Process control of polymer extrusion. Part II: Feedforward control

A feedforward plus feedback control method (FFC) and an adaptive feedforward plus feedback control method (AFFC) were proposed in this study to control the extrudate thickness of polymer extrusion. They were tested by step changes of screw speed and feedstock, and square wave type of screw speed changes. It is found that these feedforward control methods worked very well for various load disturbances but they required a good process model and accurate on‐line measurements of manipulated variables and load variables. The feedback function was necessary to compensate the over‐ or under‐corrections of the feedforward controllers and to handle other disturbances which were not considered in the feedforward model.