Motors pulsing badly in Alt hold modes

ArduCopter Copter 3.6
1

Hello all, I am having an issue with a new build with motors pulsing in alt hold modes.

Here are the specs:

Hexa
Cube on a combo carrier board running 3.6
12S 24,000mah
T-motor MN605S KV 170 motors
T-motor Alpha 60 HV escs
T-Motor 2211 Polymer props.

The build is solid with little flex, everything is secured well including batteries. I have it tuned pretty well in stabilize but when I switch to alt hold modes the motors pulse badly and the drone hops up and down a few inches. The motors get warm to the touch as well. I have tried many tuning variations and nothing seems to work. (see video and .bin in link)

Thanks for any suggestions.

2

Your copter is big and heavily overpowered.

Set ATC_RAT_PIT_FILT and ATC_RAT_RLL_FILT to 10.

Fly with the desired payload and tune for that weight.
If this is your intended fly configuration then you need to tune PSC_VELZ_ * and PSC_ACCZ_ parameters

The Throttle Accel PID gains convert the acceleration error (i.e the difference between the desired acceleration and the actual acceleration) into a motor output. The 1:2 ratio of P to I (i.e. I is twice the size of P) should be maintained if you modify these parameters. These values should never be increased but for very powerful copters you may get better response by reducing both by 50% (i.e P to 0.5, I to 1.0).

3

Thanks for the suggestions. The payload is simulated with a brick so the copter is already close to the weight it will stay at. Maybe a bit heavier by the time I add FPV gear etc. I will try changing the parameters you suggested and report back. Thanks!