3.1 Introduction

This chapter discusses the issues involved in combining a set of mathematical models to produce a complete simulation of a dynamic system. Using the techniques of Chapter 2, one begins by constructing models of suitable fidelity that describe the components of the system and its interactions with the environment and then assembles a system simulation from these models and from other elements such as numerical integration algorithms.

A s imulation is defined as a set of models executing over time [1]. A simulation begins execution by initializing the values of state variables and any parameters associated with its models. As the run executes over a span of simulated time, the simulation evaluates the model dynamic equations and performs state variable integration. In addition to these tasks, the simulation provides a user interface that allows the operator to specify initial conditions and model parameters and to control its execution. The user interface must also enable the selection of variables for display and storage as the simulation executes.

The techniques and numerical algorithms required for implementing a dynamic system simulation that produce valid, accurate results need to be examined. This chapter will focus primarily on non-real-time simulation. Chapter 4 covers the issues specific to real-time simulation. Before getting into the details of simulation algorithms, I will first discuss the characteristics of a good simulation user interface, some concerns to address in combining a disparate group of models into a unified simulation, and the topic of configuration...