Fuzzy logic direct force control of surface permanent magnet linear synchronous motors without speed sensors

The paper presents a sensorless direct force (DFC) control method for a surface permanent magnet linear synchronous motor (SPMLSM) drive that provides high-performance speed control without position and speed sensors. To solve the practical problem of sensorless propulsion, DFC method is selected to control the thrust force and stator flux linkage of SPMLSM. The sensorless control scheme is based on the measurement and observation of stator current, voltage, and flux vector. Two phase voltages and two stator currents are measured and processed. The rotor speed is estimated through the stator flux and its derivative estimation. Flux and its derivative are calculated in the stationary reference frame and used to estimate the speed. In this paper a DFC based on fuzzy logic is adopted, so that the proper stator voltage vectors can be selected according to the force error. To test the control strategy a simulation using SIMULINK is built. The results show that the proposed control technique gives a good performance for tracking applications.