利用磁力测量增强视觉惯性SLAM
Enhancing Visual Inertial SLAM with Magnetic Measurements
AI总结：
针对水下洞穴等磁场缓变环境中视觉惯性里程计的方向漂移与回环困难问题，提出紧耦合磁力计测量的VIO扩展框架，通过椭球校准磁误差、优化多类误差项，显著提升了方向精度与系统鲁棒性。
摘要：
本文提出了一种视觉惯性里程计（VIO）的扩展方法，引入了磁力计测量值的紧耦合融合。该方法通过最小化重投影误差、相对惯性误差和相对磁力计方向误差，对关键帧滑动窗口进行优化。IMU方向传播的结果用于在帧间高效转换磁力计测量值，生成连续帧之间的相对方向约束。软铁效应和硬铁效应通过椭球拟合算法进行校准。引入磁力计数据后，方向误差显著降低，并且能够恢复相对于磁北的真实偏航方向。所提出的框架可在所有磁场缓慢变化的环境中运行，主要是户外和水下环境。我们的工作聚焦于水下领域，尤其是水下洞穴，因为狭窄通道和湍流使得回环检测与定位漂移重置难以实现。水下洞穴因缺乏环境光且环境封闭，对VIO构成挑战，但同时也是淡水的重要来源，还保存着宝贵的历史记录。水下洞穴的实验结果表明，所提出的VIO扩展方法提升了精度和鲁棒性。
英文摘要：
This paper presents an extension to visual inertial odometry (VIO) by introducing tightly-coupled fusion of magnetometer measurements. A sliding window of keyframes is optimized by minimizing re-projection errors, relative inertial errors, and relative magnetometer orientation errors. The results of IMU orientation propagation are used to efficiently transform magnetometer measurements between frames producing relative orientation constraints between consecutive frames. The soft and hard iron effects are calibrated using an ellipsoid fitting algorithm. The introduction of magnetometer data results in significant reductions in the orientation error and also in recovery of the true yaw orientation with respect to the magnetic north. The proposed framework operates in all environments with slow-varying magnetic fields, mainly outdoors and underwater. We have focused our work on the underwater domain, especially in underwater caves, as the narrow passage and turbulent flow make it difficult to perform loop closures and reset the localization drift. The underwater caves present challenges to VIO due to the absence of ambient light and the confined nature of the environment, while also being a crucial source of fresh water and providing valuable historical records. Experimental results from underwater caves demonstrate the improvements in accuracy and robustness introduced by the proposed VIO extension.
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