Digital implementation of parallel control loops in electric drives

The author proposes and analyzes a digital implementation of parallel control loops in electrical drives that allows fast and accurate switching from one control loop to the other. Problems such as those caused by the presence of ripple and noise on the feedback signals are addressed. Experimental results obtained on a microcontroller-based DC servo-drive indicate the excellent performance achieved with this scheme. Performance comparisons are made with the cascaded loop structure to show the advantages of parallel loops. In the case of DC motor drives, the speed regulator gains for an equivalent performance are smaller than in the cascade structure, making the system more immune to noise