This book describes how to design the real-time software for embedded systems. This chapter provides an overview of real-time embedded systems and applications and then describes the major characteristics of real-time embedded systems, both centralized and distributed. This chapter also provides an overview of the emerging field of cyber-physical systems, for which real-time software is a critical component. This chapter then introduces COMET/RTE, the real-time software design method for embedded systems described and applied in this book, which uses the Unified Modeling Language (UML), Systems Modeling Language (SysML), and MARTE (Modeling and Analysis of Real-Time Embedded Systems) visual modeling languages and notations.

THE CHALLENGE

In the twenty-first century, a growing number of commercial, industrial, military, medical, and consumer products are real-time embedded software intensive systems, which are either software controlled or have a crucial software component to them. These systems range from microwave ovens to Blu-ray™ video recorders, from driverless trains to driverless automobiles to aircraft that “fly by wire,” from submarines that explore the depths of the oceans to spacecraft that explore the far reaches of space, from process control systems to factory monitoring and control systems, from robot controllers to elevator controllers, from city traffic control to air traffic control, from “smart” sensors to “smart” phones, from “smart” networks to “smart” grids, an ever-growing volume of mobile and pervasive systems – the list is continually growing. These systems are concurrent, real-time, and embedded. Many of them are also distributed. Real-time software is a critical component of these systems.

Real-Time Embedded Systems and Applications

A real-time embedded system is a real-time computer system (hardware and software) that is part of a larger system (called a real-time system or cyber-physical system) that typically has mechanical and/or electrical parts, such as an airplane or automobile. A real-time embedded system interfaces to the external environment through sensors and actuators, as depicted in Figure 1.1. An example of a real-time embedded system is a robot controller that is a component of a robot system consisting of one or more mechanical arms, servomechanisms controlling axis motion, multiple sensors to provide inputs to the system from external devices, and multiple actuators to control external devices.

Real-time systems are computer systems with timing constraints. The term real-time system usually refers to the whole system, including the real-time application, real-time operating system, and the real-time I/O subsystem, …