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