Controllability of Lumped Parameter Chemical Reactors Rafael Maya-Yescas*, Javier Lara-Romero, Ricardo Aguilar-López ‡ Facultad de Ingeniería Química. Universidad Michoacana de San Nicolás de Hidalgo Santiago Tapia 403, Centro, 58000, Morelia, Michoacán, México Tel: (+52-443) 322 3500 Ext. 3011, Fax: (+52-443) 327 3584, *E-mail: rmayay@zeus.umich.mx ‡ División de Ciencias Básicas e Ingeniería. Universidad Autónoma Metropolitana-A México, D.F., México Keywords: Control, controllability, CSTR reactors, nonlinear dynamics, steady state. ABSTRACT The choosing and pairing of control and manipulate variables in lumped parameter chemical reactors, usually Continuous Stirred Tank Reactors (CSTR), is not an easy task because of the lack of methodologies for systematic evaluation of control schemes in nonlinear systems. Furthermore, intrinsic nonlinearities of this kind of systems provoke responses to control actions that are difficult to predict. The classical procedure to identify stable operating steady states in CSTR does not help in the evaluation of the “easiness to control”, sometimes called controllability, at each desired operating state. It is important to note that controllability problems could yield to high operating costs and safety risks, which are non-convenient for economic and human results. Nonetheless, there is an interesting feature of CSTR, they present control affine structure; which means that manipulated variables affect in a linear way the dynamics of the process. In this paper, a simple proposition for the evaluation of pairs of control and manipulated variables is developed for nonlinear control affine systems; it is based on the relationship between zero dynamics and control stability. The resulting strategy is simple, easy to understand and easy to apply for the analysis of control schemes. Also, it is independent of the type of controller used. An industrial system, fluidised bed catalyst regenerators, is used to illustrate the application of this analysis. INTRODUCTION The choosing and pairing of control and manipulate variables in lumped parameter chemical reactors, usually Continuous Stirred Tank Reactors (CSTR), is not an easy task because of the lack of methodologies for systematic evaluation of control schemes in nonlinear systems. Furthermore, intrinsic nonlinearities of this kind of systems provoke responses to control actions that are difficult to predict. The classical procedure to identify stable operating steady states in CSTR does not help in the evaluation of the “easiness to control”, sometimes called controllability, at each desired operating state. It is important to note that controllability problems could yield to high operating costs, which are non-convenient for economic results. Nonetheless, there is an interesting feature of CSTR, they present control affine structure; which means that manipulated variables affect in a linear way the dynamics of the process. In this paper, a simple proposition for the evaluation of pairs of control and manipulated variables is developed for nonlinear control affine systems; it is based on the relationship between zero dynamics and control stability. The resulting strategy is simple, easy to understand and easy to apply for the analysis of control schemes. Also, it is 32nd International Conference of SSCHE May 23–27, 2005, Tatransk´ e Matliare, Slovakia Le-Fr-2, 124p.pdf 124–1