Modeling and observability of electric drives in view of mechanical sensorless control

Thesis defended on May 18, 2016, 2:00 PM at CentraleSupelec (Gif-sur-Yvette) Amphi F3-06

High-performance control of electric drives requires an accurate knowledge of the rotor position and/or speed. These mechanical variables are traditionally measured using sensors, which increases the cost and reduces both the robustness and the reliability of the system. This emphasizes the importance of electric drives control without shaft sensors, often referred to as sensorless control: it consists of replacing sensors with a state observer algorithm, that estimates the desired mechanical variables from currents and voltages sensing and based on the system’s model. Nevertheless, before designing a state observer, the observability of the system should be examined, that is, it should be checked whether the states to be estimated can be reconstructed, unambiguously, from the input/output signals of the system.

This work addresses the modeling and the observability analysis of electric drives in the view of mechanical sensors removal. Firstly, electrical machines models are elaborated, and it is shown that a unified modeling of alternating current machines is feasible, for the purpose of designing unified control and estimation strategies.

The observability of the machines’ models is next studied in the view of sensorless control. The local instantaneous observability theory is applied, which enables us to formulate physically insightful analytic conditions that can be easily interpreted and tested in real time. The validity of the observability conditions is confirmed by numerical simulations and experimental data, using an extended Kalman observer.

This work contributes to novel outlooks on the sensorless alternating current drives and to a deeper understanding of its properties, in order to develop higher performance estimation techniques in the critical operating conditions (mainly at standstill and/or zero stator- frequency).

The concepts introduced throughout this thesis, such as the equivalent flux and the observability vector, with the obtained results, open new horizons in a domain that seems to become mature enough.


M. Jean-Pierre BARBOT          Professeur des Universités, ECS-Lab, ENSEA                                          Rapporteur    

M. Guy CLERC                         Professeur des Universités, AMPERE, Univ. Claude Bernard Lyon I        Rapporteur    

M. Maurice FADEL                   Professeur, ENSEEIHT, Laboratoire LAPLACE                                         Examinateur  

M. Philippe MARTIN                Enseignant-Chercheur, CAS, Ecole des Mines de Paris                          Examinateur

M. Eric MONMASSON            Professeur des Universités, SATIE, Université de Cergy-Pontoise         Examinateur

M. Gilles DUC                         Professeur, L2S, CentraleSupélec                                                           Directeur de thèse

M. Guillaume SANDOU          Professeur, L2S, CentraleSupélec                                                            Co-encadrant 

M. Abdelmalek MALOUM      Docteur, Renault                                                                                       Co-encadrant