Composite suppression method for gradient and uniform field disturbance in magnetic shielding cylinders using DL-LESO-PDR

External magnetic field disturbance poses significant challenges to magnetoencephalographic (MEG) and magnetocardiographic (MCG) measurements. Traditional active magnetic compensation systems, such as PI controllers, struggle to address gradient disturbance and periodic disturbances, which can degrade imaging accuracy. This paper proposes a dual-loop Linear Extended State Observer with a Proportional-Derivative-Resonant (DL-LESO-PDR) controller that integrates a dual-loop structure with gradient coils to suppress both uniform and gradient field disturbances simultaneously. Additionally, the proposed method enhances the suppression of high-amplitude disturbances at specific frequencies, which is critical for improving MEG and MCG imaging precision. Experimental results validate the effectiveness of this method, demonstrating its superiority in addressing external magnetic field disturbance and optimizing spatial magnetic field compensation compared to traditional approaches.