Joël BAFUMBA LISELI : Design and control of high-resolution piezoelectric positioning systems

PhD work : Design and control of high-resolution piezoelectric positioning systems with multiple degrees of freedom with a measurement embedded by self-sensing.

Abstract :
Currently, systems integrate more and more functionalities into smaller volumes thanks to embedded micro-components. The assembly of those components requires precise and repeatable systems of manipulation. Substantial amounts of research have been carried out for developing actuators and microrobots to perform positioning or manipulation with micron- or even submicron accuracies. Piezoelectric technologies play a fundamental role in positioning applications with nanoscale or even lower resolution. These materials make possible the design and development of positioning systems with high resolution and bandwidth. However, nonlinear effects such as hysteresis and creep affect the position accuracy of piezoelectric-based systems if not controlled. Often, position sensors are mounted to these systems to permit a feedback control and the elimination of the hysteresis and creep effects. Nonetheless, the integration of sensors to enable quality and robust servo control poses specifie problems for microrobots. This is especially true when the number of degrees of freedom (DOF) increases. Precision position sensors are usually very bulky and expensive. Alternative solutions to the integration of external position sensors can be grouped into two categories: either by open-loop control, also called feedforward control schemes or by Self-Sensing Actuation (SSA) control-based techniques, that is, a feedback control that uses the piezoelectric actuator as its own sensor. In this thesis, the objective is to design and control a piezoelectric-based positioning system with an embedded measurement by SSA method and having several degrees of freedom. To this end, the two classes of SSA, namely SSA based on the piezoelectric direct effect and the SSA based on the change of electrical properties of the piezoelectric actuator (PEAs), are studied in depth to determine the more adequate for force and position control in piezoelectric actuators typified by creep and hysteresis nonlinearities and devoted to precise operations. Additionally, from this study, an improved constitutive madel and parameter identification technique are presented which includes the electromechanical coupling effect on the piezoelectric material properties (elastic and dielectric constants). A novel technique for real-time evaluation of the PEA's electrical properties is developed.
This evaluation is based on the measurement of the amplitude of the detection current that results from the application of highfrequency low amplitude input voltage that is superimposed to the control input voltage which actuates the PEA. Then an estimator that uses the detection current to estimate the PEA's position is designed. Finally, a microrobotics platform for planar positioning with high resolution and the developed embedded measurement by SSA is presented.

Composition of the jury :
Micky RAKOTONDRABE, Assitant professor, Université Bourgogne Franche-Comté, PhD Supervisor
SEETHALER RUDOLF, Assistant professor, Univeristy of British Columbia – Okanagan, Reviewer
Joel AGNUS, Ingénieur de Rcherche, ENSMM, Examinateur
Philippe LUTZ, Professeur des Universités, Université Bourgogne Franche-Comté, Co-PhD supervisor
Nicolas Chaillet, Professeur des Universités, Université Bourgogne Franche-Comté, Reviewer
Sandar BASROUR, Professeur des Universités, Université Grenoble-Alpes, Reporter
M. Mathieu GROSSARD, Ingénieur de Recherche, Institut CEA LIST – laboratoire de Robotique Interactive, Reporter

Location : ENSMM École Nationale Supérieure de Mécanique Microtechniques 26 Rue de l'Épitaphe 25000 BESANCON, Salle : Amphithéâtre Jules Haag