4.1 Introduction

Chapter 3 discussed general dynamic system simulation techniques, many of which are applicable to both non-real-time simulations and real-time simulations. This chapter focuses on issues that are specific to real-time, hardware-in-the-loop (HIL) simulation. An HIL simulation incorporates some of the actual embedded system hardware into a larger system simulation. It supports a variety of application areas such as system-level testing during early product development, embedded software verification, and operator training. The HIL simulation approach is particularly valuable because it provides a controlled environment in which significant parts of the actual system hardware and software operate under realistic conditions.

One incentive for HIL simulation system testing is that it may be quite expensive to perform testing of the actual system. For example, an aircraft flight control system requires expensive and potentially dangerous flight operations to perform full system testing. As an alternative to flight testing, one could build a realistic simulation of the behavior of the aircraft and its environment and integrate the actual flight control system hardware and software into this simulation. This would allow the system tests performed to be in a laboratory environment on the ground typically a much quicker and cheaper way to produce the desired results.

HIL simulation testing can be performed before a full prototype of the system has been built. This allows system hardware and software development to proceed in parallel while enabling software integration in the HIL simulation. Without the availability of the HIL simulation, the integration effort cannot begin...