Error Modeling and Compensation Analysis of North Finder Based on FFT

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Error Modeling and Compensation Analysis of North Finder Based on FFT

Post by hamousi »

North finder can provide accurate heading information for the carrier and plays an important role in the military and civilian fields of national defense. The conventional methods to improve the accuracy of north seeker are mainly to select high precision gyro, improve the precision of rotation, increase the number of rotations, and eliminate external interference by digital filtering. Due to the limitation of working principle, technology and cost, the accuracy of the conventional elector-mechanical gyroscope is difficult to break through, and the resolution of the new fiber optic gyroscope is not satisfactory due to the influence of noise. Although the theodolite, gyro compass and rotary modulate north seeker can improve the north finding accuracy, the theodolite’s measuring time is long and expensive, the gyro compass is difficult to manufacture and debug, and the rotary modulate north seeker’s structure is complex. These inherent characteristics limit its application range, so the static measuring north finder is still the main north finding means.

In order to improve the accuracy of the north seeker, the constant drift of the gyro can be suppressed by multi-position rotation. The common rotation methods include two-position method and four-position method, and three-position method can also be used for single-axis fiber optic gyroscope. The transposition mechanism can be driven by a stepper motor or a torque motor, and then the transposition position can be controlled by blocking the motor by mechanical limit or reading the position information by photoelectric encoder. In order to meet the requirement that north seeker can find the carrier correctly in pitch and tilt state, it can adjust the level of north finder platform before measurement and then find the north, or introduce an accelerometer to compensate by measuring the attitude angle accurately. In this paper, the error characteristics of static measurement type north seeker are analyzed, and a comprehensive compensation scheme is proposed by establishing the FFT model of the system measurement error, which can effectively improve the north finding accuracy while maintaining the existing gyroscope accuracy, rotation accuracy and leveling accuracy.

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