Coupling influence of ship dynamic flexure on high accuracy transfer alignment

Abstract

This work investigates a new error source for angular velocity or attitude-based transfer alignment, which is caused by the coupling influence of dynamic flexure with ship angular motion. Most traditional studies do not consider this coupling error, as they often assume that dynamic flexure and ship angular motion are uncorrelated. However, the correlation between the dynamic flexure and the ship angular motion generally exists, which will cause a static error in measurements. We adopt the Bernoulli-Euler beam as a simplified ship vibration model to obtain the phase and amplitude relationships for the ship dynamic flexure angle and the ship angular motion. Simulation experiments are then conducted to test the phase delay on alignment accuracy based on the angular velocity matching approach. It is found that the estimation error has a strong correlation with this phase delay, and the error behaves like a sin wave function with the phase delay angle variation. The coupling error of ship dynamic flexure with ship angular velocity is deduced based on the spatial geometric modelling method, and the analysis demonstrates that this coupling error exists in angular velocity or attitude matching systems, which depends on the phase delay and amplitude ratio of ship dynamic flexure and angular velocity.