Robust motion control based on a two-degrees-of-freedom servosystem

Recent topics on motion control are reviewed with special emphasis on robust control. Acceleration control is the most important key. A two-degrees-of-freedom (2-DOF) servosystem is the most effective method of realizing acceleration control. It realizes independent joint control for a robot manipulator. The same idea can be applied to the design of a robust force controller. An instantaneous speed observer which achieves strong robustness when a low precision shaft encoder is used is introduced. The importance of acceleration control even in disturbance rejection and vibration suppression controls in flexible systems is stressed.