Good morning to everybody,
This is my first post on the PX4 forum and English is not my native language. So please don’t judge me to hard. I am in to RC flying for over 20 years, fixed wing and I have only recently (2 years ago) bought a drone as I would like to learn about autonomous flight. My dream is to do some RC glider towing/ huckepack where the towing/ carrying plane is controlled by a flight controller.
I found a thread on the PX4 forum -> Very agressive oscillation in Position mode which describes a similar problem but was not really closed. After a warning from the forum that this thread was over a year old, I decided to start a new one.
My hex copter is a foldable Tarot 680 clone with fixed landing gear and an attached tarot 2 axle gimbal which is currently turned off.
- Controller -> Pixhawk 2.4.8 with release V1.11.1
- GPS -> UBLOX 7M with compass
- Motors -> Brushless MC 3508 with 700kv
- ESC -> HAKRC 35A with BLHELI_32 with latest firmware
- Propellers -> 12x4.5
- Batterie -> 4S Lipo with 5000mAh
- Telemetry -> Sikradio version 1
- RC -> either Multiplex M-Link connected via PPM encoder or Spektrum satellite
- Take-off weight -> around 1900 gram with an additional payload of 1500 gram tested with Naza V1
It flew previously with an upgraded Naza V1- lite and it was flying decently well, but it lacked quit a lot of functions compared to PX4 so I decided to go for an upgrade.
My first flight with the Pixhawk and PX4 flight stack was not really successful as the drone is very unstable if you roll or pitch with the RC controls in Position mode. Yaw just looks fine and positions hold is good.
Link to the log: https://review.px4.io/plot_app?log=a6e5f9a1-6452-45cc-aa83-36832b7e0819
After reading quit a lot of stuff about PID tuning I started to decrease both MC_PITCHRATE_K and MC_ROLLRATE_K from 1 to 0.5. These new settings did not resolve or even reduce my problem.
Link to the log: https://review.px4.io/plot_app?log=d94671a5-f831-4018-b325-c6285d1577b3
So, my next test were two complete autonomous flights including a take-off, three waypoints and a return to home with landing.
Here it looks as if the drone is flying fine with still some PID’s to be tuned.
Link to the 1. log: https://review.px4.io/plot_app?log=94979dad-3a88-451c-9eb9-26088c5494b8
Link to the 2. log: https://review.px4.io/plot_app?log=9d39fe0d-4543-46f4-bb4d-920a63f29f48
At this point in time I was ready to believe that my problems where caused by the PPM encoder as also take-off and landing were not going sweet in position mode. Decent was way to slow and land detector not working reliable as it was in autonomous mode or when landing via the land function in Qgroundcontrol.
For the next step, I borrowed as Spektrum rc set to test this. But unfortunately I did not see a difference in reaction of the drone in position mode.
Link to the log: https://review.px4.io/plot_app?log=a092047f-9037-4766-8c1a-c62552d7b518
As I was now almost ready to try everything, I switch to Altitude mode and all looks different. Both roll and pitch commands from the RC are followed by the drone as expected.
Link to the log: https://review.px4.io/plot_app?log=6203e444-8f0c-48a4-8011-aa1032dd4d60
P.S. Yaw was a little bit trimmed out of centre in the beginning of the flight which I corrected with the trims on the transmitter.
I have tried to upload the current settings of my drone. But I did not find a way to do this in the thread. In general the are the standard setting from the hexacopter provided by PX4 except for the above described parameters. If needed anyway, please let me know.
As for now I really hope that someone out there can help / guide me in the correct direction to tackle this problem. So at least I can start with PID tuning and do some nice camera flights. Any help would be appreciated.
I have tried to describe and document my problem as clear as possible, but as a newbie in PX4 I am not sure that I wrote down everything. So please, if you have any questions, feel free to ask.
Best regards, enjoy your weekend and stay save/ healthy in these strange times,
Maarten from Bavaria