Abstract
In the strap-down inertial navigation system (SINS), the initial attitude matrix is acquired through alignment. Though there were multiple valid methods, alignment time and accuracy are still core issues, especially regarding the condition of the motion carrier. Inspired by the idea of constructing nonlinear vectors by velocity in a different coordinate frame, this paper proposes an innovative alignment method for a vehicle-mounted SINS in motion. In this method, the core issue of acquiring the attitude matrix is to calculate the matrix between the inertial frame and the initial body frame, which can be constructed through the nonlinear velocity vectors’ information from the GPS and the odometer at different moments, which denominate the multi-vector attitude determination. The possibility of collinearity can easily be avoided by a turning movement. The characteristic of propagation of error is analyzed in detail, based on which an improved method is put forward to depress the effect of random noise. Compared with the existing alignment methods, this method does not use the measurement information of accelerometers. In order to demonstrate its performance, the method is compared with the two-position alignment method and the traditional two-stage alignment method. Simulation and vehicle-based experiment results show that the proposed alignment method can establish an attitude reference in 100 s with an azimuth error of less than 0.06°, and that the accuracy does not have a strong correlation with the accelerometer.
Highlights
Alongside the significant advances in the inertial sensors and navigation technologies, strap-down inertial navigation systems (SINS) have reduced in structure complexity and become a key member of the navigation system [1]
To testify to the analysis results, a comparison could be conducted between the “alignment error” and the “calculation error”, which represent the error of the alignment process and the error computed in Equation (31), respectively
Impact the the performance performance of Tackling the requirement of fast initial alignment for a marching vehicle, a novel alignment procedure is proposed for the SINS aided by the GPS and the odometer
Summary
Alongside the significant advances in the inertial sensors and navigation technologies, strap-down inertial navigation systems (SINS) have reduced in structure complexity and become a key member of the navigation system [1]. The strap-down inertial navigation system, simplified as SINS, is fixedly installed in the carrier, and the gyroscopes and accelerometers immediately sense and detect the dynamic characteristics of the carrier. The SINS is an independent navigation system that has been used in a wide range of applications, covering the navigation of marines, vehicles, missiles, and aircraft [2]. It is widely known that the state update of the SINS is achieved based on numerical integration [3]; it is necessary to know the initial navigation parameters, including velocity, position, and attitude for navigation calculation. The initial alignment of the SINS is mainly about the determination of the initial attitude matrix between the body frame and the navigation frame, since the velocity and position can be obtained by external reference [4]. Initial alignment is one of the core technologies for the SINS; the requirements of initial alignment are high accuracy and short time [1]
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