Ramp rate limiter to control stress during ramping
AssigneeTokyo Electron Limited
InventorsMark Erickson, Thorkell Gudmundsson, Sunil C. Shah
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Abstract
The present invention includes a method and system for limiting the ramp rate of a variable under control in order to control stress in a process or plant under control. The present invention takes a limit curve provided by the user and combines that limit curve with a scale factor curve obtained from a model of the system to produce an allowable limit curve. A ramp rate limiter then uses the allowable limit curve to control the ramp rate of the variable under control such that the ramp rate of the variable under control is able to achieve the maximum allowable limit but no more.
Claims18
A method to limit a ramp rate of a variable under control in a system under control comprising:
- a) determining an allowable limit of the variable under control;
- and
- b) comparing a difference between a requested value and a previous output of a limiter to the allowable limit of the variable under control;
- and
- c) setting a new output of the limiter based upon a result of the comparison in step b).
A method to limit a ramp rate of a variable under control in a system under control comprising:
- a) entering a limit curve;
- b) obtaining a scale factor curve from a model of the system under control;
- c) producing an allowable limit curve;
- d) determining an allowable limit of the variable under control;
- and
- e) comparing a difference between a requested value and a previous output of a limiter to the allowable limit of the variable under control;
- and
- f) setting a new output of the limiter based upon a result of the comparison in step e).
A system for controlling stress during ramping of a variable under control comprising:
- a limiter;
- at least one controller;
- a plant, wherein the at least one controller is coupled between the limiter and the plant.
Dependencies are inferred from the claim text.