Vibration cancellation controller design of magnetic levitation stage for fast and precise positioning

High-speed and high-precision positioning technology is widely used in industrial machinery such as manufacturing equipment and processing machines. In semiconductor manufacturing equipment, a magnetic levitation (maglev) stage is used to prevent the effects of non-linear friction, which deteriorates positioning precision. In the maglev stage, multiple motors and sensors are arranged to enable control of six degrees of freedom, i.e., a multi-input multi-output (MIMO) system. A decoupling method is effective for MIMO control because it reduces the interaction between the motors and sensors and converts the control target into multiple single-input single-output (SISO) systems. The purpose of this study is to develop decoupling that includes vibration cancellation in the high frequency range. The proposed decoupling cancels vibration modes by combining motors for orthogonal translation axes (horizontal and vertical directions) and using orthogonal motors to excite the vibration modes in opposite phases. In the proposed method, the conditions for cancelling vibration modes are derived and shown in the frequency domain. The proposed decoupling method, which includes dynamics, is designed to satisfy the derived conditions. The effectiveness of the proposed approach is verified by analysis and experiments using a prototype coarse-fine maglev stage.