Abstract:Underwater navigation of autonomous underwater vehicles (AUVs) is a challenging task that requires the fusion of multiple sensors used as aiding to the vehicle inertial navigation system. In this paper, we focus on the problem of fusing heading measurements under different maneuvering conditions. We analyze the observability of the heading measurement fusion problem and derive the observable and unobservable subspaces as a function of the AUV's maneuver. Using this analysis, we are able to predict the converge… Show more
“…In 2010, Iozan, and Collin, reported achieving 1-degree accuracy in determining true North orientation with a low-cost MEMS gyro, while accounting for small errors such as g-sensitivity and cross-axis coupling [31,32]. Among other works over the past decade, Ali (2011) presented a second-order divided difference filter (DDF) [33], Du (2016) introduced a disturbance observer-based Kalman filter (DOBKF) [34], and Klein (2018) demonstrated how kinematic constraints, when coupled with appropriate observability analysis, can effectively enhance unobserved states [35][36][37].…”
Inertial navigation systems (INS) are widely used in both manned and autonomous platforms. One of the most critical tasks prior to their operation is to accurately determine their initial alignment while stationary, as it forms the cornerstone for the entire INS operational trajectory. While lowperformance accelerometers can easily determine roll and pitch angles (leveling), establishing the heading angle (gyrocompassing) with low-performance gyros proves to be a challenging task without additional sensors. This arises from the limited signal strength of Earth's rotation rate, often overridden by gyro noise itself. To circumvent this deficiency, in this study we present a practical deep learning framework to effectively compensate for the inherent errors in low-performance gyroscopes. The resulting capability enables gyrocompassing, thereby eliminating the need for subsequent prolonged filtering phase (fine alignment). Through the development of theory and experimental validation, we demonstrate that the improved initial conditions establish a new lower error bound, bringing affordable gyros one step closer to being utilized in high-end tactical tasks.
“…In 2010, Iozan, and Collin, reported achieving 1-degree accuracy in determining true North orientation with a low-cost MEMS gyro, while accounting for small errors such as g-sensitivity and cross-axis coupling [31,32]. Among other works over the past decade, Ali (2011) presented a second-order divided difference filter (DDF) [33], Du (2016) introduced a disturbance observer-based Kalman filter (DOBKF) [34], and Klein (2018) demonstrated how kinematic constraints, when coupled with appropriate observability analysis, can effectively enhance unobserved states [35][36][37].…”
Inertial navigation systems (INS) are widely used in both manned and autonomous platforms. One of the most critical tasks prior to their operation is to accurately determine their initial alignment while stationary, as it forms the cornerstone for the entire INS operational trajectory. While lowperformance accelerometers can easily determine roll and pitch angles (leveling), establishing the heading angle (gyrocompassing) with low-performance gyros proves to be a challenging task without additional sensors. This arises from the limited signal strength of Earth's rotation rate, often overridden by gyro noise itself. To circumvent this deficiency, in this study we present a practical deep learning framework to effectively compensate for the inherent errors in low-performance gyroscopes. The resulting capability enables gyrocompassing, thereby eliminating the need for subsequent prolonged filtering phase (fine alignment). Through the development of theory and experimental validation, we demonstrate that the improved initial conditions establish a new lower error bound, bringing affordable gyros one step closer to being utilized in high-end tactical tasks.
“…The inaccurate description of the system noises, measurement errors, and uncertainty in the dynamic models lead to unreliable estimates and degradation in accuracy, especially during GNSS outages when KF operates in prediction mode based on the predefined state error models, which are not necessarily correct. In addition, there are several significant drawbacks of KF, such as sensor dependency and observability problems (Hong et al, 2005;Klein & Diamant, 2018;Tang et al, 2008).…”
Aiming to improve the position and velocity precision of the INS/GNSS system during GNSS outages, a novel system that combines unscented Kalman filter (UKF) and nonlinear autoregressive neural networks with external inputs (NARX) is proposed. The NARX‐based module is utilized to predict the measurement updates of UKF during GNSS outages. A new offline approach for selecting the optimal inputs of NARX networks is suggested and tested. This approach is based on mutual information (MI) theory for identifying the inputs that influence each of the outputs (the measurement updates of UKF) and lag‐space estimation (LSE) for investigating the dependency of these outputs on the past values of the inputs and the outputs. The performance of the proposed system is verified experimentally using a real dataset. The comparison results indicate that the NARX‐aided UKF outperforms other methods that use different input configurations for neural networks.
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