Abstract
In this paper, we proposed a coarse-alignment method for strapdown inertial navigation systems based on attitude determination. The observation vectors, which can be obtained by inertial sensors, usually contain various types of noise, which affects the convergence rate and the accuracy of the coarse alignment. Given this drawback, we studied an attitude-determination method named optimal-REQUEST, which is an optimal method for attitude determination that is based on observation vectors. Compared to the traditional attitude-determination method, the filtering gain of the proposed method is tuned autonomously; thus, the convergence rate of the attitude determination is faster than in the traditional method. Within the proposed method, we developed an iterative method for determining the attitude quaternion. We carried out simulation and turntable tests, which we used to validate the proposed method’s performance. The experiment’s results showed that the convergence rate of the proposed optimal-REQUEST algorithm is faster and that the coarse alignment’s stability is higher. In summary, the proposed method has a high applicability to practical systems.
Highlights
The strapdown inertial navigation system (SINS) is an autonomous system that calculates the position and orientation of a carrier relative to an initial point and orientation using inertial-sensor measurements [1,2]
18, 239 reference frame aligned with inertial measurement unit (IMU) axes; b0-frame: orthogonal reference frame that is non-rotating relative to the i-frame, which is formed b0-frame: orthogonal referenceinframe that is space; non-rotating relative to the i-frame, which is by fixing the b-frame at start-up the inertial formed by fixing the b-frame at start-up in the inertial space; e-frame: Earth-centered Earth-fixed (ECEF) orthogonal reference frame; 5. e-frame: Earth-centered Earth-fixed (ECEF) orthogonal reference frame; e0-frame: orthogonal reference frame that is non-rotating relative to to thethe i-frame, which is formed e0-frame: orthogonal reference frame that is non-rotating relative i-frame, which is by fixing the ate-frame start-up the inertial space. space
We proposed, based on the OPREQ algorithm, a coarse-alignment method for the inertial frame
Summary
The strapdown inertial navigation system (SINS) is an autonomous system that calculates the position and orientation of a carrier relative to an initial point and orientation using inertial-sensor measurements [1,2]. The method, which was proposed in [12], did not achieve a favorable coarse-alignment performance, as the acceleration of the observation vectors measured by the inertial measurement unit (IMU) contained random noise Another solution to the AD problem involves the determination of the corresponding attitude quaternion [16,17,18,19,20,21]. In order to improve both the convergence velocity and alignment accuracy, this paper proposes a coarse-alignment method based on the optimal-REQUEST (OPREQ) algorithm. Based on the swaying motion’s properties, the coarse alignment of the inertial frame transforms the determination of the initial-attitude matrix into the constant-DCM calculation; we adopted the integral algorithm in order to filter the inertial sensors’ random noise.
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