A Contract-Based Installation Methodology for Safety-Related Automotive Systems 2013-01-0192

Today's automobiles contain a lot of electrical and electronic (E/E) systems with safety-related functionality. In a design-process compliant to the industrial standard ISO 26262 unknown dependencies between events and elements are risks that potentially violate safety requirements or safety goals. Therefore, the identification and analysis of dependent failures is important. Physical environment influences like temperature are one class of factors which can lead to coupling effects and cause dependent failures.

In this paper we show a novel contract-based approach to deal with geometric installations of elements in an automobile. It avoids violations of safety requirements by identification and prevention of dependent failures resulting from coupling effects between elements. The influences of an element on environment factors and the failure effects of such environment factors on elements are explicitly specified as physical conditions. A spatial distribution of possible areas of interference with the environment factors is derived by analyzing an application of the elements' physical conditions to a geometric installation model. Dependent failures which lead potentially to a violation of safety requirements are identified. This is done by matching the actual physical space claimed by elements with all possible areas of interference with the environment factors. In a further activity the potential safety requirement violations are evaluated by analyzing the causes of the dependent failures. Unacceptable violations of safety requirements are resolved by introducing means of compensation.

This approach is evaluated in a scenario with an automotive electrical power steering (EPS) system.