Two-dimensional methods for MD and CD estimation and control: Recent progress

The paper describes recent progress in two-dimensional estimation and contr ol methods for web forming processes such as paper making. In particular, i t outlines some of the developments in two-dimensional methods that have ta ken place in the Control Systems Centre since the Control '92 Conference [1 ] and relates them to recent sensor research. The basic premise for this pa per is that continuous web forming (such as takes place at the wet-end of a paper machine) or related coating processes are two-dimensional dynamical processes in which the machine direction (MD) and cross direction (CD) form the two dimensions. The two-dimensional paradigm leads to a set of techniq ues with which to estimate, predict and potentially regulate the MD/CD proc ess in a way which acknowledges and accounts for the mutual dependence of t he machine and cross machine directions.