Disabled servos message on TVBS build

ArduPlane Plane 4.4
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1

Hello, I am building a thrust vector belly sitter but am running into trouble with the motor outputs.

The vehicle has two, wing mounted motors, tilted by servos.

The autopilot is a Pixracer R15, running Arduplane 4.4.4 (flashed a few days ago with latest stable).

Following the instructions here I have set the following:
Q_TAILSIT_ENABLE → 1
Q_TAILSIT_MOTMX → 0
Q_FRAME_CLASS → 10
Q_FRAME_TYPE → 1

Also, following the instructions here I have setup the outputs as follows (channel - servo function - description):

1 - 77 - Elevon Left
2 - 75 - Motor tilt left
3 - 73 - Motor throttle left
4 - 74 - Motor throttle right
5 - 76 - Motor tilt right
6 - 78 - Elevon right

When I boot, I get the following strange messages in Mission Planner:

PreArm: SERVO2_FUNCTION=75 on disabled channel
PreArm: SERVO1_FUNCTION=77 on disabled channel

The channels in the messages correspond to my left elevon and motor tilt.

When arming, I can:

  • spin both motors via RC.
  • Get correct responses from right elevon via RC.
  • Get correct responses from right elevon in STABILIZE
  • Get the right tilt servo to move when switching between MANUAL and QSTABILIZE

However, I am getting nothing on the left elevon and tilt servo.

Also, before I set the correct Q_x params, I had proper functionality on the left elevon (servo channel 1). As soon as I set the Q_x params and rebooted, my elevon was inoperable and these messages started.

Does anyone know what might be causing these strange messages?

2

Possibly answering my own question, I think I got it. I saved and then did a reset of the params and started again from scratch.

Second time round, I did not get the same errors and now elevons and tilt servos respond properly. Comparing the two sets of params, I think the reason for the error was that in the old set (the one giving the error message) I had:
Q_TILT_ENABLE → 1
Q_TAILSIT_ENABLE → 0

whereas, in the new set (no error message):
Q_TILT_ENABLE → 0
Q_TAILSIT_ENABLE → 1

I think the source of the error is that, in the Tilt Rotor Planes guide, under “Setting up a Tilt-Rotor”, the docs say:
" The first thing you need to do is enable QuadPlane support by setting Q_ENABLE to 1 and Tilt Rotor support by setting Q_TILT_ENABLE = “1”"

However, the Tailsitter Planes guide, under section “Tailsitter Configuration”, it says:

firmware versions 4.1 and earlier

The key to make a QuadPlane a tailsitter is to either set Q_FRAME_CLASS =10 or Q_TAILSIT_MOTMX non-zero. That tells the QuadPlane code to use the tailsitter VTOL backend.

firmware version 4.2 and later:

To make a QuadPlane a tailsitter is to set Q_TAILSIT_ENABLE to “1” or “2” to tell the QuadPlane code to use the tailsitter VTOL backend.

Now, since I am on Arduplane 4.4.4, I set Q_TAILSIT_ENABLE → 1 but I also had Q_TILT_ENABLE → 1 from having followed the guide in section “Setting up a Tilt-Rotor”. If both these are enabled, Arduplane complains that one of them should be set to 0 as has been reported in this thread. So, in the old version I set Q_TAILSIT_ENABLE → 0 but had left other settings configured.

It seems that Arduplane 4.2 introduced this change in configuration but parts of the documentation have not caught up with it.

3

docs are correct, BUT,you do have to know what TYPE of vehicle you have Tailsitter or Tilt rotor…they are not the same thing, hence two different pages in the wiki

4

I guess the nomenclature is somewhat confusing. I would have thought the thrust vectoring of TVBS counts as a tilt rotor. Tail sitters come in vectored and non-vectored flavours and tilting rotors is a method of getting vectored thrust.

5

the wiki is very clear on not confusing a vectored yaw tailsitter as a tiltrotor…right at the top of the tiltrotor page is this note: This is distinct from tailsitters where the autopilot and main fuselage change orientation when moving between hover and forward flight. Do not use the information below for a Tailsitter, some parameters are shared, but use the instructions in the Tailsitter Planes.