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Model-based feedforward and feedback control of the verticalgradient-freeze-crystal growth process using distributed parameter methods

使用分布参数方法对垂直梯度冷冻晶体生长过程进行基于模型的前馈和反馈控制

基本信息

批准号：
276805057
负责人：
Dr. Christiane Frank-Rotsch
金额：
--
依托单位：
Leibniz-Institut für Kristallzüchtung (IKZ)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/276805057?language=en
关键词：
Model based feedforward feedback control

项目摘要

An important process for the production of mono crystalline materials is the vertical gradient freeze (VGF) process. Here, poly-crystalline material is molten in a crucible. Then crystallization starts from the bottom into upward direction until the complete melt is solidified. For this purpose the temperature field surrounding the crucible is manipulated in such a way that the melting point isotherm travels slowly from the bottom to the top of the crucible. The required controls are realized by resistance heaters placed around the crucible. In order to drive the process in an appropriate manner information about the actual state is required, especially of the crystallization rate. However, this cannot be captured. This is due to high process temperature, the reactivity of the used materials and the requirements with respect to the purity of the product preventing any measurement devices to be placed within the crucible. Only the temperatures at the resistance heaters can be measured. Because of this it is not possible to establish a real closed loop control. It is only feed forward black box controlled. From a control theoretic point of view the VGF process is a typical candidate of a distributed parameter system with free boundaries (the solid-liquid-interface) and lumped control input (the heaters). The objective of the proposed project is to develop theoretical and practical methods for a real feedback control of the process. This also includes methods for the reconstruction of the system state from available or newly introduced measurements. For this purpose it is planned to use distributed parameter methods that have been developed by the Institute of Control Theory (TU Dresden) as one of the leading institutes in this subject for several years now. Up to now the focus was mainly on the feedforward control and the parameter identification of such systems. The work will be accompanied with intensive work on modeling of the VGF process by the Institute of Crystal Growth Berlin (IKZ). These models are required for controller and observer design as well as for the validation of the developed control and reconstruction algorithms so experimental effort can be reduced. Here, the challenge is to find mathematical models of the process which on the one hand side are sufficiently precise for control and on the other hand side are real time capable. Furthermore they must meet the structural requirements given by the selected distributed parameter methods. Although the control methods developed during the project will found a highly sophisticated theoretical framework the practical meaningfulness will be guaranteed by experimental tests at the VGF growth plants.

用于生产单晶材料的重要方法是垂直梯度冷冻（VGF）方法。这里，多晶材料在坩埚中熔化。然后结晶从底部开始向上方向，直到完全熔体凝固。为此目的，以熔点等温线从坩埚的底部到顶部缓慢行进的方式操纵坩埚周围的温度场。所需的控制是通过放置在坩埚周围的电阻加热器来实现的。为了以适当的方式驱动该过程，需要关于实际状态的信息，特别是关于结晶速率的信息。然而，这是无法捕捉的。这是由于高的工艺温度、所用材料的反应性以及对产品纯度的要求，防止任何测量装置放置在坩埚内。只能测量电阻加热器的温度。因此，不可能建立真实的闭环控制。它只是前馈黑盒控制。从控制理论的角度来看，VGF过程是具有自由边界（固液界面）和集中控制输入（加热器）的分布参数系统的典型候选者。该项目的目标是为过程的真实的反馈控制开发理论和实践方法。这也包括用于从可用的或新引入的测量重构系统状态的方法。为此，计划使用控制理论研究所（TU Dresden）开发的分布参数方法，该研究所是该主题的领先研究所之一。迄今为止，这类系统的研究主要集中在前馈控制和参数辨识方面。这项工作将伴随着由晶体生长研究所柏林（IKZ）的VGF过程建模的密集工作。这些模型需要控制器和观测器的设计，以及验证开发的控制和重建算法，所以实验工作可以减少。这里，挑战在于找到一方面对于控制足够精确并且另一方面具有真实的时间能力的过程的数学模型。此外，它们必须满足所选分布参数方法给出的结构要求。虽然在项目期间开发的控制方法将建立一个高度复杂的理论框架，但实际意义将通过在VGF生长工厂的实验测试来保证。