一個構想..不知有沒有人要試試看[非同軸雙槳直昇機Twin-450XL誕生了]

tudole

Two main rotors HAS to be mechanically connected. Problem #1: NO governor can do such a good job to make two rotors rotate at same speed; if governor on each rotor interfere to each other, it might get worse.　Problem #2, as my earler post, the distance of two shafts has to be as short as possible, to make the yaw channel more stable. As the result, there are some overlapping disk area. If both rotors are not mechanically connected together, the blades will hit each other.

However, it is a good idea to use a governor in a mechanically connected tanem rotor. If the rpm is constant, the rotor torque will only come from the collective pitch setting of each rotor. That will save a lot of trouble.

I want to the link of Hirobo CH47, and breifly looked at it. It needs a "tandem rotor control mixer" and a 3 axis gyro. unfrotunately, the website doesn't say how the control logic works. My best guess is that, the gyro issues the rate damping command in all 3 axis to the mixer and the mixer will tell the lateral/longitudianl control servos in both forward and aft rotors. Can anyone confirm this?

Let see what problem we are going to face:

1. Yaw control
Yaw control has to go through a. differential lateral cyclic (one rotor to turn right and the other to turn left). b. Differential collective pitch (one rotor has higher thrust than another, so the torq on the first one rotor is higher)

2. Pitch control.
In hover, the pitch control is done by a. longitudinal cyclic in both rotors. b. differential trust (collective) in both rotors.
Also, if the CG is not dead on the center of 2 rotors, the unbalance has to be adjusted by the differetial thrust. Note that 1.a and 1.b. are coupled.

3. Roll control
Lateral control is easier compare to the other 2 channels. It can be done on lateral cyclic on both rotors.

4. Rotor coupling
Rotor blade flapping is coupled in a 90 degree phase. When you do a pitch command, the roll will be slightly affected, depends on the stiffness of the rotor in theory. Luckily, I didn't feel so much when I fly a T-Rex.

5. Wind/forward flight
When wind blows from the nose (or flying forward) the advancing blade on both rotors are in different side. That will make the helicopter to yaw.

Above are a simplified senario of the problem. I will look at more document to see how the control logic should work.

I hope someone can traslate this....