Working on DIY Dualcopter/Bicopter

[Super-Hornet]

Hi all

Here is my working in progress Dualcopter (or Bicopter). It is build from scratch from parts from:
1. Mini-Titan frame.
2. Align 1400kv motor.
3. GWS 3x propeller.
4. Castle Creations 35A and 25A (firmware upgrade and configure as Multicopter)
5. Batteries from my 500Size heli
6. Hitec Digital Servos
7. KK2.0 board (firmware in v1.6)
8. Hitec 6channel Aurora RX.
9. Square Carbon rod
10. TRex450's main blade grips

Difficulty.... Tuning the gyro sensors especially on the elevator.
Stability so far... Definitely not as stable as Quadcopter. This is due to there is no stability coming missing frontal and rear rotor/propeller. All the stability (elevator motion) is coming from the tilting the 2 rotor and required to be able to turn fast enough but not too fast and it encounter oscillation. That comes back to the above difficulty in tuning the elevator value in terms of P and I value (and limits).

So far able to hover in living room but still not satisfactory on the elevator gains.

[Ben]

Fly like Chinnock ?

[Super-Hornet]

The last time i DIY dual rotor or Chinnook heli style was around few years back..during TRex450 CDE era.. At that time.. 3 bladed rotor for TRex450 not exists yet. Do compare to this... this dualrotor behave differently. It still feels like multicopter. When elevator gain to high...the craft body rock up and down like children playground "see-saw" but the both rotor still stable. I believe it should behave more like Osprey aircraft.

[Super-Hornet]

The more i study bicopter design.. the more i feel that by tilting the rotors backward when nose dip/down to achieve stability may not be a good solution. The better solution should be using swash plate with collective pitch instead. In other word, when the nose goes down, the flight controller should adjust swash plate like in helicopter so the rotor discs are tilted backward..instead of whole rotor system. This tilting backward will have better stability. That mean... to create a better dual copter or bi copter, maybe using two main collective pitch rotor system instead..Rather than using propellers. It can be running two motors (one motor on each rotor) like in multicopter or interlink them like in Tandem Helicopter.

[Super-Hornet]

Here is the latest update. I moved the RX to rear end. Replaced ESC to 2 identical Align BL35X instead. Turn motor spinning direction similar to MV-22B Osprey. Improve the servo mounting.

Since there is no stability from rotor for pitch axis, to have the a good stability from pitch axis (elevator), the idea is to have/set the rotor react to the pitching of the aircraft frame (or nose) in such a way that, the rotor will be remain parallel to the ground level while preventing it from oscillation.
Normally the setting for P and I value is in such a way that, I is 1/2 of the P value. E.g.: If P value is 40, then the I value will be at 20. For this case, those I = 1/2 P will not have a good stability on the elevator. It will either:
1. Elevator do not respond fast enough and it cannot stabilized it (when gain too low).
2. Elevator responded too fast that, the aircraft body is oscillating/rocking/see-saw. When flying in these situation, the aircraft body can easily start rocking and if worse, keep on rocking non stop. ( can be seen by holding the craft at the motor shaft and then rocking the craft.. the whole body will keep on rocking non stop!)
Both situation will cause craft to lost control.

So, what I found out that, by having high value on I than to the P value instead. This will have the rotor to tilt (with enough turn) when tilting/pitching the craft. But the rocking of the craft will be still happen but in slower motion. Therefore, by then increase the P value. The P value now becoming something to dampen the rocking. The value of I now is more than P instead. (See attached pictures).

With the new settings, I manage to hover it easily and fly around abit in the living room. When hovering, I purposely pushing the elevator stick to fly forward and then quickly pulling it back to see whether the aircraft body will go into rocking effect or not. Results are good. No rocking. I am now satisfactory with the stability on the pitch/elevator motion. Hope can try to fly it outdoor soon to test it out.

Note:
This is how I test the gain and stability effect on the craft. Unplugged the motor wires and then goes to ARM mode. Move the throttle stick like to the middle of it. Then rest the craft onto the fingers (each motor shaft resting onto one finger). Then rock the aircraft. The aircraft should rock and then quickly dampen out and stop rocking. When hitting the aircraft nose/rear, the motor will quickly tilted in opposite direction quickly and then stop.

[nese]

Thanks for sharing your cool project SH! Hope to see a vid of the bicopter fly outdoors when it's done.