Finite-Difference Gradient Approximation-Based Phase Shift Adaptive Correction Flux Waveform Controller in Ferromagnetic Material Testing

Among various magnetic property measurement devices, single-sheet testers (SSTs) are widely used due to their adaptability. However, the inherent nonlinearity of SSTs introduce unknown phase shifts into the control process, ssignificantly complicating the precise control of sample flux waveforms. In this paper, we propose a finite-difference gradient approximation (FDGA) based phase shift adaptive correction flux waveform controller. Treating the measurement system as a black box, the controller employs finite difference methods for gradient approximation to compute the harmonic components of excitation voltage. The controller adopts the phasor form, enabling simultaneous determination of both the amplitude and phase of the excitation voltage, thereby achieving adaptive correction of phase shift. This paper analyzes the impact mechanism of phase shift on control, explains the controller’s operating principle and measurement platform structure. Magnetic performance of B30AHV1500 was measured at different frequencies, waveforms, and magnetic field amplitudes using different measurement platforms.Results demonstrate the controller’s superior adaptability, measurement accuracy, and significant testing procedure simplification.