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Old Dec 02, 2015, 04:58 PM
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Multiwii Airplane V-Tail Mix / 2 Servos for Elevator???

So I'm familiar with rc flying, off and on for about 10 years. I've just built the FF Foam Predator. I've got most everything set up, but I can't figure out how to set up this v-tail.

I have a turnigy v-tail mixer, but for some reason when I connect it to my FrSky D8, the Rx powers off.

Does anyone have any idea how to set up a V-tail mix within Multiwii? Or understand how I could use the rudder servo as a second elevator servo?

Any help is greatly appreciated
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Old Dec 03, 2015, 03:21 AM
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I use something like this on my flying plank. It adds a second servo to the tricopter.

def.h
Code:
#elif defined(TRI)                        
  #define NUMBER_MOTOR     3                              //motor[0] = D9  motor[1] = D10   motor[2] = D5            
  #define PRI_SERVO_FROM   1                              //servo[0] = A0 for nanowii
  #define PRI_SERVO_TO     2                              //servo[1] = A1 for nanowii
Output.cpp
Code:
#elif defined( TRI )                                    
    motor[0] = rcCommand[THROTTLE];                 //D9  for nanowii
    servo[0]  = 1500 -axisPID[PITCH] +axisPID[YAW]; //A0 for nanowii   
    servo[1]  = 1500 +axisPID[PITCH] +axisPID[YAW]; //A1 nanowii  
   }
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Old Dec 03, 2015, 05:29 PM
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Thank you! I did find that section in the Output.cpp yesterday. I added like this...

servo[3] = axisPID[ROLL] + flapperons[0]; // Wing 1
servo[4] = axisPID[ROLL] + flapperons[1]; // Wing 2
servo[5] = axisPID[YAW] + axisPID[PITCH]; // Elevator (VTail)
servo[6] = axisPID[PITCH] + axisPID[YAW]; // Elevator (VTail)

But it's not quite right, I will try adding the 1500 value, perhaps that will solve the bug. Will update what I find for future searchers.
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Old Dec 03, 2015, 06:07 PM
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Okay, right now not going to work on rudder control, I've been working on this plane for weeks and at this point I just want to fly!!!!
So....V-tail with dual elevator servos, and aileron servos. No rudder control...yet.

servo[5] = axisPID[PITCH]; // Elevator (VTail)
servo[6] = axisPID[PITCH]; // Elevator (VTail)
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Old Dec 03, 2015, 06:15 PM
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What copter type do you have defined in (config.h)?
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Old Dec 03, 2015, 06:26 PM
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Quote:
Originally Posted by rojowe View Post
...I will try adding the 1500 value, perhaps that will solve the bug...
2.4 uses (get_middle) instead of 1500. It's the same thing though and 1500 is a lot easier to work with for us non-programmer type.
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Old Dec 03, 2015, 06:34 PM
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Multiwii 2.4
#define Airplane

When I used the 1500 +/- etc...the servos did not respond to any commands, may try with (get_middle) tonight.
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Old Dec 03, 2015, 09:26 PM
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#define Airplane has a lot of convoluted programming going on in Output.cpp that I can't make heads or tails of so I wouldn't use it.

#define FLYING_WING looks a little better to try if you want v tail mixing.
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Old Dec 04, 2015, 11:19 AM
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RCvertt, ironic that you say flying wind looks easier, to me atleast! Fortunately PatrickE responded to my post in the Multiwii forums. We weren't far from the answer and you're recommendation was pretty close, and I thank you for your time.

PatrickE recommended code works for full V-Tail mixing!

servo[5] = axisPID[PITCH] - axisPID[YAW]; // Full(VTail)
servo[6] = axisPID[PITCH] + axisPID[YAW]; // Full(VTail)
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Old Dec 04, 2015, 09:41 PM
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Thanks for posting the solution. Glad he was able to get it working.
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