Real-Time FPGA Estimation of Eddy Currents and Hysteresis in Axisymmetric Inductors

This paper presents a FPGA application of a finite difference white box model of a electromagnetic device including the effects of eddy currents and hysteresis, applied to a loudspeaker motor and coil. The model parameters are derived from the measured coil voltage and current using an offline algorithm, and the model compared against measured and simulated data. Overall, the FPGA model shows acceptable accuracy, and is capable of running in real time at a sampling rate of 1 MHz. Due to the nature of the model, it is possible to access estimates of quantities such as the magnetic flux density B, the magnetic field strength H and the free current density Jf in real time, allowing the possibility of virtual instrumentation. The model proves to be relatively accurate across a wide frequency range allowing its use inside various control systems.