Automatic Nonlinear Grade Change Control for Paper Machines, 2012 PaperCon Conference

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The evolution of the automatic grade change package for paper machines has been documented by Chu et al [1]. Honeywell proposed its first closed loop algorithm in 1975 [2] with several other iterations following this. In 2008, Honeywell introduced a grade change package [1] that incorporates the ability to predict the whole MV (manipulated variable) and CV (controlled variable) trajectories, utilizes a first principles paper machine model to capture nonlinearities during a grade change and has an option to conduct a grade change with supervisory machine direction multivariable MPC (model predictive controls) in either open loop or closed loop. Documented results [1] show a reduction in grade change time of 50% on a fine paper machine from the previous QCS (quality control system). One drawback with the automatic grade change presented in [1] was its complex configuration. An updated version of the package with a simplified configuration was developed and this paper examines the commissioning of the simplified automatic grade change package.