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Quadcopter tilts at take-off

Hello,

I have built a drone with these characteristics:
Frame Tarox XS690
Pixhawk 2.1 Cube with Arducopter 3.5
4 x ESC T-Motor Air 40A
4 x Motor T-Motor MN4012 KV480
4 x Propeller T-Motor P16x5.4
Battery Tattu TA-15C-12000-4S1P (12000 mAh)

The motors turn in the right direction and every propeller is properly installed. After the mounting and calibration process (radio, accelerometers, compass, ESC, etc.), I tested the drone, but it tilted to the left at take-off moment.

It could fly, but I had to move the roll stick slightly to the right to level the drone, although it also is slightly forward tilted, so it moves forward once it is in the air.

I tried exchange the similar propellers between them (CW with CW and CCW with CCW) but it still tilts to the left, so I guess there is no problem with the propellers. I exchanged front ESC: left to right and vice versa and again the drone still tilts to the left, so I guess there is no problem either with the ESC.

Finally, I exchanged frontal motors and this time the drone tilts to the right. So I guess, there is problem with one motor. This motor rotates, but it probably does not rotate at the right velocity. Is there an objective way to verify this? I am a newbie and I don’t still master the log assessment.

It can be seen that the “failing” motor starts rotating slightly later than the others. I even tried calibrate ESC once at a time and all at a time, but no matter what ESC I use or no matter in what arm the motor stays, it start its rotation most of the time a bit later than the others.

Have you any further thoughts about this problem? I would appreciate it very much.

Thanks!!

I did have a similar issue one time, on a 250 racer with Pixracer, updated the firmware and it had a permanent roll to the right.
Recalibrated everything but nothing worked.
Erased the board by installing rover and reflashed copter and all was good again.

One way to address this is to do a calibrate level. place the craft level and look at the hud if the craft tilts right turn the craft a few degrees to the left and hit the acells level. the trick is to find the sweet spot altho if you add stuff like a gimbal it best to re level.

I use two or three spitrit levels across the motors when doing my accelerometer level calibration.Also worth checking the motors are all in the same plane (prop tip aligns with prop tip all the way around).

Check all trim sliders on the radio.I’ve even had a bad connection to a gimbal in the radio cause a crash by pulling hard right just after take off.

Post a log so we can see the behaviour.

Having said that I will always do a punchy take off on a first flight just to get it in the air and out of ground effect.

Thanks Mike. I don’t know if your solution would work for me. My drone tilts towards one of the motors. If I change its location, then the tilt direction changes as well. Thanks a lot for your suggestion. I will take it into account too.

Hello Brandon.

I calibrated the FC accelerometers off the frame because I could turn the FC in all positions for the calibration process. But after calibration I mounted it over a anti-vibration platform, like this one: https://rc-innovations.es/Pixhawk-Ardupilot-erle-robotics-autopiloto-codigo-abierto-drones-DIY-multicoptero-multirrotor-naze-openpilot-kk/placas-amortiguacion-controladora-vuelo-ardupilot-arducopter

After mounting it seems to me that it is not completely leveled. The HUD shows -1 or -2 instead of 0. I don’t know if this is because of the platform. I wonder if I should remove it.

Thanks

Hello Jagger,

I will buy a spirit level. It seems a nice idea to me.

The trim sliders are all to zero position.

I have not the drone by me. I will post a couple of logs later.

I thought of taking off quickly but I am afraid the drone would crash. I will try this afternoon and will post a log here. Let’s pray, hehehe.

Thanks.

Doing the accelerometers on the craft could be better idea if you can. Regarding anti-vibration I would remove it and use dbl stick tape. What your after is to get the craft flying level the bigger the frames can have a arm lower of higher in flight or a propellers can pull. Compensation adjustment can be done using the aceles level button. lets say the craft is nose heavy slightly tilt the craft back a few degrees and hit the level button before flight. There could be a FC stick combo to level not unlike arm but i am not sure what it is.

Don’t try and put in any compensation.
Calibrate the copter fully constructed and make sure that the horizon in the HUD on MP is level.
If your copter is not properly balanced it just means those motors on the heavy side will be working a bit harder to stay level.

For the first lift off of new builds they never want to go straight up.
You need to pucker up and punch it off the ground and out of ground effect.
Not too high, 1m is fine. Just work at keeping it about waist level.
Give yourself plenty of room so if it does drift you have time to catch it and put it down gently.

After the first flight check the logs to see how your vibration damping is working for you.

A couple of logs:

https://drive.google.com/file/d/1HIPkBfBnv_sKJ-JTniyCMljfFDogKiOx/view?usp=sharing

https://drive.google.com/file/d/1lyWqJJkPR_hhx7Y-FLHDqevMyjRIT5Wb/view?usp=sharing

You’re trying to coax it off the ground and it doesn’t work well for a new build.Once it’s tuned in it will take off gently but with stock PIDs you really need to grit your teeth and give it a large lump of throttle,preferably just over 50% and then settle back down to the hover point it wants in stabilize.It wll feel much better when it’s in the air.Hopefully (we all have to grit our teeth on a maiden flight).

Hello Brandon,

I am going to remove the anti-vibration item and after that I will calibrate the accelerometers again on the craft.

I calibrated the FC off the craft because the tips in Ardupilot Accelerometer Calibration web:

  • It is important that the vehicle is kept still immediately after pressing the key for each step.
  • You may need to calibrate the board before it is mounted if the size/shape of the vehicle makes this difficult.
  • The level position is the most important to get right as this will be the attitude that your controller considers level while flying.

I thought, I better calibrate on its own.

Thanks!!

Thanks for your advices Mike. I will give a try.

The copter weight is balanced (more or less). It has no gimbal, just the copter with its heavy battery (around 1 Kg) attached below.

I will try to take-off in a field with some grass. I don’t know if it will make the difference with a harder ground in case of a crash.

Is there a recomended web where I could learn to know and assess the log information, as well ass some tools to automate the assessment. I use the Arducopter web, but it seems to me a kind of reference manual which is fine to read when you are proficient but not a newbie.

Jagger, I will pray and I will try it. Hehehehe. Thanks !!

In the Wiki there are instructions for logs analysis here

Thanks Mike, that is the place I was reading. I will read it in depth. I appreciate your help.

Hello @mppt ! Did you manage to solve your problem? If yes - how?

Are you still on AC 3.5?
You need to supply a .bin log for people to look at. There’s no 1 reason or solution to the problems you are asking about.

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