Construction and Control of Ultra-precision Positioning System Driven by Leadscrew Mechanism Applied Elastic Functional Element

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This study proposes a simple method that will give extreme improvements in positioning performance of leadscrew mechanism. The method is achieved by intentionally attaching a linear elastic element to a sliding leadscrew. This study aims at investigating propriety and availability of the proposed method, and at considering control method proper to the new mechanism. A positioning system is constructed to be attached the elastic element, while design procedure of the elastic element is considered to manufacture the element practically. Moreover, the property of the developed system and control method is discussed.A positioning stage with stroke of 200 mm is newly developed. The stage is driven by a sliding leadscrew rotated by a DC servo motor of 130 W, and the motor is driven by a linear current amplifier. The table displacement is detected by a laser interferometer. A special arrangement of optical elements is introduced using a three-sided mirror set on the table to reflect the laser … More beam from the interferometer. The optical arrangement makes it possible to measure the table displacement without any influence of Abbe's error. The design method of the elastic element is shown using a cylinder with flexure hinges formed by notching. Three elastic elements with different stiffness are made practically.The stiffness of the manufactured elements are measured and compared to the design specifications. The actual stiffness is smaller than the calculation. Some experiments are performed on the developed positioning system to investigate its performance. The relation between the torque input and the table displacement shows quite linear characteristics in microscopic range, so that the availability of the method is proved. The stage is controlled by a software servo system. The controller is designed based on PI operation, and the parameters are given in coarse, fine and ultra-fine range respectively. It is ascertained that the positioning resolution of the system is 5 nm, and that the error of 20 mm step positioning is less than 6 nm. Less