Random Inputs from the APM

Okay guys and girls, this problem has me stumped and I can't figure what's causing it.

The Problem: The quadcopter will suddenly receive a sharp pitch or roll command from the autopilot in all different modes, even when hovering in stabilize mode. If I give it a roll input through RC, it will cause the problem to present itself more often, but even with very little RC input, the autopilot will cause it to suddenly roll and sometimes flip over completely. I've changed the roll rate P and stabilize P and nothing seems to fix the problem. I've also isolated the autopilot from almost all vibration by mounting it on a half inch thick rubber foam piece. It didn't seem to affect the issue either.

The Hardware: DJI f450 Frame ARF

Stock DJI motors (920KV)

Stock DJI ESC's (30 Amp)

Castle Creations BEC 10A

APM 2.5

Ublox Leah 6 GPS

Spektrum AR8000 receiver

Spektrum DX8 transmitter

The Software: The problem has happened with arducopter 2.7.4, 2.8.1 and 2.9.1b firmware.

Data Log: Attached. In this log, I landed once or twice and changed the stabilize P. It didn't seem to affect the problem.

Videos: https://www.youtube.com/watch?v=L6iAIrXEQHk&feature=youtu.be

https://www.youtube.com/watch?v=ArV33oDjvtU

See the descriptions to the videos for when the problem occurs.

Is anybody else having this same problem or does anybody have any ideas as to what is causing the problem?

I work in a research lab that develops autopilots and I can't seem to nail this problem. I would be very grateful for any advice.

2013-04-06 17-33-45.rlog

2013-04-06 17-33-45.tlog

Until you figure this out, I'd keep all flights under 2m. From watching the video it looks like you may have an issue with motor or ESC. The flight looks smooth then it gets really rough. Normally if you have bad vibration it appears throughout the whole flight. Double check for loose connections. This is not something you can tune out with PIDs. That being said it would not hurt to reload and recalibrate everything. With these 2m flights I would turn on all logging, included raw and motors. As soon as you see a problem, land and look at the logs. The tlog is telemetry, you should have a regular log with an extension ".LOG", this where raw and motor are logged. Also see if someone can video your flight from the ground. Another thing, there was some discussion about Spektrum and twitchy throttle and that the fix was changing the response on the Spektrum so that it updates faster.
Good luck and fly safe.

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Richard Boyhan April 8, 2013 at 6:18am

Until you figure this out, I'd keep all flights under 2m. From watching the video it looks like you may have an issue with motor or ESC. The flight looks smooth then it gets really rough. Normally if you have bad vibration it appears throughout the whole flight. Double check for loose connections. This is not something you can tune out with PIDs. That being said it would not hurt to reload and recalibrate everything. With these 2m flights I would turn on all logging, included raw and motors. As soon as you see a problem, land and look at the logs. The tlog is telemetry, you should have a regular log with an extension ".LOG", this where raw and motor are logged. Also see if someone can video your flight from the ground. Another thing, there was some discussion about Spektrum and twitchy throttle and that the fix was changing the response on the Spektrum so that it updates faster.
Good luck and fly safe.
Kenobi April 6, 2013 at 11:34pm

I had this problem too and I reduced it drastically with vibrationdamping. My theory was that the vibrations to my APM 2.5 caused random spikes in the stabilizing sensors on one axis or the other and made them suddenly try to compensate for this sudden imput. Maybe I am wrong but post a RAW file of your sensors lets see the vibration patterns after a 30 secs flight.

On another note, you are the second person in 1 week to have problems with the castle BEC model, the last guy did something to his BEC to solve his unstable flight problems.

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Random Inputs from the APM

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