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Electro-Damp® PLS is a new approach to the height control of pneumatic vibration isolation systems.
Typically, air isolators are self-leveling and rely upon mechanical valves and a mechanical linkage to sense and maintain the position of an isolated surface. TMC's EPPS and PEPS® were the first non-contacting height control systems to incorporate electronic height control valves and analog controls. The approach of using non-contacting height control systems has become an attractive method for metrology and microlithography tool designers to control static and dynamic position. Non-contacting control eliminates wear issues and maintains a high level of repeatability over long periods of time while providing the highest possible level of vibration isolation.
The Electro-Damp PLS builds upon TMC's PEPS® technology
by incorporating our DC-2000 Digital Controller to greatly expand
the available options and interfaces. In particular, the Electro-Damp
PLS incorporates an Information Feedforward function allowing for
dramatically less vertical displacement of the isolated surface
and improved leveling times in response to weight shifts caused
by stage motion. Feedforward is a technique in which information
controlling the position of a motorized stage is used to "anticipate" stage
motion and the corresponding change in pressure required in each
pneumatic isolator required to offset this motion. Typically, such
information is taken from the stage motion controller. This technique
is simple, requires no additional sensors, has no feedback (making
it inherently stable), and is relatively inexpensive. Feedforward
can often achieve up to a five-fold improvement in displacement
and leveling time.
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