Comments on self-tuning regulator applied to a binary distillation column

Some comments are made on a paper describing an application of self-tuning control in the presence of step disturbances. It is demonstrated that the behaviour of the self-tuning regulator observed in the paper is a consequence of the slow convergence of the regulator parameters. By an increase of the convergence rate quite different results can be obtained. For example, no steady state error in the output is observed, contrary to the results in the paper in question.