Disturbance torque compensated speed observer for digital servo drives

A speed observer for digital servo drives is proposed. The observer is composed of an inverse system calculation and a minimal-order state observer The inverse system calculates disturbance torque directly and the state observer performs an instantaneous speed estimation using the calculated disturbance torque. Characteristics of the disturbance torque estimation are analyzed by computer simulations. The speed observer is superior to the conventional identity-type speed observer at the point of the disturbance torque regulation. Experiments for the speed control drive are performed using a digital-signal-processor-based servo controller. Stable speed control at very low speed and its robustness regarding the mechanical vibration characteristics are confirmed