I built a drone with only one motor [video]
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This is similar to but different than what the creator of the one motor drone is doing since he's spinning at higher RPM with the pitch varying under CPU control much faster than fixed wing aerobatic pilots who are controlling everything manually with insane skill. I assume the one motor drone guy already knows fixed wing RC VPP exist, just mentioning for others who might not.
Too many different things I want to play with and insufficient time in the day -.-
VPP and thrust vectoring are two separate elements which do different things. A variable pitch propeller can reverse the propeller from pulling the plane forward to pushing it backward. That's what enables diving toward the ground and almost instantly reversing to start going back up. Thrust vectoring dynamically changes the angle of the motor allowing the plane to turn in an even tighter radius than a large rudder can alone. The turn can be so tight it's less than the length of the plane, technically becoming a spin.
In fixed wing RC aerobatics, thrust vectoring (TV) isn't a feature of the motor itself, it's actually a feature of the mount the motor is attached to, which can pivot left/right ~20 deg. A rudder changes the direction of travel by pushing the tail to the left from the rear indirectly causing the nose to turn toward the right. A thrust vectored motor mount increases the rate of turn by also angling the motor to directly 'pull' the nose toward the new direction. In RC the angle is usually changed mechanically by extending the rudder servo control rod forward to the pivoting motor mount and reversing the connection point so the motor pulls the nose toward the opposite direction the rudder is pushing the tail.
As a 3D pilot looking at the video, Donatas is doing things which are wildly impressive and, if you don't know about VPP and thrust vectoring, look impossible. Before we even get into VPP and TV, the first amazing thing about the video is simply the airspeed. I fly very lightweight 3D planes and the video looks slo-mo even to me. That size of plane shouldn't be able to stay in the air moving that slowly. F3P indoor-only competition planes are hand-crafted insanely light from esoteric materials using clever engineering tricks to sustain torsional rigidity. They sweat over every gram to maximize the cubic wing loading.
Second, is the insane piloting skill on display. Carving those perfectly straight lines and precisely uniform arcs so slowly in such a small volume takes years of practice. That perfection is what F3P competitions judge. Last is leveraging the VPP stopping the the plane in midair and moving back upward. Keeping the plane perfectly vertical on that down line is already like balancing an ice pick on your fingertip. Stopping and moving up is next level. The video is probably from an exhibition as I don't think they fly VPP props in F3P competition since they're heavier and these guys even test the strength vs weight of dried glues to save tenths of grams.
Normally the plane would use control surfaces, this one uses thrust vectoring with only one item providing thrust. I do think the rudder moves though, but technically that is still redirecting the thrust (because otherwise they'd have to move the motor around).
Most variable pitch propellers use a swashplate (helicopters) or just a collective yoke (also helicopters, and acrobatic planes).
If I understand what op has done is to print a propeller with NO FIXED LINKAGE to control the propeller pitch, but instead lead or follow the inertia of the propeller by rapidly-adjusted motor rpm to induce variation in the angle of attack of the propeller.
I now realize I should have explained more in my original post, since there's some confusion between the what's unique about the experimental "One Motor Drone" (OMD) and more 'normal' VPP and thrust vectoring (TV), which are fairly unusual in RC but still common enough there are existing components and designs on the market which all work essentially the same way.
The OMD technically fits the definition of VPP and TV in that the propeller pitch varies and the thrust vectors but it accomplishes this in different ways and with very different trade-offs than the existing RC components, which I mentioned because they're still new-ish in RC aerobatics, unusual enough many RC pilots aren't familiar with them and provide interesting capabilities.
The flying is absolutely off the scale, that is unbelievable skill. The OMD is also impressive but it is very much a work in progress and I think it will be a while before we see fully control of the drone. But at least he has it stabilized.
F3P indoor planes typically use de-cased linear servos which are flat and tiny. Their control rods are made out of piano wire so thin, there's no way it would show up on video. F3P plane designers go to extremes of miniaturization and weight reduction. F3P isn't the corner of RC 3D aerobatics I play in but it's fun to look at photos of crazy F3P planes and the videos just look... wrong :-). https://www.youtube.com/watch?v=lXD6vbGVROw
Unlike the larger, more powerful rotary servos I typically use which need to be mounted near the plane's center of gravity to maintain balance, F3P esoteric, custom linears are so light they can mount them right next to surface they move. F3P seems largely Euro-centric, but there's a growing scene in NA (https://nsrca.us/index.php/flying/f3pindoorsequencesseparato...) and a sub on RCGroups https://www.rcgroups.com/indoor-pattern-f3p-373/.
These days, quads get all the attention (and blowback) but fixed wing is the OG RC. In recent years, meta-materials + SDR + open source have changed fixed wing dramatically, unlocking breakthroughs leading to some crazy extreme flight envelopes and many sub-specialties. There's dynamic soaring gliders which reach sustained speeds over 400mph from hand launch with no motor, cross country motorless gliders can go a hundred miles from launch, and long-range powered FPV (long range = >25 miles), though lately the first rule of LR-FPV Club is 'Don't talk about LR FPV Club' :-)
Personally, I find outdoor 3D aerobatics and slope soaring to both be extremely fun. Although my 3D aerobats are a bit larger than F3P (~ .8 - 1.2M), they are still very light and quite unlike most RC planes in unexpected ways. My planes can fly low, slow and so close I can just launch and catch them by hand. They are quiet, don't need much space and bother no one. Yet, unlike F3P planes, mine can fly outdoors whether in a large backyard, local park or even the beach. Heading into a hint of breeze, they can slow down until they're just stopped, hanging in the air (which looks odd), then zoom off in a blink at over 30 mph, and they keep flying in high winds that ground most RC planes (in fact, it gets even more fun if you have sufficient skill). Because they all have a thrust-to-weight ratio far above 1:1 they also have pretty insane flight envelopes enabling high-torque and high-G aerobatics far beyond the reach of any full-sized planes at airshows. Yet they only cost ~$50 to $200, take maybe 90 mins of my time to build, and can survive high-speed crashes that would turn most RC planes into confetti (the old joke in RC is they tell newbies who insist on starting with too fast and fragile of a plane, "bring a trash bag for all the pieces").
That all combines to make my corner of RC: fun, cheap, low stress and easy to start yet with endless depth to learn ever-cooler aerobatics. I love doing crazy aerobatics only 3 ft off the ground and 20 ft away yet if I 'dumb-thumb' the plane into the ground, it just bounces - or worst case it's a 5 min repair I can do on the spot while changing batteries. All thanks to cutting-edge materials, new motors, HV Lipos, and tiny servos with crazy high torque. It's also engineering-centric and nerd-friendly - so very unlike the vibe of "Your Dad's RC Plane Club." No balsa wood, gas engines or special flying field needed. My radio transmitter looks like an XBox controller yet is modular, runs open source firmware, BT connects to my phone, has SDR features and can be scripted with Lua. I learn new aerobatics with an open source 3D simulator on my laptop or in VR so I can slow down real-time as I learn.
Here's a 1M wingspan outdoor foamy mixing high-energy and low/slow 3D aerobatics: https://www.youtube.com/watch?v=vgkrVimII1E
The motors, ESCs, servos and materials get ridiculously small and light. You can get a sense of it on this forum: https://www.rcgroups.com/scratchbuilt-indoor-and-micro-model..., though it covers a wide range of small models, some of which the hardcore would consider obese. Here's a 4.9 gram, 8.5 inch wingspan RC airplane with color LEDs :-) https://www.youtube.com/watch?v=4OKrL8o22uE
Most robots have at least three motors, two drive sides and a weapon motor. The trick to getting away with one is integrating an impactor into the chassis of your bot, using the single wheel to spin up to ~3k RPM, then by tracking the rotation angle of the bot as it spins, you speed up a little while the wheel is pointing where you want to go, and slow it down a little when it's pointing the other direction.
You can run your cylinders in parallel, however that means whichever cylinder has its easiest time moving is going to capture a proportion more share of the power. If things are not perfectly balanced, which in reality they're never going to be, that means the cylinder that needs to work the hardest is going to work the least. And so it's going to take a huge amount of effort to control.
Alternatively, you can run your cylinders in series, however that means that if you're trying to feather one to move slow, all the others are going to have to move slower too.
You end up needing multiple pumps in order to make this work well, but pumps are rather expensive and so that's going to bring your costs up. Plus, multiple pumps mean that you're going to potentially want more power than your motor can deliver.
All the above can be solved with careful engineering. However, engineering is expensive too in order to get this right and it's going to take a lot of work.
I presume aircraft hydraulics must do something like that, as they have multiple moving parts under servo control (which must involve some clever valves).
they are not humanly pilotable without computers. they are inherently unstable.
>Not sure if it counts as under-actuated
You're referencing the fact that it's dynamically unstable, and thus needs to be stabilized with a computer. That's a different thing.
You can also have aircraft which are under-actuated yet are dynamically stable. One example is a parafoil, which achieves controlled flight using only two actuators (pull lines).
Inspires me to try and start doing some robotics.
I was fighting a lot of similar instability when making my drone only to realize that a software regression many versions prior had introduced a bug that made flying the drone next to impossible. After fixing that bug a whole pile of issues went away. Debugging that on a drone that does not fly is super hard because you never get to the point where you can properly observe what is going on. So improving the observability by doing that camera trick was just what was needed here.
The single motor does have the pretty major downside that it spins the moment it's in the air. I suspect a 2 motor drone with a tail motor would be a lot more practical. But I really like how mechanically simple the rotor hinge design is - it pushes all the complexity into the control algorithm.
https://hackaday.com/2020/06/25/building-and-flying-a-helico...
This kind of project is extremely rewarding. What's interesting here is how many things we did different. I used four servos and vanes in the airstream so that the whole thing would be mechanically as simple as possible, which makes this solution even more impressive to me (though I think mine is a lot more stable in flight judging by the video).
I think I went through 10 prototypes before the first one actually flew and #13 flies very well.
It is possible to get full control with just one motor and one control surface but not with offset payloads.
I have to wonder why this guy didn't give his drone a leash while testing so it couldn't go flying off. It's the first thing that popped into my head, so I'm sure it's something he thought of as well and didn't use for a good reason. Maybe a string would get caught in the blades?
I like how he built a test stand near 7:22, which solves the motor flying off problem and is probably easier to iterate on. It reminds me of how rockets are tested.
https://www.youtube.com/watch?v=K0POjjIC5xs
It does use a bunch of external sensors but the control is all with just the prop and rapid speed changes, they don't even use a variable pitch prop.
Quadcopters that are designed for 45 min to 1 hr loiter time carrying a useful payload, while not being too big for a person to move around seem to be converting on 15 to 18 inch size prop and motor and esc combinations carefully chosen for optimal grams/watt thrust.
I've built a whole slew of drones over the last couple of years, quadcopters are hard to beat on many axis. But I have some proof that it may be possible to do substantially better with a monocopter in terms of efficiency. The hard problems you will then have to solve are payload attachment because unbalance is very tricky to deal with (whereas that is trivial in a quadcopter) as well as transitioning to level flight so that you can make good forward speed.
And what can be learned from full-scale classical helicopters that frequently carry underhanging payloads?
(I don't at all wanna be the typical HN person who thinks their questions about a field they know nothing about are in any way insightful. I'm just trying to learn.)
For a fixed payload it is indeed possible to set up the balance beforehand, even then you will probably end up with a drone that will translate slower or faster depending on the inbalance instead of hovering in place.
https://www.google.com/search?client=firefox-b-d&q=darpa+lif...
I used to be super stoked about it.
But watching drones kill civilians kind of ruined it. [0]
Then again ... they do put a dent in superpowers powers apparently so ... like I said ... I am torn.
My prediction is that future wars will actually involve increasingly fewer humans and will be more about tech+manufacturing vs. tech+manufacturing. And of course insurgents + lowcost tech vs. increasingly nonlethal hightech.
This would allow wars to continue without as much of the growing political backlash.
A significant portion of Russia's attacks are purely on civilians. Even Ukraine's attacks on RU targets have civilian side casualties.
Terrorism will probably always be a thing.
I guess the most important thing is to spread the tech then... make it fair at least? (Like this guy is doing)
If you have some time available definitely worth it.
- How to correctly hang a pre-framed door (shim it, tack it in place with 16 gauge nails, and use one wood screw in the top 2 hinges to prevent the door from sagging)
- How to properly adhere MDF trim to the ceiling to hide a closet door track (screw a furring strip or a header board to the studs above the drywall, shim it so it’s level in case the ceiling is uneven, and then nail through the face of the trim into the strip)
- What the difference is between the 27 DAP putties and spackles in the paint aisle (turns out Painters Putty 53 is typically used to hide finish nail holes, because you tend to make a lot of them and can just smoosh it in and level it off with a palette knife!)
But I do agree about using LLMs for learning new things - it's great to just get those answers, hopefully the LLM doesn't hallucinate too much and cause you to destroy your project in the process ;) On the flip side, it removes the useful skill of learning to communicate with fellow human beings, and atrophies the skill of how to ask questions, which often can lead to answers just by phrasing the question correctly. It also removes the chance to join a community of like-minded individuals. It's a completely soulless interaction. Maybe it's a boon for anti-social types, but I think it might also be creating more anti-social behaviors in humans, in a time when IMHO we should be learning to become more social and accepting of each other.
I went down a similar rabbit hole soon after covid started to build a small, eh, 'hand sanitizer factory' (that's my story and I'm sticking to it). By the time it was done I had a fully automated distillation setup complete with load cells, six different temperature readouts, solid state current control, flow/temp control for liebig condenser recycle, hierarchy of pid loops largely managing output flow and an attempt at live specific gravity testing. That with a nifty little dashboard to show live progress and compare metrics from various runs. Spent a couple grand on it in total and learned a LOT in the process.
Exploration and tinkering! But you have to have passion and deep interest in that topic/problem
I want to build a robot that does one simple thing - follow my voice and deliver something to it's original location. That means I need to learn batteries and power loads, electronics, audio processing, directional acoustics, more programming, soldering, and a half dozen other things.
AI + deep thinking about the problem.
The goal is not the objective but to learn everything along the way.
Even with the amount of open source software for this sort of application out there it will still take you at least a month but more likely two or three to get something that can be controlled.
If you want a nice place to start with building then I think Dhremflight's videos are an amazing resource as is liftoff on Steam because you can get some flying skills before you actually control something irl.
That's actually quite doable. The problem is that when the environment changes you will drift and then it becomes very hard to distinguish between actual heading changes and external influences. But if you can make a full spin you can (usually!) obtain magnetic North again. For drones this is a problem because they will drift and spin all the time. When you're on the ground and you have encoders on your axis you can do a lot better than with a drone.
RTK GPS is very nice to have but may not always be available (GPS itself may not always be available). I have some stuff in the works just for that. It does well in the lab but I still have (serious) problems in the field.
gps also won't give you orientation really anyway, and indeed, is mostly outdoors, and rtk is needed for this resolution but also rather inaccessible to amateurs.
If you're working on indoor navigation, that's very cool, when I used to do it, in my context it was easier because we controlled the environment of the robots (markers on walls of a known colour type stuff). We also explored passive radar type arrangements for picking up wifi repeaters, but it became complicated to eg. ignore bluetooth.
Though in the case of this video, the wii sensor bar style approach seems fine, assuming you control reflections
It's insanely complex stuff, I've had to do a lot of re-studying math and this whole project has given me more respect than I already had for the engineers behind modern positioning systems.
I imagine an alternative design with single motor mounted horizontally controls 4-wings like the dragonfly in Dune. It would eliminate the spinning.
This is a newer trend in mechanical design that leverages more complex control software to overcome mechanical issues. A good example is https://turntide.com/
Even cheaper:lift-off on Steam. It's a simulator, you can then just get a controller (I'd recommend a TX10 to start with, a TX16 if you think you're going to be serious about this stuff) and hook it up to the computer.
Good luck & have fun!
Smaller, cheaper, more numerous offensive drones?
What's interesting is that the Ukrainians are building drones near their front lines because if they build them too far away and ship them in, the game has evolved and those drones are already yesterday's news.
It's cool in that it can hover and do quadcopter type flight with only a single motor, and it's that second part that is interesting, because a fixed wing can also do a prop hang, but it can't do quadrotor-like flight from there.
It's usefulness is likely to be in other areas -- mainly applications where that flight mode is important.
Both sides 3d print parts near front lines. Just to be clear.
Especially when it comes to drops.