| As real-time computation costs continually decline, both mechanical robustness and economic considerations increasingly favor the replacement of mechanical sensors and transducers by software-based state estimation methods. The elimination of encoders or resolvers on induction machine drives is a prime example.;Prior to this work, state estimation and control techniques for electric machines developed independent of machine design and thus had limited robustness and accuracy. Furthermore, the limitations of these existing and also newly emerging observer-based estimation techniques were not well understood or acknowledged.;This work first focuses on evaluating and improving existing rotor flux and velocity estimation and control methods for induction machines, but without integrating machine design. A means of understanding, assessing, and designing observers for induction machines is presented. A closed-loop flux observer topology is developed that is ideally suited for wide speed range direct field orientation (DFO) provided that rotor position information is available. A transducerless DFO system is developed that is an improvement over existing approaches, though it still suffers from the fundamental limitations of parameter sensitivity and lack of zero and low speed operation.;To overcome these limitations, the machine design is incorporated to develop an accurate, parameter insensitive, means of state estimation over a wide operating range including sustained zero speed. The estimation scheme is based upon tracking spatial modulations or saliencies in the machine via high-frequency signal injection with demodulation involving heterodyning and a closed-loop observer. Induction machines can be designed such that saturation in the stator core creates a saliency, permitting the stator flux to be tracked. Introducing a fixed spatial modulation in the rotor leakage inductance enables rotor position and velocity to be tracked.;These integrated machine design and estimation techniques are applied to rotating machines and to a linear induction motor-based transport system for flexible manufacturing systems. |
