Functional Safety Takes Center Stage as Robotics Technologies Evolve
How Robot Manufacturers Can Work with UL to Drive Down the Costs and Complexity of Safety Evaluation
The fact is that we are on the leading edge of a new era in robotics. Significant technological advances— the microprocessor, artificial intelligence, and dramatic improvements in automation and control systems (viz. software)— have led us to where early futurists and visionary engineers only imagined. Their dreams are now our reality: but how do we evaluate them when the standards formerly used did not anticipate these developments with any degree of precision or detail?
“We have reached a cusp,” says Daniel Posner, senior project engineer, industrial controls and robotics, at Underwriters Laboratories. “All the technologies are starting to jump— or leapfrog— older technologies; and as these technologies get more complex, they need a different type of standard to evaluate them. So now we’re using these generally accepted functional safety standards, which are risk-based or risk management-based, and do not hold anyone to a specific type of technology.”
This makes it much easier to evaluate emerging robotic technology, and it is a central reason that functional safety has become a key topic in this important market.
The original robotic standard in North America was established in 1992 with ANSI/RIA R15.06-1999. This standard was significantly updated in 1999, establishing major changes in the safety requirements for industrial robots and robotic systems. The Robotics Industry Association (RIA) proposed to the International Organization for Standardization (ISO) that RIA 15.06-1999 be adopted internationally; and while the ISO thought that the standard was good, they wanted to improve its organization and also accommodate new developments such as software-based safety and soft axis restriction.
As a result, the standard was worked on further, and has been developed into two separate standards— ISO 10218-1 and ISO 10218-2. ISO 10218-1 was published in 2006 and has been adopted in North America. It replaces Part 4 of RIA 15.06-1999. ISO 10218-1 specifies requirements and guidelines for inherent safe design, protective measures, and information for use of industrial robots. It describes basic hazards associated with robots, and provides requirements to eliminate or adequately reduce the risks associated with these hazards.
The new edition of ISO 10218-2 is scheduled for publication in 2011. When ISO 10218-2 is adopted in the U.S., ISO 10218-1 and ISO 10218-2 will be published as RIA R15.06.
To accommodate the development of technology, the industry is pointing to a further standard, ISO 13849-11. ISO 13849-1:2006 provides safety requirements and guidance on the principles for the design and integration of safety-related parts of control systems (SRP/CS), including the design of software. For these parts of SRP/CS, it specifies characteristics that include the performance level required for carrying out safety functions. It applies to SRP/CS, regardless of the type of technology and energy used (electrical, hydraulic, pneumatic, mechanical, etc.), for all kinds of machinery, including robotics. It does not specify the safety functions or performance levels that are to be used in a particular case.
ISO 13849-1:2006 provides specific requirements for SRP/CS using programmable electronic systems. It does not give specific requirements for the design of products that are parts of SRP/CS. Nevertheless, the principles given, such as categories or performance levels, can be used.
"The standard also provides a quantitative approach to risk assessment and safety validation," adds Thomas Maier, principal engineer, functional safety, at Underwriters Laboratories. Under this standard, the risk assessment for a given safety function will yield a Performance Level (PL). PLs quantify the required and achieved level of safety in probabilistic terms. Earlier safety standards still exist, as another parameter of a Performance Level, and measures for diagnostic capability and common cause failures are also defined. This ensures that safety is not solely a matter of component reliability, but also relies on common sense safety principles such as redundancy, diversity, and fail-safe behavior. "The bottom line is increased confidence that the required level of safety, as yielded by risk assessment, is accurate," says Maier.
A New Mark for Robotics
In the past, UL had not been able to offer ISO 13849-1 certification as part of the robotics certification program associated with the UL listing mark. Now it can.
UL has a new functional safety mark that can incorporate ISO 13849-1 and the functional safety aspects that didn't exist until recently - and this can now be incorporated with the UL listing mark.
"This mark can be used for safety control systems of robots, a robotic arm, an AGV, whatever safety control system has been certified to functional safety standards," says Anura Fernando, research engineer at Underwriters Laboratories. "If there are components in the robots, such as motor drives, we can also evaluate them for functional safety and mark those on a component basis using standards such as IEC 61800-5-2 to facilitate those safety functions required of a robot. So we can deal with the functional safety of robots per se, but also from the perspective of the robotic supply chain."
The result is that the evaluation process for robotics manufacturers is streamlined while simultaneously cutting the costs of that process.
“In my experience, this is precisely the case,” says Posner. “Robots that have had their systems evaluated separately make the specification process much easier for designers, developers, and integrators. A lot of robot manufactures may not have the in-house ability to do functional safety evaluations, so increasingly they will look to get the UL functional safety mark on the components they are using as a means to satisfy the needs of and establish confidence among their customers. And this will be so not only for robot manufacturers, but also manufacturers of associated safety products for robotic systems.”
How to Benefit
Consolidating product testing and certification at one global organization creates significant efficiencies that can deliver greater return on a company’s compliance investment. “This certainly holds true for functional safety in the robotics market,” says Kevin Connelly, business development manager at Underwriters Laboratories.
For more information on UL’s new functional safety mark or how to be recognized or listed for compliance with functional safety standards like ISO 10218-1, ISO 13849-1, IEC 61508, IEC 62061, and IEC 61800-5-2 through UL, please contact Kai Christiani at Kai.Christiani@ul.com.
foot note 1: Paragraph 5.4.1 of the new version of ISO 10218-1 also allows for IEC 62061 (derived from IEC 61508) as an alternative to ISO 13849 (based on the principles of IEC 61508)