Disturbance Suppression Method for Three-Axis Active Magnetic Compensation System Based on ISMC-LESO

The three-axis active magnetic compensation (TAMC) system is widely used to suppress environmental magnetic disturbances in a magnetically shielded room (MSR), enabling stable ultraweak magnetic measurements with reduced cost. Nonlinear, time-varying, and coupled behaviors induced by the shielding material's magnetic properties pose challenges to accurate modeling and disturbance suppression. A composite control strategy combining linear extended state observer (LESO) with integral sliding mode control (ISMC) is proposed. The LESO is implemented for each axis to provide real-time estimates of external disturbances, model uncertainties, and interaxis coupling. Based on the LESO estimates, the ISMCs are designed to enhance robustness against parameter variations and nonlinearity while compensating for disturbances. Experimental results on a TAMC platform demonstrate that the proposed method effectively suppresses magnetic disturbances, which significantly reduces magnetic fluctuations inside the MSR and ensures reliable conditions for high-precision biomagnetic measurements.