Transducerless speed control with initial position detection for low cost PMSM drives

This paper presents an approach for vector control of IPM synchronous motor without position transducer, applicable for low cost PMSM drives with unpredictable load and inertia. To achieve correct drive operation from zero speed, two different techniques are combined with crossover function, based on the speed reference. The rotor initial position is determined prior the control action, for the drive to deliver the full start up torque. Since back-EMF observer estimations are insufficiently accurate under limited angular speed, the zero speed startup and low speed acceleration is used. The back-EMF observer detects the generated motor voltages induced by the permanent magnets. An angle tracking observer uses the back-EMF signals to calculate the position and speed of the rotor. The experimental results based on DSP MC56F8025 show sufficient performance for washing machine, pumps, and fan applications.