Design of a mode-based controller for 3-DOF vibration isolation system

This paper presents an active suspension technique for a three-degrees-of-freedom (3-DOF) vibration isolation system using negative stiffness. A mode-based digital controller is designed based on a theoretical model to generate negative stiffness by active suspension. The active suspension mechanism, in conjunction with a conventional spring in series, can generate infinite stiffness against direct disturbances on the isolation table. Three-axis motions of the isolation table in the vertical directions are actively controlled by the proposed system. Experimental results show that the active suspension system using the proposed controller well evaluates and describes the zero-compliance against direct disturbances.