Rotor's Position and Speed Estimation in Sensor-less Permanent Magnet Synchronous Motors via Shifting Sliding Mode and Adaptive Control

Permanent magnet synchronous motors (PMSM) without sensor are widely used in many fields by virtue of smaller volume, lighter weight and higher power density. There are mainly three types of control strategies for PMSM, among which the so-called vector control one is most widely used. How to obtain real-time and accurate rotor's position and speed is essential for implementing vector control. To accomplish sensor-less position and speed estimation, we propose an improved strategy that combines sliding mode control (SMC) to model reference adaptive observer (MRAO). More precisely, we embed SMC into the traditional MRAO to reduce dependence on motor parameters and improve robustness. However, SMC brings chattering and hampers stability. To suppress chattering, we use hyperbolic tangent function instead of sign function to define the SMC surface switching function, together with an auxiliary shifting term. Numerical examples are given to illustrate the main results.