A Method towards the Systematic Architecting of Functionally Safe Automated Driving -- Leveraging Diagnostic Specifications for FSC design

With the advent of ISO 26262 there is an increased emphasis on top-down design in the automotive industry. ISO 26262 lacks detailed requirements for its various constituent phases. The lack of guidance becomes evident for the reuse of legacy components and subsystems, leaving vehicle architects and safety engineers to rely on experience without methodological support for their decisions. This poses challenges in the industry which is undergoing many significant changes due to new features like connectivity, electrification and automation. Here we focus on automated driving where multiple subsystems, both new and legacy, need to coordinate to realize a safety-critical function. This paper introduces a method to support consistent design of an ISO 26262 work product, the Functional Safety Concept (FSC). The method addresses a need within the industry for architectural analysis, rationale management and reuse of legacy subsystems. The method makes use of an existing work product, the diagnostic specifications of a subsystem, to assist in performing a systematic assessment of the influence a human driver, in the design of the subsystem. The output of the method is a report with an abstraction level suitable for a vehicle architect, used as a basis for decisions related to the FSC such as generating a Preliminary Architecture (PA) and building up argumentation for verification of the FSC. The proposed method is tested in a safety-critical braking subsystem at one of the largest heavy vehicle manufacturers in Sweden, Scania C.V. AB. The results demonstrate the benefits of the method including (i) reuse of pre-existing work products, (ii) gathering requirements for automated driving functions while designing the PA and FSC, (iii) the parallelization of work across the organization on the basis of expertise, and (iv) the applicability of the method across all types of subsystems.

ATRIUM -- Architecting Under Uncertainty for ISO 26262 compliance

The ISO 26262 is currently the dominant standard for assuring functional safety of electrical and electronic systems in the automotive industry. The Functional Safety Concept (FSC) subphase in the standard requires the Preliminary Architectural Assumptions (PAA) for allocation of functional safety requirements (FSRs). This paper justifies the need for, and defines a process ATRIUM, for consistent design of the PAA. ATRIUM is subsequently applied in an industrial case study for a function enabling highly automated driving at one of the largest heavy vehicle manufacturers in Europe, Scania CV AB. The findings from this study, which contributed to ATRIUM's institutionalization at Scania, are presented. The benefits of the proposed process include (i) a fast and flexible way to refine the PAA, and a framework to (ii) incorporate information from legacy systems into safety design and (iii) rigorously track and document the assumptions and rationale behind architectural decisions under uncertain information. The contributions of this paper are the (i) analysis of the problem (ii) the process ATRIUM and (iii) findings and the discussion from the case study at Scania. Keywords: ISO 26262, functional safety, automation, HCV, HGV, architectures, highly automated driving, ATRIUM, decision making, architecting, uncertainty management