This paper presents a robust speed controller for 2-mass resonance systems. Torsional vibration can be occurred in such system that
a driving motor and a driven load are connected with a flexible long shaft. Torsional torque generating the vibration is compensated
with disturbance observer or neural network estimator, which estimates the torsional torque and inertia value by using actual motor
torque and speed. The simulation results of the proposed control method based on the neural network estimator are presented to
show its effectiveness, especially against the system parameter variations.