Abstract
In this paper, an improved inertial frame alignment algorithm for a marine SINS under mooring conditions is proposed, which significantly improves accuracy. Since the horizontal alignment is easy to complete, and a characteristic of gravity is that its component in the horizontal plane is zero, we use a clever method to improve the conventional inertial alignment algorithm. Firstly, a large misalignment angle model and a dimensionality reduction Gauss-Hermite filter are employed to establish the fine horizontal reference frame. Based on this, the projection of the gravity in the body inertial coordinate frame can be calculated easily. Then, the initial alignment algorithm is accomplished through an inertial frame alignment algorithm. The simulation and experiment results show that the improved initial alignment algorithm performs better than the conventional inertial alignment algorithm, and meets the accuracy requirements of a medium-accuracy marine SINS.
Highlights
A strapdown inertial navigation system (SINS) is a dead-reckoning navigation system, and the initial alignment is an essential procedure for a SINS, since it directly affects the precision of navigation parameters [1,2]
The main purpose of the initial alignment is to determine the initial strapdown attitude matrix between the body frame and navigation frame, and its accuracy is especially important for a marine SINS, which usually has to work for a long time [1,2,3,4]
In order to test the technique proposed in this paper, a simulation is carried out to compare with the conventional inertial frame alignment algorithm
Summary
A strapdown inertial navigation system (SINS) is a dead-reckoning navigation system, and the initial alignment is an essential procedure for a SINS, since it directly affects the precision of navigation parameters (position, velocity, and attitude) [1,2]. Due to the presence of the disturbed acceleration and angular velocities, accurate gravity and Earth rate are difficult to obtain directly, which leads to the low precision of the coarse alignment. While in the fine-alignment phase, usually the standard Kalman filter or the compass loop method can be implemented based on the coarse-alignment result, and under the assumption of a small misalignment angle linear error model [1,2]. If an accurate horizontal coordinate frame is established, the interference caused by sway can be isolated Based on this idea, we proposed an improved alignment scheme in [9]. Because of the low precision of the traditional inertial frame alignment algorithm in the mooring environment, it is usually employed as a coarse alignment for a marine SINS.
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