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Functional Safety: a technology challenge

03 September 2019

Today components and systems frequently become available which are too technologically advanced for current standard requirements and cannot support the assessment of device functional safety appropriately. Suitable approaches are therefore required to protect systems against unauthorised access and safety-relevant manipulation of the safety functions embedded within hardware and software, argues Stewart Robinson MIET MInstMC.

The main requirement for complex semiconductors used in functionally safe embedded systems is a high degree of miniaturisation with the goal of reducing area and cost. Furthermore, modern design requires compatibility, reusability and embedded safety features. The challenges in this domain are short innovation cycles, a high degree of design complexity and increasing integration density.

This has a massive impact on the assessment of device functional safety, especially as new fault models caused by new technologies must be considered. This is particularly the case for Systems-on-Chip (SoC), where dependent faults have to be evaluated, and already known failure modes - such as transient failures - take on increased relevance in the context of integration of smaller structures.

In addition, adequate verification approaches, which show the effectiveness of safety measures, must be developed. Due to increasing system complexity, a high-quality development and lifecycle process is required to ensure a low level of systematic faults. 

The assessment of design and manufacturing processes is another factor in avoiding the consequences of systematic faults. Those using semiconductor components therefore need informative and complete documentation, in order to realise a safe and straightforward system design. This means that great care must be taken when generating the user documentation with respect to completeness of system integration. Consequently, the generic normative requirements should be interpreted and extended, based on the current state-of-the-art and the specific technology being considered.

Management
Ultimately it is organisations and people that have the responsibility of realising functionally safe products and systems. Implementation of the many different requirements of functional safety thus requires a management framework, which regulates the processes and organisation of the activities to be performed. 

Functional safety management is a key element of relevant functional safety standards. This includes the definition of the roles and tasks of the individuals involved, proof of their competence, and the qualification measures necessary to ensure up-to-date knowledge. 

Further elements that must be defined within the scope of the safety life cycle include both the type and scope of the required documentation and quality assurance. This spans the preparation of documented procedures, work instructions and checklists, as well as official signature authorisations. Recording of field experience must also be regulated, as must modification and configuration management. 

Functional safety management should have numerous interfaces with the higher-level quality management system. 

It has also proved good practice to define the responsibilities of the individual parties clearly and early on in the quotation phase. This is because functional safety is not solely the responsibility of the component or system supplier alone.

Process focus
Growing digitalisation and automation across all areas of life and industry increases the significance of functional safety and industrial IT security and offers economic opportunities. Safe product design, early prevention of conformity-related problems, fewer product recalls, and shorter time to market are just some examples. Manufacturers and owners can therefore exploit these opportunities by establishing a systematic process focus. This should include consideration of the entire system life cycle, at an early stage - ideally in the development phase.

A holistic approach to functional safety is therefore required, which requires expertise in various application fields across all project phases, from design and development to manufacturing and installation, testing, certification, placing into service, and decommissioning.  While there are software packages that help to guide users through the process, the growing complexities caused by ever greater technology innovations and integration means ensuring functional safety compliance is becoming a more complex and resource hungry task.

Stewart Robinson MIET MInstMC is principal engineer and functional safety expert at TÜV SÜD.


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