Using low resolution position sensors in bumpless position/speed estimation methods for low cost PMSM drives

A bumpless position/speed estimation method which uses only a low-resolution position sensor is presented for low cost permanent magnet machine (PMSM) drives. By integrating methods, i.e. using a speed reference for zero speed startup, a low resolution Hall sensor for low speed acceleration, and back-EMF for high speed operation, the rotor position can be estimated and controlled over the entire speed range. In order to achieve bumpless transitions, the three techniques are combined with a crossover function based on the speed reference. The proposed method can be used in applications with unpredictable variation in loads, such as horizontal drum washing machines.