Offshore alignment method of autonomous underwater vehicle based on second order interpolating filter

Abstract

The invention provides an offshore alignment method of an autonomous underwater vehicle based on a second order interpolating filter, comprising the following steps of: (1) collecting data output by an optical fiber gyroscope and a quartz flexible accelerometer, and primarily ensuring transfer matrix Cb<c> from a carrier coordinate system to a computing navigation coordinate system; (2) building anonlinear state equation which takes speed error and three error misalignment angles as state variable and a linear observation equation which takes speed error as observed quantity when a fiber optic gyro strap-down inertial navigation system has a lager azimuth error angle; (3) discretizing a nonlinear continuous system, filtering the discretized nonlinear system with the second order interpolating filter, and estimating the azimuth error angle; and (4) error compensating attitude matrix Cb<c> with the estimated azimuth error angle to obtain the exact attitude matrix, obtaining carrier attitude according to the attitude matrix, completing initial alignment and entering into navigation. The method can meet requirement with higher applicable precision, has high alignment precision and short alignment time, and is easily realized.

Description

(1) Technical field [0001] The present invention relates to a measurement method, in particular to an initial alignment technology of a strapdown inertial navigation system, and in particular to a rough alignment when the fiber optic gyro strapdown inertial navigation system of an autonomous underwater submersible is separated from the mother ship at sea. An alignment method with relatively large quasi-azimuth error angle. (2) Background technology [0002] Autonomous Underwater Vehicle (AUV) is a new type of underwater vehicle developed rapidly on the basis of manned submersibles and unmanned remote-controlled submersibles (ROV) in the late 1980s and early 1990s. Lower the carrier platform. After the AUV leaves the mother ship, it can no longer achieve its own initial alignment by methods such as transfer alignment. Therefore, finding an alignment method that can quickly align and guarantee a certain accuracy has become a difficult point in AUV research. Due to the small ...

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Problems solved by technology

When the azimuth error angle is large, the alignment error model is nonlinear. In terms of nonlinear filtering, there are two widely used methods. One is the nonlinear function represented by the extended Kalman filter (EKF). Perform a linearization approximation, using a discrete nonlinear equation around the filtered values Expanding into Taylor series, omitting the second-order and above items, the linearized model of the nonlinear system is obtained, but this filtering method introduces high-order truncation errors, and the estimation accuracy is relatively low; the other is the filtering estimation based on the approximate probability density distribution method, UKF is one of them, UKF captures the mean and variance of the system state by constructing a set of sampling points, each sampling point is converted by a nonlinear function, and the mean and variance of the system state prediction are determined by It is given that the number of sampling points determines the filtering time. Under the same sampling frequency, the estimation time is relatively long

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