Hello,
My motors don’t seem to be commanding in unison as I’d expect.
I’m getting ready to do my first flight on custom frame. My setup includes:
-Vertiq motors
-Ark GPS and FMU
-Herelink Radio Air/Ground
I believe I’ve configured everything properly:
-CAN for motors
-Offsets for motors, GPS, & FMU
-Confirmed motor spin direction
Before attempting to fly the drone - I wanted to run it up on the ground. What I found was the motors spool up evenly, then seemed to have different RPM when I returned to sticks center, and finally when spooling down were very uneven (back left stop way earlier than the rest).
Is this normal? Or is something not configured correctly?
Log and video linked.
Log link here: https://logs.px4.io/plot_app?log=8c513da1-1109-44b6-84df-57a042b7b71f
Video: https://drive.google.com/file/d/11wfZwgmXfJy6wZuaAsBsevq7LcsuHVJu/view?usp=sharing
Motor 1 and 4 look reasonable, but 2 and 3 are just doing their own thing at the end
When you arm in a stabilized mode (stabilize, altitude, position) the controllers try to keep the frame level. Without props this is obviously not possible. In your log you have a slightly positive roll, which means the controllers will wind up in that direction. Given that, we should expect to see the motors on the right side commanded a larger value (we do see that in the log, output 0 and output 2).
To verify the motors spin with the correct RPM throughout the full output range I would instead recommend using QGC Actuators page and the motor test slider.
Copy that - with the sliders they do appear to work more as expected.
I went to try another ground test in manual mode but it won’t arm because the throttle was too high. I assume this is because the middle stick position would be commanding the throttle up. Is that correct?
Yes that’s correct. Full stick down is 0 throttle, mid stick is 50%. I think this can be configured with parameters
k - yeah I put the throttle in full downwards position and was able to arm that way.
So how do you know if you’re ready for a flight test? Just seems a little like I’m wingin’ it.
I know the procedure is to start in Alt mode and ensure that the vehicle can recover okay prior to autotuning. Is there anything else to verify before starting the first flight?
I know the feeling… the first flight test of a new airframe is very nerve wracking.
Eensure your props are installed properly. Use the QGC Actuator page and ensure the Geometry is correct and the spin direction of each prop matches the diagram. Ensure you have the motor locations mapped to the correct actuator outputs. By default its:
Motor 1 –> Front right
Motor 2 –> Back left
Motor 3 –> Front left
Motor 4 –> Back right
Also using QGC verify the instrument indicator shows correct roll/pitch/yaw when you rotate the frame. Make sure you’ve calibrated all of your sensors. I would start with the Generic Quad X airframe and autotune from there. Set up your RC, use a 3 position switch to set modes stabilize/altitude/position and map a toggle switch to emergency kill. Keep your finger ready to kill the drone if things go badly after taking off. Always start with a short hop test in stabilize and ensure there are no rapid oscillations before autotuning. And check out the doc here Multicopter Auto-Tuning | PX4 Guide (main)
Copy thanks that helps!
I did all of that an alas had a “controlled” crash. Immediately after take off the aircraft was quit wobbly, started to yaw, and then I brough it down and killed it.
Trying to understand what caused the wobbles.
I did notice that the vibrations were quite high.
