# Swashplateless helicopter control.

A swashplate controls a helicopter by moving up and down (vertically) on a shaft and tilting. Vertical movement makes the rotor blades increase pitch (angle of attack). Tilting the swashplate changes blade pitch sinusoidally, meaning the pitch increases and decreases by the same amount. The blades will change pitch relative to a position on the helicopter, this position can be moved by tilting the swashplate in a different direction (This advances (adds an angle) or delays (subtracts an angle) the sinusoidal motion of the blades). Doing so creates an difference in lift which rolls the helicopter.

This same motion can be done with high speed solenoids (devices which hold a specified orientation/angle):

This can oscillate (move up and down) at very high frequencies (speed at which it moves up and down) and relatively high amplitudes (how much it moves up and down). This makes it excellent for helicopter control as it requires high frequency, high amplitude oscillations which a swashplate normally provides.

The solenoid consists of a lever axised at it’s center (center of mass) with two elastics and hydraulics attached to it. Moving it from the center decreases load on the elastics and hydraulics, as they do not fight the levers linear momentum (only it’s angular momentum).

The elastics have a very high force constant (the amount of force applied they when expanded/contracted is very high) with minimal damping (resistance to movement). The hydraulics contract/expand to move the lever. The levers acceleration will be very fast as the net force acting on it (the sum of elastic and hydraulic force) will be very high.

Connecting these solenoids to rotor blades yield excellent results:

To know what’s the angle of the rotor relative to the body, a beacon sensor linked to a locator is used. Getting the bearing between the two gives accurate positioning. Multiplying the sine and cosine of that angle (the bearing) by a desired cyclic input (roll/pitch control of the helicopter) and changing the length of the solenoids with it, one achieves the same sinusoidal motion a swashplate makes.

To control collective (up and down control), the solenoids simply move in opposite directions, changing the pitch of both rotor blades by the same, non varying amount. Increasing the total lift the blades produce.

The advantages of swashplateless control are:

• Decreased vibrations.
• Increased adjustability (as cyclic phasing/delaying or advancing the sine/cosine motion is simpler and precise).
• Increased duplication resistance. (Not dupe raped as much).

swashplate is cooler. but this is cool too :dance:

Awesome. But where is the tail rotor

Torque-less power system means no need for a tail rotor.

And I was there when you discovered these

spinning camera makes my brain hurt.

Nice work on the system

nice. I tried something similar a while back, using hydraulics and feedback loops (servos)

I long for the day when swashplates are simple and common like suspensions.

The only issue I noticed is that it seems to have trouble moving forward without losing altitude. I suppose that could be fixed with a few edits to the angles here and there?

Don’t bump

quit fucking whining about bumps. this wasn’t a horribly long bump but it was also a good post.

The loosing altitude part is simply pilot control. To retain a certain forward speed, an increase in collective (up/down force) is necessary to retain altitude as some of the rotor’s lift is vectored forward (thus pushing the craft in that direction).

PS: Thanks TGI for defending my work.

haha np

Strangest part is, even though I’m a railfan, not an aircraft fan, I understood everything you just said. o.O