PERFORMANCE COMPARISON OF PAPER-MACHINE STOCK CONCENTRATION CONTROLLERS

A New Zealand pulp and paper company wishes to improve its stock concentration control, and has needed therefore to investigate the performance of various alternative control systems The paper reports the results of a simulation study that formed a part of this investigation. A model of the stock concentration system contains pure delay elements and dominant disturbances. The pulp and paper company is thus interested in applying deadtime compensation, possibly combined with one or more feedforward control loops. In this paper, the performance of six control strategies is simulated, including three-term, deadbeat and optimal multi-variable controllers, each with and without the inclusion of a Smith predictor. For each strategy, a pure feedback control solution is calculated, as well as a number of feedforward-feedback control solutions, depending on the disturbances measured The work was done with the aid of a commercially marketed computer aided control system design package.