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EAST-ADL and automotive system modelling (Part 2)

Posted: 06 Jun 2013     Print Version  Bookmark and Share

Keywords:EAST-ADL  ABS  AUTOSAR  verification  validation 

Besides the assertion in the ABS function, we can check many other properties of the entire brake system, including the ABS function, driver's brake command, wheel and vehicle body dynamics.

Dependability modelling
As an overall system property, safety is concerned with faults and failure cases and how they influence to the system. EAST-ADL aims to express precisely the safety requirements and related information along with the nominal system model in all the phases covered by the ISO 26262 reference safety lifecycle. This means that for any safety requirement EAST-ADL provides support for specifying its allocation, precise meaning, and integrity level based on the ASIL (Automotive Safety Integrity Level) classification scheme of ISO/DIS 26262.

EAST-ADL covers the specifications of safety requirements as well as their system dependability implications, including:
1. Safety goals of the overall system characterized by the vehicle level perspective
2. Functional safety concepts derived from the safety goals and their allocations to high level system functions
3. Technical safety concepts derived from the functional safety requirements and the allocations to hardware and software specific design solutions
4. Hardware and software safety requirements allocated to the hardware and software architectures at the implementation level.

Figure 6: SPIN Verification Result. (Click on image to enlarge.)

Figure 7: An overview of EAST-ADL support for safety requirements and their allocations to system artifacts. (Click on image to enlarge.)

Along with the specification of safety requirements, EAST-ADL allows the formalisation of system functions and operational situations for safety analysis at various levels of abstraction.

Figure 7 shows part of the modelling support for PHA (Preliminary Hazard Analysis), which is focused on hazard identification and risk assessment and thereby the definition of safety goals. According to ISO/DIS 26262, an item refers to the function(s), component(s) or system(s) that is of particular concern with regard to functional safety. With EAST-ADL, a PHA is performed at the vehicle level by examining the potential malfunctions of system features, which represent the items of a target system. To shape the top-level safety requirements, each hazard definition captures potentially dangerous item behaviours and the associated hazardous events triggered by such item behaviours occurring in specific operational situations.

Figure 8: Deriving hazardous events and safety goals of braking function through Preliminary Safety Analysis (PHA). (Click on image to enlarge.)

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