VTOL 2-motor tailsitter, motor test, A, B, C, and D, all spin up the same motor

ArduPlane VTOL Plane
1

I’m building a 2-motor, non-vectored tail sitter using an FX-61 as the frame.

I have all electronics hooked up (Kakute F7, Arduplane v4.6.3), and am attempting to do the motor test.

A, B, C, and D, all spin up the left motor (when viewed from behind) - the right motor does not spin at all.

I know the wiring and the servo settings are all correct - well - 99.9%.

Physical Pin Parameter Value Function
M1 SERVO1_FUNCTION 74 ThrottleRight
M2 SERVO2_FUNCTION 73 ThrottleLeft
M3 SERVO3_FUNCTION 0 Disabled
M4 SERVO4_FUNCTION 0 Disabled
M5 SERVO5_FUNCTION 77 ElevonLeft
M6 SERVO6_FUNCTION 78 ElevonRight

Q_FRAME_CLASS is 10, Q_FRAME_TYPE is 1, and Q_TAILSIT_MOTMX is 0.

This is my first tailsitter VTOL - so I don’t know what to expect from teh motor test, but what I’m seeing doesn’t seem right.

Thanks…

P.S. One more thing - strange - I do not have a parameter called MOT_PWM_TYPE, and, if I go the the Mission Planner ESC CALIBRATION screen, “ESC Type” is non-selectable - the field is blank, and clicking on it does nothing.

2

Try:

Q_TAILSIT_ENABLE,1

Edit: Never mind, that’s probably already done.

If you have the plane in manual (fixedwing) mode, can you run the motors there?

3

Here’s another weird thing - even if I have servos 1 thru 4 set to zero/disable - the left motor spins on A, B, C, and D.

4

I have it in my head that motor test doesn’t work with fixedwing throttle controlled motors (SERVOx_FUNCTION, 73 and so on) and only works with quad motors (SERVOX_FUNCTION,33 …) But I could be totally off the mark here.

With the props removed, Arm (force-arm if needed on the bench) the plane in fixedwing manual mode and try the throttles that way. Don’t use the motor test. See if that works as intended.

5

Thanks guy - before I get to your suggestions, I have another very weird thing going on.

If I change Servo3 to whatever, and “refresh parameters”, then that “whatever” sticks. But if I pull power and reboot, Servo3 changes to TiltMotorFrontRight.

WTF?

I cannot get my change to Servo3 to STICK (after a power off/on).

6

Posted to github:

This was the reply…

That is expected. So long as Q_TAILSIT_VHGAIN is zero it will have no effect in flight.

And this is my reply…

Thanks Pete - so now I can relax.

IMHO that behavior should be corrected.

I spent OVER A WEEK trying to track this issue down (didn’t even know I could post to Github, was using the Ardupilot forums) - the issue is QUITE unintuitive, IMHO, as well as dangerous, because in fact, my Q_TAILSITE_VHGAIN was set to .5 - so if I had attempted a takeoff, who the heck knows what would have happened.

Anyway again, thanks, but I would NOT call this firmware behavior “normal” - it might be “expected” (given the state of the firmware), but it’s not “normal” to have your servo assignments changed, and certainly not to something quite possibly dangerous - at the VERY least, if the firmware is going to be changing servo assignments on a power cycle, the firmware should also set any other values to make operation safe, in this case, the q_TAILSIT_VHGAIN value set to ZERO.

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