Research on wide-band disturbance observation and compensation for electro-optical stabilized sighting system

Electro-optical stabilized sighting system (EOSSS) utilizes a disturbance observer (DOB) to obtain and compensate external disturbances, ensuring the stability of the line of sight (LOS) direction. Expanding the effective monitoring band of the disturbance observer is the key to improving the stabilization precision of the system. To achieve broadband disturbance observation and compensation, design method of disturbance observer is studied. Low-pass filter design is regarded as the core. Based on the basic principle of disturbance observer, contradiction between estimation of disturbance with low and high frequency is pointed out. After analyzing the characteristics of low-pass filters in frequency domain, we propose a compromise principle to reconcile the contradiction. According to the principle of robust stability, H∞ norms of different low-pass filters are calculated and the order of optimal low-pass filter is determined ultimately. Simulation results show that compared with existing disturbance observers, the proposed method widens the disturbance isolation frequency band from 25Hz to 32Hz. Experimental results demonstrate that the isolation degree of the system against interference below 6Hz is increased by more than 10dB, and the critical frequency of significant disturbance compensation reaches 25Hz. The effective monitoring band of the disturbance observer fully covers the principal components of actual disturbance. As a result, disturbance observation and compensation ability of electro-optical stabilized sighting system is further improved, which plays an important role in promoting stabilization precision.