Occasionally in Q_Stabalise I get these oscillations, usually at the end of the flight rather than the beginning. I know there is not much ‘overhead’ in terms of hover power but Im not convinced its this. (new props ordered to help with this)
I guess it could just be airframe harmonics?
If anyone bettter at the logs than be would care to take a look, that would be great.
The oscillation seems to occur on roll while it tries to correct for yaw. PIQR.D oscillates and seems to correlate with yaw error on 1st harmonic.
Maybe d-gain is too high and it shows on low battery only.
I have to point out, that I have no experience with q-planes or tri-planes in particular.
On a quad copter you would sort out frame torsion as a cause by reversing all motors and swap props. Then torsion would go the other direction and may even benefit yaw.
Thanks for taking a look at it. I didnt notice a problem until I replaced the tilt servos. It had many hours flying before that. Ill probably just go back and do a manual tune. All 3 props are well balanced but there seemed to be a ‘buzz’ noise coming from the airframe.
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I have been through the setup again before starting a re-tune. Thought I had everything ‘in the ballpark’ but then I ran the ‘initial tune’ and it came up with a few completely different values.
Any advice on what these values should be please?
Its a yaw vectoring tri-vtol of about 3.6kg 4s with 15" props. Thanks
Check out JB’s videos on PID tuning.
As an engineer I truly respect his early work for the practical approach before he became a full-time youtuber.
Part 1 describes the basics, Part 2 and 3 have sound examples.
If the Frequency of the buzz stays the same, it’s P-Term, if it’s warbling over a frequency band, it’s D-Term.
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Have slackened off the tune a bit and it seems much better. I think rate roll D was the main problem.
Have been taking a look at the PID tool. Should I worry that the ‘step response’ often dosent actually get to the target as in the pic? The default of many ‘I’ terms is zero anyway? It seems to fly ok though. Just done my first totally auto mission - see vid. It also showns the ‘weathervane’ function at the landing hover.
I see slight oscillation in flight on the roll axis which can be the plane version of i-gain.
Other thing that I see is the tail waggling which indicates that you constructed a pendulum, tail boom + motor weight - vertical stabilizer , typical Y-Tail issue.
You may want to evaluate a traditional or a T-Tail on next iteration of the plane.
I can’t deny the plane looks good. Well done!