Software-based position control of a permanent magnet synchronous motor

This paper contains the description of a software-based position control for a permanent-magnet synchronous motor, implemented on a microcomputer. The aim was to implement a simple but reliable position-control strategy that does not involve the use of bulky, costly control hardware and feedback transducers. Thus the only rotor-condition sensor used is a low-resolution, incremental position encoder, that has three channels including the zero marker. Both position and velocity control loops were implemented in software, and there was the additional need to compute the absolute position, speed and direction of rotation of the rotor from the incremental encoder signals. The task of generating the control signal and speed estimation was carried out on the microcomputer, while that of processing the encoder pulses to obtain absolute position was implemented externally using a combination of counters and ROMs.