OBSERVER-BASED CONTROLLER FOR INDUCTION MOTORS J. De Leon-Morales *, R. Alvarez-Salas **,l, J. M. Dion ** and L. Dugard** * University of Nuevo Leon, Department of Electrical Engineering, P.O. Box 148-F, 66450 San Nicolas de Los Garza, N. L. MEXICO Tel. (52) 83 76 45 14 - Fax: (52) 83 76 45 14 E-mail: jleon@ccr.dsi..1Lanl.mx ** Lab. d’Automatique de Grenobk, CNRS/INPG UMR 5528, ENSIEG-BP 46, 38402 Saint Martin d’H6res Cedex FRANCE Tel. (33) 4 76 82 62 36 - FAX: (33) 4 76 82 63 88 E-mail: Luc.Dugard@inpg.fr Abstract: This paper deals with the observation and control of a class of nonlinear syst,ems. A cascade observer for a class of state affine nonlinear systems is proposed. Considering an output feedback tracking controller, a stability analysis of the resulting closed-loop system is given. The proposed observed-based controller is then shown to be closed loop stable and is applied to an induct,ion motor industrial setup to show the proposed methodology. Keywords: Induction motor, nonlinear control, nonlinear observer. 1. INTRODUCTION The use of induction motors is widespread in industry, due to their reliability, ruggedness, and low cost. However, they are difficult to control for several reasons. They are nonlinear, coupled, multivariable processes. The rotor electrical state variables are usually unavailable for measurement, and the motor parameters can vary considerably from their nominal values, which degrades the control performances. In this paper, one considers the problem of de- signing a control input in order to track a de- sired output reference when the state is not fully measurable. Several solutions have been proposed by using nonlinear techniques to design controls laws, e.g. differential geometric approach (Marino et al., 1993), sliding-modes methods (Utkin et al., 1999), backstepping (Dawson et al., 1998), passivity (Ortega et al., 1998) and adaptive tech- niques (Marino et al., 1999). For nonlinear sys- tems with stable zero dynamics, and assuming that all components of the state are measurable, a state feedback controller can be designed such that the state is bounded and the tracking error converges to zero. However, the vector state, in general, is not com- pletely measurable and it should be estimated. Nonlinear observer design for a particular class of state affine nonlinear systems is considered. Moreover, the stability analysis of the closed-loop system, when the controller is a function of the estimated state, is performed for particular classes of nonlinear systems. Supported by CONACYT MCxico Copyright © 2002 IFAC 411 www.elsevier.com/locate/ifac Copyright © 2002 IFAC 15th Triennial World Congress, Barcelona, Spain