Ph.D Thesis

Ph.D StudentLeus Vitaly
SubjectNew Efficient Methods for Modeling, Design and Actuation
of Electrostatic Micro Mechanical Devices
DepartmentDepartment of Mechanical Engineering
Supervisor PROF. David Elata
Full Thesis textFull thesis text - English Version


Electrostatic actuation is a prevalent method of driving micro-electro-mechanical systems (MEMS) because it is compatible with microfabrication processes and requires very low power consumption. Ongoing progress in microfabrication technology offers new prospects for innovative designs and actuation/sensing schemes in electrostatic MEMS devices. Efficient modeling and simulation tools are needed to facilitate design and to optimize actuation techniques of these devices.

In the present work new efficient methods for modeling and simulation of electrostatic actuators are developed. The transient dynamic response of electrostatic micro actuators is analyzed using a systematic approach based on energy methods. Linear relation between important time measures and measures of the voltage applied to electrostatic switches, is derived despite the inherent nonlinearity of electrostatic forces. The electromechanical response of actuators pre-loaded by a controlled amount of charge and actuated by independent voltage is examined. The correct way of analyzing this kind of system using energy considerations is presented, revealing a prevalent misinterpretation of electrostatic co-energy. An actuator with an electrostatically floating electrode is introduced and analyzed. It is shown that the induced charge behaves as a bias which effectively increases or reduces the applied voltage according to the charge polarity. A non-disruptive way of measuring floating charge is proposed and demonstrated.

A new efficient method for simulating the transient dynamic response of electrostatic switches which are subjected to a step-function voltage is proposed. The method uses an adaptive single-mode approximation and employs energy methods to reconstruct the electromechanical response of electrostatic switches. Very good prediction capability of the proposed method is demonstrated.

The research also proposes a new strategy for actuation of electrostatic switches using a short-pulse voltage waveform, thus improving performance and reliability of existing actuators.

The thesis includes analytical predictions derived for simple model problems. 2D and 3D model structures are simulated using different numerical approaches (i.e. finite differences and finite-elements) showing applicability of the new methods. The theoretical analysis is validated experimentally using specially designed and fabricated micro structures.