Nichtlineare Beobachter für Drehfeldmaschinen

This thesis deals with observer design methods for a certain type of nonlinear systems and its application to the induction machine. Therefore, the mathematical model of the induction machine, the controller design for the exact input/output linearisation and the controllers for magnetic flux, torque and speed are discussed. The mathematical structures of a full- and a reduced-order state observer are introduced and the error systems are derived. Then a criterion for exponential stability of nonlinear systems is discussed. The application of this criterion to the mathematical structure leads to a new method of observer design. Finally, this method is used to derive observers for the induction machine. These observers are tested in simulation and on the test bench. The tests show, that the reduced observers combined with the i/o linearisation lead to poorer results than the trivial observer. The full-order observers show hardly better results than the trivial observer. Nevertheless, an example shows that the discussed method of observer design can be applied to unstable systems for which a trivial observer fails. In addition, electromagnetic disturbance and measures to improve electromagnetic compatibility (EMC) of the test bench are discussed. Thus, the test bench, a model for electromagnetic disturbance and measures to improve EMC are explained. Tests on the testbench show, that the effect of the disturbance on the current measurements is reduced by those measures. Finally, the control of power electronics considering free-wheel currents is discussed.