Online CD Performance Monitoring and Automatic Alignment Correction, 2011 PaperCon Conference

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Cross Directional (CD) alignment is a key component used in modeling and control of papermaking processes. It specifies the spatial relationship between the center of individual CD actuators and the center of the corresponding measurement responses. A poor CD alignment may cause the quality degradation of the finished product and unnecessary CD actuation at higher spatial frequencies which in turn can lead to higher production cost. This paper presents techniques for monitoring CD performance and correcting poor CD alignment in closed-loop. A revised accumulated sum algorithm is used to detect the onset of CD performance degradation and the pseudo random binary sequence (PRBS) is used in the identification of new CD alignment. The techniques presented in this paper have been implemented in industrial CD control systems and validated in multiple paper mills.