I came across this interesting video:
As you can see in the video they have managed to control the coaxial design without using a swash plate and all the complicated mechanisms required for that. It looks like this is an excellent concept for very light weight systems. I do wonder how easy this can be scaled up into a device that can actually carry any additional equipment. This could be useful to obtain the under 2 kg UAV weight for the Canadian regulations.
Comments
1. Get rid of the coax and use one massive efficient rotor.
2. Use a small tail rotor to counter torque.
3. Now you have only four moving components, like a quadcopter, on an airframe that is much more efficient.
4. The death of multirotors.
With brushless motors (like stepper motors), the magnetic field controls the position of the output shaft. So the ESC controls the position of the motor. Instead of having a servo control signal, their controller directly controls the power to each of the motor's leads.
:-) I guess an optical encoder
Aaron, good explanation of where they need the pitch change and how speeding up and slowing down gets the blade to pitch. Any idea how they know the location of the blade?
Tiziano, si, fewer motors is molto bene.
We clearly are facing a new technology. Let's leave it to grow up to become reliable. I see the less are the motors the lower is the weight, the bigger can be the propellers
Harry, lets see if I can explain it.
At a constant speed the pitch of both blades are steady.
Each blade reacts differently to changes in speed. Blade "A" will increase in pitch as speed increases and decrease in pitch as speed decreases. Blade "B" will do the opposite, decrease in pitch as speed increases and increase in pitch as speed increases.
So if you increase the motor speed briefly as blade "A" is towards the "front" of the craft, blade "A" will increase in pitch (at front of craft) and blade "B" will decrease in pitch (at back of craft) causing more lift in the front than the back (causing the nose to come up.) Then if you decrease the speed as blade "A" is toward the "back" of the craft, blade "A" will decrease in pitch (at back of craft) and blade "B" will increase in pitch (at front of craft) again causing more lift in the front of the craft (causing nose up again.)
So in my example, to cause the nose to go up, you have to briefly increase motor speed as blade "A" is near the front of the craft and decrease motor speed as that same blade (blade "A") is near the back of the craft.
This example ignores gyroscopic procession, so sorry if I have confused anyone that understands gyroscopic procession and how it affects actual rotorcraft flight. :)
Dave, that's a good point. You would definitely have Y-axis vibrations at 1/N at the least. You'd also get some crazy stuff going on, disymmetry of lift and external airflow would cause lead/lag... it's a bit nightmarish honestly. I really would like to see this is real world operation.
I also went to the site and still have a little trouble understanding how they control it. The blades are hinged at an angle which means it will pitch as it swivels on the hinge - I get that part just looking at it. To control the pitch of the blade, they dork the motor signal which causes the blade to pitch? How do they know where the blade is located in 360 degrees?
Very interesting experiment!
But IMHO this sheme need more tests, sinusoidal shift rotating speed may cause unballancing and additional vibration, automatic set AoA have some inertia and may lead to troubles in control for dynamic flyghts regimes. .
There still needs a large number of tests in different conditions. Good Luck! =)
Pretty interesting concept. I'm also interested in real-world usability.
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