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Impact-Free, Time-Saving, Non-Overshooting Position Control

IP.com Disclosure Number: IPCOM000041334D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Baier, H: AUTHOR [+4]

Abstract

Fast and accurate positioning of wafers is particularly important in wafer-exposure machines. For an impact-free position control of the tables, operated by DC motors, the speed profile must be continuous. The predetermined speed profile for position control is corrected by a travel-deviation detector. For this purpose, the table system to be controlled must be capable of continuously following the motor-dependent forces, so that the voltage profile to be predetermined for motor energization must be based on the time behavior of the table system. For a cosine-shaped speed curve for obtaining a maximum speed, there is a constant sinusoidal acceleration function.

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Impact-Free, Time-Saving, Non-Overshooting Position Control

Fast and accurate positioning of wafers is particularly important in wafer- exposure machines. For an impact-free position control of the tables, operated by DC motors, the speed profile must be continuous. The predetermined speed profile for position control is corrected by a travel-deviation detector. For this purpose, the table system to be controlled must be capable of continuously following the motor-dependent forces, so that the voltage profile to be predetermined for motor energization must be based on the time behavior of the table system. For a cosine-shaped speed curve for obtaining a maximum speed, there is a constant sinusoidal acceleration function. For accelerating (and decelerating) the table system without overshooting, which still permits obtaining the maximum speed, a particular minimum time and travel (smallest travel) are required; otherwise, the table system is no longer capable of following the predetermined acceleration curve. For shorter travels, the acceleration curve per unit of time must also correspond to a sinusoidal function. Since in such a case the maximum speed cannot be obtained, the acceleration and the resultant forces are reduced. This ensures an impact-free position control for smallest travels.

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