I finally finished my T1 VTOL but have not been able to get it in the air so far. There are errors of all kinds (GPS, EKF, IMU…), the craft is rotating, tilting (motor/prop directions are correct) on the ground. I’ve never seen anything similar before on anything I’ve built.
clearly, the GPS is having issues…the EKF is showing very large horizontal position innovations indicating that it cant reconcile the incoming GPS positions with its inertial predictions from the IMUs…and since vibs are low, the IMU predictions should be correct…
either the GPS is wonky or getting electrical or RF interference…that’s all I can dig out of the logs
Thanks a lot, I never would have guessed at the GPS. It’s a brandnew Flywoo GOKU GM10 Pro V3 (with compass), not in the vicinity of any ESC, pretty close however to the Crossfire RX antenna. Not sure if the rather low output when transmitting telemetry would be enough to confuse a GPS, but of course I’ll try placing both further apart.
It just came to my mind however, that some earlier logs, created indoors without GPS lock. also showed signs of nonexistant horizontal movement: Unique Download Link | WeTransfer (discovery courtesy of @andyp1per )
Also check that you have connected motor 1 and motor 2 correctly, that the direction of rotation is correct and that the propellers are mounted correctly. You will notice in the log file that DesRoll and Roll immediately diverge when lifting and that the two front motors are controlled with completely different power. Usually you have similar PWM values on the two front motors when a TRI takes off.
Correct, sorry I forgot to mention this (the whole thing has been going on for weeks) - motor 1 + 2 were indeed still swapped when I recorded this indoor log. I fixed it before taking the T1 outside.
Turns out the assignment was in fact correct indoors:
S4 = left ESC = motor 2 = 34
S6 = right ESC = motor 1 = 33
as per
and has indeed been incorrect since I first took it outside. I thought I had checked it repeatedly
between attempts and can only blame this on increasing frustration with the project, as well as all the other types of errors that came up (EKF).
I can’t understand why the indoor log (with still correct motor config) shows the same effect, but I guess it doesn’t matter now, as the current config is definitely incorrect.
Side note: I placed counter-rotating props on the front motors as shown in the picture and always wondered if there are additional settings to be made because of that but didn’t find anything in Tricopter Configuration — Copter documentation
Will test suggested fixes (GPS/motor) next week and report back. Thanks again!
Opposite motor direction of the frontmotors is obviously, but I would not adopt the direction of rotation from the copter wiki if you interpret the direction of rotation from above. In tiltrotor VTOLS the right motor should be CCW, and left motor CW. The copter is a different matter, as it does not normally have tilt rotors. The reason for this is that during transition while props are not yet vertical, the torque should not work against the rolling movement of the fuselage if an increase in power is required (in order to control roll).
This time it almost looked a bit like flying for the first time (max alt: ~1m), but I wasn’t able to get it into a stable hover. There was some wind too (starting exactly at that time of course), but I’m not sure that’s the only reason. So I’m still grateful for any analysis / hints on what to improve.
You can see that you only climbed to a maximum of 50 cm and then landed again quickly. Presumably because the VTOL started to oscillate around the roll axis?
Have you had carried out “Initial Tune Parameter” of the Missionplanner ?
You must proceed according to the instructions in the above linked WIKI-Page , whereby you must note that the parameters that begin with ATC_RAT_… are called Q_A_RAT_… on the VTOLS.
In your case, the roll axis appears to oscillate with increasing amplitude. You should reduce Q_A_RAT_RLL_ P/I/D by 50%.
Something like that, yes, although the direction of oscillation was a bit hard to make out on some attempts. Wind had picked up, pushed the craft towards me, away from the grass and towards concrete surface instead, so I aborted quickly to prevent damage. Here’s a clip (not sure it’s the same attempt as in the log though): Unique Download Link | WeTransfer
Additionally, before I started this thread, @andyp1per and I were already at it, ironing out the worst in the PIDs (first takeoff attempts indoors showed massive fast oscillations), and I also compared my PIDs to his, the aim being able to get the craft to QAUTOTUNE at some point to let it fix the rest by itself.
My Q_A_RAT_RLL_P is already much lower than his (0.05 versus 0.3652097), suggesting I probably already lowered it multiple times, but will set it to 0.025 now, and also half I and D. Looking at the wind forecast, next chance to test will be on Thursday.
