RESEARCH INITIATION AWARD:Efficient Control of ManufacturingSystems with Buffer Costs

本研究的主要目的是为半导体制造系统开发一种有效的控制方法。为了实现这一目标，将解决两个子问题。然后，总体聚合控制将是这些结果的直观混合。第一个子问题是确定具有缓冲成本的可再入制造系统的最优控制。求解的方法是利用最优控制的结构性质，如分段连续性和单调性，从而将问题简化为具有已知解的问题。第二个子问题是确定控制对几台不可靠机器的影响。我们将证明，对于某一类控制，缓冲级概率密度满足一组线性双曲型偏微分方程。这些方程的解将用数值和模拟方法来探讨。聚合控制将使用三个标准对系统缓冲区进行分区：机器可靠性、缓冲区利用率和机器停机和停机时间的分布。然后，子问题的结果将用于确定适当的控制。此外，将实施监管措施，以使物料流动顺畅，从而减少二阶效应。仿真将用于测试聚合控制的有效性。＊＊＊

9410242 Perkins The primary objective of this research is the development of an efficient control for semiconductor manufacturing systems. To achieve this objective, two subproblems will be solved. The overall aggregate control will then be an intuitive blend of these results. The first subproblem is to determine an optimal control for a re-entrant manufacturing system with buffer costs. The method of solution is to exploit structural properties, such as piecewise continuity and monotonicity, of an optimal control in order to reduce the problem to one with a known solution. The second subproblem is to determine the effect of the control on several unreliable machines. It will be show that, for a certain class of controls, the buffer level probability densities satisfy a set of linear, hyperbolic partial differential equations. The solution of these equations will be explored using numerical, and simulation methods. The aggregate control will partition the system buffers using three criteria: machine reliability, buffer utilization, and distribution of the down and up times of machines. The results of the subproblems will then be used to determine the appropriate controls. In addition, regulators will be implemented to smooth out the material flow, thus reducing second-order effects. Simulation will be used to test the efficiency of the aggregate control. ***