Issue: Large QUAD initial tune

ArduCopter
1

I am struggling to get an initial tune for my large quad that is somewhat stable. Right after liftoff, the drone pitches forward and if I pitch backward to correct it, the vehicle starts to yaw to the right. I can barely get to a hover before I need to bring it back down. I’ll attach the param file and if anyone has any setup suggestions, I’ll try just about anything at this point.

Vehicle:
25kg, v-type frame, orangeCUBE, hobbywing x8 motors & 30" props,

quad_paramsV1.param (17.3 KB)

  • I can attach the recent flight log if that would help as well. I could barely get the vehicle to a hover before needing to land it.
2

It is better to post a log file… but from these symptons, it seems that you have motors spinning on wrong direction or at least a heavy motor imbalance, that can have many root causes.

3

Here’s a link to the last log file I have:
https://drive.google.com/file/d/1pR1UpdCbL8dVU39ZqBXFrIaqqZAqUzcN/view?usp=sharing

I checked that the motors were spinning in the correct direction and the propellers were also correct (CW vs CCW).
What is a heavy motor imbalance? If their is a motor imbalance (E.q. drone is front heavy) is there a way to correct this in software?

  • If needed, I could also add a link to a video of the flight
4

It is a bad practice to try to solve hardware problems in software. It might work, but it will not be robust enough to work reliably in all circumstances.

Fixing the hardware is the proper way to go. it will get you a robust, safe and reliable system.

  • So get your center of gravity in the geometrical center of the vehicle
  • Make sure the arms are not twisted
  • Fix propeller and motor imbalance (vibrations)
  • Prevent wind and prop wash for hitting your baro
  • Keep compass away from high current wires
  • Keep GPS antennas away from other antennas and electronics.
  • Make sure your propulsion system (battery, ESC, motor and prop) are powerful enough for your use case.

Beginners sometimes think that the above problems can be solved with some kind of magical parameter combintion. They can`t. You can sometimes hide them for a while. But they will pop up again at some point.

If you are putting some serious money on dangerous 25Kg vehicle, please be responsible and do your homework to avoid harming yourself and other people.

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5

I appreciate the detailed response! I was looking through the data log and I got a “Compass: failed” so I’m assuming this has something to do with one of my issues.

I may be getting terminology wrong here but the specific vehicle I’m working on is a spraying drone with a largish spraying boom on the front. This adds weight that is located forward on the vehicle and could be causing issues. Are their detailed ways to go about tuning or modifying the flight software to operate well with odd vehicle characteristics?

I definitely think that I am working through this build in a safe way. The vehicle has a multi-point tether to the ground which limits altitude and directional range.

6

Once you fix the hardware problems you tune all the vehicles the same way,

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7

You have to open the access man, I am not able to see it.

8

I appreciate you’re doing this in the name of safety, however if the drone is at all impacted by the tether then you won’t be able to tune it. As soon as the tether restricts any movement the PID loop will react inappropriately (particularly I-term) and this in itself could lead to the drone becoming uncontrollable.

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