Novel model-based digital controller for facilitating soft magnetic material measurement under controlled magnetizing conditions
Résumé
Dealing with requirements for modelling and simulating precisely performance of soft magnetic materials, magnetic measurement must be now conducted under different magnetizing conditions imposed by waveform, frequency and amplitude of flux density. The well-known nonlinearity of materials gives rise to a mandatory use of automatic controller in magnetic testing. Many studies about controllers were published. In [1], Zurek et al. reported an adaptive iterative feedback solution for 1D, 2D and even 3D measurement using any type of testers for diverse materials, wide range of frequency and high amplitude of flux density. In [2], the association of an analog circuit into a digital system helps to reduce 95% the convergence time comparing to results of [1], but the application range is narrow in terms of frequency (2 Hz to 100 Hz). We propose in this paper a novel digital controller which has two control loops, one for regulating amplitude and one for adjusting waveform of flux density based on equivalent circuit of magnetic testers such as Epstein frame and ring specimens. The adaptive ability and the high convergence speed of this controller are demonstrated by testing results with various families of materials (non-oriented SiFe, CoFe and amorphous alloys), diverse waveforms (sinusoidal, triangle, trapeze, user-defined periodic), wide range of frequency (up to 5 kHz) and high amplitude (up to 90% of the saturation) of flux density. Its principle and implementation in LabVIEW are also described.