This paper describes the practical design method of an advanced servo system for industrial robot manipulators, where it includes a disturbance and velocity observer. It is first assumed that the feature on frequency response of the robot is approximated to the feature of two-mass mechanism. Actually this is confirmed by some experiments. On the other hand, it is insisted that the actual servo system should be simple for industrial use. The observer is designed for the load which has the feature of single moment of inertia. Based on the assumption that there is a difference between these features, it is introduced that the servo system can be effectively used if only the qualified gains are selected considering lowstiffness. The special relation between the frequency analysis and the pole allocations are then shown, and Finally the experimental results are introduced.
Keywords: Observer, Disturbance, Velocity, Robot, Servo, Low-stiffness