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Title: | Optimal control strategy using linear programming for load disturbance compensation in thermal processing systems | Authors: | Ho, Weng Khuen Tay, Arthur Schaper, Charles D. |
Issue Date: | 1999 | Citation: | Ho, Weng Khuen,Tay, Arthur,Schaper, Charles D. (1999). Optimal control strategy using linear programming for load disturbance compensation in thermal processing systems. Proceedings of SPIE - The International Society for Optical Engineering 3882 : 24-35. ScholarBank@NUS Repository. | Abstract: | An optimal control scheme is designed to improve repeatability by minimizing the loading effects induced by the common processing condition of placement of a semiconductor wafer/photomask at ambient temperature on a large thermal-mass bake plate at processing temperature. The optimal control strategy is a model-based method using linear programming to minimize the worst-case deviation from a nominal temperature set-point during the load disturbance condition. This results in a predictive controller that performs a pre-determined heating sequence prior to the arrival of the wafer as part of the resulting feedforward/feedback strategy to eliminate the load disturbance. This procedure is based on an empirical model generated from data obtained during closed-loop operation. It is easy to design and implement for conventional thermal processing equipment. Experimental results are performed for a commercial conventional bake plate and depict an order-of-magnitude improvement in the settling time and the integral-square temperature error between the optimal predictive controller and a feedback controller for a typical load disturbance. | Source Title: | Proceedings of SPIE - The International Society for Optical Engineering | URI: | http://scholarbank.nus.edu.sg/handle/10635/72836 | ISSN: | 0277786X |
Appears in Collections: | Staff Publications |
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