Top-Down approach for safety engineering in autonomous and semi-autonomous machinery systems

Needs to improve productivity, cost efficiency and safety are driving the development in industrial sectors towards highly automated or autonomous work-machine systems. The shift towards automated mobile work-machine systems takes machine safety considerations to a higher, system safety, level. The full utilisation of work machine automation and improved productivity require also a change in safety strategies and safety concepts. Traditional isolated operating areas and fixed machinery safety solutions based on single risk reduction need to be changed into adaptive and proactive system-safety solutions utilising protection layers, situational awareness information and dynamic risk assessment. A Top-Down approach for safety risk management is needed to integrate risk control options systematically from all system levels and to consider all available risk reduction measures.
To answer this need a new three-level approach for the assessment of safety risks in automated work-machine systems has been developed following the general systems engineering principles and processes. New virtual engineering tools and machinery specific system simulators have also been developed and applied to support this risk assessment approach and the design and evaluation safety solutions.
The results from case studies have shown that safety of complex mobile machine application cannot be solved by machine level safety solutions. The top-down safety engineering approach supports the sharing of system safety information and improves the common understanding of the system operations, human-system integration and interactions between sub-systems. System thinking and top-down approach support the allocation of the risk control options and safety measures to right system levels considering technical solutions and operational, managerial and organizational actions. The recently published machinery safety standard for autonomous work-machine systems, ISO 17757:2017, also emphasises the importance of systematic and hierarchical risk assessment process, the integration of the autonomous system in the overall site planning and the utilisation of different protection layers in safety solutions.