Tandem rotor helicopter

Programing help and example for all firmwares based on thus's th9 firmware.
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TheCirodi
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Country: Italy

Tandem rotor helicopter

Post by TheCirodi » Tue Mar 19, 2019 3:20 pm

Hello.
I’m putting together a flybarless-variable pitch, 3-blades per head, tandem helicopter, 450 class, Boeing Vertol CH-46/47 style.
The configuration will be as follows as per the attached picture.
I need to manage the 6 servos and motor.
Taking advantage of the powerful ER9X firmware I would like at least to evaluate the feasibility.
For people who don't know how a tandem rotor helicopter works, I briefly summarize here below.
Forward/backward: cyclic will raise one swash and lower the other for elevator control and aileron works as normal.
For yaw: you mix the rudder servo channel into the aileron servos so that you have opposing cyclic at the front and back when you input left/right rudder.
You can not however just tack two 120 degree rotor heads and two FBL controllers together and expect it to work. If you try to move the machine forward with only elevator cyclic the machine will only drift slowly forward.
Having said this, anybody willing to help will be welcome.
Thanks a lot in advance.
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Last edited by TheCirodi on Wed Mar 20, 2019 3:21 pm, edited 1 time in total.


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MikeB
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Re: Tandem rotor helicopter

Post by MikeB » Tue Mar 19, 2019 6:31 pm

Being FBL, am I correct you basically have 6 channels going from the Tx, pitch, roll and collective for each rotor head?
From your description, it seems you don't need to use the pitch for control!
I the above is correct, then try:
Starting position:
CH1: roll for forward rotor
CH2: pitch for forward rotor
CH3: collective for forward rotor
CH4: roll for rear rotor
CH5: pitch for rear rotor
CH6: collective for rear rotor

Basic mixes:
CH1 +100% Ail
CH2 0%
CH3 +100% Thr
CH4 +100% Ail
CH5 0%
CH6 +100% Thr

For pitch, add mixes to channels 3 and 6:
CH3 +100% Ele
CH6 -100% Ele

For yaw, add mixes to channels 1 and 4:
CH1 +100% Rud
CH4 -100% Rud

You may need to reduce the 100% values so if you apply both Ail and Rud you don't exceed 100%.

Mike
erskyTx/er9x developer
The difficult we do immediately,
The impossible takes a little longer!

TheCirodi
Posts: 9
Joined: Tue Jan 10, 2017 3:11 pm
Country: Italy

Re: Tandem rotor helicopter

Post by TheCirodi » Wed Mar 20, 2019 7:10 am

Mike,
your understanding is correct.
ASAP I'll setup the mechanics and I'll test your program.
In the meantime, I'll simulate it with eepe.
This is another proof that ER9X is truly powerful and unique.
People who purchase famous branded radios, get less, spending much more......

I'll feedback my results.

Mike, your statement "The difficult we do immediately..." is perfectly true with you!
THANKS A LOT!

Sergio

TheCirodi
Posts: 9
Joined: Tue Jan 10, 2017 3:11 pm
Country: Italy

Re: Tandem rotor helicopter

Post by TheCirodi » Wed Mar 20, 2019 8:45 am

Mike,
I here attach EEPE MODEL where I implemented your hints.
I simulated it and corrected your setup about pitch, "add mixes to channels 3 and 6" and reversed the weights as follows:
CH3 -100% Ele
CH6 +100% Ele
Motor is on CH7 with Throttle Cut.
On CH8 will go gyro gain control.
I simulated and seems to work as needed.
Would please double-check it?
Then I'll introduce motor and "pitch" curves.
Thanks a lot again!

Sergio
Attachments
TANDEM.eepm
(1.45 KiB) Downloaded 34 times

TheCirodi
Posts: 9
Joined: Tue Jan 10, 2017 3:11 pm
Country: Italy

Re: Tandem rotor helicopter

Post by TheCirodi » Fri Mar 22, 2019 12:27 pm

Mike,
I have been too much optimistic.
There is no way to get the help of a gyro.
This is the real limit with helicopters.
Cheers,

Sergio


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MikeB
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Re: Tandem rotor helicopter

Post by MikeB » Fri Mar 22, 2019 12:42 pm

Is the gyro just for yaw or does it handle all three of pitch, roll and yaw?

Mike
erskyTx/er9x developer
The difficult we do immediately,
The impossible takes a little longer!

TheCirodi
Posts: 9
Joined: Tue Jan 10, 2017 3:11 pm
Country: Italy

Re: Tandem rotor helicopter

Post by TheCirodi » Wed Mar 27, 2019 8:02 am

Mike,
sorry for the late reply.
All three (pitch, roll and yaw).
Thanks.

Sergio

Ikerd
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Re: Tandem rotor helicopter

Post by Ikerd » Sat Apr 27, 2019 10:15 am

I've actually had an idea like this in my head for a while now. Too bad a gyro can't handle that. It would have been an elegant solution.


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