rotor system much more attractive than a normal helo. The traditional helicopter pitch control system is complex and requires precise high stress components that are well built and maintained. But it's a very inelegant brute force system in my opinion. The pitch control could be improved a lot as well if you have powerful electromagnetics with very precise control. You still need a tail rotor though. The real helicopter is seeing some real progress at the moment as well, all in the name of higher speeds. There's Sikorsky's X2 and AVX's modified Kiowa. They have coaxial main rotors with a pushing tail rotor and two pushing fans respectively. Then there's tilt rotors by Bell and Boeing, IIRC. These were, at least at some point, all part of a US scout helicopter competition. And then there's the Eurocopter X3, with no tail rotor but twin pulling rotors like a twin prop airplane. X2 and X3 have flown.