COLLABORATIVE ROBOT DEVELOPMENTS WAREHOUSING, HANDLING & STORAGE
AUTOMATION & ROBOTICS R
obots are now being specifically designed to work alongside humans in a ‘collaborative workspace’, so they can perform tasks simultaneously with the robot often operating in the human-occupied workspace, sometimes without safety guarding. Besides the robot itself, the collaborative application will include an ‘end effector’, that is the tool adapted on the robot arm with which the robot performs tasks, and the objects moved by it. In tandem with this new way of working, there of course comes new safety concerns. The increased need for adequate protection of people from the safety risks associated with industrial robot systems led to the development of EN ISO 10218:2011, 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. In order to ensure that humans are not exposed to unacceptable risks when working collaboratively the current standards describe four separate measures that can be used to provide risk reduction. It is required that at least one of these is fulfilled, in addition to having visual indication that the robot is in collaborative operation. The four measures are:
1. SAFETY-RATED MONITORED STOP This measure requires that when it is detected that a human has entered the collaborative workspace, the robot shall be stopped. The stop condition shall 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, which is a three- position device that has to be held in the centre position.
1. 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.
It is required that at least one of these requirements needs to be fulfilled, in addition to having visual indication that the robot is in collaborative operation. In all four of the measures described above, the safety-related control system that provides this functionality needs to meet either: • 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.
36 APRIL 2023 | FACTORY&HANDLINGSOLUTIONS
Stewart Robinson MIET MInstMC, Principal Engineer and Functional Safety Expert at TÜV SÜD
ENHANCED GUIDANCE
While EN ISO 10218 contains some guidance on collaborative applications, with the rapid pace of technological development, it was widely 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 workspace • The design of the collaborative operation • Methods of collaborative working • Changing between: o Collaborative/non-collaborative o Different methods of collaboration
• Operator controls for different 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. Published in 2012, a Health & Safety Executive (HSE) Research Report, (RR906) - Collision and injury criteria when working with collaborative robots, also offers some useful guidance. Robots designed for use in collaborative applications are now expanding the possibilities of automation and, as they are a core element of Industry 4.0, manufacturers are integrating greater numbers of such applications factory wide.
While the advent of collaborative applications offers exciting possibilities for industry, some end-effectors may create hazards, especially as contact between the collaborative robot and the operator can lead to the possibility of collision. It is therefore vital that a complete risk assessment is undertaken before a collaborative application is deployed, as you would with any machinery in the workplace. This must cover the intended use of the robot, 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 in the European Union and the Supply of Machinery (Safety) Regulations 2008 in the UK.
TÜV SÜD
www.tuvsud.com/uk
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