This paper proposes a motion control technique for robot manipulators. And the strongest point of the technique is high performance on vibration suppression based on an exact dynamic model. The robot control system proposed is characterized by a function that considers the rotor dynamics including rotor masses and the low rigidity in the mechanical reduction gears like the Harmonic Drive Gears. The controller is designed as a sampled-data optimal servo control system with a digital disturbance observer expressed by a state space form. Finally, an experimental results on a real two degrees of freedom robot manipulator are shown by using the servo acceleration sensors.