Yan Guo

The integrate-and-dump filter is a core component of satellite navigation receivers, enabling the tracking of navigation satellite signals and significantly influencing receiver performance. Currently, satellite navigation receivers, particularly onboard unmanned aerial vehicles (UAVs), are vulnerable to spoofing. Whether counterfeit signals can successfully hijack a receiver depends critically on how these signals alter the integrate-and-dump filter output. Existing research on satellite navigation spoofing often uses an output signal model for the integrate-and-dump filter derived from continuous-time integration. However, this model deviates from practical implementation because most modern navigation receivers are built on digital circuits that approximate continuous-time integration through discrete-time accumulation. Consequently, the discrete-time nature of actual hardware introduces errors that are not captured by the conventional continuous-time model. In this study, a mathematical model for the output signal of an integrate-and-dump filter was implemented via discrete-time accumulation. The accuracy of the proposed model was verified through simulations, and a comparative analysis with the traditional continuous-time integration model was conducted to highlight the impact of discretization errors.

Most existing deep learning-based camera pose estimation methods rely solely on visible images, making them vulnerable to challenges such as drastic lighting variations and poor nighttime imaging quality. These limitations reduce the robustness and accuracy of traditional approaches. To address these issues, we propose VIFPE (Visible- and Infrared-Fusion-Based Pose Estimation), a novel framework that integrates features from both visible and infrared images to enhance pose estimation in urban environments. By leveraging the complementary advantages of visible images, which are rich in texture, and infrared images, which are resilient to illumination changes, VIFPE achieves robust and accurate localization across diverse lighting conditions. The framework consists of multiple key modules, including a feature extractor, a multimodal fusion module, a pose regressor, and a multi-task learning strategy. Specifically, VIFPE employs Multi-axis Vision Transformer (MaxViT) encoders to extract features from both modalities, which are then fused in a shared feature space through a cross-modal fusion module. A pose regression network is subsequently trained to estimate the camera’s position and orientation based on the fused representation. Our experimental results on diverse urban datasets demonstrate that VIFPE significantly outperforms conventional methods in terms of both accuracy and robustness, particularly under challenging lighting conditions. This work underscores the potential of multimodal fusion for camera localization in large-scale urban environments and lays a foundation for future advancements in the field.

With the rapid advancement of unmanned system technologies, their applications in transportation, scientific research, economy, resource exploration, and military fields have become increasingly widespread. The navigation system, as a fundamental component of unmanned systems, plays a crucial role in ensuring their stability and reliability. However, as technology evolves, interference targeting Global Navigation Satellite Systems (GNSSs) has escalated, posing significant challenges in the research of unmanned systems. Navigation interference not only disrupts the normal operation of unmanned systems but also emerges as a pivotal element in counter-unmanned system strategies. This paper provides a comprehensive review of the classification of GNSS navigation interference and its potential impacts, thoroughly analyzing and comparing the strengths and weaknesses of various anti-GNSS interference technologies. Finally, the paper offers insights into the future development trends of anti-interference technologies for unmanned systems, aiming to provide valuable references for future research.

Benefiting from its structural simplicity and low cost, the inertial/ranging integrated navigation system is widely utilized in multi-agent applications, particularly in unmanned aerial vehicles (UAVs). As the deployment of UAVs in complex environments becomes more prevalent, accurate positioning in sparse observation scenarios has become increasingly important. In satellite-denied environments with few anchors, traditional filtering methods for positioning suffer from poor effectiveness due to the lack of constraints. This article proposes a method to enhance positioning accuracy in such environments by optimizing the inertial outputs of each UAV. The optimization process is based on the range measurements between the UAVs and a single anchor. By solving the optimization function derived using Bayesian theory, the optimized inertial outputs of the UAVs can be obtained. These optimized inertial data are then used in place of the original measurements for position estimation in the filter, resulting in improved performance. Simulation and real-world experiments validate that the proposed method can enhance UAVs’ positioning accuracy in single-anchor environments, surpassing the performance of a single optimizer or filter. Furthermore, the positions estimated by cooperative agents demonstrate higher accuracy than those estimated by individual agents, as more ranging measurements are incorporated.

To address the problem of low accuracy for the regular filter algorithm in SINS/DVL integrated navigation, a square-root unscented information filter (SR-UIF) is presented in this paper. The proposed method: (1) adopts the state probability approximation instead of the Taylor model linearization in EKF algorithm to improve the accuracy of filtering estimation; (2) selects the most suitable parameter form at each filtering stage to simply the calculation complexity; (3) transforms the square root to ensure the symmetry and positive definiteness of the covariance matrix or information matrix, and then to enhance the stability of the filter. The simulation results indicate that the estimation accuracy of SR-UIF is higher than that of EKF, and similar to UKF; meanwhile the computational complexity of SR-UIF is lower than that of UKF.