Adaptive Model-Following Control of a Certain Class of Non-Linear Process Unit

ELIÇABE, G. E.; FRONTINI, G. L.; MEIRA, G. R.

CHEMICAL ENGINEERING SCIENCE

Año: 1986 vol. 41 p. 1833 - 1841

0009-2509

An adaptive model-following control (AMFC) technique is developed which considers: (a) non-linear process unit models of the class x dot p = g(xp) + P(xp)up with dim (xp) = dim (up) and P(xp) invertible for all xp; and (b) non-linear reference models of the class x dot m = m(xm, r). The basic control consists of a type of model-following scheme, and the adaptation mechanism is obtained through an approach which is equivalent to that utilized for the linear case. In order to apply the proposed control algorithm, the unknown (or slowly time-varying) process unit model (PUM) parameters must be "extracted" from the non-linear terms of g(xp) and P(xp). This is performed through an appropriate PUM transformation which requires the unknown parameters to appear linearly in each of the original PUM terms. If this is not the case, then series expansions are necessary prior to the transformation. The proposed technique is applied to a simulated example investigated previously by Liaw and Bailey (1974, AIChE J 17, 924-932), which consists of a chemical reactor operated under periodic control. Although the present method requires a relatively higher control effort, an improved performance is obtained.