Position estimation of linear switched reluctance machine with iron losses based on eddy-current effect

The voltage pulse injection method (VPIM) is widely employed in the sensorless control of switched reluctance machines (SRMs) and linear SRMs (LSRMs) at the starting and low-speed operations. However, the existing iron losses in SRMs/LSRMs will lead to the distortion of the phase currents, especially in the VPIM, and will in turn affect the accuracy of estimated results. This study presents a novel mover position estimation method for the LSRM based on the eddy-current effect. The effects of the eddy-currents on the phase currents and winding terminal voltages are discussed, and the equivalent eddy-current resistance model is presented through the finite element analysis. Furthermore, the eddy-current resistance and LSRM magnetic circuit are analysed, obtaining that the positions vary monotonically along with the differences between the rising time and falling time of the response pulse currents. On the basis, the starting and low-velocity operation methods are proposed. A designed double-sided LSRM test platform is established, and the proposed methods are verified by the experimental results.