Using Signals from Two Gauges to Estimate MD Variations for CD Control Systems

Scanning gauges continue to be the most common form of gauging system used by cross-directional (CD) control systems for sheet processes. However, scanning gauges have a number of shortcomings, such as the inability to separate cross-directional variations from machine-directional variations and the irregular time intervals between samples at a given CD location. To overcome these problems, array sensing systems have been developed for a number of sheet industries but these tend to be expensive and it can be difficult to calibrate the individual sensors within the array. In this paper, the signals from two gauges, one fixed and one scanning, are combined with an observer to estimate both the MD variation and the CD variation across the whole sheet at any given time. Simulation results are presented that show the performance of the observer. The system is currently being evaluated on data from a production process.