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Über dieses Buch

Mechanical engineering, an engineering discipline borne of the needs of the industrial revolution, is once again asked to do its substantial share in the call for industrial renewal. The general call is urgent as we face profound issues of productivity and competitiveness that require engineering solutions, among oth­ ers. The Mechanical Engineering Series features graduate texts and research monographs intended to address the need for information in contemporary areas of mechanical engineering. The series is conceived as a comprehensive one that covers a broad range of concentrations important to mechanical engineering graduate education and research. We are fortunate to have a distinguished roster of consulting editors on the advisory board, each an expert in one of the areas of concentration. The names of the consulting editors are listed on the facing page of this volume. The areas of concentration are: applied mechanics; biomechanics; computational mechanics; dynamic systems and control; energetics; mechanics of materials; processing; thermal science; and tribology. I am pleased to present this volume in the Series: Electromechanical Sensors and Actuators, by Ilene Busch-Vishniac. The selection of this volume under­ scores again the interest of the Mechanical Engineering series to provide our readers with topical monographs as well as graduate texts in a wide variety of fields.

Inhaltsverzeichnis

Frontmatter

Basic Tools for Transducer Modeling

Frontmatter

1. Introduction

Abstract
A typical technical field had evolved from infancy through the efforts of a number of researchers. As the evolution progresses, a consensus on the scope of the field and the fundamental definitions of associated objects or parameters emerge. When the technical area is dominated by a single major discipline, such as mechanical engineering or physics, the consensus on definitions and scope can be achieved quite rapidly. However, when the emerging technical area is truly multidisciplinary, as is the case with the technical field of transduction, then the consensus can be difficult to forge. Indeed, the field of transduction has involved virtually all of the major technical disciplines, each having its own perspective on the fundamental definition of a transducer. As a result there are many different definitions of transducers in use. The most common of these definitions are included in what follows:
1
A transducer is a device which transforms nonelectrical energy into electrical energy or vice versa. (See, e.g., Middlehoek and Hoogerwerf [1].)
 
2
A transducer is a device which transforms energy from one domain into another. (See for example Rosenberg and Karnopp [2].) Typical energy domains are mechanical, electrical, chemical, fluid, and thermal.
 
3
A transducer is a device which transforms energy from one type to another, even if both energy types are in the same domain. (See Busch-Vishniac [3] for instance.)
 
Ilene J. Busch-Vishniac

2. System Models

Abstract
The academic discipline of transduction necessarily covers a broad range of energy domains In the course of this book we will discuss translational, rotational, fluid, thermal, magnetic, electrical, and optical systems. In order to have a common language and common tools, it is necessary to use a system modeling procedure which can easily span these domains.
Ilene J. Busch-Vishniac

Transduction Mechanisms

Frontmatter

3. Transduction Based on Changes in the Energy Stored in an Electric Field

Abstract
We begin our transduction mechanism discussion with transducers which are based on changes in the energy stored in an electric field. This class of mechanisms is capacitive. Some of these transducers accomplish energy conversion in a manner that is structurally dependent; some in a manner that is material dependent.
Ilene J. Busch-Vishniac

4. Transduction Based on Changes in the Energy Stored in a Magnetic Field

Abstract
In Chapter 3 we discussed many transduction mechanisms associated with changes in the energy stored in an electric field. Similarly, we may build transducers in which the mechanism of energy conversion relies on changes in the energy stored in a magnetic field. These transducers are inductive devices, and are similar to the capacitive transducers described previously in many fundamental ways. The major difference between the two classes of transducers is that the magnetic field-based devices are often designed for higher power than their electric field counterparts. They are thus used quite frequently in actuation. Examples of inductive transducers include motors and moving coil disk drive heads.
Ilene J. Busch-Vishniac

5. Piezoelectricity and Pyroelectricity

Abstract
In the previous chapters on transduction we have concentrated on those mechanisms which depend on changes in the energy stored in magnetic and electric fields. Virtually all of the constitutive relations linking mechanical and electrical or magnetic variables have been nonlinear (generally quadratic). In addition to these mechanisms there are linear transduction processes, some of which are capacitive and some of which are inductive. Of these processes, the most common and well studied is piezoelectricity, a phenomenon exhibited by some materials in which application of a strain causes the establishment of an electric field and vice versa. In this chapter we focus on piezoelectricity and piezoelectric transducers. The related phenomenon of pyroelectricity is also presented.
Ilene J. Busch-Vishniac

6. Linear Inductive Transduction Mechanisms

Abstract
Given that magnetism was discovered earlier than electricity, it should come as no surprise that the first magnetic (inductive) transducers predate the earliest electric (capacitive) transducers. Linear magnetomechanical coupling is among the most common transduction mechanisms, particularly for actuators, because magnetic devices have energy advantages on large scales.
Ilene J. Busch-Vishniac

7. Transduction Based on Changes in the Energy Dissipated

Abstract
In the preceding chapters of this book we have discussed transduction mechanisms associated with energy storage, capacitive or inductive, and energy transformation (linear magnetic transduction). In all of these cases the transduction mechanism is fundamentally reciprocal in that it can be used either to produce an electrical signal in response to a mechanical input, or to produce a mechanical signal in response to an electrical input. In this chapter we discuss the broad class of transduction which is based on changes in the resistance of the device. Given that resistance causes the irreversible transformation of energy from a form that could be used to perform work into that which cannot perform work, these transducers are not reciprocal. In other words, the process has only one way it can work: typically to produce an electrical signal in response to a mechanical input.
Ilene J. Busch-Vishniac

8. Optomechanical Sensors

Abstract
In the last decade, one of the most rapidly growing sensor areas has been that of optical sensors. Partly, this trend has been prompted by the rapid decline in optical sensor prices, partly it is the result of a growing need for noncontact sensors with high precision, and partly it stems from the advent of new types of optical devices which are easily used. Optomechanical sensors are devices in which some aspect of light propagation is changed (modulated) by a mechanical variable. As will be demonstrated in this chapter, the precise nature of the modulation can take many different forms. This chapter discusses optomechanical sensors in general and concentrates on fiber optic devices in particular. Please keep in mind that the intent of this chapter is an introduction. It is not possible to do justice to optomechanical sensors in one short chapter, and the interested reader is referred to the many books on the topic. (For instance, see[1]—[3].)
Ilene J. Busch-Vishniac

Analysis of Transducers

Frontmatter

9. 2-port Theory

Abstract
In the previous parts of this book we have developed tools which are useful in the modeling and analysis of transducers, and we have discussed various mechanisms through which electrical signals can be generated from mechanical signals and vice versa. In this section of the book we abandon our detailed concentration on transduction mechanisms, in favor of a discussion of general transducer characteristics. We begin this discussion with a presentation of the classical view of transducers as 2-port elements. Using 2-port models, we will develop reciprocity relations and discuss arrays of transducers which are connected. Following this development, the next chapter will discuss transducer measurement specifications, concentrating on the precise definitions (when they exist) for the various measures of performance.
Ilene J. Busch-Vishniac

10. Response Characteristics

Abstract
Because transducers may take advantage of many different transduction mechanisms, we might think that it would be difficult to compare and contrast transducers in terms of performance. However, this problem is avoided by use of performance measures which can be applied generally to transducers (and, in fact, to many other sorts of devices). In this chapter we discuss the measures by which the operation of a transducer is quantified. In the first section, we define the characteristics. In the second section, we talk about calibration of transducers and errors. In the third section, we discuss time and frequency scaling.
Ilene J. Busch-Vishniac

11. Practical Considerations

Abstract
The previous chapters in this book considered electromechanical transducers in detail: the fundamental energy conversion mechanisms, performance characteristics, and models which permit performance prediction. While this myopic view can be justified from the perspective of the design of electromechanical sensors and actuators, it does not lay the foundation for the practical use of such devices. This chapter is intended to be an introduction to the practical considerations of electromechanical transducers, particularly as they are used as components in larger systems.
Ilene J. Busch-Vishniac

Backmatter

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