Blown film thickness control with a scanning down-the-line measurement

The thickness profile of the tubular bubble in blown film extrusion is deduced from delayed measurements made downstream in the flatted web consisting of the bubble. Scanner moving across the web measures only a portion of it at a time and the measurement results are matched to the bubble profile at actuators controlling the thickness. The delayed profile is predicted to current time and used for LQR feedback control. The control architecture is tested in a simulation of the process.