Electrical Actuators: Applications and Performance

Chapter 4

Linear Estimators and Observers for the Induction Machine (IM) ¹

4.1. Introduction

Controlling alternating-current machines requires the implementation of complex algorithms for signal processing: the observation and estimation of quantities necessary for the control and regulation of output variables for speed drives made up of machines and associated static converters. To carry out these controls, it is necessary to have certain information for electrical and mechanical quantities measured from the power system. Ordinarily, these measures are obtained from physical sensors where the characteristics in terms of precision and bandwidth must be efficient, resulting in high cost for these devices and their maintenance, in addition to the significant structural fragility and sensitivity to unavoidable electromagnetic interferences. All these lead to a progressive suppression of physical sensors in relation to the mechanical structure of the machine, that is, flux, torque, rotation speed, and position sensors.

However, since knowing these quantities is vital for ensuring efficient control, estimators and observers constituting of indirect sensors were developed. The rest of this chapter explains several types of estimators and deterministic and stochastic observers. Order reduction methods are studied (see Chapter 5) to reduce calculation times. In this chapter, we will only consider linear structures of complete order observers, that is, on the basis of the hypothesis that ...