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  • 1
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    Identification and control of a multizone crystal growth furnace (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: This paper presents an intelligent adaptive control system for the control of a solid-liquid interface of a crystal while it is growing via directional solidification inside a multizone transparent furnace. The task of the process controller is to establish a user-specified axial temperature profile and to maintain a desirable interface shape. Both single-input-single-output and multi-input-multi-output adaptive pole placement algorithms have been used to control the temperature. Also described is an intelligent measurement system to assess the shape of the crystal while it is growing. A color video imaging system observes the crystal in real time and determines the position and the shape of the interface. This information is used to evaluate the crystal growth rate, and to analyze the effects of translational velocity and temperature profiles on the shape of the interface. Creation of this knowledge base is the first step to incorporate image processing into furnace control.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Journal of Crystal Growth (ISSN 0022-0248); 119; 3-4,
    Format: text
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  • 2
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    Self-tuning multivariable pole placement control of a multizone crystal growth furnace (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: This paper presents the design and implementation of a multivariable self-tuning temperature controller for the control of lead bromide crystal growth. The crystal grows inside a multizone transparent furnace. There are eight interacting heating zones shaping the axial temperature distribution inside the furnace. A multi-input, multi-output furnace model is identified on-line by a recursive least squares estimation algorithm. A multivariable pole placement controller based on this model is derived and implemented. Comparison between single-input, single-output and multi-input, multi-output self-tuning controllers demonstrates that the zone-to-zone interactions can be minimized better by a multi-input, multi-output controller design. This directly affects the quality of crystal grown.
    Keywords: CYBERNETICS
    Type: International Journal of Adaptive Control and Signal Processing (ISSN 0890-6327); 6; 2; p. 127-138.
    Format: text
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  • 3
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    Characterization of directionally solidified lead chloride (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A directionally solidified PbCl2 material was prepared and analyzed and subsequently used to grow single crystals. It was found that silicon, halogens, sulfur, magnesium, and phosphorus were the hardest impurities to remove by the single-pass directional freezing. Single crystals grown from the purified material displayed good scattering beam quality and showed no absorption peaks between 0.30 to 20 microns. Direct photographic observations of the solid-liquid interface at several G/V (denoting the temperature gradient and the translation velocity, respectively) ratio values showed that, as the G/V ratio decreased, the interface varied from a smooth convex surface to dendritic.
    Keywords: MATERIALS PROCESSING
    Type: Journal of Crystal Growth (ISSN 0022-0248); 89; 1, Ju
    Format: text
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  • 4
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    Adaptive temperature profile control of a multizone crystal growth furnace (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An intelligent measurement system is described which is used to assess the shape of a crystal while it is growing inside a multizone transparent furnace. A color video imaging system observes the crystal in real time, and determines the position and the shape of the interface. This information is used to evaluate the crystal growth rate, and to analyze the effects of translational velocity and temperature profiles on the shape of the interface. Creation of this knowledge base is the first step to incorporate image processing into furnace control.
    Keywords: MATERIALS PROCESSING
    Type: 1991 American Control Conference; Jun 26, 1991 - Jun 28, 1991; Boston, MA; United States
    Format: text
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