Crash Diagnosis

Info and discussion about the autonomous Micro FC, suitable for nanos, micros and mini multirotors

Crash Diagnosis

Postby pilotnbr1 » Mon Jul 04, 2016 12:13 am

Hey everyone I was hoping I could get a hand with analysis of this log. The flight basically was manual up to about 10 meters, then position hold engaged, a further climb in position hold with me pushing the quad around a bit. At altitude it acted odd a few times and breifly did not respond to my inputs where I thought I had lost my radio link. after a time I disengaged position hold and was able to get it back on the ground. The whole thing just seemed odd.

So I did another very short flight at the very end of the log file. I lifted off about a meter and the quad flew backwards right into a patio table. Completely out of my control and di not respond to my inputs.

I looked at the logs but as a rookie I did not see much. Radio link was good gps vac and hac seemed normal. I did see 2 places where there were radio errors though- not sure how significant those are.

I also have a video from my fpv cam if anyone is interested...

I couldnt upload the file becuase of the 5mb max so here is a google drive link-
https://drive.google.com/file/d/0BzvIcW ... sp=sharing

Thanks!

Luke
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Re: Crash Diagnosis

Postby chschmid » Mon Jul 04, 2016 9:16 am

Hi Luke

On your log is only one short flight. I can see very high vibrations. The motors go wild.
Do you have some more info about your craft?

Best
Christof
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Re: Crash Diagnosis

Postby pilotnbr1 » Mon Jul 04, 2016 3:03 pm

Hi Christof, Thanks for looking. Yes it really all was one short flight with two landings just before the crash. The quad is an-

280 mm Nighthawk carbon fiber frame just running pids.

Other than balance props are there pid changes I can do to improve vibration? My motors do get warmer (not hot) after a 10m flight.

Edit- I was also going to ask what the units of time are on the bottom? Is that milliseconds? Additionally what would be a normal range of imu_acc (I am assuming this is what you see with vibration)?


Its funny you mention vibration because I have been trying to eliminate vibration as I have been getting alot of jello and even malfunction of my fpv system. Just before this flight I had balanced my 3 blade carbon fiber probs but still obviously have some vibration in the video. The fpv system is wifibroadcast that I was testing with 5.8 ghz and a cloverleaf antenna on the quad.

Heres the video. The crash is in the last 10 seconds.
https://drive.google.com/file/d/0BzvIcW ... sp=sharing
pilotnbr1
 
Posts: 86
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Re: Crash Diagnosis

Postby chschmid » Tue Jul 05, 2016 4:33 am

Hi Luke

I guess you are using an M4. Maybe try to use quatos. I am not so much the PID man. But I know that many people use PID. The wiki gives a good overview about tuning. You will also find posts here.
The logs are taken at 200Hz. What you see in the log is the timestamp from logstart in ms.
A good ballpark for acc values is between 0.5 and 2.0 although 0.5 is hard to achieve. It needs very rigid frames and a very good tuning. See afernan's posts about his. Angel researched a lot on vibs.

Cheers
Christof
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Posts: 1800
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Re: Crash Diagnosis

Postby pilotnbr1 » Tue Jul 05, 2016 1:15 pm

chschmid wrote:Hi Luke

I guess you are using an M4. Maybe try to use quatos. I am not so much the PID man. But I know that many people use PID. The wiki gives a good overview about tuning. You will also find posts here.
The logs are taken at 200Hz. What you see in the log is the timestamp from logstart in ms.
A good ballpark for acc values is between 0.5 and 2.0 although 0.5 is hard to achieve. It needs very rigid frames and a very good tuning. See afernan's posts about his. Angel researched a lot on vibs.

Cheers
Christof

Thanks Christof! Yes it is an M4- unfortunately I am running the cheap Simonk esc's that came with the nighthawk kit so I am running pids.
So my logs show 10+ on the vibration, way outside the normal range lol... I am going to do some more searching and try some things -playing with pids, more balancing, prop change etc. Thanks again for taking the time!

Luke
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