Discussions

I recently updated to 2.6d and had a short flight which ended with a snap roll-over crash while about 5 metres up, and I would love to find the cause so that I can avoid it from happening again. I'm not sure if it was related to my pids, or something in the code? I had flown extensively with 2.5.4, albeit with different pids and never had a problem like this.

Hardware: APM1 2560

Tricopter frame

Unfortunately I don't have a log since my logs stopped working with 2.6d, but I do have the onboard video.

What happened, was the copter would start to want to roll slowly to one side or the other, and I would have to provide opposite stick input to keep it level. While I was doing this, my minimosd was showing the virtual horizon was slanted quite a bit when I had the copter held level with stick input, and the first couple of times, it just did it mildly, and eventually re-centered itself. I tried to land because it was getting sketchy, but it was trying to roll to the left, so I put in right stick to oppose it, but it climbed while it levelled, so I backed off on the throttle, and then it rolled over to the left past 90 degrees over the course of about half a second. I provided full opposite stick to try and keep it level, and then it suddenly snapped back and rolled about 270 degrees before plowing into the ground.

My pids were as follows:

RATE_RLL_D,0.004
RATE_RLL_I,0.001
RATE_RLL_IMAX,500
RATE_RLL_P,0.14

STB_RLL_I,0
STB_RLL_IMAX,4000
STB_RLL_P,3.6

STAB_D,0.001

Is there any way the RATE_RLL_I built up enough to cause this? From the video, does it look like a built up RATE_RLL_I term would cause an increasing lean over to one side that needed to be countered? If not, which parameter would likely be the culprit?

Here's the video: