Abstract
Due to the lack of true ship angular flexure data, it is difficult to evaluate its measurement error of the angular velocity matching method in practice. In this paper, the cause of the measurement error of the ship flexure angle is analyzed in theory, and an evaluation method for the ship angular flexure measurement error based on the principle of relevance is proposed. The proposed method provides a prediction formula to describe the estimation error of the static flexure angle based on the off-diagonal elements of the error covariance matrix P in Kalman filtering. In addition, the optimized coefficient F is introduced to make the prediction error range better describe the real error variation. The optimized coefficient F ensures that the proposed formula has good prediction effects in all three directions. Simulations based on the actual measured ship flexure data are carried out, and the simulation results verify the capability of the prediction formula. The proposed method can be used in the evaluation of the ship flexure measurement error.
Highlights
Modern battleships are equipped with different kinds of sensors and weapon systems, such as radars, guided missiles, optoelectronic collimator, and other peripheral apparatus.e coordinate system misalignment caused by the ship flexure affects the performance of these systems
There will be slow-varying flexure caused by the change of the ship’s mass distribution and temperature variation, which is named as the static flexure. e ship flexure measurement methods are widely studied by researchers all over the world, and the main solutions include the optical autocollimation method [4], photogrammetric method [5], GPS-based method [2], and the inertia vector matching method [6]
Verification of the Proposed Method. e 19-hour measured ship flexure data of “Yuanwang No 3” [23] with the large steel pipe-based method, which can be regarded as the real flexure data, are utilized to validate the proposed method. e angular velocities measured by the master inertial navigation system (MINS) and slave inertial navigation system (SINS) are from actual navigation systems installed on the ship
Summary
Modern battleships are equipped with different kinds of sensors and weapon systems, such as radars, guided missiles, optoelectronic collimator, and other peripheral apparatus. Many research studies [11,12,13,14,15] point out that this estimation error is caused by the coupling effect between the ship angular motion and the dynamic flexure. E dynamic flexure and angular motion are all the response of the ship structure to the wave loads, and they are likely to be correlated, which introduced a coupling error on the estimation of static flexure. The estimation error of the static flexure angle, which is caused by the coupling between the ship angular motion and the dynamic flexure, is analyzed in theory. Due to this coupling effect, it is difficult to measure the ship flexure accurately by the inertia vector matching method, and there is no clear report to evaluate its measurement accuracy so far. Simulations with real measured flexure data from a ship are implemented, and the results demonstrate the effectiveness of the proposed method
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