Robotics is a relatively young field with only about 40 years of deployment history in workplace environments, but technology within this field is advancing incredibly fast. So, compliance needs to keep current with these rapid changes. The challenge is how to convey compliance comprehensibly to end-users and integrators. Among the most common compliance questions : “When is a robot system really compliant?” “What requirements must the robot and robot system comply to?” “Why can’t I just do A, B and C and be done?”
The first things to clarify are the industry and purpose for which a robot system will be used. Compliance requirements differ from application to application—e.g., EMC thresholds, temperature, indoors/outdoors, performance or accuracy, work environment and whether there are employees that can come into contact with the robot application. For other work environments like electronics, pharmaceutical production or food, there could be additional requirements, such as cleanroom use or wash-down. A robot is the arm, or manipulator, and its controller, while the robot system is the robot and the end effector for the intended application or use.
Depending on the application and industry, there are very different expectations. This also holds true for compliance in a safety context, especially when it comes to human-robot-collaboration without guards (cage-free).
What are the Issues?
The biggest area of concern is the desire for collaborative applications. But there are more factors than simply the robot. Robot arms are often mountable in many different ways (to a wall, upside-down or on top of a table or integrated with a mobile platform), and robots can be equipped with various end effectors. Which end effector should be selected? This is also a question for non-collaborative applications. What are the ranges in the workpieces for the application?
The robot integrator faces further challenges: Will the application remain compliant for collaborative use after the addition of an end effector and workpieces? After all, the workpiece is sometimes sharp or jagged, which poses high risks in the event of contact.
What are the needed parameters (payload, reach, performance, etc.)? These need clarification for the intended robot application. From a compliance point of view, many different additional factors exist when a collaborative application is desired. Universal Robots (UR) tackles this challenge in two ways:
First, the company only guarantees compliance of its partial machine—the robot arm and controller—to enable its use in collaborative applications. Second, it emphasizes to its distributors and to the end customers that a risk assessment is required to make the robot application (robot system and any additional parts and equipment) compliant (for example, application safety standards and robot safety standards, including the technical specification ISO/TS 15066).
First, risk assessment is easy—and it gets easier each time. It is always the first risk assessment that is a challenge because it is new. A risk assessment consists of identifying all tasks (operation, programming, setup, maintenance) and all hazards that are associated with the tasks. For each task/hazard pair, determine what is the most likely:
- Severity that could result (not theoretical, but credible)
- Exposure (frequency and/or duration)
- Avoidability of the hazard
Then the question is whether there is desire for this to be a collaborative application. For this application, will the robot be a PFL (power and force limiting) robot? PFL robots are also called cobots. If yes, there are a few ways to accomplish this:
- Contact is permitted by the robot application to a person when the contact pressures and forces are within allowed threshold limits (see ISO/TS 15066, which is also RIA TR R15.606)
- If limits are exceeded when running at the needed production speed (for the required cycle time), then a protective device is used (often a safety scanner), enabling the application to run at its full speed when there is obstruction detected. This is called speed and separation monitoring (SSM). When a person is detected (typically through an added safety scanner, light curtain or safety mat), either a stop or No. 3 occurs.
- PFL and SSM are sometimes combined so the application runs at full speed with no one nearby; when an object is detected, UR provides the capability of triggering reduced settings of its safety functions. One example would be a robot dropping to 20% of its speed, so as to not exceed the PFL limits when a person is detected entering its work envelope.
Who is Responsible for Compliance?
Manufacturers need to be precise in their communication with their customers and partners, and customers need to understand and look for this precision, as it will enable useful comparisons. Robot manufacturers can only guarantee compliance of their product to their specifications and approvals. These can state that the robot is accurate to the tenth of a millimeter and/or the robot complies to be used in accordance with ISO/TS 15066, including Annex A, which covers a range of biomechanical threshold limit values in which a collaborative robot system can be used without guards and protective devices.
Manufacturers need to provide safety function information because this is critical to the safe integration and application of robots. Yet it is common to see claims of a “safe cobot” with nothing to back it up. The premise is that almost all cobots limiting (of harm) is by setting the appropriate parameters for the robot safety functions to comply with ISO/TS 15066. Functional safety compliance requires that the safety comply to either ISO 13849 or IEC 62061.
Each safety function needs to be listed, described and provided with functional safety data sufficient for integration of the robot. It is often difficult to determine what safety functions, if any, are provided with a robot. Robots are sometimes used in many different sectors in which manufacturers cannot cover all the applications their partners and end customers might develop.
Manufacturers worldwide do their best to ensure compliance of their products to the intended use and to as many use cases as they can envision. For the robot (manipulator and controller), the robot manufacturer is responsible. But for the robot application, the integrator is responsible for compliance. Even the end-user has responsibilities because they know their environment, culture and the skills of their personnel.
However, just as robotic technology is ever-advancing, so is the ingenuity of integrators and end-users. Therefore, as inventive integrators uncover unprecedented ways to use and develop robot applications, they have to ensure the complete application complies with applicable requirements. For collaborative applications, these requirements depend on the robot application’s work environment, force values, shape and weight of the end effector and part, and the maximum permissive speed of the robot to remain within selected pressure and force values. Then end-users are responsible for addressing risks unique to the installation and for maintaining safety of the application. For more information, see ISO 10218-2 (Part 2 of ANSI RIA R15.06) and ISO/TS 15066, which has been nationally adopted as RIA TR R15.606.
Need for Common Ground
There is no unified means to test whether an application meets the contact threshold values, and many have come up with their own testing methods as a consequence. This results in different pressures and forces being measured. Thus, differences can arise in determining the appropriate limits to configure the robot so the application complies. This is why a common and comprehensively accepted tool is needed to measure or simulate the quasi-static and transient contact values for a given application. These are some of the next challenges for standardization to aid in the compliance or collaborative robotics technology.
Roberta Nelson Shea is the global technical compliance officer at Universal Robots responsible for product safety and reducing barriers to global acceptance and deployment. She has spent more than 40 years as a manufacturing automation professional, 23 of them additionally chairing the American National Robot Safety Committee. Most recently, as chair of the committee ISO/TC 299 WG3 (previously known as ISO/TC 184/SC2/WG3), Nelson Shea led the introduction of ISO/TS 15066, an extension of the established ISO 10218 standards. ISO/TS 15066 is the first document defining standardized safety requirements with human-robot collaboration.