Safety - Critical Systems Design

Introduction Embedded systems are like normal desktop systems in that they have functional requirements, that is, functions that the system is expected to perform, such as moving the robot arms. One of the ways embedded systems differ from desktop systems is that they also have significant quality of service (QoS) requirements as well. In real-time embedded systems, for example, timeliness and predictability are significant QoS requirements. In fact, in “hard” real-time systems, missing a single deadline is considered to be a systems failure of some kind. Other types of QoS requirement include the reliability and safety of the system in potentially harsh environments. Systems ranging from microwave ovens to automotive “drive-by-wire” electronics to avionics systems to nuclear power plants all have very significant safety and reliability requirements. Failures in such systems can lead to death of from one to potentially several million people.