The method of modelling and control based on characteristic variables chosen according to system output distributions is presented. Simulation results are satisfactory. Experiments are carried out in a pilot binary distillation column (15 trays with feed of alcohol and water mixture) controlled by a microcomputer system. It is shown that the simlified model can approximate the complete model of distillation column very well and the control strategy has significant advantage compared with a conventional control strategy. This method can also be applied to a kind of high order

nonlinear

distributed parameter systems

which is difficult to deal with.