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Über dieses Buch

Bondgraphs are a powerful tool in the simulation of mechanical, hydraulic, electric and thermal systems. They are used to represent engineering systems in written form by means of letter elements and their interconnections, called bonds, instead of in the form of numerous equations. They may be used to increase the efficiency of new product design. This book introduces the reader to bondgraphs and their use on PCs. A broad variety of applications of this method in the simulation of the above systems is presented. Twenty fully worked examples complement the presentation.

Inhaltsverzeichnis

Frontmatter

1. Simulation and Graphical System Models

Abstract
In this book we are concerned with the efficient simulation of engineering systems, essentially machines, devices or interconnected apparatus. The purpose is to get a quantitative understanding of their operation, improve their performance by variation of parameters and to find possible critical points before the actual system is built at a high expense. Our great tool is the modern microcomputer on which engineers wish to work whenever they have a new idea.
Jean Ulrich Thoma

2. Bondgraphs as Networks for Power and Signal Exchange

Abstract
For simulations of any complexity it is good to use a systematic way of building the model in small steps. A first step is to write a word Bondgraph; it contains words, not standard symbols for the main items (a subgroup) and normal bonds for power and signal exchange.
Jean Ulrich Thoma

3. Simulation and Design of Mechanical Engineering Systems

Abstract
Good modelling and simulation has many faces and Fig. 3.1 gives an overview. We have started from the left and met Bondgraphs in the first 2 chapters. Now we are at a point where the way splits into the art of writing Bondgraphs (upper path) and into computation from Bondgraphs (lower path). Later they will approach each other again and become the Bondgraph way of life.
Jean Ulrich Thoma

4. Simulation of Fluid Power Systems and Hydrostatic Drives

Abstract
Since the time of Pascal (about 1650) fluid under pressure has been used for many engineering purposes, especially for hydraulic presses. Such presses are able to exercise large forces at moderate speeds, today mainly for the deformation of sheet metal in automobile bodies, earlier (1800) for compacting textiles. Since 1950 the technology is called fluid power engineering and includes the transmission and control of rotary motion in hydrostatic transmissions. Fluid power itself is defined as the technique of transmission of energy and information by fluid under pressure. Here Bondgraphs help to clarify the interaction of the many variables. For efficient design and control, the technique requires a special way of thinking, a mixture of standard mechanical engineering, hydraulics and control engineering.
Jean Ulrich Thoma

5. Electric Circuits, Drives and Components

Abstract
We shall treat here circuits and components and further in sec. 5.2 electric motors from an elementary standpoint, sufficient for most applications. In sec. 5.3 we shall examine the interaction of electric and magnetic fields with mechanical members in more detail. In this section we shall neglect parasitic effects of resistors, capacitors and inductors and treat them as R-, C- and I-elements. Thus, we neglect effects like inductivity of a resistance, leakage of a capacitor and winding capacity of an inductor. Such effects can always be added from the known electronic equivalent circuits once the systematic writing of Bondgraphs is familiar.
Jean Ulrich Thoma

6. Computational Overview, Practical Procedures and Problems

Abstract
Most worked examples in this book are done from TUTSIM, because it is powerful and fast. However, Bondgraphing is universal and not limited to one or the other program. In essence, a fully augmented Bondgraph (with all power directions and causalities) is equivalent to a set of equations that can be programed directly in language like BASIC, PASCAL, FORTRAN or C.
Jean Ulrich Thoma

7. Applications to Thermodynamics, Chemistry and Biology

Abstract
Entropy often appears as a mysterious concept yet it is really quite simple: Entropy flow is the thermal flow variable in the sense of Bondgraphs (Table 2.1) and entropy itself is accumulated entropy flow (Thoma 1970B). Hence the fundamental point to know is that thermal power in conduction, usually called heat flux, is absolute temperature times entropy flow. This fundamental equation appears in Fig. 7.1. Some important observations:
  • The fundamental equation is strictly valid for conduction of thermal power (heat flux) without mass flow.
  • With mass or convection there is a correction to the fundamental equation, which remains approximately valid. It is expressed by the convection factor of sec. 7.2.
  • We have to take the absolute temperature (expressed in Kelvins) in the fundamental equation.
  • Entropy is often associated with disorder. This is true but not necessary for most practical engineering including Bondgraphs.
Jean Ulrich Thoma

8. Selected Questions

Abstract
We treat multibonds and robotic mechanisms together here because robots contain many of them; they are sometimes called vector bonds. They are a group of simple bonds that are somehow related. An example would be the movement of a robot hand in three dimensional space with speeds in the x, y and z directions. We can also think about the transformation into other coordinates, say polar coordinates, and this establishes the connection to mechanisms.
Jean Ulrich Thoma

9. Further Worked Examples

Abstract
Figures 9.1a to 9.1d show a single acting one cylinder water pump; the Bondgraph includes the dynamics of the intake valve for investigation of erosion of its seat in a form similar to Fig. 4.23. The delivery valve is represented (without dynamics) as nonlinear resistor R35 (R351 and FNC35). Realistic parameters are used.
Jean Ulrich Thoma

Backmatter

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