Category Archives: 61508

(Paper) Functional Safety Extensions to ASPICE According to ISO 26262


과거에 있던 회사에서 자동차 분야에서 functional safety관련된 인증 체계를 구축하기 위한 연구 자료이다.

요약. 자동차 산업은 현재 안전한 개발에 집중하고 있다. 이런 feature의 구현은 전자 하드웨어뿐만 아니라 소프트웨어에서의 복잡성 및 기능 통합을 증가시킨다. 복잡하고 통합된 환경에서 안전을 유지하기 위해서 ISO26262 기능 안전 표준이 이를 지원할 것이다. 자동차 제조사들은 ISO26262도입을 통해 이득을 얻을 것이다. ISO26262의 요구사항 중의 하나는 표준에 부합하도록 사용되는 개발 프로세스 역량(capability)을 평가하는 것이다. 기능 안전 확장은 Automotive SPICE와 함께 사용될 수 있다.

ISO26262 프로세스와 A-SPICE는 굉장히 유사하다. overlap되는 부분이 많다. ISO26262와 A-SPICE에 대한 harmonized integrated process에 대해서는 이 당시 study했던 때와는 많이 생각이 다르다. 과거보다 훨씬 깊이있고 radical하게 변화했다고 생각한다. 그런 idea를 언제쯤 공유하게 될지는 모르겠으나, 일단 여기서는 그 얘기는 하지 않고 논문 이야기만 한다.

고려대상

  • ISO26262
  • Automotive SPICE
  • +SAFE(CMMI계열이다)
  • ISO/IEC 15504-10 – Safety Extension

Assessment Framework

결국 이것이 인증 체계의 골격이라고 할 수 있을 것이다.  이 논문에서 생각해 낸 것은 3가지이다.

  • Use the Automotive SPICE framework
  • Develop custom framework based on ISO 26262
  • Use framework from other domains

 

1) Use the Automotive SPICE framework

이 방법은 인증 체계를 SPICE체계의 표준에 align시키는 방법이다. 개인적으로 이 방법을 가장 선호한다. 다양한 분석이 가능하고, 궁극적인 목적인 supplier의 weak point 식별 및 OEM으로서 어떻게 supplier를 이끌어 갈 것인지에 대한 계획을 수립할 수 있다. 그렇게 하려면 ISO 26262를 SPICE스타일로 변환시키는 과정이 필요하다. 이것은 일반 OEM회사에서는 접근하기가 쉽지는 않다. 그러한 평가 모델을 만든다는 것이 말처럼 간단한 것은 아닐 것이다. SPICE는 Plug-in play방식같이 새로운 것을 끼워 넣는 것이 유연해서 가능한 방식이라고 생각된다. 적어도 인증 기관에서 운영을 한다면 이 정도의 품위는 있어줘야 하는게 아닐까 생각을 하기도한다.

2) Develop custom framework based on ISO 26262

26262를 분석해서 checklist를 만들어서 rating하는 방식이다. 만들기는 아주 간단하다. 그러나 평가기관의 품위가 없고 굉장히 평가 점수가 의미하는 바는 너무 단순하다. all or nothing이다. 50점과 70점의 점수의 차이가 굉장히 정성적인 느낌이다. 어차피 안된건 마찬가지다. 그런데 어느 부분에 개선이 필요할까? 이런 부분에 대한 답을 주지 못한다. 그냥 못한거다. 또한 A-SMGCS의 프로젝트에서 TTA가 감사원의 세력을 등에 업고 지적질을 하면서 A-SMGCS 프로젝트를 drop을 시킬 때 이런 방법을 썼었다.

Continue reading (Paper) Functional Safety Extensions to ASPICE According to ISO 26262

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Determining boundaries of Sys, HW and SW


Recently, I perceived that documents among sys, hw and sw are overlapped. In some cases, they are not consistent. To solve this problem, I have to suggest a policy. (In most cases, safety engineers cannot perceive such a problem, because their work scope is not wide. It is not personal problem.)

If I were a system safety engineer, what extent should I cover? If I know SW parts, then I would try to specify sw related specification in the system document. Then many contents will be overlapped. If I know HW parts, then I may cover too much contents of HW details in the system document. If I know both parts, then what are benefits regarding HW and SW documents?

It is true that system documents are associated to HW and SW documents.

Similar problem is that when safety engineers conduct safety analysis, what is unit in the system aspect? I think that there should not be overlapped between not only system result and SW result but also system result and HW result. How safety engineers do not intrude other competencies territory(scope)?

As a Solution for this problem, I recommend a picture from ISO 26262-4.

26262-4.PNG

I have an insight from this picture. Based on this structure, I ask several question to myself.

  • What are system scope?
  • What are sub-systems in our system?
  • How safety requirements in the system scope are allocated to sub-systems?
  • Based requirements allocated to sub-systems, how requirements are detailed?
  • How system building blocks in system design are traceable to blocks in FMEA or FTA?
  • What is unit in the system design and how it is associated to SW and HW?

Logical scheme for these work products help safety engineers to do their tasks. and it will be easier to defense against  customer audit or argue our safety concept in the court. This structure will help our works to have consistent.

 

 

View Points in the Architecture


Purpose of the design is to help stakeholders to understand author’s intent. To do this, having several view points are necessary. But what happens if an author tries to contain all knowledge in one view?

As I know, an engineers knows too much and it prohibit him to explain simply. She/He might think that the reason the other persons do not understand her/his documents is humble knowledge that readers have. It may be true, but too much information do not help readers to understand author’s point.

To achieve this, proper abstraction is necessary. Less important parts are recommended to be deleted to help reader’s understanding. Or proper hierarchical structure helps readers to understand.

When we think why this documents are existing, purpose of the document is to let others understand author’s point. By the reason, viewpoints are necessary.

When we consider a design in the system level, he/she wants to communicate to hardware and software team. As you know, One to One communication is better than multi to multi. System designer’s point of view, a viewpoint specific to software is easy to communicate than a viewpoint to all.

And many contents are contained in the design, readers don’t like to read because too much information is contained. They will lost their concentration and miss some contents. This situation will not be what the author want to.

Do not try just to contain all knowledge that you know in the design. Functional safety manager has to help engineers to write documents by guidelines, policies. In the functional safety standards, not only system design but also SW/HW design is required. To have balance between system, SW and HW design, structure and contents detail level needs to be considered. And proper viewpoints are required to guide engineers’ documentation.

As I emphasized in the previous post, scope of safety analysis depends on what engineers contain in the design document. If they omit some view points, safety analysis for the missed contents cannot be analyzed.

 

Related Article(in Kor)