Sensorless DTC propulsion of a 1/2-scale controlled-PM LSM vehicle with minimum energy-loss attractive-levitation

This paper presents a sensorless direct torque control (DTC) propulsion control method for a 1/2-scale controlled permanent magnet (PM) linear synchronous motor (LSM) Maglev vehicle with minimum energy-loss attractive-levitation. To solve the practical problem of sensorless propulsion, DTC method is selected to control sensorlessly the thrust force and stator flux linkage of LSM, combining a voltage prediction control to decrease the variation of flux. To verify the controlled-PM Maglev propulsion theory, the vehicle is propelled by sensorless DTC method at standstill-levitation status with minimum energy-loss method. Experimental results show that, even under an extremely unbalance condition that coercive fore of one the four PM's installed on board is reduced strongly by 25%, the 256 kg-heavy-vehicle could be levitated very well with minimum energy-loss method. At levitation status, the vehicle also has been propelled sensorlessly following the demand position and speed above a low speed of 0.2 m/sec, even in acceleration and deceleration as well as constant speed phases, though there is a strong detent fore due to the large semi-closed slots which give a strong influence to the propulsion operating of DTC.