Abstract
Since the inertial sensor error has been modulated effectively by the Rotation Modulation Technique (RMT), the Rotation Strapdown Inertial Navigation System (RSINS) has been widely used for submarines in order to satisfy the requirement of high-accuracy and long working duration. The performance of the initial alignment is main factor affecting the accuracy of the Strapdown Inertial Navigation System (SINS). The traditional initial alignment algorithm based on the compass method has bad performance when the misalignment angle is large, which will make the submarine SINS fail to launch properly in a complex operating environment. Since the RSINS uses the mathematical platform to calculate the navigation information, it allows multiple algorithms to run simultaneously, and different algorithms do not interact with each other. Thus, to improve the alignment accuracy, an initial alignment algorithm based on the Dual Mathematical Calculation System (DMCS) is proposed; moreover, to solve the problem of large azimuth misalignment angle, an improved DMCS-based alignment algorithm is also presented in this paper. Both simulations and experiments showed that the novel algorithm can effectively improve the initial alignment performance under the large misalignment angle environment, enhancing the environmental suitability of the RSINS.
Highlights
The Strapdown Inertial Navigation System (SINS) can provide the attitude, velocity and position of a vehicle by utilizing the gyroscope and the accelerometer to measure its linear velocity and angular rate, respectively
45.7796◦ and 126.6761◦, respectively; The accelerometers’ biases are set as 10−4 g0 ; the gyroscopes’ biases are set as 10−2◦ /h; The random noises of the accelerometer and the gyroscope are set as 5 × 10−5 g0 and 5 × 10−3◦ /h, respectively; Scale factor errors of the accelerometer and the gyroscope are set as 10 ppm; The natural oscillation frequency ωn is set to 0.02 Hz; The initial horizontal misalignment angles are set as 0.2◦,and the azimuth initial misalignment angles are set as 125◦ and −170◦, respectively
Since the azimuth misalignment angle has more influence on system performance and the errors of horizontal misalignment angles are not much different, we focus on errors of azimuth misalignment zs zs xs o ys o ys xs zs zs ys xs o xs o ys angles with different initial alignment algorithms here
Summary
The Strapdown Inertial Navigation System (SINS) can provide the attitude, velocity and position of a vehicle by utilizing the gyroscope and the accelerometer to measure its linear velocity and angular rate, respectively. A self-compensation method based on single-axis RMT was proposed in [10,14] to inhibit the constant deviation of inertial sensors in the Rotation Strapdown Inertial Navigation System (RSINS), and the navigation accuracy improved significantly compared with traditional navigation systems. In order to improve the performance of the RSINS for submarines, firstly a novel initial alignment algorithm based on the DMCS and traditional compass self-aligning method is presented in this paper.
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