ISO/TS 15066, Robots and robotic devices - Collaborative robots

PD ISO/TS 15066:2016 is a Published Document from BSI, being the UK implementation of the international Technical Specification ISO/TS 15066:2016. In this review we will refer to ISO/TS 15066, but all comments apply equally to PD ISO/TS 15066. As stated in its Foreword, ISO/TS 15066 is relevant only in conjunction with the safety requirements for collaborative industrial robot operation described in ISO 10218-1 (Robots and robotic devices - Safety requirements for industrial robots - Robots) and ISO 10218-2 (Robots and robotic devices - Safety requirements for industrial robots - Robot systems and integration), the UK implementations of which are BS EN ISO 10218-1:2011 and BS EN ISO 10218-2:2011. As it is only a Technical Specification, ISO/TS 15066 does not carry the same weight as a standard, but its use would give integrators significantly more confidence that a collaborative robot application is safe.

The Introduction outlines how ISO/TS 15066 provides guidance for collaborative robot operation, where robotic systems share a workspace with people; the focus throughout is only safety of collaborative robots, not other aspects of their technical specification and performance. It highlights the importance of the integrity of the safety-related control system, particularly where process parameters such as speed and force are being controlled. ISO/TS 15066 is intended to supplement and support ISO 10218-1 and ISO 10218-2 where collaborative operation is required.

Scope

This makes clear that the Technical Specification relates to safety of collaborative robots used in industrial environments, though the principles presented may also be useful in non-industrial robot applications. Note that ISO/TS 15066 does not apply to collaborative robot applications designed prior to its publication, but the nature of collaborative robots means that they are often relocated and reprogrammed to perform different tasks; a new task should be treated as a new application, so the requirements in ISO/TS 15066 should therefore be considered.

Normative references

As would be expected, the list of normative references (six in total) includes ISO 10218-1 and ISO 10218-2. Also included is ISO 12100 (Safety of machinery - General principles for design - Risk assessment and risk reduction). Given the concept underlying collaborative robots - that they can operate alongside people without the need for guarding - some readers may be surprised to see that another of the normative references is ISO 13855 (Safety of machinery - Positioning of safeguards with respect to the approach speeds of parts of the human body).

Terms and definitions

Interestingly, the first term defined is collaborative operation, which is modified from the definition in ISO 10218-1:2011. Collaborative operation is defined as 'state in which a purposely designed robot system and an operator work within a collaborative workspace.'

In addition, the definition of collaborative workspace has been modified from that in ISO 10218-1, becoming 'space within the operating space where the robot system (including the workpiece) and a human can perform tasks concurrently during production operation.

Other helpful definitions cover quasi-static contact, transient contact, protective separation distance and body model.

Collaborative industrial robot system design

Subclause 4.1 (General) makes the point that collaborative robot system design requires protective measures to ensure operatives' safety, so a risk assessment is necessary in order that hazards are identified, risks estimated and proper risk reduction measures selected.

Subclause 4.2 (Collaborative application design) lists a number of factors that should be taken into account, ranging from the established limits of the workspace, through to ergonomics and use limits.

Hazard identification and risk assessment are addressed in subclause 4.3. This includes helpful points such as involving the user in both the risk assessment and the design of the workspace. There is also a list of the minimum hazards to consider in the risk assessment, but reference is made to the list of significant hazards for robots and robot systems contained in Annex A of ISO 10218-2. To assist in the hazard identification and risk assessment process, subclause 4.3.3 covers task identification and subclause 4.3.4 relates to hazard elimination and risk reduction - and this refers the reader to clause 5 (see below).

Requirements for collaborative robot system applications

This clause (5) may be one of the most useful for many readers. It makes several references to ISO 10218-1 and ISO 10218-2 but also contains a wealth of detailed information and formulae specific to collaborative robots. In particular, it addresses the design of the workspace, design of the robot operation (including resetting after a protective stop has been triggered), transitions between collaborative and non-collaborative operation, and requirements for enabling devices (and situations in which an enabling device may not be required).

Considerably more detail is provided for the following collaborative operations:

• Safety-rated monitored stop
• Hand guiding
• Speed and separation monitoring
• Power and force limiting

In subclause 5.5.5.3 (Risk reduction for potential contact between robot and operator) there are two points to highlight:

Objects with sharp, pointed, shearing or cutting edges, such as needles, shears, or knives, and parts which could cause injury shall not be present in the contact area.

Contact exposure to sensitive body regions, including the skull, forehead, larynx, eyes, ears or face shall be prevented whenever reasonably practicable.

Great care should be taken with interpreting 'reasonably practicable'.

Verification and validation

Readers are referred to Clause 6 in ISO 10218-2.

Information for use

In addition to references to ISO 10218 parts 1 and 2, this clause also contains requirements relating to descriptions of the collaborative robot system, the workplace application and the work task, and information specific to power and force limiting applications.

Annex A. Limits for quasi-static and transient contact

This annex, which is informative not normative, provides guidance on how to establish threshold limit values on the collaborative robot system, particularly in applications relying on power and force limiting. The underlying basis is 'pain sensitivity thresholds' when a robot comes into contact with various parts of a person's body. Tabulated limit values for pressure and force are based on conservative estimates and scientific research on pain sensation. Guidance is provided for when the pressure or force value will be the limiting value. However, the Introduction to ISO/TS 15066 notes that 'values for power and force limiting stated in this Technical Specification are expected to evolve in future editions'; it can be assumed that values for pressure will evolve as well. Furthermore, subclause A.3.6 reminds readers of the limitations of the body model used for assessing power- and force-limited collaborative robot operations, and that this field of study is the subject of ongoing investigation and research.

Conclusion

ISO/TS 15066 presents a wealth of information and the level of detail may come as a surprise to readers who have previously formed the view that 'collaborative robots are easy and safe to implement because they are designed with built-in force and speed limitation.' When first reading the Technical Specification the requirements and calculations may seem daunting and, for any given application, it is necessary to decide which subclauses are relevant and which are not. It may be helpful if suppliers of collaborative robots develop guidance to help integrators who wish to comply with the requirements of ISO/TS 15066; this could indicate which subclauses are applicable and show how integrators can perform the necessary calculations and demonstrate compliance - perhaps apps or online calculators would be beneficial.

Currently there is no obligation to comply with the requirements in ISO/TS 15066 but those wishing to adopt best practice may choose to comply.

PD ISO/TS 15066:2016 is available in PDF or hard copy format from BSI priced at 182 or 91 for Members of BSI.

* [See also this article with contributions from consultants and cobot suppliers who have experience of working with ISO/TS 15066 - Ed]