Polaris: Accurate, Vision-free Fiducials for Mobile Robots with Magnetic Constellation

Fiducial marking is indispensable in mobile robots, including their pose calibration, contextual perception, and navigation. However, existing fiducial markers rely solely on visionbased perception which suffers such limitations as occlusion, energy overhead, and privacy leakage.

We present Polaris, the first vision-free fiducial marking system, based on a novel, full-stack magnetic sensing design. Polaris can achieve reliable and accurate pose estimation and contextual perception, even in NLOS scenarios. Its core design includes: (1) a novel digital modulation scheme, Magnetic Orientation-shift Keying (MOSK) that can encode key information like waypoints and coordinates with passive magnets; (2) a robust and lightweight magnetic sensing framework to decode and localize the magnetic tags. Our design also equips Polaris with three key features: sufficient encoding capacity, robust detection accuracy, and low energy consumption. We have built an end-to-end system of Polaris and tested it extensively in real-world scenarios. The testing results have shown Polaris to achieve an accuracy of up to 0.58 mm and 1 • in posture estimation with a power consumption of only 25.08 mW.