Pixhawk Unstable Yaw

rdaries29

New Member
Hello, I have been testing with my recently acquired Pixhawk Autopilot for my Quadcopter. Here is my current components on the flight vehicle:
Frame: HobbyKing H-Copter H4-650
ESC's: RCTimer 45A NFS/Opto ESC
Motors: RCTimer 5010-620KV
Propellers: 10x4.5''
AP: Pixhawk PX4FMU
RC Remote: Spectrum DX8


We used QGroundControl to load the TBS Discovery Frame (H-Frame) configuration onto the Autopilot. We calibrated the ESC's and have tested the response of the system similar to that mentioned
in http://diydrones.com/forum/topics/arducopter-tuning-guide . We then flew the Quadcopter with the default gains of the TBS H-Frame and it rotated about the yaw axis continuously.
We then saw that as the throttle increased the built in magnetometer of the Pixhawk started seeing a slight rotation due to EMI, thus we thought it might be compensating for it. After viewing
https://groups.google.com/forum/#!topic/px4users/TbXFZf4EKDc , we adjusted the input to the Kalman Filter
EKF RC2 100 -> 1000000
to try and eliminate the interference. The problem in yaw still persisted.
The maximum attitude angles were adjusted accordingly but the response in pitch and roll seemed suitable for flight.
MC_MAN_P_MAX 35 -> 15
MC_MAN_R_MAX-35 > 15

However, when flown the Quadcopter continued to rotate about the yaw axis almost in a cyclic nature.


Initially, we thought it was the ESC's calibration that was a problem, we re-calibrated and the problem persisted. We then thought of increasing the proportional gain P for the Yaw Rate and the Yaw to try and compensate for yaw disturbance faster, the behavior remained the same after the flight test.
YAWRATE_P 0.28 -> 1
YAW_P 2.8 ->10
YAWRATE_MAX 120 -> 10



We then limited the max manual angles as a last attempt:
ACRO_Y_MAX 120 -> 10
MAN_Y_MAX 120 -> 10
MAN_P_MAX 35 -> 15
MAN_R_MAX 35 - 15

But the problem is still present. Please could anyone help with this problem. I thought it should work straight out of the box. I forgot to put the Micro-SD card in the APU to log the data during testing, so I do not have data but I will attach a video shortly.





 

JoeBob

Elevation via Flatulation
My Disco Pixhawk flies well with either 'X' or 'V' frame designations. Why 'H' ?
 

rdaries29

New Member
Hello All, here is the link to the aircraft in flight, http://youtu.be/cwYIXlxe6So . As you can see the Pixhawk fails to control in the Yaw Axis.
[MENTION=12080]JoeBob[/MENTION] , we thought of trying to fly it in a different configuration but based on the recommendations we saw in one of the forums they recommended H . I just checked http://diydrones.com/forum/topics/b...-frame-layout-option-in-mp?xg_source=activity as you recommended I will try and test with an X frame configuration. I will let you know how it goes. Thanks.
 

Old Man

Active Member
It does appear to be something that is set incorrectly since it will yaw in both both directions. QGroundControl I'm not familiar with but a bit later I'll try to grab a screenshot of the PID's on my X-8 and post for possible reference. If I recall correctly there is an "H" selection in Mission Planner for the set up phase but there may also be a reference to use an "X" config instead.
 

dazzab

Member
I've had quite a few copters fly well with the APM/Pixhawk. But like you, I had a Droidworx XM6 hexa that had the same type of yaw issue. I tried everything to get rid of it to no avail. In frustration I changed the flight controller which took care of it. Never did figure it out so I'm most interested to see how you go.
 

Old Man

Active Member
Meant to get back to this sooner but things got in the way.

It does appear that APM/Pixhawk has some notes about H frame configuration and motor prop directions in their Wiki, You can find those here: http://copter.ardupilot.com/wiki/initial-setup/configuring-hardware/ There is some more info and depictions in the mandatory hardware set screens in Mission Planner. It may well be that down loading Mission Planner and its drivers could be more effective for your set up.

Attached a couple of screen shots for the PID's in use on my X-8. Obviously they won't be the same for you but the copter sizes are not that far apart so they might be reference helpful

attachment.php
attachment.php
 

Attachments

  • Pixhawk PID-2.jpg
    Pixhawk PID-2.jpg
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  • Pixhawk PID.jpg
    Pixhawk PID.jpg
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R_Lefebvre

Arducopter Developer
Can you attach a datalog of one of these flights? I'm wondering if the problem is simply the Yaw Rate Imax being too low.
 

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