In the field of accurate positioning system, such as semiconductor lithograph machine, an active isolation system is widely used. Especially, it is an indispensable unit in the system which is required a highly accurate isolation performance from outside in the machine. There are many development elements of the semiconductor lithograph machine, such as improvement of isolation performance using pseudo auxiliary tank with servo-valve. By the way, in the present time, there are many huge earthquake in any other country of the world, such as Sumatra in Indonesia, Sichuan in China. This huge earthquake generate a powerful long-period ground motion, and this motion cause a lot of troubles in lithograph manufacturing machine. This ground motion is vibrating for a long time as 1-hour or more. Sumatra earthquake transfer to Korea, Sichuan earthquake transfer to Japan. And the ground motion cause a lot of damage to the production using lithograph machine. The newest machine is very expensive, so semiconductor firm have to establish countermeasure to long period ground motion without too much economic damage to their profits.
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