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ROBOTICS FEATURE THE RISE OF THE MACHINE, AND THE REDUCTION OF RISK


acknowledged that this guidance needed to be enhanced. Consequently, a Technical Specification (ISO/TS 15066 Robots and robotic devices — Safety requirements for industrial robots - Collaborative operation) was published in 2016. ISO/TS 15066 covers: • The design of the collaborative work space


• The design of the collaborative


operation • Methods of collaborative working • Changing between: Collaborative/


non-collaborative; Different methods of collaboration • Operator controls for different


Stewart Robinson, principal engineer and functional safety expert at TÜV SÜD Product Service, describes the developments in safety standards covering the human/cobot workspace


T


he advent of a human-robot collaborative workspace has


increased the need to address the adequate protection of people from the safety risks associated with industrial robot systems. In order to ensure that humans are not exposed to unacceptable risks when working collaboratively, EN ISO 10218:2011 has been developed - an international and European standard which covers the safety requirements for industrial robots. The standard replaced the 2006 version, and is in two parts: • EN ISO 10218-1:2011 Robots and


robotic devices — Safety requirements for industrial robots — Part 1: Robots. • EN ISO 10218-2:2011 Robots and


robotic devices — Safety requirements for industrial robots — Part 2: Robot systems and integration. These describe four separate measures that can be used to provide risk reduction, and it is required that at least one of these is fulfilled, in addition to having visual indication that the robot is in collaborative operation: 1. Safety-rated monitored stop This measure requires that when it is detected that a human has entered the collaborative workspace, the robot should be stopped. The stop condition should then be maintained until the human leaves the workspace. 2. Hand guiding In this mode the human can guide the robot at the end effector by hand. Additional requirements for safety include safe-limited speed monitoring, a


local emergency stop, and the use of an enabling device - a three position device that has to be held in the centre position. 3. Speed and separation monitoring In this mode, the robot must maintain a specified separation distance from the human and operate at a predetermined speed. This measure requires careful risk assessment and needs to take account of safety distances, which should include the consideration of approach speeds of parts of the human body as described in EN ISO 13855. 4. Power and force limiting by


inherent design or control In this mode the power and force of the robot actuators need to be monitored by safety related control systems to ensure that they are within limits established by a risk assessment. In all four of the measures described above, the safety related control system that provides this functionality needs to meet either: • The Safety Performance Level d (PLd),


with Category 3 architecture (the identified level to which the safety related parts of a control system resist faults and their subsequent behaviour if a fault occurs) as outlined within the standard EN ISO 13849, or • Safety Integrity Level 2 (SIL 2) with


hardware fault tolerance (HFT) 1, as set out in EN [IEC] 62061. While EN ISO 10218 contains some


guidance on the use of collaborative robots (cobots), with the rapid pace of technological development, it was widely





Besides the robot itself, the cobot might have an ‘end effector’, some of which may create hazards. So it is vital that a complete risk assessment is undertaken before deployment


applications There are also working groups of the standards organisations reviewing various aspects of human-machine interactions, which will also inform the development of future standards. But for now, EN ISO 10218 Parts 1 and 2, and the ISO/TS 15066 specification defines the safety requirements for the sphere of collaborative robots, with the most relevant published guidance being contained in EN ISO 10218. Published in 2012, a Health & Safety Executive (HSE) Research Report, (RR906) - Collision and injury criteria when working with collaborative robots, identifies several areas that the HSE considers need more consideration within ISO/TS 15066. For example, it concludes that the psychological, behavioural and organisational aspects affecting the level of human-robot collision risk, along with the effects of human movement velocities, are not strongly represented in ISO/TS 15066. While more traditional machines in the


manufacturing environment are ‘caged’ by a guarding mechanism, collaborative robots (cobots) often operate in the human-occupied workspace without safety fencing. Of course, not all cobots are guard-free, as this depends on their function and any related safety requirements. Besides the robot itself, the cobot


might have an ‘end effector’, some of which may create hazards. It is vital that a complete risk assessment is undertaken before a collaborative robot is deployed. This must cover its intended use, as well as any reasonably foreseeable misuse, with the basis for this risk assessment being EN ISO 12100, in order to provide a presumption of conformity with the Machinery Directive.


TÜV SÜD Product Service www.tuv-sud.co.uk


PROCESS & CONTROL | JUNE 2018 19


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