＜正＞For the outputs of two nth-order linear control systems to work in synchronization and meanwhile to track their commands, a H∞synchronization control scheme is presented. In terms of two uncoupled single variable linear systems, a multivariable coupled system is established by choosing one output and the difference of the two outputs as a new output vector, so that both command tracking and synchronization properties can be demonstrated by a H∞performance index. To improve the synchronization and tracking performance and to guarantee the system robust stability, the mixed sensitivity H∞design methodology is adopted. The presented synchronization scheme is then extended to the case where one of the two systems include two input variables, and then applied to the position synchronization control of a wafer-retical stage. The wafer-reticle stage consists of a wafer stage, a reticle coarse stage, and a reticle fine stage. The reticle coarse stage picks up the reticle fine stage. The three stages ought to
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