A.N. Tarau, B. De Schutter, and J. Hellendoorn, "Model-based control for throughput optimization of automated flats sorting machines," Control Engineering Practice, vol. 17, no. 6, pp. 733-739, June 2009.
Mail items of A4 size are called flats. In order to handle the large volumes of flats that have to be processed, state-of-the-art post sorting centers are equipped with dedicated flats sorting machines. The throughput of a flats sorting machine is crucial when dealing with a continually increasing number of items to be sorted in a certain time. But, the throughput is limited by the mechanical constraints. In order to optimize the efficiency of this sorting system, in this paper, several design changes are proposed and advanced model-based control methods such as optimal control and model predictive control are implemented. An event-based model of the flats sorting system is also determined using simulation. The considered control methods are compared for several scenarios. The results indicate that by using the proposed approaches the throughput can be increased with over 20%.