Unit Manufacturing Processes Issues and Opportunities in Research (1995) / Chapter Skim
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12 Process Control
12 Process Control
Pages 143-152
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From page 143... ...
The trend for process controllers is to incorporate a greater degree of "intelligence" and to be integrated into a plant-wide information network that automates many management tasks, such as detailed scheduling (Considine, 1993~. This chapter addresses issues and opportunities for the individual process controllers.
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From page 144... ...
This technology is adequate for traditional machining operations in which the machining speed is low. Also, the performance limitation ofthese PID controllers provides for only a low level of closed-loop performance in unit manufacturing processes, which is reflected in the final product quality level.
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From page 145... ...
The research addresses the problem of how to attain optimum system performance when a process model is not known precisely in advance, the operating conditions are variable, the process parameters vary nonlinearly during operation, etc. The philosophy behind adaptive control theory is that the controller must adapt its control gains so that the overall system remains at or near the optimal condition in spite of varying process dynamics.
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From page 146... ...
Learning control can be used to learn the optimum control input through repeated trials (Dagli, 1994~. When unit processes repeat the same task, this control methodology fine tunes the controller's performance.
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From page 147... ...
Standard configurations cannot accommodate nonmachining devices such as work-holding accessories, force sensors, vision sensors, and other subsidiary devices. Although they use advanced electronics, computer numerical controls design concepts are conservative, especially in terms of hardware and user interfaces.
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From page 148... ...
For example, a self-sustaining machine, for any kind of processing operation, would be serviced by a dexterous manipulator or other automatic loading device, dedicated to the continuous needs of the process, such as supplying material and unloading finished parts. A variety of on-machine sensors would provide vision, touch, force, and temperature senses in order to recognize unexpected events, perform in-cycle inspection, and optimize the production parameters.
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From page 149... ...
The machine should be adaptable to the changing environment and tasks and thus be modular in terms of its controller's computer configuration and its mechanical construction. RESEARCH OPPORTUNITIES Advanced control architectures, such as adaptive and robust control, should be extended for application to unit processes that have time-varying dynamics and a high level of uncertainty regarding control inputs.
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From page 150... ...
Learning control can be applied to unit processes that involve the repetition of the same task or cyclical operations. Research issues include appropriate models for the design of leaning-control algorithms and analytical and experimental investigation concerning the convergence characteristics of learning-control algorithms.
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From page 151... ...
1988. An autonomous, self loading machine tool.
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From page 152... ...
1987. Selection and implementation of a factory automation LAN, Autofact '87 Conference Proceedings held November 1987.
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