Quadcopter flipped by itself and now losing power in flight

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FightingFlight
Posts: 16
Joined: Sun Jun 07, 2015 9:04 am

Quadcopter flipped by itself and now losing power in flight

Post by FightingFlight »

Hi all,

Wondering if anyone might have some insight as to what happened -
I flew for about 20 minutes already without issues, I swapped the battery, ran it for 2-3 minutes and was flying my quadcopter low to the ground in Angle mode (I always stay on Angle mode - I'm a beginner), it was wobbling a little bit and then all of a sudden it flips a few times and crashes - https://www.youtube.com/watch?v=6ChjAzbaBoc

I've probably done 20 or so flights in total, have had worst wobbles than this where it falls but continues to wobble (though I think it's more my fault with that) but haven't had any weird flips happen. I checked my TX and it was still on Angle mode. I sometimes have a bit of drift in Angle mode and find it's best to land, wait a few seconds and then take off again.

My setup
MultiWii 2.4 on an Arduino Pro Mini (from ebay) - powered from ESC BESC
MPU-6050 3-axis accelerometer + 3 axis gyroscope
ZMR250 250mm Fiberglass
DYS 2300KV Brushless
TURNIGY Plush 12amp (2A BEC) BESC
Gemfan 5x4
Turnigy TGY-i6 AFHDS Transmitter and 6CH Receiver (Mode 2)


Interested to see if this has happened to anyone else?

Thank you!
Last edited by FightingFlight on Sun Jul 05, 2015 8:14 am, edited 1 time in total.

Cereal_Killer
Posts: 221
Joined: Fri Mar 06, 2015 5:44 am

Re: Quadcopter flipped by itself

Post by Cereal_Killer »

There are several things that might cause that, what other symptoms can you give us now? Take the props off and do some testing; hows it working on the ground?

Was it windy? Have you started tuning it or running default gains? What's your RC rate and any expo? Are the RC inputs at an even 1500? Did you go threw the radio setup?

FightingFlight
Posts: 16
Joined: Sun Jun 07, 2015 9:04 am

Re: Quadcopter flipped by itself

Post by FightingFlight »

Thanks for your reply, I'm starting to suspect that it may have been a prop failure as I did crash into a tree a few minutes before but didn't replace any props so I think I'll always inspect them for any white stress points when I crash and replace them, I'll keep monitoring and see how it goes.
I've now replaced the spinners with nyloc nuts and it's all working ok again.

Yes it was a little bit windy but I've been in much worst.

Yep I had to tune everything much lower than the defaults as it wasn't flyable at all, here are my PIDs at the moment but I think it still needs tuning for the level I setting. RC rate / expo are default 0.90 and 0.65. The RC inputs without trimming are around 1498 to 1502, when moving the stick and letting go it jumps a little lower or higher than 1500, but sometimes does go to 1500, I hear that's normal. I went through most of the TX settings, is there anything I should look into?

Also another thing I don't understand is, when you trim the TX in acro mode so that the quad doesn't move, then you switch to Angle/Horizon mode to trim the Accel. Do you leave the TX trims as they are or put them back to 0?
If you leave them as is, won't that mean that you aren't completely in Level mode as you are slightly putting input on the sticks via the trim to adjust the quad and thus Accel trim may not be fully correct?

Image

Thanks again!

Edit: I flew again today, the 5x4 props made it wobble a bit so switched back to 5x3 and they seemed to work good. I am looking to go into Horizon mode as there were some times where I needed it to move forward but it felt like it wasn't moving much at all. I have tried Horizon mode before but I find that the sticks are a bit too sensitive, all I need is a bit more power than Angle mode at the moment.

Cereal_Killer
Posts: 221
Joined: Fri Mar 06, 2015 5:44 am

Re: Quadcopter flipped by itself

Post by Cereal_Killer »

FightingFlight wrote:I have tried Horizon mode before but I find that the sticks are a bit too sensitive, all I need is a bit more power than Angle mode at the moment.


Your rates are both set to 0! these are the green boxes right of the PID's in MWConfig. Try bumping the ELE/AIL up to .80-1.00 and the yaw to ~.75 and try that.

As for the trimming question, you shouldnt actually add and stick trims on your Tx, you trim the ACC to stop drift. Disarm motors, throttle full up then hold the right stick in the direction of trim you want to apply. It'll flash / beep to confirm. Each "click" is one TINY step so you may have to give it 5-10 clicks in a direction before you notice any difference. I NEVER touch my Tx trims (sub-trim at setup yes, trimmers never).

Also remember, any time you re-calibrate the ACC you will loose your ACC trimming and have to redo it, get a bubble level and a deck of cards to calibrate the acc and then leave it, dont redo it out at the field or anything...

FightingFlight
Posts: 16
Joined: Sun Jun 07, 2015 9:04 am

Re: Quadcopter flipped by itself

Post by FightingFlight »

Thanks, I've increased it and I think there's good difference, need to go somewhere with more space to give it a real test.

FightingFlight
Posts: 16
Joined: Sun Jun 07, 2015 9:04 am

Re: Quadcopter flipped by itself

Post by FightingFlight »

I set my PIR PR rate to 0.3 which is sufficient enough for my needs and seems to work good.

Although I have had it flip another 2 times, once left and once right. When it flipped, I went home, left it for a few hours, changed the bottom left prop and then 2-3 minutes it happen again, when flying ~1m off the ground insideand just hovering in Angle mode with some small corrections on the TX sticks by me. I inspected the props, only the 2 left ones were damaged. I think it's fair to say it couldn't have been the left props as if they broke then it wouldn't have had enough power to lift the left side of the quad.

So I'm starting to suspect it might be MPU6050 sensor, possibly the i2c between it and the Arduino or maybe the Arduino is resetting itself (I did see another person have this issue and other users say they should add more caps). I have purchased an Arduino with MPU6050 built into the one board which should arrive in 2-3 weeks and I'm looking to swap to that so I have more space on the quad to work with (planning to add GPS).

Edit: Early today when trying to fly the quad outside, I did notice that MultiWii LED keep blinking and wouldn't let me take off, I just had it on some grass and it looked like the blink sequence it does when the quad isn't positioned in a flat surface but it pretty much was (related to accelerometer). I re-connected the battery like 4-5 times and then it finally worked.

Also I starting testing the MPU6050 and there could be a bug in MultiWii but it's a rare condition and not something you would do but if you power it up, have the quad at an angle so the Multiwii LED blinks that says you aren't positioned in a flat surface and then arm it. What I notice is the accelerometer freezes in the GUI and then it looks like it restarts MultiWii on the Arduino because the cycle time goes negative and then you can see the Arduino keep resetting / GUI shows no updates(as long as ARM is on) and then once you put ARM off, it slowly comes back. Also the same thing happens if you have the TX on with ARM on, then plug in your quad battery, it keeps resetting.

Edit 2: Hmm, when testing the i2c connection, if you have the motors spinings (no props of course), then disconnect an i2c wire, the accelerometer view does show it flipped at 90 degrees and 1 side of the motors max out, though in more attempts of doing it, it can sometimes go all over the place. But then again, since the MultiWii GUI shows i2c errors, it would be good to keep the last known state or to set the quad motors to operate in the fail safe mode. I see there is a fail safe, I'm not using it (my RX does it) but it doesn't mention an i2c fail safe.

I'm using pin headers at the moment, I guess I could try just soldering a direct connection. Also just for reference I'm not using an 3.3V to 5V i2c interface board which could be an issue but I heard of others doing the same thing, I guess we'll see when the MPU6050 + Arduino all in one board arrives.

Edit 3: I re-did the wiring soldering a direct connection between MPU6050 and Arduino, added a 10uF elec cap on the MPU6050 and an 100uF elec cap on the Arduino, so far it hasn't flipped yet.

FightingFlight
Posts: 16
Joined: Sun Jun 07, 2015 9:04 am

Re: Quadcopter flipped by itself

Post by FightingFlight »

So things have been fine until yesterday, I was flying it around a big open field and then I got close to the one edge of the field (only 50m away), rotated the quad and then it loses power then 3 seconds later the motors start back up (I put the throttle down and then to max which I think made it start back up as they did), it landed flat and only the camera LCD broke.

https://www.youtube.com/watch?v=mgHeZd6mBx0

I had the new MultiWii board I was expecting so it was a good chance to change the board and I put in a 100uF elec cap on the 5V just for good measure and took it out for a try, a 3 minutes in and I had the same problem, this time I was pretty close to a mobile tower and when it turned I felt that my pitch forward wasn't doing anything so I gave it full forward pitch and still didn't seem to do anything and then it lost power.

I've tested the Turnigy TGY-i6 AFHDS Transmitter and 6CH Receiver to 300m and haven't had any issues before. I have the RX failsafe to turn off the motors and ARM off too. So I'm thinking it's either the transmitter/receiver or the 5V BEC I'm taking from one of the motor controllers or could it be something else?

Edit: I tried running with props off at mid to full speed for a while, didn't see any issues with the BEC, gave a steady 5.045V. I tested the transmitter and I never really noticed the error rate, I put my phone close to it and started using the wifi, it got to 50% error but the motors still keep spinning (this was inside the house). I wonder if there is a way to alert you if the error rate is too high. I put the transmitter in the microwave, closed the door and the motors stopped as expected. So I guess that's another possibility, too much interference.

FengShuiDrone
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Re: Quadcopter flipped by itself and now losing power in fli

Post by FengShuiDrone »

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Last edited by FengShuiDrone on Fri Aug 07, 2015 1:48 pm, edited 1 time in total.

FengShuiDrone
Posts: 234
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Re: Quadcopter flipped by itself

Post by FengShuiDrone »

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Last edited by FengShuiDrone on Fri Aug 07, 2015 1:49 pm, edited 1 time in total.

FightingFlight
Posts: 16
Joined: Sun Jun 07, 2015 9:04 am

Re: Quadcopter flipped by itself and now losing power in fli

Post by FightingFlight »

Thanks for your reply, I've left throttle as is by default, I'm changing batteries when flying and I don't seem to mind adjusting a little bit to suit each one.

I'm arming via aux1 because I did see that you could also arm with yaw and was a little concerned about that so I switched it off and only arm via aux1. I've also got aux2 to switch between angle, acro and horizon.

In acro mode I just use the trim buttons on the TX and fly it around a little while switching between acro and angle to see how much more trim I need. I haven't used subtrims. Once trimmed then I double check acro and use the sticks to adjust the ACC if needed (usually not needed). Though now when I do the trimming it's usually ok, it drifts a little bit but since I've got different batteries I tend to expect some drift now, but it's all controllable. I have had it once or twice be perfect, but maybe because there wasn't much wind.

I think you are right about the COG because I usually have to trim it way up to the top max for 2200mah batteries to counteract the battery not being right in the center due to the camera.

About my power loss, I think I'll go back next weekend to the same spot and check my TX error rate when flying near the mobile tower, though many people say mobile towers shouldn't really affect the signal.

FengShuiDrone
Posts: 234
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Re: Quadcopter flipped by itself and now losing power in fli

Post by FengShuiDrone »

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Last edited by FengShuiDrone on Fri Aug 07, 2015 1:49 pm, edited 1 time in total.

FightingFlight
Posts: 16
Joined: Sun Jun 07, 2015 9:04 am

Re: Quadcopter flipped by itself and now losing power in fli

Post by FightingFlight »

Took it out to the same place and it happened again, seems to happen when 15-20m high up, I briefly saw the error rate go to 10% - https://www.youtube.com/watch?v=DnfQnG_LS0E

Went to a different park, got up to 30% error without issues. So something is definitely up with the previous location.

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