用物理约束提升磁导航中噪声数据的去噪能力。
Physics Aware Neural Networks: Denoising for Magnetic Navigation
- 通过旋度定义磁场并保证无散度,结合三维对称性约束模型输出
- 在多种网络结构上验证,连续时间建模的Contiformer表现最优
- 适合需要高精度磁导航的飞行器与无人系统应用
磁异常导航利用地球磁场的小尺度变化,在GPS失效或受干扰时提供替代方案。机载系统面临的核心挑战是飞机自身引起的磁噪声。尽管经典Tolles-Lawson模型能部分解决此问题,但难以应对随机污染的磁数据。为此,我们引入两个物理约束:无散度矢量场和E(3)等变性,确保学习到的磁场符合麦克斯韦方程,且传感器位置与姿态变化时输出正确变换。无散度通过训练神经网络输出矢量势A,并以∇×A定义磁场实现;E(3)等变性则通过球谐函数表示的几何张量张量积实现。这些约束作为隐式正则化,提升了时空建模性能。我们在CNN、MLP、LTC和Contiformer上进行消融实验,结果表明连续时间动态与长期记忆对磁时序建模至关重要,其中Contiformer表现最佳。为缓解数据稀缺,我们使用世界磁场模型(WMM)和条件时间序列生成对抗网络(GANs)生成真实、时序一致的磁序列。实验表明,嵌入物理约束显著提升预测准确性和物理合理性,优于经典方法与无约束深度学习模型。
原文摘要 · Abstract (English)
Magnetic-anomaly navigation, leveraging small-scale variations in the Earth's magnetic field, is a promising alternative when GPS is unavailable or compromised. Airborne systems face a key challenge in extracting geomagnetic field data: the aircraft itself induces magnetic noise. Although the classical Tolles-Lawson model addresses this, it inadequately handles stochastically corrupted magnetic data required for navigation. To handle stochastic noise, we propose using two physics-based constraints: divergence-free vector fields and E(3)-equivariance. These ensure the learned magnetic field obeys Maxwell's equation and that outputs transform correctly with sensor position and orientation. The divergence-free constraint is implemented by training a neural network to output a vector potential A, with the magnetic field defined as its curl. For E(3)-equivariance, we use tensor products of geometric tensors represented via spherical harmonics with known rotational transformations. Enforcing physical consistency and restricting the admissible function space acts as an implicit regularizer that improves spatiotemporal performance. We present ablation studies evaluating each constraint alone and jointly across CNNs, MLPs, LTCs, and Contiformers. Continuous-time dynamics and long-term memory are critical for modelling magnetic time series; the Contiformer, which provides both, outperforms existing methods. To mitigate data scarcity, we generate synthetic datasets using the World Magnetic Model (WMM) and time-series conditional GANs, producing realistic, temporally consistent magnetic sequences across varied trajectories and environments. Experiments show that embedding these constraints significantly improves predictive accuracy and physical plausibility, outperforming classical and unconstrained deep learning approaches. Acknowledgement: This work was done in collaboration with Dirac Labs.
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