A method of controlling the thickness of sheets manufactured by the
extrusion of a material from a die having a plurality of thickness
adjusting means by repeating, at specified timings, the following steps of
1) measuring the distribution of thickness of the sheets in lateral
direction, 2) evaluating a predicted future variation in sheet thickness
by using a specified evaluation function and based on a process model
representing a relation between the amount of operation and the sheet
thickness and sheet thickness measured values and leading an operating
amount time series to minimize the evaluation function, and 3) outputting
at least the initial amount of operation of the led operating amount time
series to the thickness adjusting means.
