Hierarchical Approach to Optimized Control of Drying of Coated Paper

摘要

A new optimum moisture control strategy for a coating machine has been developed. Optimum setpoints for the dryers can be achieved by the strategy. The control strategy is based on a two-level hierarchical control structure. Subsystems, which reside at the lower level of the hierarchy, are described by non-linear, constrained, steady-state models of the dryers. The goals of the subsystems are expressed by non-linear objective functions which signify the operating costs of the individual dryers. The overall goal is defined by the attainment of the optimum drying cost in terms of paper grade specific drying strategy. A suitable open-loop coordination method has been searched for solving the resulting two-level problem. The input prediction and balance method was observed to be powerful for the existing problem. The solution method is based on a search for the saddle point of the primal-dual function. The saddle point is found by making simultaneous iterations of the Lagrangian multiplier and interaction input variable at the high level. The solution of the coordination problem is achieved when the balance condition is satisfied.