Hi All!
My Pixhawk is installed on Mariner quad (500). With the version 3.2 it has many nice flights, with very good ALT Hold control and AUTO flights.
After recent upgrade to 3.3.2, it changed its behavior: in Stabilize all is OK, stable and smooth control, hovers on 50% Throttle. When switch to Alt Hold, it starts rising up at full throttle! When switch back to Stabilize, all is OK with the control. Sometimes the rise up is hard to compensate with the trottle....
Looking at the logs, all seems OK, except the inconsistency in the IMU - accelerometers 1 and 2 shows different phase after switching to Alt Hold.
Do you have any explanation? Hardware fault or 3.3.2 software bug?
The last test flight log is enclosed.
Replies
I had baro issues on both copters, the Mariner is closed and watertight....
There is bed for foam on the lower half of the Pix box. The original foam is very light and cannot damp the wind and propeller bursts.
You shouldn't glue - need a free access to the air, but thru the polyurethane structures.
The absolute value is not important, and even can rise slightly. The baro is not thermostabilised, and the readings depend of the temperature.
Most important is to give correctly the relative height between the launch position and the current height.
In the mission planner you can put the actual height of the launch point.
Hi,
First i can see, that you fly at high speed - 10-12 m/s, that is not good for non tuned machine.
When you switched to RTH at the end, the satellites drop to 7.
The copter went in roll oscillation, that shows not good tune. Should tune the PIDs.
There is a lot of magnetic field change - seems there are magnetic parts (screws), that interfere with the compass. Have to replace all around with plastic screws.
Do you use the compass on the GPS post? In the log only one is shown.
The copter is overpowered - ThrOut – 300 average - have to tune that, and use damped controls for throttle, pitch and roll - machine seems too "nervous"
You should set proper Failsafes - Battery about 13 volts (all the times generates FS)
And the fence should be real one in circle and height, to avoid FS
The radio control was OK, all commands were received, but the copter cant respond properly.
Did you switched 3 times the RTL or the copter breach itself the fence?
Sometimes the bad reaction to the radio commands are result of receiver bad wiring.
I always use second 5V BEC to the receiver and the Pixhawk servo rail. And use additional ground wires between receiver and Pixhawk.
The FPV should independent BEC from the battery. No any connections to Pixhawk.
There is issue with the compass, you should never use the internal for main compass.
It is good to have it working, but not as main.
The compass that is in the NEO8M should be perfect, as away from the copter body. Look at all screws in the NEO body - maybe are magnetic? Remove them and test. Then you can just glue the plastic parts. If still compass bad - it is damaged.
But there are some more issues...
Look at the picture:
The ATT Roll doing huge Roll variations (ATT DesRoll is good), that means that copter cannot balance itself, due to kind of mechanical failure - huge motor/arm vibrations, not good ESC/motor/cables, or problem in propeller.
Liik at the left/right arms, there should a problem.
In general the machine is over powered, the ThrOut should be close to 500.
Probably the platform need the weight of the gimbal/camera added to have proper weight. You can use larger battery if no plan to use camera.
If you plan to add camera, use dummy weight around 400-600 gramm (or more) depend to the camera/gimbal weight you plan to use.
Then test and see what is the ThrOut. Could be in range of 400-600.
Battery is not so bad - it still gave 13V at full throttle at the end!
cool detailed .bin log file analysis :)
Yes! After removing the buzzer away, all working perfectly!
No any issues with the baro, compass, etc.
It is same good result with the other Pixhawk clone.
You should reduce the vibrations to minimum - do you use damper plates?
It is the only way to use the Pixhawk. Here is photo of mine.
Normally I use tethered set with bungee for precise manual tune of the PIDs.
The procedure is well described here.
My set photos enclosed. I do separate Roll and Pitch tunes if non symmetrical frame.
Yaw is easy to fine tune on the strings also.
Mariner2.jpg
Mariner3.jpg
I use the same tune procedure for S900 - just tie the bungee to the copter body, and use two poles outside.
Do you have the 15.bin published to look on?
The log looks good.
Do you have barometer air damping with dense polyurethane, as described there?
I had same with the S900, the air blow from propellers offsets the barometer, and the alt hold is dropping.
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