High resolution position control under 1 sec. of an induction motor with full digitized methods

A method of high resolution position control using an induction motor drive system is proposed. Two control methods are combined. One is an ultralow-speed control based on principles of impulsive torque drives and using a high-frequency dither signal which can compensate standstill frictions at low speed. The other is a linear control along an optimum sliding line which is decided by free-run characteristics of the mechanical load. The control circuit is composed of a high-resolution position sensor (1296 K pulses/rev), a controller using by a digital signal processor (DSP) and a pulse-width modulation (PWM) inverter having optimized PWM switching patterns. The accuracy of the position control obtained in the experiment is 1/1296000 (rev), which corresponds to one second of the mechanical angle.<>