Abstract
This paper discusses the current trends in the evolution of hardware for computer control and the implications of these trends for the papermaking industry. This discussion covers, in addition to computer main frames, the development of remote analog signal multiplexing, conversion and digital data transmission, the evolution of graphic displays as operator panel replacements and the elimination of long cable runs from instruments by the use of laser data links.
As an overview of the future, an indepth presentation is given of an integrated papermill computer control hierarchy (of the sort to be expected within five years). In this configuration, the actual process control is performed by a number of freestanding (that is, no special computer room), small (20 in x 20 in x 60 in) computers dedicated to the direct digital control of the process sub-units (for example, grinders, bleaching plant, head box, dryer section and coaters). These first level computers are subservient to a larger foreground/background computer, performing such functions as control parameter optimisation, management information reduction and presentation, as well as on-line optimum production scheduling.
This portion of the paper also includes a discussion of the control techniques and strategies that will be in common use at this date and the additional process variables that will be on computer control (gloss, air permeability, colour and caliper). A part of this discussion covers the future state of the art, which will be approaching the control of the distributed parameter aspects of the process (such as cross-machine moisture and basis weight control).
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