High performance ultra-low speed servo system based on doubly coprime factorization and instantaneous speed observer

This paper proposes a new speed servo system for a wide speed range based on doubly coprime factorization and instantaneous speed observer. The proposed speed controller is a new two-degrees-of-freedom speed servo system considering the robust stability according to inertia variation, which is designed on the basis of doubly coprime factorization and disturbance observer. In an ultra-low speed range, a speed sensor based on a rotary encoder cannot detect a motor speed. In this paper, a speed information in a very low speed range is estimated by the proposed instantaneous speed observer which mounts the parameter identification algorithm to cancel out the estimation error caused by parameter variation. Therefore, the two-degrees-of-freedom speed servo system connecting the instantaneous speed observer regulates a motor speed robustly in a wide speed range including an ultra-low speed range, and it keeps the desired speed response for all speed reference including an ultra-low speed range.