Adaptive Profile Control for Sheetmaking Processes

Abstract Successful control of cross-machine direction (CD) or profile variations in sheet properties is difficult to achieve consistently using conventional control methods. Due to coupling in the cross direction and constraints on the actuators used for profile control, a sophisticated multivariable controller is necessary to compute optimal control corrections. Changing machine speeds, environmental conditions, product grades, and raw material quality will change the profile process response making on-line adaptation of the controller necessary. This paper presents an adaptive control algorithm which is being used to control the weight profile on paper machines. The controller minimizes a quadratic cost function based on a process response model and the necessary actuator constraints. The process model is identified on line using a modified generalized least squares algorithm. Results from simulations and many actual paper machine installations have shown this approach to be superior to less sophisticated methods.