Design of high-accurate magnetic field control system based on improved ADRC strategy and low-noise coil actuator

Active magnetic field compensation can provide a near-zero magnetic environment for ultra-weak magnetic signal measurement. Affected by the parameters of coil actuators and the traditional PID controller, the compensation system is usually exposed to insufficient dynamic compensation capability and higher noise. This study proposes a new improved active disturbance rejection control (IADRC) strategy for increasing the dynamic compensation capability with higher accuracy, and presents a low noise coil actuator design method with small coil constant for reducing the magnetic noise. Compared with the conventional method, the coil constants in x, y, z directions are decreased from 219.6 nT/A, 279.0 nT/A, 2370.9 nT/A to 64.9 nT/A, 51.4 nT/A, 109.1 nT/A, with reductions of 70.4 %, 81.5 %, 95.4 %, respectively. In x, y, z directions, the statistical average of residual magnetic field is 0.0038 pT, 0.0096 pT, 0.0091 pT, and the magnetic noises are suppressed to 56.5 fT/Hz^1/2, 67.2 fT/Hz^1/2, 67.1 fT/Hz^1/2 at 1 Hz, respectively. The proposed method provides a new strategy to obtain more-accurate and low-noise near-zero magnetic conditions for frontier scientific research.