Page 50 - Mechatronic Systems Modelling and Simulation with HDLs

3

Modelling and Simulation

of Mixed Systems

3.1 Introduction

The majority of technical systems are mixed; i.e. they incorporate components from
various fields, such as electronics, mechanics, software and other domains. This
raises significant design problems because hitherto design methodologies and the
associated design tools have usually been developed for a single field only. This
means that the overall function of the system cannot be investigated until the pro-
totype construction phase. However, by the time this stage is reached, changes to
the design have already become very expensive and time-consuming. The consid-
eration of virtual prototypes, which allow virtual experiments to be performed on a
computer by simulation, offers an elegant solution to the problem described above.
This chapter introduces the consideration of the simulation of mixed systems by
describing common ground and differences between electronics and mechanics in
Section 3.2. This lays the foundation for the modelling and simulation of electro-
mechanical systems.
This chapter also describes various approaches to the modelling of mechatronic
and micromechatronic systems. One possibility is to transfer mechanical models
into the form of electronic models (and vice-versa). This permits the consideration
of the mechanics in a electronics simulator (and vice-versa), see Section 3.3. Thus
half of the modelling problem can take place using standard methods. On the other
hand, this raises the question of how to formulate electronics within the modelling
world of mechanics (and vice versa). For the transformation of mechanics into
a circuit simulator the use of hardware description languages is the method of
choice. This approach — the main theme of this work — will be discussed in detail
in Chapters 4–6. Before hardware description languages became widely accepted
in recent years, equivalent circuits were often developed to describe the behaviour
of mechanical components. Relatively few attempts were made to consider elec-
tronics along with mechanics in a mechanical simulator. Although some mechanical
simulators permit the inclusion of simple components such as capacitors, resistors

Mechatronic Systems Georg Pelz
 2003 John Wiley & Sons, Ltd ISBN: 0-470-84979-7