Crius AIOP 1.1 bucks to the rear when turning upwind

[clough42]

I just finished building a DJI 450 quad with a Crius AIOP 1.1, simonk 30A ESCs, RCTimer 2830-11 (1000KV) motors and 10x4.5 props. I'm running Multiwii 2.1.

I'm trying to tune it, and having trouble. I've got my pitch and roll PID values at 3.5, .040 and 25, and it's behaving oddly. It stays fairly level in a hover--though not nearly as stable as a 450-sized heli. I can hear the motors adjusting quite a bit-and it rocks around a little. Nothing rhythmic--just a little snarly. This is my first quad, so I don't know what's normal.

The big problem comes when I make a gentle banked turn and head upwind (4-5mph). If I let it come around the turn and level out, it bucks hard (30-45 degrees) to the rear. I have to give heavy forward elevator to regain control and keep it in the air.

With I-gains below .040, it's quite severe. I've tried raising the I-gain to .050, but the quad gets much less stable in the air. I've raised the D-gain as well (to 35) also with strange results. It tips to the rear and drops coming out of turns. It feels like the motors are all dropping to idle for a moment and it loses altitude rapidly. From 20 feet, I can recover, but barely.

I have calibrated the ESCs so they spin up reliably and set the min throttle so I can't get a motor to stop by shaking it around at low throttle. I balanced all the props with a Du-Bro balancer, but I'm wondering if I've still got a vibration problem. The AIOP is hard-mounted with standoffs to the DJI frame.

[clough42]

More info:

I did adjust the subtrims in my radio to get 1500 in the telemetry and the endpoints to get 1000 and 2000 at the bottom and top of the range. The quad shows no significant drift tendency in hover.

[Peter]

I have the same sort of problems. Same frame, motors, normal escs and crius se. 4.5 0.30 25. Think it still are vibrations. Lpf is already at 42hz. Soft pad under control board.
I also have a homemade wooden tri and quad and those are flying great.

[clough42]

Does anyone have this combo flying well?

[clough42]

Okay, I'm fairly certain the problem was vibration related.

I noticed that the domed nuts on the RCTimer prop adapters were off-center and wobbled when they rotated, so I replaced them with M5 nuts and washers. That seems to have reduced the vibrations audibly. I also turned on the 42hz LPF on the gyros, and it flies smooth as butter now.

I will work on reducing vibrations further and backing down the filters.

Is there a version of the vibration test program that will work on the AIOP board? I could only find the 1.8 version and couldn't get it to work.

[Peter]

Tried the nut thing, balanced the props again. Removed the stickers from the motor, replaced a bent prop adapter. Still problems.
Then I thought it was time for lpf of 20Hz.
And it works great! Been flying it quite aggressively yesterday in 3 bft wind and no bad habits!

Finally as good as the default 1.9 firmware I got on the crius se.
1.9 is a lot less sensitive to vibrations or they shipped with a lpf of 20 Hz.

By the way, the next step would have been the MMGYRO option.