Thanks all, we’ll be doing some more tests within the next few days taking your advice into account.
We will set up the current sensors, lower ATC_RAT_PIT_FILT to 10 or 7 and play with ATC_INPUT_TC. For now, no autotune yet. Like we previously said, we have experienced crashes using autotune on a previous copter. At the time, we were using a Combo Air Gear 350 from T-motor. We read a few posts which reported crashes using Flame ESCs (Crash on a X8 after starting AutoTune and Drone crash at AutoTune step 4). Since our configuration is based on some Flame 60HV ESCs, we are really apprehensive about trying the autotune on this machine.
In order to tune this large copter, our first guess is to slightly increase the D values on the rate roll and pitch (compared to the stock values) in order to kill the slow oscillations if they still occur as suggested by Cornel Fudulu. We will set it up on a knob in order to make very fine adjustments during flight.
Does any of you have some typical PID roll/pitch rate values that you find to work well for larger copters? We were wondering if the PID had any specificities for large copters or if the fact that the motor power increases with the size and weight was making the PIDs very similar.