Adaptive sheetmaking machine control system

Abstract

Partitioning control of the wet end and dry end, by introducing estimates of physical properties such as dry weight: and percent ash at the wire, allows for machine direction (MD) controls to continue during loss of scanner measurements. A mathematical model estimates the controlled, variables, such as dry weight, basis weight, and ash percent at the wire, and these estimated values are then controlled. When scanner measurements resume, parameters in the model are recursively updated to compensate for any model errors and ensure an accurate model. MD controls consist of a cascade set-up where the estimated wire-dry weight or wire basis weight and estimated wire ash percent are controlled by manipulating stock flow and addition of filler to stock. When scanner measurements are available, they become the downstream variables in the cascade control and are controlled by manipulation of the setpoints for the estimated wire weight and ash.

Description

technical field [0001] The present invention relates generally to techniques for monitoring and controlling a continuous sheet manufacturing system, such as a paper machine, and more particularly to the assessment of one or more physical properties of the sheet formed at the wire. The wet and dry ends of the machine are controlled separately. This technique provides for paper machine direction control to continue in the event of sheet breaks or other disturbances that lead to loss of scanner measurements at the dry end. Background technique [0002] A wide variety of systems are available and used to make paper sheets and other paper products. The paper sheet being manufactured often has properties that are monitored and controlled during the manufacturing process. For the standard method of machine direction (MD) control, the controlled variables—such as the basis or dry weight of the paper and the ash content of the paper—are measured at the reel and controlled by adjust...

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Problems solved by technology

This results in a loss of time and material

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