2D systems theory and applications-a maturing area

Two dimensional systems propagate information in two separate directions, usually termed ´horizontal´ and ´vertical´ respectively. Applications include web control in paper making and systems with repetitive dynamics. These processes cannot be controlled, except in very special and restrictive cases, by direct application of existing theory and design algorithms. This paper uses a combination of recent and new results to give a critical overview of progress towards the development of a comprehensive control theory and controller design algorithms for these systems with emphasis on their use in the area of iterative learning control schemes.