Mechanical resonance suppression technique for inertial reference unit based on band-pass filter disturbance observer

Inertial reference unit (IRU) has been recognized as an effective method for photoelectric tracking and pointing system to suppress the disturbance. Its flexible support usually results in a low-frequency mechanical resonance within the bandwidth. Experimental identification indicates an obvious resonant peak at near 36.7 Hz with an amplitude of 26.6 dB. In this paper, disturbance observer based on band-pass filter (BPF-DOB) is combined with a notch filter to suppress the mechanical resonance. The asymmetry of the resonance peak and variation of the controlled object over the time are both addressed. Simulation and experimental results show that the stability accuracy of IRU system is improved to be 1.09 mu rad, indicating an improvement of 9.9 % relative to the traditional method and high robustness for time-varying resonance.