Are Asimov’s Three Laws of Robotics enough?

Posted on 06/01/2020

David Green, Certified Machinery Safety Expert, TÜV Nord

ESC’s associate director David Green was asked to answer a question within the ‘Ask the Experts’ section of the InstMC Precision magazine.   David’s response within the article “Are Asimov’s Three Laws of Robotics enough?”, below, looks at the evaluations required to define the specific safeguarding for robots in today’s busy automated factories.

Are Asimov’s Three Laws of Robotics enough?

Risk Assessment

It’s over 75 years since Isaac Asimov formulated his three laws of robotics but, in today’s  busy automated factory, maybe we need more specific safeguarding for robots. I’ve seen a  few videos on LinkedIn where robots have hit the fence-line, so shouldn’t they be far  enough away that they can never hit the fences/ guards? Organisations are required to  ensure that there are adequate controls in place that prevents this impact with guarding to  occur.

The integration of robots into cells is covered by the international standard ISO 10218-2ⁱ.  This standard requires an evaluation of the integrated cell looking at above other things  the space limitations that the robot has to work within. A machinery risk assessment  should be conducted to the ISO 12100 standardⁱⁱ.

The integration standard (clause 4.5) defines the priority of eliminating the risks:

1. The elimination of hazards by design or the reduction of their risk by substitution
2. Safeguarding to prevent operators coming into contact with hazards or to ensure the hazards are brought to a safe state before the operator can come into contact with them
3. The provision of supplementary protective measures such as information for use, training, signs, personal protective equipment, etc.

The placing of the guarding outside of the robot’s maximum reach would be a way of  achieving the safeguarding.

This cannot be achieved for all installations due to a number of reasons:

• Integration with other machine parts or systems
• Interaction with personnel in collaborative robot areas
• Floor space availability in the factory

How have robot suppliers tried to address this issue?

Robot suppliers have been working hard to resolve the issues and evolve the technology to support the elimination of hazards and safeguarding to prevent harm to the personnel in the area of the robots.

The limitation of the movement of the robot needs to take account of the use to which the  robot will be put and the tasks required of it. If the robot has very limited movement  requirements then the robot can be fitted with ‘hard stops’ which physically stop any further movement in the axis limited.

There are many manufacturers who now integrate safety software within their robot controllers. The setting of the software with allowable zone definitions for the exact movement areas for the robot. These settings are three dimensional, usually, as the robots  have x, y and z movement abilities. There are many alternative solutions provided by  different robot suppliers.

The safety software usually provides rules and settings for the extremities of the robot movement (all parts) and extremities of the tool locations. This must be set-up for each installation and commissioned and tested with the integration activities.

So, with this software I won’t need any further protection. Correct?

Unfortunately, the fact that the software is within the control system means that there is  usually still a requirement to supplement the protection for personnel with other systems.  The machinery risk assessment conducted should include malfunction of the robot leading to impact with personnel. This is heightened when robots work in collaborative spaces with personnel (operator loading parts for the robot to weld for example).

It is likely that secondary protection is required designed and installed in line with the requirements of IEC 60204ⁱⁱⁱ, ISO 13849^iv and ISO 13850^v. These protection circuits are normally hardwired to limit the robot movement to a maximum speed (in teaching mode on a pendant) or to stop movement of the robot if the detection sensor (gate interlock, area scanner, light curtain, emergency stop device etc) is activated.

Conclusion

There is no one simple answer, this is a scenario in which adequate risk assessments and  designs are required. In the European Union these requirements and commissioning of  the systems are part of the requirements to be assessed and controlled under the Machinery Directive for providing the whole machine with a Declaration of Conformity (CE mark).

This article was written by:

EUR ING David Green BEng(Hons) CEng MIET FInstMC RFSE CMSE®
FS Expert (TÜV Rheinland, #277/17, S I S), CMSE® – Certified
Machinery Safety Expert (TÜV Nord)
Associate Director – Warrington
InstMC Local Section Chair – Central North West

To find a copy of the full magazine please visit:
https://www.instmc.org/Publications Issue No.14.

Footnotes

i. ISO 10218-2 (Robots and robotic devices – Safety requirements for industrial robots Part 2: Robot systems and integration)
ii. Safety of machinery – General principles for design – Risk assessment and risk reduction
iii. IEC 60204 Safety of machinery – Electrical equipment of machines
iv. ISO 13849 Safety of machinery – Safety-related parts of control
systems
v. ISO 13850 Safety of machinery – Emergency stop function – Principles for design

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