# Safety-Oriented System Hardware Architecture Exploration in Compliance with ISO 26262
###### Abstract  
Safety-critical intelligent automotive systems require stringent dependability while the systems are in operation. Therefore, safety and reliability issues must be addressed in the development of such safety-critical systems. Nevertheless, the incorporation of safety/reliability requirements into the system will raise the design complexity considerably. Furthermore, the international safety standards only provide guidelines and lack concrete design methodology and flow. Therefore, developing an effective safety process to assist system engineers in tackling the complexity of system design and verification, while also satisfying the requirements of international safety standards, has become an important and valuable research topic. In this study, we propose a safety-oriented system hardware architecture exploration framework, which incorporates fault tree-based vulnerability analysis with safety-oriented system hardware architecture exploration to rapidly discover an efficient solution that complies with the ISO-2626 safety requirements and hardware overhead constraint. A failure mode, effect, and diagnostic analysis (FMEDA) report is generated after performing the exploration framework. The proposed framework can facilitate the system engineers in designing, assessing, and enhancing the safety/robustness of a system in a cost-effective manner.  
functional safety; ISO-26262; system hardware architecture; safety mechanism +
Footnote †: journal: Applied Sciences
design, and pre-production tests. All these issues put emphasis on functional safety consideration. At the product development phase, the V-model [3] is adopted as the primary design, verification, and validation flow. This phase is further divided into three different levels: System level, hardware level, and software level. For these levels, functional safety requirements are verified and validated through failure mode and effect analysis (FMEA), fault tree analysis (FTA), and safety-related metrics.  
The ISO-26262 standard adopts the ASILs (Automotive Safety Integrity Levels) to measure whether the developed systems have achieved the demanded safety level or not. There are four ASILs defined in the standard--from A to D, where ASIL A defines the lowest and ASIL D defines the highest safety level. More strict requirements need to be fulfilled if a higher ASIL is specified.  
In this study, based on the ISO-26262 functional safety standard, we propose a safety-oriented hardware architecture exploration framework for safety-critical automotive systems. The proposed framework integrates the hardware architecture exploration algorithms with the FTA-based weak-point analysis to quickly find an efficient system solution that complies with the ISO-26262 ASIL requirement as well as the hardware overhead constraint. We employ the autonomous emergency braking (AEB) system to demonstrate the effectiveness of the proposed design framework. The AEB system integrates the brake-by-wire system proposed in [4] with automotive radar sensors and a speed sensor to implement a front-vehicle collision avoidance system.  
The paper is organized as follows. Section 2 discusses the related works and Section 3 introduces the ISO-26262 hardware architecture metrics. The safety-oriented system hardware exploration framework a including fault tree analysis with vulnerability identification, safety mechanism deployment, and hardware overhead constraint conformation is proposed in Section 4. A case study demonstration is illustrated in Section 5. Conclusions and future works appear in Section 6.