Composite Suppression Method of Magnetic Interference in Magnetic Shielding Cylinder Based on Adaptive Frequency Estimator

The high-amplitude magnetic field interference in the environment causes serious distortion of the cardiac magnetic signal measured in the central area of the magnetic shielding cylinder. The integration of a linear extended state observer (LESO) and a proportional resonance (PR) controller can effectively suppress high-amplitude magnetic interference at specific frequencies. However, the frequency of high-amplitude magnetic interference in the environment is variable, bringing challenges to conventional PR method. To address this issue, this article proposes a novel approach (LESO-AFE-PR) for suppressing magnetic interference by integrating an adaptive frequency estimator (AFE), PR, and LESO. The LESO-AFE-PR method can improve the capability of the active magnetic compensation (AMC) system to attenuate high-amplitude magnetic interference with random frequency. Experimental results show that the LESO-AFE-PR can adaptively track the frequency of magnetic field interference, effectively suppress interference in the range of 1<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula>40 Hz, and attenuate the amplitude of magnetic field interference from 32.9 to 3.6 pT. Compared to the uncompensated state, a remarkable attenuation of approximately 89<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> in magnetic field interference is achieved.