Design for robustness of complex automotive electronic systems

The continual expansion in requirements for vehicle features results in a rapidly increasing complexity of automotive electronic systems. Automotive electronics exhibit properties of systems of systems including that of emergent behaviour and validation complexity. This brings with it major financial risks for automotive manufacturers due to field failures, launch delays, recalls and loss of customers. The contention of this thesis is that robustness, i.e. the ability of a system to avoid service failures resulting from external faults, is a key design criterion for automotive electronics as a mass-market system of systems. Hence effective tools and techniques for the robust design of complex automotive electronic systems are required, but initial research suggests that limited published work on robustness, as opposed to safety, has been done in this field. This thesis addresses the research question of whether a viable framework of methods to substantially improve robustness in the design of complex automotive electronics systems can be developed. A literature review is conducted of potential methods for robust design from automotive and other domains, which identifies opportunities for contributions to knowledge in the following areas. The development of domain knowledge of the prevalence and causes of robustness related failures in the area of automotive electronics. The development of a “design for robustness” framework for complex automotive electronic systems, which should leverage best practices identified during the literature review. Particular items identified to be addressed are the adaptation of safety cases to robustness cases and the development of an approach to robustness modelling based on understanding of what are important factors to model pertaining to robustness of automotive electronics. A review is conducted of 43 well-documented field issues in the area of automotive electronic systems. It is found that these were predominantly (60%) robustness related issues, supporting the need for improved techniques. The results confirm robustness issues as complex, interactive and emergent in nature which are generally not present during normal operation but under transient conditions, in particular during initialisation and shut-down, during failures in other systems, as a result of tolerance spread and of unforeseen (ab)use cases. A design for robustness framework approach is developed incorporating the two proposed new methods of “robustness cases” and “robustness modelling”. A “robustness case” is a structured argument for the robustness of a system analogous to a safety case. A “robustness model” is a model based approach to early robustness verification of complex systems. These new methods are developed through their application to case study of infotainment and evaluated through subsequent application to a hybrid propulsion system. The design methods and artefacts are described in detail, including as generic approaches, and the test results from their use are shown and discussed. Finally the viability of the methods developed and their contribution to knowledge is discussed. The knowledge gained through the study of field issues of root causes of robustness issues in automotive electronics ensured the methods were well targeted. From the application of the methods to infotainment and hybrid propulsion systems a number of positive indicators of the effectiveness of the technique are observed. An analysis is conducted of whether the likely benefits would justify the incremental costs of implementing the methods. This shows that the methods became viable at the point where they can detect a single issue which would otherwise have been undetected until final testing. Deployment approaches, known limitations and areas for further work are also described.