Polynomial Fitting-Based Design Method for Nonuniform Dynamic Magnetic Field Compensation Coils

Magnetic shielding is the key technology to create a near-zero magnetic environment. Nevertheless, the inherent characteristics of passive magnetic shielding result in a residual field that is generally non-uniform and highly vulnerable to interference by environmental magnetic fields. To achieve a stable, low-remanence near-zero magnetic environment, this study proposes a design method for magnetic compensation coils capable of dynamically compensating non-uniform residual fields in the magnetic shielded room (MSR). A polynomial is defined for fitting the residual field distribution. Applying the principle of shared symmetry, the polynomial terms are grouped, leading to the design of a non-uniform magnetic compensation coil system comprising five bi-planar coils. Simulations and experiments show that the proposed coils can achieve effective compensation of irregular non-uniform magnetic field distributions through adjustment of the applied current and have effective dynamic compensation performance for alternating magnetic fields within the [0.01 Hz, 1 Hz] frequency band. Compared to compensation approach relying solely on the superposition of uniform and gradient field, the proposed non-uniform coils system exhibits superior adaptability to the irregular magnetic fields. This work provides a method for the design of single-axis dynamic non-uniform magnetic compensation coils and further establishes a scalable framework for three-axis non-uniform magnetic compensation.