Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting
Patent
1993-06-25
1995-03-14
Vargot, Mathieu D.
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
264 405, 425141, 425162, 364473, B29C 4792
Patent
active
053975146
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a process for producing flat and annular-cross-section extrudates, and to a device for implementing the process.
BACKGROUND OF THE INVENTION
One process for regulating the thickness of extruded flat sheets or plates of thermoplastic has been disclosed by DE 31 07 701 C2, for instance. In this process, measurement values are found during continuous measurement of the thickness of the flat sheet or plate using a thickness gauge transversely to the draw-off direction; these values are averaged, and control is carried out as a function of the ascertained deviation between the actual values and a specified command value.
This is a classical process of readjustment as a function of the ascertained differential signals between actual and command variables.
A similar method has also been disclosed by EP 0 203 479 A2. Once again, a specific mean value is formed via measurement value pickups, a command value is fixed, and after the deviation of the actual value from the command value has been found, the control device is altered to make a correction.
Although partial improvements are attainable with such processes and devices, it has nevertheless been found that particularly in a closed-loop control process that is dependent on a number of control parameters, the fastest possible optimization and subsequent stabilization of the attained optimal control can be achieved only with difficulty, particularly if the variation in the deviation is to be as slight as possible.
SUMMARY OF THE INVENTION
It is therefore the object of the present invention to create a process that is improved compared with the prior art and a device pertaining to it, as a result of which more-optimal control in view of a particular stated target is possible, particularly in the field of the production of flat and annular extrudates.
According to the invention, the object is attained with respect to extrusion processes and devices in accordance with an evolution strategy for optimization.
The present invention incorporates a completely novel approach wherein control is performed as a function of stated target, employing the method of evolution strategy.
In the method of evolution strategy, an at least partially and/or tendentially random variation in the control parameters, that is, the control variables, is carried out by means of the basic principles of "mutation" and "selection", so that after the varying quality standards have been checked, it can be ascertained from the subsequently performed "selection" whether a variation toward the desired optimization and an increase in quality in accordance with the standards as a result of the mutation can be ascertained. If an improvement is ascertained, then an improved set of parameters resulting from a "mutation" can be chosen as a point of departure for further improvement in the machine setting. That is, the mutation varies the machine setting via a random process, or substantially via a random process; within the context of the selection, the improved machine settings are selected as a point of departure for the next mutation step.
Evolution strategy per se is known in principle for optimizing industrial systems. In this respect, reference can be made purely as an example to the publications by I. Rechenberg, "Evolutionsstrategie, Optimierung technischer Systeme nach Prinzipien der Biologischen Evolution" [Evolution Strategy: Optimization of Industrial Systems by Principles of Biological Evolution], FromannoHolzborg, Stuttgart, 1973, and H. P. Schwefel, "Numerische Optimierung yon Computer Modelien" [Numerical Optimization of Computer Models], Birkhauser, Basel and Stuttgart, 1977. However, these publications do not even hint at the idea that evolution strategy processes might also be employed in the production of flat and annular-cross-section extrudates in extrusion systems.
Yet employing evolution strategy precisely in this field creates surprising and unexpected advantages.
Evolution strategy is a parameter optimizing process that can be
REFERENCES:
patent: 4124342 (1978-11-01), Akatsuka et al.
patent: 4711747 (1987-12-01), Halter
patent: 4800050 (1989-01-01), Hahn et al.
Breil Jurgen
Haupt Martin
Bruckner Maschinenbau Gernot Bruckner GmbH & Co. KG
Vargot Mathieu D.
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