Digital Motor Speed Control

Digital motor speed control is a unique method of highly accurate pulse frequency modulation as applied to speed control of a hysteresis synchronous motor. This method utilizes digital techniques to obtain motor speed accuracy and stability of better than 0.001 percent of the desired value. The device described is basically a digitally controlled variable frequency oscillator whose output pulse frequency is a function of an input command to the system. Frequency modulated pulses, after suitable shaping and power amplification, are applied to the windings of a two phase hysteresis synchronous motor. The speed of the motor is therefore controlled by the input command. A variety of auxiliary feedback loops can be utilized with the method presented to perform various types of control functions.