ANALYSIS OF THE RELATIVE PLACEMENT OF THE SENSITIVE MASSES OF ACCELEROMETERS IN ALGORITHMS FOR STRAPDOWN INERTIAL NAVIGATION SYSTEMS

Abstract

The present study introduces a method for algorithmic compensation of the displacement of the centers of sensitive elements of accelerometers within a high-precision inertial navigation system. Previous considerations omitted this compensation due to the potential for minimizing its impact through structural features—specifically, the close proximity of accelerometers to each other. With the upgrading of components in the inertial sensors, the influence of size-effect errors could become significant compared to gyroscopes and accelerometers errors. This study aims to analyze the impact of these errors on solving navigation tasks under the precision conditions of modern inertial sensors. The compensation scheme is elaborated in detail: compensation to an arbitrary center of the inertial measurement unit is separately discussed, considering the spreading effect of the accelerometer triad, and to the center of rotation of the vehicle, accounting for the installation location on the operational object. Additionally, designs of accelerometer placements on platforms of high-precision and compact inertial navigation system sensor blocks are analyzed. By conducting a series of rotations on an inclinable turntable, the spreading of accelerometers is calculated using the least squares method concerning the intersection point of the rotation axes of the stand used. An estimation of the discrepancy of the calculated spreading coefficients of sensitive elements from their nominal values is obtained. Through calibration rotations, the reduction of all parasitic phenomena in the accelerometer signal due to centripetal and tangential accelerations is achieved. The influence of parasitic accelerometer signals during the roll of the product on coordinate computation is analytically derived, revealing the dependency of the studied error on the product's operational time under constant rolling conditions. Real tests on the inclinable turntable were conducted for verification, and the obtained results of compensation effectiveness are presented. The compensation results from flight tests on a two-seat vertical takeoff and landing helicopter are provided. The flight test calculations were conducted through physical modeling based on recorded data with the synchronization of the employed sensors considered. Compensation in the mode of aligning the accelerometer triad to an arbitrary point and aligning accelerometers to the center of the vehicle's rotation is separately discussed