Hi all,
I know that this is a very recurrent question and I apologise for any redundancy.
I assembled recently a Tarot T960 frame, T-Motor MT3514 400 (X6), T-Motor ESC 40a (X6), emax 6 axis power board, Pixhawk, 3DR GPS module(X2), 3DR telemetry radio, RC Taranis X9E and receiver X6R.
I managed to get it airborne during first trial, but unfortunately, one of my props was not tight enough and came off in the middle of a flight. The hexa landed with the arm missing the prop, which obviously broke. It also inutilise one of the land gear arms.
After getting the spares and assembly the hexa again, it doesn't want to fly. Instead, it flips as the video shows.
Any ideas on what could be wrong?
Yes, props are all spinning correctly, motors seem to have the same speed, no weird noises, frame set to X shape, etc.
https://drive.google.com/file/d/0B_iZNL5M2cKIU2dxN0FqMHNZZ28/view?usp=sharing
Replies
Arnoldo, I think your ESCs may be plugged into the wrong ports. Lets call your motors 1 o'clock, 3 o'clock, 5 o'clock, 7 o'clock, 9 o'clock, and 11 o'clock. That corresponds to A B C D E and F in Mission Planner. When performing the motor test, they should go in order starting with 1 o'clock and going all the way around each motor to 11 o'clock. Please trace the ESC wires and tell me which port number corresponds with which o'clock number.
Hi Stephen,
Thank you for the time and effort. It is very weird, the motors and esc are wired according to this diagram
hexacopter.png
Regarding your motor spin test video it looks you put the esc into the pixhawk not in the correct ports. I assume you clicked down from A to F down. So it should run the motors clockwise round your frame. Like Stephen said, 1 o'clock starting.
Could you provide a video with the hex in flight configuration performing motor test from A to F? Even i have a Tarot Folding Frame myself i get the arms in folded configuration sometimes wrong.
What i did to get the ESCs plugged in correctly: Took all out the Pixhawk and plugged them according to the motor test and the graphics you got in. Started with a random esc, plugged it in and watched which motor spins. Than i took it in the correct port of the Pixhawk. And that i've done with all of the ESCs. For me it was fool-proof because i can check for spinning direction and the correct port in my pixhawk
edit:
even it looks all correctly alligned you could check the board orientation in full parameter list. That was something i got wrong one time after reset. Parameter ist AHRS_ORIENTATION. I got the yaw off by 180 degrees and that causes direct flip on takeoff. Doesn't look like this is your problem but you never know..
@Niels,
I would like to turn your excellent manual on how to avoid flipping
into Self Diagnostic Tool (pre-flight diagnostics on arm).
Since IMU.Gyro is highly sensitive instrument, IMU.Gyro output can be
processed to detect variations in horizontal plane due to thrust/ lift force generated by individual motor set on ( RPM limited within safe range to avoid flip during diagnostic test).
Mission Planner can support such pre-flight Self-Diagnostic Test.
Could you tell me how to contact developer of Mission Planner to discuss
the implementation ?
Anti-Flipping Diagnostic Self-Test could be run before every take-off by default, disarming motors if failed.
There is a Mission Planner section of this forum used by the developer, you could make a thread to propose this feature. However, my bet is he'll want to keep using the existing feature due to the K.I.S.S. principle, it already lets you inspect visually. Plus depending on your landing gear configuration, the vehicle may not tilt "away" from the motor under thrust.
Stephen is right.
If ESC ports on Pixhawk are mixed and no fixed thrust can be assigned to all ESC on take off, it means Pixhawk processes sensors' output data from the very beginning on take off.
So any roll, pitch detected gets increased not corrected.
I would like to implement, Pixhawk ESC ports correct matching diagnostic tool, since
learning mode is not supported.
Pointing smartphone's camera from top downwards to have all propellers in the field of view and let pixhawk to switch every motor individually on and have image processing software to detect which propeller is active, sending layout feedback to Pixhawk.
No need, there is a simple solution already implemented.
http://copter.ardupilot.com/wiki/connect-escs-and-motors/#checking_...
When testing the motors in order, they spin starting with the motor at the 12 o'clock position (motor A), and goes through each subsequent motor in a clockwise direction.
Now, for my actual advice. Scott W already said some good stuff. Please post your flight log. From that, we will be able to determine if the autopilot commanded the vehicle to flip (software error), or if the vehicle flipped despite the autopilot's best intentions (hardware error). This is one of the most fundamental requirements for troubleshooting.
Examples of hardware errors include: ESCs not wired to the correct ports on the pixhawk, motor spin direction backwards, prop on upsidedown/backwards, excessive vibrations, ESCs not calibrated properly.
How to fix: describe to us exactly which wire in which port of the Pixhawk goes to which ESC. Trace the wires carefully. Send us pictures of the props installed to make sure they are all on correctly. Do a motor test in Mission Planner to check motor direction. And ask for help properly calibrating your ESCs.
As for software problems... we'll cross that bridge if we come to it. There are others more qualified than me to troubleshoot that.
Obviously ESC timing sync problem
or unbalanced airframe, or ESC power distribution problems.
On idling, propellers don't spin at the same RPM,
what is clearly seen from your video (strobo effect).
Not sure have been ESCs are pretested ( Drone Certified) and preselected by a manufacturer to match RPM within full RPM range to a 1 RPM.
If not you get different RPM spins on idling
and different RPM spins on taking off, making your Hexa to flip.
Ok, within few days I am ready to test RPM of individual propeller with strobo
and test all Hexa propellers at the same time to discover RPM irregularities, if any.
Ask ESC manufacturer if all your ESC can read Pixhawk clock heartbeat to sync
before taking off.
I am afraid, you should be given an opportunity to buy preselected set of 6 + 2 spare ESCs for your copter, the same for motors and propellers.
Try to fix your drone to the ground and apply safe RPM range to propellers, to keep them spin at higher RPM but still not ready to take off
and use strobo to study individual RPM irregularities, if any.
(email me directly to not give trolls a chance to spam your thread)
Open Technology Park
Open Fabrication Lab
Peer To Drone Crash Investigators
manta103g@gmail.com
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