For anyone involved in risk assessment and control, there are always questions regarding the amount of force it takes to injure a person. As a reminder, force is a vector quantity that has magnitude and direction and, if unopposed, will cause an object to change its velocity.
As soon as we decided that products that hurt people were not OK, engineers wanted to know what the limits were on forces applied to people. In the US military, these questions applied to airmen flying military fighters, and submariners fighting below the surface. Divers that were used for tactical actions and for salvage, repair and recovery missions needed to know how deep they could dive and for how long.
A study was done by the US military in the 1950s regarding the forces that could be applied to the human body. Because volunteers were hard to come by, cadavers were used to test the forces necessary to puncture the skin, lacerate tissues, and amputate or crush various parts of the body. These tests were also done with pig cadavers. It was shown that cadavers don’t behave the same way live people do and that the forces and speeds were highly variable.
Since those days, scientists and engineers have continued to study these questions. A key application that is bringing this work to the forefront is collaborative robotics. The industrial applications are many, from using the speed and discrimination of robots to aid humans in assembly tasks, to the strength and precision that robots can add to a work task.
Collaborative Robots – early years
In the early 2000s, researchers were working with ways to limit speeds, forces and joint torques to try to protect workers. I made a little video mashup to give you an idea of where things were then.
One important area for future development outside of the industry is in healthcare. There are many applications where robots can offer humans help, including surgery and patient care. Patient care workers often suffer back injuries from assisting patients to get in and out of bed or to the toilet. There are manual hoists that can be used for these purposes, but to use them a patient care worker is needed every time. Patient care work is often very intimate, since patients may need significant help to bathe or toilet properly.
A collaborative healthcare robot could be used in these cases instead of a human worker, bringing extra speed and strength, and eliminating the chance of injury or abuse by or to the patient and the patient care worker. Here are a few examples of the types of assistance I’m thinking about as I write.
Healthcare is certain to be a growing area for these types of personal assistance robots.
Since then, the potential for all kinds of physical forms of collaborative robots has developed. Here’s another short video mashup of where things are today.
More information needed
All of this work is great, but coming back to injury prevention is key. The Boston Dynamics Spot Mini is great at avoiding hitting people and objects, but there are many applications where robot-to-person contact is necessary. ISO/TC 199 started a project in 2012 to develop a new standard to help guide machine designers with respect to the level of force that can be tolerated by people.
Led by Professor Yoji Yamada from Nareda University in Japan, ISO/TC 199/WG12, Human-machine interactions, is nearing the end of development for ISO 21260, Safety of machinery — Mechanical safety data for physical contacts between moving machinery or moving parts of machinery and persons.
ISO 21260 is now at the international review stage, so I can tell you a bit more about the standard. If you are interested in reviewing the standard and submitting comments to the committee regarding the work, your National Standards Body can help you do that. In Canada, the Standards Council of Canada operates the review portal. In the USA, ANSI operates the review portal, and in EU member states, the individual countries operate their own ISO/IEC related review portals.
ISO 21260 Scope
The scope of a standard tells you what the standard covers, and may also provide specific exclusions.
This document specifies force and energy-related limits for physical contacts between the machine or parts of the machine and people that are caused by the movement of the machine or parts of the machine as part of its intended use or foreseeable misuse.
It defines limits that meet the criteria for “inherently safe design by physical aspects” (see ISO 12100:2010, 22.214.171.124).
This document covers all types of machines that are designed to function where people can be present and the machine can make physical contact with those people.
This document deals with contact between machines or parts of a machine and people during their normal interaction as part of their function and contact not necessary for the functioning of the machine. It encompasses interactions that are intentional or unintentional.
This document is limited to defining threshold values to avoid harm caused by physical contact
This document does not cover effects from contact due to
- electrical shock
- cutting or any risk due to contact with a dangerous tool used or supported by the machine
- additional effects due to the contact causing a fall.
The focus of the standard is on assisting designers to apply the first level of the Hierarchy of Controls; Inherently Safe Design. The standard deals specifically with forces applied by the machine, and not to any thermal or electrical effects, all of which require more study.
Since the standard is still in development, ISO has not committed to publication date. It is reasonable to expect the first edition to be published in 2020, so follow the RSS feed for the document to stay on top of developments, or check the ISO document page now and then. If you are new to using RSS feeds, you need to use an application like Feedly or something similar to read the feed and provide the information in an easily human-readable form.
ISO/TS 15066 – Collaborative Robots
This standard is one of two documents that are destined to hold important places as we develop closer physical relationships with our robotic creations. The second document was developed by ISO/TC 299, Robotics, and is currently an ISO Technical Specification (TS). ISO/TS documents are used by Technical Committees to publish information that is believed to be important to the sector served by a TC, but which has not yet developed to the stage where it can be standardized. ISO/TS 15066:2016, Robots and robotic devices – Collaborative robots (RSS feed), applies to industrial robot systems as described in ISO 10218 – 1 (RSS feed) and ISO 10218 – 2 (RSS feed). It does not apply to non-industrial robots, although the safety principles presented can be useful to other areas of robotics. The document specifies safety requirements for collaborative industrial robot systems and the work environment and supplements the requirements and guidance on collaborative industrial robot operation given in ISO 10218 – 1 and ISO 10218 – 2.
If you are involved in the development of collaborative robots, these documents are required reading. They will also be useful to anyone designing collaborative robotic applications since the force limits will be very helpful during risk assessment of the application.
If I can answer any questions regarding the documents or their development, please feel free to drop me an email or leave a comment below.