System-theoretic process analysis for safety analysis of cooperative material handling machinery – Concept and initial experiences

Abstract

In material handling and logistics, there's a trend towards increasingly adaptable and flexible approaches on all system levels: from the supply chain and logistic network level down to the factory and warehouse floors. Recent examples of increasingly flexible material handling technologies on the floor level are autonomously navigating automated guided vehicles (AGVs) and plug-and-work material handling systems, the first allowing adaptable material flow systems with minimal fixed infrastructure, the latter allowing the user to easily re-configure steady conveyor systems on demand. In the field of safety engineering, there has recently been research towards safety assurance of open adaptive systems (OAS) with frameworks such as runtime certification as potential enabler for these novel systems. In this work, we seek to combine recent concepts from the safety engineering community with traditional and advanced technologies from the area of material handling machinery to enable the next step in operational flexibility in this application area. We suggest potential application use cases which would be enabled by the use of dynamic safety contracts: safely cooperating material handling machinery. Compared to machinery with traditional, fixed interfaces, the machine-to-machine cooperation will increase the complexity of the required safety-related control systems and software, which will in turn require new approaches for the risk assessment and safety engineering of these types of systems. We suggest the use of STPA for safety-driven design of cooperative material handling machinery. We discuss one novel application concept, AGV-Storage crane cooperative handover, in detail and present initial results of STPA analysis for the application.