On the globally defined sensorless control of induction motors

The sensorless control problem of induction motors imposes a Current challenge since the nonlinear model of this kind of machines does not exhibit global observability properties., i.e. there are some operation regimes for which speed observability is lost. One way for dealing with this unavoidable limitation. and at the same time provide globally defined controllers, is to consider that the rotor variables are estimated via in open-loop observer. In this paper a globally defined passivity-based speed controller that belongs to the aforementioned class is presented. It is shown that the structure of previously reported passivity-based controllers, developed under the assumption that the mechanical variables are available for measurement, can be extended to operate under sensorless conditions if I speed observer is included in the control scheme. Since the controller design methodology leads to inherent drawbacks regarding robustness issues, to evaluate the usefulness of the proposed scheme a numerically based Study is included that cover topics such as parameters and disturbance (load torque) uncertainty. The advantages and limitations of the proposed scheme are established with respect to other globally defined sensorless controllers. Copyright (C) 2008 John Wiley & Sons, Ltd.