Sensorless Control of Tubular Permanent magnet synchronous Linear Motor Considering the End Effect

Due to the end effect of tubular permanent magnet synchronous linear motor, the inductance of the motor is complex, and it is difficult to realize sensorless control. To solve the problem, the analytical expression of the inductance was derived based on the axial magnetomotive force (MMF) and axial specific permeance. Then the inductance was studied by the analytical model and the finite element method. And the characteristics of the inductance were analyzed. The DC components of self-inductance and mutual-inductance are not zero and the amplitudes of their second harmonics are not equal. Based on the characteristics of the inductances, a high-frequency square-wave injection method in the stationary reference frame was proposed. This method compensates the DC component of the induced current by off-line measurement, and the position information is obtained by an orthogonal phase-locked loop. Experiments show that this method can estimate the mover position accurately.