The optical inertial reference unit (OIRU) can provide a reference beam for the line-of-sight stabilization system to achieve precise pointing and tracking. Inertial sensors are mounted to the OIRU platform to provide feedback of angular motions being experienced by the reference beam. However, disturbances and noises existing in the OIRU system will inevitably prevent the reference beam be stabilized within microradian. In this paper, an improved noise reduction disturbance observer (IMNRDOB) is proposed to enhance the disturbance suppression performance of the OIRU. Simulations results verify the effectiveness and experiments data show the disturbance is suppressed by 88.60% with the proposed method.
In order to achieve precise pointing and high-resolution imaging, acquisition, tracking and pointing (ATP) system is usually required to stabilize the line-of-sight (LOS) within arc-second or even higher level. In case of ATP system mounted on moving platform, broadband angular disturbance is the most serious factor to prevent the LOS being stabilized. Due to the limited sampling frequency of detectors, the angular disturbance is usually mitigated by incorporating inertial stabilized platform (ISP) and fast steering mirror (FSM) into ATP system. The need for small, inexpensive inertial angular rate sensors(ARSs), which may be employed in these devices to measure angular jitter at sufficiently wide bandwidth, is urgent. However, there is no single angular rate sensor (ARS) currently available that could measure angular jitter from DC to hundreds of hertz while maintaining comparable accuracy. Multi-sensor fusion is a practical solution to broadband angular jitter measurement for the purpose of jitter control. In this paper, the measurements from Magnetohydrodynamics (MHD) ARS and MEMS gyro are blended together using closed-loop fusion (CLF) method. The approach does not rely on accurate models or transfer functions of sensors, and meanwhile, can be easily implemented in real-time system. Experimental results indicate that the measuring bandwidth of CLF method is within overall frequency range covered by MHD ARS and MEMS gyro.
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