Hardware-in-the-loop Simulation Testbed for Geomagnetic Navigation

TL;DR

This work introduces a hardware-in-the-loop testbed for geomagnetic navigation that combines a FEM-based digital twin with a physical square Helmholtz coil to synthesize target magnetic fields in an unshielded lab. It advances coil design through parameter optimization to maximize field uniformity and develops a convex combination coil control that balances convergence, stability, and accuracy, with formal convergence and stability proofs. The testbed is validated in both shielded and unshielded environments, showing favorable tradeoffs against LMS, SVS, and ATLMS in terms of response speed, RMSE, and stability, while remaining cost-effective due to off-the-shelf hardware. The approach enables repeatable, low-cost geomagnetic navigation experimentation and lays groundwork for extending field synthesis to three dimensions and tighter integration with navigation algorithms.

Abstract

Geomagnetic navigation leverages the ubiquitous Earth's magnetic signals to navigate missions, without dependence on GPS services or pre-stored geographic maps. It has drawn increasing attention and is promising particularly for long-range navigation into unexplored areas. Current geomagnetic navigation studies are still in the early stages with simulations and computational validations, without concrete efforts to develop cost-friendly test platforms that can empower deployment and experimental analysis of the developed approaches. This paper presents a hardware-in-the-loop simulation testbed to support geomagnetic navigation experimentation. Our testbed is dedicated to synthesizing geomagnetic field environment for the navigation. We develop the software in the testbed to simulate the dynamics of the navigation environment, and we build the hardware to generate the physical magnetic field, which follows and aligns with the simulated environment. The testbed aims to provide controllable magnetic field that can be used to experiment with geomagnetic navigation in labs, thus avoiding real and expensive navigation experiments, e.g., in the ocean, for validating navigation prototypes. We build the testbed with off-the-shelf hardware in an unshielded environment to reduce cost. We also develop the field generation control and hardware parameter optimization for quality magnetic field generation. We conduct a detailed performance analysis to show the quality of the field generation by the testbed, and we report the experimental results on performance indicators, including accuracy, uniformity, stability, and convergence of the generated field towards the target geomagnetic environment.

Figures (13)

• Figure 1: A system architecture of the proposed Hils testbed.
• Figure 2: The schematic diagram for magnetic field strength calculation in the Hils testbed. (a) Field strength calculation at point Q for the magnetic field generated by the current element parallel to the y-axis (b) field strength calculation at point Q for a square Helmholtz coil.
• Figure 3: The schematic diagram of the convex combination coil control method. The International Geomagnetic Reference Field (IGRF 13th) block in the figure provides the reference geomagnetic field for a specific location on the Earth.
• Figure 4: The schematic diagram for the weight transfer in the proposed coil control.
• Figure 5: (a) The Helmholtz coil built in this study (b) Measurement diagram that records the field strength by the Helmholtz coil.