Effects of finite switching frequency and computational delay on PWM controlled servo DC drives

Effects of (low) switching frequency and of delays (due to digital control implementation) on DC servomotor drives with a PWM power supply are examined. A modeling procedure and analytical formulae to quantify deviations from standard (idealized) fixed-gain models are presented, and illustrated by simulations and hardware experiments. Necessary and sufficient conditions for the existence of a periodic steady state in the operation of a DC servomotor drive are also described.