Estimation and compensation of unknown disturbance in three-axis gyro-stabilized camera mount

Abstract

Gyro-stabilized camera mounts are used to maintain and stabilize airborne remote sensing sensors, such as aerial cameras, light detection and ranging, and imaging spectrometers, for the purpose of isolating the line-of-sight of optical sensors from disturbing aircraft movements. However, it is difficult to achieve accurate line-of-sight pointing and even the system stability cannot be guaranteed due to the influences of unknown disturbance, such as mass imbalance, gimbal friction, aircraft attitude turbulence and model uncertainty. In order to realize high-precision disturbance rejection and robustness stability, a kind of compound control system is configured and designed in the framework of active fault-tolerant control. The basic idea of this paper is to handle the disturbance as a fault for disturbance compensation by applying online fault estimation and accommodation. Based on H_∞ norm sub-optimization, a robust disturbance observer is designed to estimate the fault and then a fault compensator is employed to compensate for it. Based on an exosystem description, the internal model controllers are designed to achieve perfect tracking performance as well as robustness against model uncertainty. Finally, the experimental results demonstrate the effectiveness of the proposed compound control strategy in comparison with the traditional method.