System safety concept defined

The ANSI/ISA-84.00.01-2004 (lEC 61511) standard (Ref. 1) defines a safety instrumented system (SIS) as an "instrumented system used to implement one or more safety instrumented functions. A SIS is composed of any combination of sensor(s), logic solver(s), and final element(s)." lEC 61508 (Ref. 2) does not use the term SIS but instead uses the term "safety-related system." That term defines the same concept but uses language that can be broadly applied to many industries. 

We define intrinsic safety as safety designed and built into a system. Yes, this is an overlap with system safety. The two concepts are converging. Intrinsic safety is certainly a noble goal and one that should be continually pursued. 

The idea, concept, or process of system safety has been defined in many ways, by a wide variety of scientific and technical professionals. However, since its inception,... 

Preliminary hazard analysis is one of the early steps in a system safety project. This step also creates assessments of risks associated with each hazard. This step defines possible corrections for the risks. The product of this step is a tabular inventory of hazards for the system under consideration. The PHA fits best during early system stages, such as concept definition, design, and development. 

ISO 26262 is based on the system architecture. The vehicle itself consists of different systems their electric and electronic architecture is modeled in the according development process. The design and development of the EEA of a vehicle is based on the work products from preceding development phases like the design of a broadly defined system architecture concept. In the future it has to consider the results of analysis, considerations and classification of safety aspects, demanded by ISO 26262. The electric and electronic (EE) part of the system architecture is iteratively refined and detailed during the development process. The impact of ISO 26262 to the modeling of the EEA and the contribution of the EEA modeling towards the fulfillment of the overall safety concept is discussed in this paper. 

The central concept in system safety is the definition of a hazard. It is important to spend some time nnderstanding what appears intnitive to all of ns. For snccess, a design or production engineer has to be able to identify and correct or control these hazards. Once a hazard is defined, the system safety process can start to unfold and make sense. The hazard reduction precedence is the philosophical basis for most safety control systans across industry. And finally, engineering standards are part of the structure that ensures that all technological systans have some level of safety. System safety optimizes the safety process. 

The term SMS is a relatively new term. As defined earlier, the concept of system safety is to merge the engineering with the management of the systan development and operation into the concept of system safety. Over the last 20 years or so, the term SMS has been coined. Chapter 4 is dedicated to discussing SMSs. Briefly an SMS is a... 

As a next step, the Safety Concept is derived. It is defined as the specification of the safety requirements, their allocation to system elements and their interaction necessary to achieve safety goals [4]. The construction of the safety concept is a generic step which is compliant to all considered safety standards. However, the necessary content of the safety concept may differ from domain to domain. 

Existing well-defined process for the derivation of safety requirements have been followed and applied within the new fiamework. The author analysed the concept of the safety requirement fiom the system point of view and proposed a minor clarification of the definition and the topology of a safety requirement as a system safety objecU in relation to defence/protection measures. 

Our paper is organized as follows. The goal structuring notation is introduced in Sect. 2.1. In Sect. 2.2, we give a brief overview of ISO 26262. Our method is presented in Sect. 3. This section also describes our UML profile, which is used to express the functional safety concept. Based on this profile, we define the validation conditions. The tool support is outlined in Sect. 4. We introduce the illustrative example of an electronic steering column lock system as case study in Sect. 5. Section 6 presents related work, while Sect. 7 concludes the paper and gives directions for future work. 

Which general targets could be formulated for a safety concept. ISO 26262 clearly defined that the functional and technical safety concept should be defined derived from the ITEM Definition, a system on vehicle level and the resulting safety goals from the Hazard and Risk Analysis. 

---