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.
I built a drone with only one motor [video] (youtube.com)
253 pointsby hakonjdjohnsen13 hours ago46 comments
TGower 3 hours ago
Underactuated robotics are so cool. In the hobby BattleBots community, there is a design where the whole robot only has a single motor, but it's able to move in any direction and damage the opponent, all just by controlling the single motor's speed.
Onavo 2 hours ago
Well not just battlebots, real life 6th gen fighters now all lack the vertical stabilizer so they have to rely on very sensitive real-time software control of the elevator/spoilerons to do banks and yaws. Not sure if it counts as under-actuated but they are tremendously difficult to steer without computer control.
jmaw 2 hours ago
I'm not super familiar with heavy equipment like dozers and such, but some of them may also have a single motor to pressurize hydraulic fluid and valves to articulate the various pistons. So may be able to make the argument there too
bluGill 2 hours ago
That is common and you can't run two different cylinders at the same time. Depends on how the pump and valves are plumbed of course. Sometimes you can run more than one but you split power.
HPsquared 2 hours ago
That sounds like it could be solved with more valves.
solyin an hour ago
Or more power ;)
nomel 2 hours ago
In that case, the valves/pistons pairs are all independent actuators. The hydraulic motor is more a constant power source for all of them.
muti 23 minutes ago
Yeah, the analogy for drones is hydraulic piston -> electric motor and hydraulic pump -> battery
KolmogorovComp 2 hours ago
> but they are tremendously difficult to steer without computer control.
they are not humanly pilotable without computers. they are inherently unstable.
schiffern an hour ago
>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).
nadermx 2 hours ago
This is well worth the entire watch. It feels like what would any hacker do in trying to figure out how to make something they want to exist. Also very well presented and good pace.
Inspires me to try and start doing some robotics.
mikeyouse an hour ago
Love the little side project of building a high resolution high speed camera to investigate the flutter.
JacobAsmuth an hour ago
Only to figure out that the vibration in his drone was due to vibration and it was easily fixed by swapping to rotors that he should've used in the first place. Oh well! Live and learn.
_joel an hour ago
This is from the same guy (Joshua Bird) that built the 4 axis 3d printer (and special algo for it too) https://www.youtube.com/watch?v=VEgwnhLHy3g
leoedin 11 hours ago
A really neat concept. It uses a special hinge design, a magnetic encoder and torque modulation to control the lift of the rotor as it spins. Completely negates the need for a conventional helicopter's swash plate.
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.
schiffern 7 hours ago
Note that the concept itself has been done before in RC helicopters. The only difference here is using a one-propeller drone.
https://hackaday.com/2020/06/25/building-and-flying-a-helico...
fwipsy 3 hours ago
Yep, he mentions the video you linked as well. (Mentioning because I watched the video you linked first.)
Aboutplants 3 hours ago
Perhaps there are specific applications where the payload spinning could be an advantage, imaging/scanning perhaps (which in the video is going to be in the next iteration for the builder).
mr_coffee 28 minutes ago
Serious question - how do you even learn all of the skills to do something like this? Where would you start?
whatever1 13 minutes ago
Now with LLMs? Super easy. Just ask for step by step instructions to build a standard drone. You will learn about micro controllers, physics, pcbs, 3d printing etc.
If you have some time available definitely worth it.
coderenegade 12 minutes ago
A good engineering course would cover most (if not all) of the skills necessary to do this. This is notable because the person is young and wielding a broad slice of the discipline with maturity.
orliesaurus 12 minutes ago
I wanted to learn more about photography, I started asking an LLM and it helped me immensively. Definitely not the same realm but if you wanna pick up new skills, LLMs have tons of beginner friendly ways to explain things!
sastra 2 hours ago
The Picocolissimo also uses only one motor: https://www.youtube.com/watch?v=UE47bcCxT_I
jcims 2 hours ago
Side note, I used those same moteus controllers for a decidedly less energetic use case (two axis gimbal for RF satellite tracking) and found them to be super high quality and the lead developer always super helpful. Been a few years but def worth a look if you want to get into motor control.
justinator 35 minutes ago
Yeah that's probably the coolest thing I've seen all month. How could you not like this?
subprotocol 3 hours ago
Reminded me of the Manhack: https://half-life.fandom.com/wiki/Manhack
mogili 2 hours ago
It's a pretty cool concept, however, fails to mention coaxial rotor design that has a single motor and has much simpler control systems. I am also curious on how this affects frame vibration.
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/
stbtrax 2 hours ago
It’s an entertainmening YouTube video not a phd thesis. Bizzare standard to hold him to
nomel 2 hours ago
If I understand correctly, those are single rotor but NOT single motor. This is a single motor design, which is why it's neat. There are no additional control servos/motors.
razster an hour ago
Slap a MEMS gyroscope on that bad boy. https://www.vectornav.com/resources/inertial-navigation-prim...
ddlsmurf 33 minutes ago
gyroscopes drift over time, that's why typically you need a kalman filter to combine the strengths of various sensors, magnetometers, where available, are bad at resolution, but don't drift.
mainecoder 10 hours ago
Amazing work this is really innovative and it could be applied to a larger drones provided that the margin of error is reduced.
tintor 2 hours ago
How will this new tech affect the current drone war between Russia and Ukraine?
Smaller, cheaper, more numerous offensive drones?
eimrine 2 hours ago
maybe new breakthroughs for the darpa project. kamikazes drones do not need so advanced prop tbh it is against the idea of being cheap.
gpm an hour ago
I strongly doubt adding a ton of extra weight in aerodynamic surfaces, and drag, and complex mechanical parts, to avoid a few motors/servos is worth it in that context.
solyin 26 minutes ago
Every gram of weight you remove is another gram of explosive you can add. Also consider the difference in supply lines for aerodynamic surfaces and mechanic parts and motors and servos. If you have four hundred servos, you can make one hundred quadcopters, or four hundred of these things. If you only have one hundred control boards powerful enough to control the single motor design though, you can still only make one hundred. (Tho the quadcopter can lift 4x the weight)
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.
nhma an hour ago
This tech is more than a decade old, originally from UPenn AFAIK[0].
russellbeattie 3 hours ago
It's incredible that changes in velocity still work to adjust the angle of the blades even at the insane speeds they're moving at. I would never have thought that was possible.
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?
z3ugma 2 hours ago
Possibly the fact that the TPU fin body doesn't stop all counterrotation so the leash would get twisted into a cord and interfere with flight?
maximilianthe1 an hour ago
print a slipring
johnnyApplePRNG 2 hours ago
I am torn about drone tech now.
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.
aeternum an hour ago
To be fair, a lot of it is moving to drones killing drones.
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.
_joel an hour ago
The next iteration is the drones removing those pesky humans from the command chain too :/
walrus01 2 hours ago
There's also been a few people building monocopters with a fixed, non tilting motor and prop, and four servo motor actuated fins at the bottom that can be used for thrust vectoring and to counter rotational forces.
gspr 2 hours ago
I love this angle so much! Do you know if there's been more detailed analysis of performance?
razster an hour ago
Neat. I wonder if you could use the air it generates by having directional ports louvers that open and allow the air to flow for more control.
Would need 2 more servo, left/right port louvers.