Dual motor tailsitter

Hi team,
Its been a long time im working on cube. I have successfully made quad plane with cube and few other projects and they were grand success. Now i am working on Dual motor tail sitters. I have already made 3 prototype models and they were running on arduplane 4.0.0 firmware.

its been few weeks since i m testing and tuning up the pid’s few things i have still in confusion and strange things happens with my setup.
Confusion things:

  1. what mode should i let the aircraft turn on and let it initialise, is it fw mode or q hover mode?
  2. in which orientation should i do accel and level calibrations.
  3. if i place my tailsitter on its tail and takeoff in q hover mode why does it will drift in terms of yaw let say if i place tailsitter top exposing north and take off it wont hold north in terms of yaw.

strange things observed:

  1. in q hover mode aircraft is fine and flying good, but when i take into fbwa mode my pitch oscillates too much as both the elevons servos are oscillating too much which resulted in a crash. I have tried tuning fw pid gains and found to be good for 2 flights later on 3&4 flight they started oscillations and crashed(3&4) Test was done in little wind where in 1&2 test was done in no wind.
  2. auto mission takeoff in vtol mode transition to fw mode and do mission in fw mode while RTL and vtol land it is triggering from fw mode to vtol mode but not coming to land at home point.

Please help me with this problem.

Thanks indeed.
Vinod nayak
UAV development engineer India.

Hello sir,
As far as I know its better to power up the tail sitter in horizontal position and then place it vertically, so that you wont get any pre-arm issues.
Accel calibration is done for FW mode.

Sir I also need some inputs from you for tuning my Tail sitter. So it will be helpful if you can give me your thoughts on it.
In Q_Hover mode the motors wont respond to my stick inputs and they rev upto max once they start spinning. Its not hovering properly also because I am using a flat bottom airfoil. So there is lift generated on wings and my Tail sitter tips towards that side.
To overcome this problem I have given 2 input channels to my motors even if they are fixed and they are not tilt rotors. This makes vectored thrust possible and I am able to control it better. Please let me know if this setting causes a problem for transition.
I am not able to tune the PIDs because I am not able to keep it in air (HOVER). So if there are any basic PIDs to start with please let me know about it sir.

Thanks in advance,
Nihal Y.

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Try checking in with the min mot speed parameters. please contact me through vinnenayak1112@gmail, (Nayak rc )YouTube search call me on 7981146424