PrefaceThe focus of this book is concerned with the modeling and precise numerical simulation of mechatronic sensors and actuators. These sensors, actuators, and sensor -actuator systems are based on the mutual interaction of the mechanical field with a magnetic, an electrostatic or an electromagnetic field. In many cases the transducer is immersed in an acoustic fluid and the solid-fluid coupling has to be taken into account. Examples are: piezoelectric stack actuators for common-rail injection systems, micromachined electrostatic gyro sensors used in stabilizing systems of automobiles or ultrasonic imaging systems for medical diagnostics.The modeling of mechatronic sensors and actuators leads to so-called multifield problems, which are described by a system of nonlinear partial differential equations. Such systems can not be solved analytically and, thus a numerical calculation scheme has to be applied. The schemes discussed in this book are based on the finite element (FE) method, which is capable of efficiently solving the partial differential equations. The complexity of the simulation of multifield problems consists in the simultaneous computation of the involved single fields as well as in the coupling terms, which introduce additional nonlinearities. Examples are: moving conductive (electrically charged) body within a magnetic (an electric) field, electromagnetic and/or electrostatic forces.The goal of this book is to present a comprehensive survey of the main physical phenomena of multifield problems and, in addition, to discuss calculation schemes for the efficient solution of coupled partial differential equations applying the FE method. We will concentrate on electromagnetic, mechanical, and acoustic fields with the following mutual interactions:
• Coupling Electric Field -Mechanical FieldThis coupling is either based on the piezoelectric effect or results from the force on an electrically charged structure in an electric field (electrostatic force).
VI
Preface • Coupling Magnetic Field -Mechanical FieldThis coupling is two-fold. First, we have the electromotive force (emf), which describes the generation of an electric field (electric voltage respectively current) when a conductor is moved in a magnetic field, and secondly, the electromagnetic force.
• Coupling Mechanical Field -Acoustic FieldVery often a transducer is surrounded by a fluid or a gaseous medium in which an acoustic wave is launched (actuator) or is impinging from an outside source towards the receiving transducer.In Chap. 2, we give an introduction to the finite element (FE) method. Starting from the strong form of a general partial differential equation we describe all the steps concerning spatial as well as time discretization to arrive at an algebraic system of equations. Both nodal and edge finite elements are introduced. Special emphasis is put on an explanation of all the important steps necessary for the computer implementation.A detailed discussion on electromagnetic, mechanical, and acoustic fields including their numerical c...