Digital DC motor speed control with phase locked loop regulation

Abstract

The object of the thesis is to study the speed control of direct current motor by using phase locked loop principle and compare alternative methods applied in practice. The operation of phase locked servo systems is described and a linear discrete model is developed to describe their behavior. This model explains the observed phenomenon that the system becomes unstable at low speeds. Also discussed are the design problems, speed variations, and the extension of lock range by lag-lead networks. A phase locked loop speed control system: incorporating a digitally controlled single-phase thyristor bridge is described and the experimental results are given for the case of a separately excited d.c. motor.