ISO 26262: segurança funcional no desenvolvimento de sistemas automotivos

Abstract

The technological advances of recent years have resulted in embedded automotive systems increasingly complex. The use of more advanced technologies, combined with the development and integration of new functionalities, provides several benefits for customers, society and the environment. On the other hand, this increasing complexity also leads to an increase in the criticality of the applications and an increase in the probability of hardware and software failures. Several cases of accidents are known that have resulted in material damage and fatalities that have been attributed to problems in automotive systems or that could have been minimized or even avoided through the use of improved safety vehicle systems. Considering all these facts, the functional safety of automotive embedded systems has become a major challenge for the current automotive development. In this context, the ISO 26262 establishes several guidelines to be used in the design of electrical and/or electronic safety-related systems that are installed in road vehicles. The standard proposes an automotive safety lifecycle from management to decommissioning and also provides several recommendations to be used along the concept phase and product development at system, hardware and software level. During the concept phase, it is realized one of the most important processes of the safety lifecycle, the hazard analysis and risk assessment, which identifies the potential risks and estimate the probability of exposure, the controllability and the severity of the hazardous events caused by malfunctioning behavior of the items under development, and the junction of these parameters determines the automotive safety integrity level, called ASIL. With this analysis, the safety goals are then determined, which are detailed in functional safety requirements and successively refined during subsequent phases up to hardware and software technical safety requirements. The product development at the software level is based on the “V” model, with the requirements specification, design and implementation on the left branch and the integration and testing and the verification of requirements on the right branch. The standard suggests several methods to be used for the software unit and integration testing, such as requirements-based test, interface test, fault injection test, resource usage test and back-to-back comparison test. The most appropriate test method for a certain level of product integrity and that represents the degree of rigour that must be applied in the verification, in order to avoid a residual risk in the final product, is determined by the corresponding ASIL. ISO 26262 recommends the use of the fault injection technique as a software test method, and is highly recommended to meet the most critical ASILs C and D. A fault injection test aims to introduce faults into the item using specific means and test if the fault-tolerant mechanisms are efficient enough to keep the system according to the expected safety goals.