[HN Gopher] Flexible Monocopter Drone Can Be Completely Rolled Up
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Flexible Monocopter Drone Can Be Completely Rolled Up
Author : YeGoblynQueenne
Score : 168 points
Date : 2021-11-15 08:48 UTC (14 hours ago)
(HTM) web link (spectrum.ieee.org)
(TXT) w3m dump (spectrum.ieee.org)
| mirekrusin wrote:
| Great idea. Wouldn't it be more stable with two rotor-wings?
| usrusr wrote:
| Symmetry would ruin the self-stabilizing autogyro descent on
| unexpected power down.
| Kaibeezy wrote:
| Would it? Aren't most autogyros 2-blade? Multi-blade
| helicopters also use autorotation for emergency landings.
| usrusr wrote:
| Helicopter autogyro requires deliberate control input. This
| one enters self-stabilizing autogyro when control input
| stops at any given operational state.
| moffkalast wrote:
| That does not fly in the way I initially presumed it does.
| BasilPH wrote:
| I would never have thought of something flying like that. It's
| a nice reminder for me that we don't know what we don't know.
| cutemonster wrote:
| I also thought the small propeller would point upwards
| (rather than to the side).
|
| Now afterwards it feels so obvious.
|
| First i thought, but the propeller, it's so small
|
| Turns out the whole thing was the propeller :-)
| usrusr wrote:
| > The total weight of F-SAM is just 69g, of which nearly 40% is
| battery, yielding a flight time of about 16 minutes.
|
| Nice to see mechanical performance qualities (battery mass
| percentage), and battery/aerodynamic performance qualities
| (minutes per mass percentage) condensed to such a small set of
| numbers. Unfortunately battery and aerodynamic qualities aren't
| really separable, but if we assume batteries to be a constant
| between designs (they are all generic off-the-shelf parts after
| all) "minutes per mass percentage" becomes a quite interesting
| metric.
| netgusto wrote:
| Amazing tech. Combined with a fast fixed cam it would maybe be
| possible to get a 360 degree FOV.
| usrusr wrote:
| A line scanner, like the proposed LIDAR implemention. We use
| line scanners for paper. You could certainly put a line scanner
| behind a conventional lens but it would feel kind of weird to
| "waste" an entire dimension of the lenses projection qualities.
| Would there be opportunities for design compromises favoring
| one direction over the other? (I'm thinking of the weird eyes
| we find in flight animals like sheep that need full horizon
| perception more than point of interest focus)
| [deleted]
| bvm wrote:
| what a beautiful piece of engineering, its flight seems
| so...biological.
| [deleted]
| londons_explore wrote:
| I tried to do a similar thing with a single actuator frisbee. The
| goal would be a frisbee with a single fin could fly anywhere when
| launched out of some high power launcher.
|
| The goal was to make a single-use aircraft which could go
| anywhere in a city for under $1. By making the aircraft unpowered
| and under 250g, lots of regulations no longer apply, and it
| becomes practical to use them to deliver small items.
|
| The fin was actuated by a 10 cent microcontroller using a ultra
| low cost GPS and light sensor (for sun position), powered for up
| to 2 minutes by a coin cell.
|
| The challenge was that it seems gyroscopic effects means that if
| a frisbee has lift and moves forward in the air, it will always
| see a (very slow) turning moment that requires a massive fin to
| counteract. The end result is the frisbee eventually turns to
| vertical and falls out of the air.
|
| My prototype could still land gently anywhere in a football field
| when thrown by hand, which I was pretty pleased with, and had a
| BOM under $1!
|
| If anyone has any ideas to make this not happen, I'd like to hear
| them.
| 0x0203 wrote:
| I'd love to see your setup and how you attached the fin. I've
| thought of doing something similar, but instead of a fin, I
| figured the easiest way to steer the frisbee would be to bend
| the disc either up or down. Depending on spin direction this
| should, at least according to my theory, gently steer it left
| or right. A single actuator mounted to the center of the disc,
| pushing or pulling on two points on the bottom lip would be all
| it should take. Intuitively I think this might also eliminate
| the effects of the asymmetric lift torque since it could
| continually bias which side of the disc has more lift based on
| speed, rotation frequency, and angle to keep it balanced.
| icegreentea2 wrote:
| If by vertical you mean that the frisbee has rotated so the
| disc is perpendicular to the ground, that effect is actually
| aerodynamic, not gyroscopic. It comes from imbalance of lift
| due to two halves of the disc see different relative airspeeds.
|
| In competitive disc sports this is usually mitigated by adding
| more spin (to add more moment of inertia in the spin axis to
| gyroscopically resist the turn), and by releasing the disc with
| the advancing edge pointed down to extend the period before it
| over rotates.
|
| If this is what you were talking about, then you should be able
| to just make the disc more edge heavy to try to counter act
| that. Or maybe you can try to someone add more drag to the
| forward spinning edge. Presumably if you have a single fin,
| that fin will usually be at the 6 o'clock position (from top
| view). Assuming we have a forward moving disc rotating clock
| wise (from top view), and the fin is at 6 oclock, then the
| forward rotating edge would be at 9 oclock. If you had a second
| fin (or some other type of feature) basically mounted at 9
| oclock (so at 90 degrees relative to your main steering fin),
| then it should always spoil that air... might be able to use
| that to somewhat counter act the rotation.
|
| However, if you were actually talking about the gyroscopic
| effect (trying to rotate a spinning disc along it's axis
| pointing in the forward direction should cause a torque in its
| pitch axis)... I don't really know how to deal with that.
| londons_explore wrote:
| I was talking about the fact that the center of lift is ahead
| of the center of mass of a circularly symmetric wing with
| positive lift. [1]
|
| That force would normally cause an aircraft to 'pitch up'
| (and hence planes have tail's and carefully balanced weight
| to stop this happening). In a frisbee, the gyroscopic effect
| means that this 'pitch up' force actually translates into a
| 'roll right' motion. By making the rim heavier, you can make
| this happen slower, but as far as I can see, you can never
| eliminate it entirely.
|
| My fin is on the outer edge of the disc, spinning with it, so
| it can oscillate at ~50Hz to get independant roll and pitch
| control, while also being able to trade off loss of angular
| momentum vs lift. It also has the benefit that it can be made
| from cardboard in a single pressing with the disc with no
| glue or assembly labor.
|
| [1]: http://ffden-2.phys.uaf.edu/645fall2003_web.dir/Mike_Abr
| ams/...
| icegreentea2 wrote:
| Ah hm. I wonder which one of our two effects is dominant. I
| can see that your explanation must plainly exist - it's
| just not part of the standard "intuitive" model taught to
| frisbee players.
|
| That's a really clever fin design.
|
| If the dominant component of rotation was due to the center
| of pressure being ahead of the center of mass, could you to
| use timing of the fin being in a "high drag" configuration
| to pull the time averaged center of pressure back towards
| to the center of mass?
| londons_explore wrote:
| > could you to use timing [...] back towards to the
| center of mass?
|
| Yes, but sadly the effect isn't large enough until you
| end up with a very large fin and a very powerful actuator
| to move it. That difficulty is what made me put the
| project on the backburner for now.
| tyingq wrote:
| Sounds like something the military would like. Cheap way to see
| if anyone is behind a barrier in front of you.
| fvdessen wrote:
| It folds into a small storage tube, is lightweight, has good
| autonomy, makes little noise, and safely autogyrates to the
| ground on failure. If you could somehow add a camera and
| stabilise it, it could make an excellent search drone for search
| / rescue / military ops.
| 14 wrote:
| What would be the advantage over existing drone technologies?
| Look at these autonomous drones [0]that can fly through the
| forest at high speeds. High speed, highly maneuverable and can
| hold other equipment like a camera. [0]
| https://electronics360.globalspec.com/article/17357/video-fl...
| ebawho44 wrote:
| And there are already relatively cheap commercial offerings
| with very impressive collision avoidance and path planning
| (www.skydio.com)
| Kaibeezy wrote:
| Cheap. Not every mission requires a stable camera.
| tshaddox wrote:
| If you don't need stable hovering or tricky maneuvering, a
| traditional airplane design is almost certainly going to be
| even cheaper.
| adfm wrote:
| Since it folds into a cylindrical shape, it's easier to
| transport and could potentially be fired off from something
| like a grenade launcher. It's the computer vision and shaped
| charge that I'd worry about.
| wnkrshm wrote:
| The first thing I thought of was a single-'wing' maple seed [0].
|
| https://www.researchgate.net/figure/The-Samarai-MAV-design-i...
| trhway wrote:
| The first maple seed inspired 100+ years ago
| https://en.wikipedia.org/wiki/Monocopter
| wnkrshm wrote:
| Interesting and thanks for sharing, I also ran into another
| design that is maple-seed like in terms of aerodynamics.
| Sadly this is one of the cases where human ingenuity is
| misdirected and is still causing harm today:
|
| The BLU-43 Dragontooth mine [0][1] and the Soviet PFM-1 [2]
| which still are responsible for children losing limbs in
| Vietnam, Laos, Cambodia and Afghanistan.
|
| The BLU-43 came with a chemical deactivation mechanism but of
| course that failed in a subset of dispersed mines. The PFM-1
| in Afghanistan came without a deactivation mechanism, the
| later PFM-1S had one.
|
| [0] https://en.wikipedia.org/wiki/BLU-43_Dragontooth
|
| [1] https://johnryle.com/?article=the-invisible-enemy
|
| [2] http://www.one-step-
| beyond.de/en/countries/afghanistan/mines...
|
| Edit: formatting
| robbedpeter wrote:
| https://youtu.be/n_q_DD_4LNg
|
| In action, neat flying mechanism!
| jack_riminton wrote:
| I wonder if you attached a 360 camera whether the footage could
| be stabilised or 'fixed'
| Kaibeezy wrote:
| Not all images must be video. With a rotation of only 5Hz, fast
| shutter speeds should produce clear snapshots.
| [deleted]
| ls15 wrote:
| It looks dangerous, but awesome.
| dustintrex wrote:
| The whole thing weighs 69g, meaning that the kinetic energy
| even when rotating at full speed is quite low. You'd still want
| to avoid getting your eyes in its way tho.
| tromp wrote:
| If you added a vertically oriented 1-dimensional camera, i.e. a
| single column of pixel sensors, then it could automatically
| extend that into 360 degree video.
| magicalhippo wrote:
| The ones used in barcode scanners have quite a high refresh
| rate (100kHz IIRC) so that could be doable.
|
| Mounted on a hinge in a kind of ! shape with a weight at the
| end (hinge at left, sensor then weight at bottom right), it
| could perhaps capture at an angle in self-stabilizing manner,
| ie independent of the tilt of the main body.
| alexvoda wrote:
| Don't these cameras require to be stabilized? You only have one
| column of pixels so you can not correctly align the columns
| through stitching (as in panorama mode on phones).
|
| As impressive as the stabilization used is that these dromes
| manage to hover in roughy the same spot (instead of drifting
| everywhere), I do not believe it will be sufficient for a
| rotating line camera.
| ncmncm wrote:
| The column images can be tagged with samples from an onboard
| gyro and compass. The stitcher does not need to rely only on
| the pixels themselves. Normally the next pass will be
| pointing a little higher or lower, so such annotations will
| be essential.
| michaelmior wrote:
| I don't know how well it would work, but I think you could
| still perform alignment using a single column assuming that
| you would expect to see patches with the same color connected
| together more often than not. Especially if you're trying to
| do video since then you can also exploit temporal coherency
| (meaning that you expect many objects to be stable over
| time). I'm sure in my head it's much simpler than practice,
| but it seems like it is achievable at least in theory.
|
| Sounds like a very fun problem for computer vision researcher
| to work on. Probably not terribly difficult to generate a
| bunch of test data from existing 360 cameras by downsampling.
| thenewwazoo wrote:
| It spins at ~5 Hz. 5 fps isn't great, but this is a cool idea.
| phire wrote:
| Use 6 of them, each facing at 60 degree angles. That would
| give you 6 updates per spin, for ~30hz video.
| jcun4128 wrote:
| that would be cool, then you could do your visual inertial
| odometry stuff with that data, even if low quality might be
| like working with IR
| jcun4128 wrote:
| I guess it's using thrust to control cyclic? Fast pulse to pitch
| up/turn opposite way and then minimum throttle to stay airborn
| keeps it level?
| aclatuts wrote:
| I wonder if it could be even better and lighter with carbon fiber
| instead of basla wood.
| gillesjacobs wrote:
| Carbon fiber is much more difficult to iterate on though. Using
| accessible and cheap materials is beneficial for adoption by
| hobbyists or other researcher.
| dotancohen wrote:
| Probably not by much. Balsa wood is extremely light, cheap, and
| easy to form into a wing. It is also easily repairable.
|
| The real weight savings would probably come from the motor -
| and a carbon fiber casing might work here instead of the
| presumably steel casing currently in use. And though shaving
| weight off the wing would almost certainly move the center of
| mass further outwards, shaving the mass off the motor would
| move it further in. That might be detrimental, though, as the
| motor needs some leverage on the COM for this design.
|
| This is a terrific project that invalidates many traditional
| ideas that we have about flying machines.
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