Application of Optimization Theory to the Control of the Optical Fiber Drawing Process

Smithgall, D. H.

doi:10.1002/j.1538-7305.1979.tb02262.x

Cited by 18 publications

(5 citation statements)

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“…For this, we define the perturbed state variables in (12b) as a combination of the numerical eigenfunctions. As derived in Section II, two of the manipulating inputs: the preform feedrate and the fiber draw speed are specified as boundary values in (2). To ease the controller design, we explicitly define the feedrate and draw speed as system inputs…”

Section: Galerkin's Proceduresmentioning

confidence: 99%

“…They suggested a feedback control of drawing speed to reduce low-frequency diameter variations. Smithgall [2] experimentally obtained an empirical transfer function (that relates the fiber diameter to draw speed) by heating a preform (7 to 25 mm in diameter), drawn at a nominal speed of 1 m/s, and measured the fiber diameter using an interference fringe counting technique (with an accuracy of 0.25 at a rate of 1000 measurements per second). Due to physical limitations, measurements made at some point below the heat zone were modeled as a transport delay (40 to 100 ms) to characterize the fiber diameter responding to geometrical variations in the molten neck-down region.…”

Section: Introductionmentioning

confidence: 99%

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Modeling by numerical reduction of modes for multivariable control of an optical-fiber draw process

Lee

Wei²

2006

IEEE Trans. Automat. Sci. Eng.

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Motivated by a need for a method to derive practical and physical-based dynamic models that capture the essential characteristics of an optical-fiber draw process for precision control of diameter uniformity, we extend the Karhunen-Loeve decomposition technique with a Galerkin procedure to derive a reduced-order model (ROM) for a multivariable distributedparameter system. We validated the ROM derived from a highfidelity physics-based model by simulating a modern optical-fiber draw process, the numerical solutions for which have been experimentally verified in our earlier studies. Perturbation studies demonstrated that the 24th-order ROM agrees remarkably well with the original nonlinear semi-two-dimensional and quasione-dimensional distributed models. We further examine the efficiency of the ROM in the context of a model-based H LQG fiber drawing control system for the regulation of the fiber diameter and tension. The results show that variations in fiber diameter can be reduced significantly by appropriately distributing the number of retained eigenmodes among the physical state variables in the ROM. We also demonstrate that controlling the surrounding air temperature in addition to the draw speed is very effective in regulating both the fiber diameter and tension while simultaneously keeping the draw speed and temperature fluctuations to a minimum.Note to Practitioners-Because of the stringent production requirements (on draw speed, tension, and temperature), diameter uniformity is a challenging distributed control problem in modern fiber production where progressively larger diameter preforms are drawn at higher speeds. The reduced-order model offers an effective way to observe physical variables in a multivariable distributed-parameter system, which may not be physically measured. While developed in the context of fiber diameter control, the modeling techniques presented in this paper are applicable to other material processing systems, such as deposition thickness control in semiconductor wafer manufacturing.Index Terms-Distributed parameter systems, fiber draw process, H LQG, Karhunen-Loeve (K-L) decomposition, K-L Galerkin method, model-based control, optical fibers.

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Section: Galerkin's Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modeling by numerical reduction of modes for multivariable control of an optical-fiber draw process

Lee

Wei²

2006

IEEE Trans. Automat. Sci. Eng.

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“…A . signal generated from the measured data after being processed is sent to the fiber feedback control system to further reduce the diameter variation [51].…”

Section: B Pressurized Applicatormentioning

confidence: 99%

High-speed high-strength fiber drawing

Paek¹

1986

J. Lightwave Technol.

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A review of high-speed drawing and coating of optical waveguide fiber, and related work is given. This paper also includes a discussion on the effects of fiber pulling at a high draw rate on the optical and mechanical properties of the silica fiber. The coating mechanics that describes high-speed coating application in terms of process variables is explained. Finally, recent achievements with fibers coated at high speeds are presented.

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“…Experimental results indicate that the fiber dynamic response is much more sensitive to the draw speed, than to the preform feed in rate [23]. It is very convenient, therefore, to choose either the draw speed or the draw force as the control variable.…”

Section: Modal Control Problem Formulationmentioning

confidence: 97%

“…It i s reported that the system works well, even in the presence of large changes in the preform feed-in velocity. Smithgd [23] applied optimization theory, based on a mean square error criterion, to quantdy and control fiber diameter fluctuations resulting from random mechanical and thermal disturbances. In that work, the mechanical and thermal disturbances were modeled together as a bandlimited Gaussian noise process.…”

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confidence: 99%

Modal diameter control of linear isothermal optical fibers

Mulpur

Thompson

Proceedings of IEEE International Conference on Control and Applications

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In this paper, a simulation-based investigation of a strategy to control optical fiber diameter variations is reported. The proposed control scheme is based on the principles of modal control. A model of the fiber manufacture is presented and its sensitivity to the fiber draw speed is demonstrated. A control methodology, utilizing the basic concepts of modal control approach, is attempted on the linear isothermal optical fiber model, and this approach is shown to yield satisfactory results. The proposed approach can be modified and extended for nonlinear control of the fiber diameter.Optical fibers are currently used in diverse applications such as biomedical instrumentation, comunicationS, and space applications. These fibers are usually manufactured by the drawing process. In the single fiber drawing process, a glass preform, of acceptable physical and optical properties, is fed into a fumace, and heated until it becomes soft. The temperature at which the preform is soft enough for drawing fibers, ranges from 1500 to 2 5 W C, depending on the physical properties of the particular glass preform [ 11. The soft. glass is then pulled by means of a winder to form optical fiber. The performance of optical fibers and related optical components depends critically on the evenness of the fiber diameter [2]. Very precise control of the fiber diameter, therefore, is an important manufacturing consideration. Sufficiently large winder speeds have been shown to induce a hydrodynamic instability in the steady fiber flow, called draw resonance [3]. It is known that this instability causes periodic variations in the fiber diameter, which degrade product performance, and may even cause fiber breakage [4].Experimental work with polymers [5.6] has shown that the most significant parameter affecting the onset of draw resonance is the fiber draw ratio U, which is the ratio of the logarithms of the final and initial fiber velocities. This was confirmed theoretically through linearized perturbation analyses [7.8]. In addition, the fiber drawing process is also susceptible to small external disturbances, resulting from unsteady preform feed-in rates, heat sources and sinks. and noise induced vibrations. The effects of these disturbances are as important as the effect of winder speed variations [2]. The need to improve product quality and yield of the drawing process has motivated numerous investigations of modeling and stability analysis of the process [2-201, and several attempts to devise better diameter controllers [21-261.Imoto and coworkers [21,25] devised an optical fiber drawing process which features a gas flow controlling system, in addition to the drawing speed controlling system. Gas flow in the fumace is regulated such that faster fluctuations in fiber diameter are controlled, and the winder speed is varied such that slower fluctuations are reduced. It i s reported that the system works well, even in the presence of large changes in the preform feed-in velocity. Smithgd [23] applied optimization theory, based on a mean squar...

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Application of Optimization Theory to the Control of the Optical Fiber Drawing Process

Cited by 18 publications

References 1 publication

Modeling by numerical reduction of modes for multivariable control of an optical-fiber draw process

Modeling by numerical reduction of modes for multivariable control of an optical-fiber draw process

High-speed high-strength fiber drawing

Modal diameter control of linear isothermal optical fibers

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