NC State
J.S. Harris and G.J. Mummery. Process control at the wet end using an analog computer. In Papermaking Systems and their Control, Trans. of the IVth Fund. Res. Symp. Oxford, 1969, (F. Bolam, ed.), pp 286–300, FRC, Manchester, 2018.


No. I machine at Chartham Paper Mills produces a high grade of tracing at substances ranging 40-160 g/m2 . Increased process understanding of the wet end system led to the idea of using a simple analog technique to obtain a more uniform and more efficiently produced product from this machine.

The computer system was installed in January 1968 and has been fully operational since then. It consists of two basic operations, feedforward and feedback control. The feedforward control uses process equations calculated from equilibrium conditions that link together stuff gate flow, breast box flow and efflux ratio with reel-up substance and dry end speed. The feedback control maintains the required substance by feedback to the stuff gate.

Performance analysis of the computer has shown that broke at substance changes has been significantly reduced and wet end conditions are considerably more stable . Present development work consists of incorporating computer dynamic substance control on this machine.

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