I’m working on an aerial robot (a t-copter) and am having problems with Roll-axis stabilization. The PID controller works correctly but when I get the engine speed from 40% starts to destabilize. The problem is not in the PID but FEZ PWM signal or ESC output is not constant. I have measured the FEZ pwm signal with an oscilloscope, from 1 to 2 ms and vice versa and this is the result ( pwm frequency= 400Hz):
Is it normal that the amplitude change? Is it normal not maintained very stable signal?