Enhancement of Magnetic Field Disturbance Suppression for Wearable Optically Pumped Magnetometers

Wearable optically pumped magnetometers (OPMs) operating in the spin-exchange relaxation-free (SERF) regime are an emerging alternative for biomagnetic field measurements. Nevertheless, the wearable implementation of OPM inevitably entails positional variations, leading to magnetic field disturbance and the introduction of amplitude errors, consequently impacting the precision of magnetic source localization. To solve this problem, an enhanced method is presented for wearable OPMs, which can achieve real-time suppression of magnetic field disturbance without overshoot. First, we analyze the influence mechanism of magnetic field disturbance on OPMs, thereby clarifying the nonlinear impact that disturbance exerts on the system. Then, a magnetic field disturbance suppression system based on active disturbance rejection control (ADRC) is developed to estimate and compensate for magnetic field disturbance in real time. The experimental results demonstrate that the ADRC method enables overshoot-free fast response and tracking suppression for the sensitive x-axis magnetic field disturbances. Moreover, the settling time is shortened to 3.3 ms compared to 15.4 ms required by the PI method, which extends the effective duration of the signal under measurement. Furthermore, the amplitude errors in the y-axis and z-axis are reduced by 38.29% and 47.10%, respectively. Finally, the enhanced magnetic field disturbance suppression method proposed in this article provides valuable technical support for wearable medical applications of OPM.