I am working on a 1.2m Quad with Pixhawk. First I had problems with the green Turnigy Multistar ESC, but after flashing SimonK they work very smooth and sensitive.
Now the problem: When increasing yaw over 50% the two slower rotating motors start to oscillate in their RPM at about 10Hz. This happened in flight (with a successive crash) but also when the copter is tied down stationary.
Here is a screenshot from the logs, it looks like the oscillations are coming from the flightcontroller RCOU.Chan1-4 (note: the log frequency is much lower than the oscillation frequency):
- https://www.youtube.com/watch?v=D9MPRoRQCVw (here you can see in the last seconds what happens when yaw > 50%)
- https://www.youtube.com/watch?v=ZCc6QrucXbk (here you can hear the oscillation frequency, I yaw for 1s intervals)
- https://www.youtube.com/watch?v=IPVtwNXuRLU (here with more throttle, louder)
- https://www.youtube.com/watch?v=VNytjc2gNdI (hovering with little inputs on all axis is smooth)
- H Quad, 1200mm, Pixhawk
- Motors: Turnigy Multistar 6135 330kV http://www.hobbyking.com/hobbyking/store/__45362__6135_330KV_Turnigy_Multistar_Brushless_Multi_Rotor_Motors_CW_CCW_2_pcs_.html
- ESC: Turnigy Multistar 45 Amp 2-6S (OPTO) with SimonK http://www.hobbyking.com/hobbyking/store/__27777__Turnigy_Multistar_45_Amp_Multi_rotor_Brushless_ESC_2_6S_OPTO_.html
- Props: 18x4 Carbon Fiber Propellers for DJI S800 http://www.hobbyking.com/hobbyking/store/__42855__18x4_Carbon_Fiber_Propellers_for_DJI_S800_L_H_and_R_H_Rotation_1_pair_.html
- Batteries: ZIPPY Compact 5000mAh 6S 25C http://www.hobbyking.com/hobbyking/store/__21373__ZIPPY_Compact_5000mAh_6S_25C_Lipo_Pack.html