Abstract
The initial geographic latitude information is the key to the self-alignment of the strapdown inertial navigation system (SINS), but how to determine the latitude when the latitude cannot be obtained directly or in a short time? The latitude determination (LD) methods are introduced, including magnitude method, geometric method, and analytical methods 1 and 2, to solve this situation only by the output of the SINS itself. Simulation and experimental test results validate the efficiency of these LD methods. In order to improve the accuracy of the LD, the error of the LD method is derived through comparative analysis. Based on the relationship between LD error and inertial measurement unit (IMU) bias. Partial bias estimation method is introduced and executed during latitude determination. After compensating the estimated IMU bias, the accuracy of the LD will be further improved. Latitude errors are also affected by the latitude where SINS is located. Comprehensive simulation and experimental tests verify the effectiveness of the method. The IMU determined latitude can not only be used to achieve the self-alignment of the SINS, but also to correct the navigation latitude of the long-term SINS, thereby improving the autonomy and positioning accuracy of the navigation system.
Highlights
A strapdown inertial navigation system (SINS) can provide entirely autonomous altitude, velocity and positioning navigation solutions [1]
The start-up of an INS is known as the typical initial alignment [3], which consists of two phases: coarse alignment (CA) and fine alignment (FA), respectively
For the purpose of the test, a navigation grade INS with three gyros and accelerometers was taken as a candidate simulation
Summary
A strapdown inertial navigation system (SINS) can provide entirely autonomous altitude, velocity and positioning navigation solutions [1]. Compared with other navigation systems such as global navigation satellite system (GNSS) and astronomical navigation system, the inertial navigation system (INS) provides a navigation solution that is all-weather, high-frequency, continuous and not affected by the external environment. The accurate location information especially geographic latitude is a crucial prerequisite for the existing SINS initial alignment methods. Even an SINS can not work and provide navigation solutions, which limits some applications of SINS [4]. The positioning information is obtained by GNSS for self-alignment of INS. There are few studies on how to achieve alignment for applications that cannot receive GNSS satellite signals, such as tunnels, underground, Sensors 2020, 20, 2558; doi:10.3390/s20092558 www.mdpi.com/journal/sensors
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