Lin Yan

Rotation modulation technology significantly enhances the navigation accuracy of inertial navigation systems (INS), thereby facilitating the widespread application of rotational inertial navigation systems (RINS). In marine or airborne applications, it is common to install two or more RINS units on the same carrier. By employing information fusion techniques, the navigation performance can be significantly enhanced. This paper proposes an online error estimation method for two RINSs. This method is based on the information fusion of two systems. It employs two RINSs with rotation strategies around different axes and utilizes rotation modulation technology to improve the observability of inertial sensor errors. Through Kalman filtering, the online optimal estimation of the gyro drift, accelerometer bias, scale factors and installation misalignment angles of two systems can be achieved. The simulation and experimental results demonstrate the effectiveness of the proposed method in performing online estimation of inertial sensors errors for the two RINSs. Specifically, the estimation accuracy reaches about 0.001°/h for gyroscope drift, about 2μg for accelerometer bias, about 2″for misalignment angles, and about 2 ppm for scale factors in both static and dynamic conditions. Through error compensation and information fusion, the navigation accuracy has increased by 62% in a static state and by 57% in a dynamic condition, thereby validating the efficacy of the proposed methodology.

In order to avoid the decrease in navigation accuracy and damage to system brought by severe vibration, airborne, and missile-borne. Inertial Navigation System (INS) is often mounted with vibration isolators. However, if the elastic center of the vibration damping system does not coincide with the center of mass of the INS, when only linear vibration input is available, the introduction of the shock absorber will produce angular vibration, and angular vibration and linear vibration will be coupled, that is, coupled angular vibration will be generated, resulting in additional navigation errors. This paper aims at solving this problem for a rotational INS (RINS). Firstly, to theoretically analyze the cause of coupled angular vibration, the six degree of freedom coupled angular vibration model of INS is derived. We also analyze the relationship between the misalignment angle of vibration isolators and vertical angular vibration. Secondly, a vibration suppression method for RINS is proposed. We use the angular velocity measured by the gyro as feedback to control the rotational gimbals of RINS to isolate the coupled angular motion. Experimental results show that the velocity oscillation of RINS caused by the vibration is greatly suppressed and thus proves the validity of the proposed method.

The rotational inertial navigation system (RINS) modulates horizontal sensor errors by rotating the inertial measurement unit (IMU) around the vertical axis. In applications demanding high azimuth accuracy, it is essential to mitigate azimuth errors caused by vertical sensor inaccuracies through horizontal rotational modulation. Therefore, this paper proposes a novel rotational strategy that rotates the IMU around the horizontal east axis. A challenge with this approach is that constant biases of the eastward-facing inertial measurement sensors cannot be modulated. This issue is particularly pronounced during long-duration navigation, where accelerometer bias varies with temperature, leading to significant velocity oscillation error and positioning error. To address this problem, this paper primarily investigates methods for the online calibration and compensation of temperature-related errors of eastward accelerometer bias under this new rotational strategy. Simulation and experimental results demonstrate that using the proposed method significantly reduces the velocity oscillations and improves the navigation accuracy of the RINS.