Abstract
The performance of a strapdown inertial navigation system (SINS) largely depends on the accuracy and rapidness of the initial alignment. The conventional alignment method with parameter identification has been already applied widely, but it needs to calculate the gyroscope drifts through two-position method; then the time of initial alignment is greatly prolonged. For this issue, a novel self-alignment algorithm by parameter identification method under inertial frame for SINS is proposed in this paper. Firstly, this coarse alignment method using the gravity in the inertial frame as a reference is discussed to overcome the limit of dynamic disturbance on a rocking base and fulfill the requirement for the fine alignment. Secondly, the fine alignment method by parameter identification under inertial frame is formulated. The theoretical analysis results show that the fine alignment model is fully self-aligned with no external reference information and the gyrodrifts can be estimated in real time. The simulation results demonstrate that the proposed method can achieve rapid and highly accurate initial alignment for SINS.
Highlights
Strapdown inertial navigation system (SINS) has been widely used in aviation, marine, and land vehicle navigation and positioning because of its special advantages, and it necessitates an alignment stage to determine the initial conditions prior to navigation operation [1]
The theoretical analysis results show that the fine alignment model is fully selfaligned with no external reference information and the gyrodrifts can be estimated in real time
The conventional coarse alignment is based on analytical method which generally uses two feature vectors of the earth: the acceleration of gravity and the angular rate of the earth’s rotation, and it asks for the base in a static case [9, 10]
Summary
Strapdown inertial navigation system (SINS) has been widely used in aviation, marine, and land vehicle navigation and positioning because of its special advantages, and it necessitates an alignment stage to determine the initial conditions prior to navigation operation [1]. In order to solve the alignment problem on a rocking base, the method is to use the inertial frame as a transitional coordinate to realize the initial alignment by using the gravity acceleration information [11,12,13,14]. In order to better understand SINS initial alignment, it is necessary to explain the navigation coordinate system, that is, the earth frame (e frame), the inertial frame (i frame), the computed inertial frame (i frame), the navigation frame (n frame), and the body frame (b frame), together with the body inertial frame (ib0 frame), which will be introduced in the sequel, and the relationship among the various frames is denoted, where ωie is the angular rate of the earth’s rotation, g is the local gravity acceleration, and t is the time for alignment.
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