Innovative Observers for Induction Motor Control

In this thesis the problem of designing observers and controllers for induction motors has been studied and thoroughly discussed using tools from the nonlinear system theory, both for analysis and control purposes. Useful techniques have been used to identify the machine parameters off-line. In the Introduction was dealt the design a control system for a drive of asynchronous machines that uses a voltage source inverter to generate the currents and voltages which carry the drive by making use of an observer of the state rotor variables. The used control algorithms is the \textit{field oriented control} (FOC). The model of the asynchronous induction motor is described starting from the mechanical model, the electrical model through the Steinmetz equivalent electrical circuit that is the IEEE recommended equivalent circuit, the State Model of Asynchronous Motor and the mathematical model, completing with the discretization of the last model, realizing the Discrete time mathematical model. In Chapter 1 several observer are taken in account in order to be able to compare their strengths and weaknesses. At first it's developed a (FOLO) Full Order Luemberger Observer and its Reduced Order version. Other observer that was considered it's the Sliding one. Then a version of Non linear Flux observer was synthesized in order to consider the effects of saturation which introduce a nonlinear effects. At last the (EKF) Extended Kalman Filter was considered, both in complex (ECKF) and the (RAKF) Robust Adaptive Kalman Filter version. In Chapter 2 have been presented experimental and simulation results obtained by testing each of the previous algorithms. Excellent results were obtained by use of observer based on Kalman Filter, and in particular, the Extended Complex Kalman Filter, because no matrix inversion is required. In fact the operation of matrix inversion that is necessary in the classic Extended Kalman Filter is therefore translated in the inverse of a real number in the proposed Extended Complex Kalman Filter. In conclusion, a set of tools present in control theory have been applied successfully in motion control systems with induction motors. This work is certainly not a complete treatment, since many basic parts are omitted (only the references are given), and for this reasons is to be understood as completion of studies related to the subject matter.