Industrial mobile robot safety standards on the forefront

Mobile robot standards are evolving to keep up with the rapid developments on the plant floor and to help ensure workers and companies are safe going forward.

Tanya M. Anandan, RIA

Mobile robots are entering new territory usually reserved for humans and manned vehicles. In warehouses and distribution centers, to factory floors, and now laboratories and office spaces, we can expect to see these free-ranging robots more often. These are more than mobile pack mules. These robots have on-board intelligence and real-time adaptive capabilities that broaden their approach. The market is stacked with more choices, combinations, and applications.

A plethora of variations poses new challenges for safety standards writers racing to keep up. Many of these mobile platforms are in practice or in pilot programs around the world. In one case, a self-guided mobile platform is coupled with a dual-arm robot to automate the monotonous task of dipping parts into black oxide for corrosion protection. The adaptive gripper is designed to handle the parts as they are lowered into the black oxide.

There is no safety fencing around this robot. That's because the company uses safety-rated lidar sensors to detect and navigate around obstacles in its path: one located on the front and one on the back of the platform. It has four emergency stop (E-stop) buttons for manual emergency stopping. This mobile manipulator moves the industry closer to its goal of lights-out manufacturing for 24/7 operation.

Autonomous, self-guided vehicles

Mobile robot platform coupled with a dual-arm articulated robot works autonomously processing parts for lights-out manufacturing. Courtesy: Otto Motors/RIAConsumer goods giant Procter & Gamble is putting mobile robots to work in various sectors and applications.

"We have many different types of mobile platforms in use," said Mark Lewandowski, robotics network innovation leader at Procter & Gamble (P&G). "All the way from large-scale mobile platforms, to high-lift mobile platforms, and all the way down to small mobile platforms that can be used in office or lab environments where there are more people. Between manufacturing, warehousing and distribution, we have many different needs across a broad scale of sizes, shapes, and platforms."

Lewandowski noted that these are all self-guided vehicles. This means they navigate autonomously to determine the best route from point A to point B according to pre-learned maps of their environment. Using sensors and software, they navigate around unexpected obstacles with real-time intelligence.

This is in contrast to a traditional automatic guided vehicle (AGV) that typically requires existing infrastructure or facility modifications, such as magnetic strips or navigational beacons embedded in the floor, to guide it on a path.

Not your grandfather's AGV

P&G is either using or testing three main categories of industrial mobile robots: large mobile platforms with high-payload capacities, smaller self-guided vehicles, and mobile manipulators (mobile robots combined with a robotic arm).

"The biggest and most active (application of mobile robots) right now is in the realm of autonomous mobile platforms," Lewandowski said. "These are large-scale platforms that move around pallets or large unit loads. The mobile platforms are in our warehouses and distribution centers where there is not a lot of human and vehicle interaction."

He said they use smaller autonomous vehicles for moving input materials, works-in-process, or finished goods in between processes. These smaller platforms can move more nimbly in crowded environments.

"An example of an application we're piloting right now is moving quality and lab samples from production processes to the lab where they need to be tested," Lewandowski said. "This involves bringing these smaller vehicles into an environment with a lot people and changing processes, so the vehicles need to be able to adapt to these highly dynamic environments."

P&G is using and developing pilot applications for mobile robots.

Autonomous mobile robot outfitted with shelves transports materials between departments while navigating around obstacles. Courtesy: Omron Automation/RIA"Safety is fundamental," Lewandowski said. "Many of these mobile systems are based on the same technology (lidar), so from a safety standpoint, the point of entry is to make sure you have what is recognized as a capable safety system to detect objects and people and to react appropriately.

"Some of these new people (startups) coming in are starting to use these vision-based types of technologies that have more spatial awareness," he continued. "It's important to not only know where the platform is going on the floor level, but also know where it's navigating in its environment. Are there doors or overhangs, or tables or conveyors? It needs to be able to see those and react appropriately to avoid those types of obstacles as well."

Unlike their fixed platform siblings or their cousins on the traditional AGV side, autonomous mobile robots are free-roaming. Safety is a major concern.

Safety standard in the works

The Robotic Industries Association (RIA), in conjunction with the American National Standards Institute (ANSI), is developing safety standards for industrial mobile robots. RIA has assembled the R15.08 committee to write the standards documents for Industrial Mobile Robot Safety.

Work is underway and the goal for publication is early 2019. Though it seems far away, the standards development process is moving at an accelerated pace.

"I've been involved with the safety standards (process) since 2007. To me, this schedule has been lightning fast," said Michael Gerstenberger, PE, a roboticist and the chair of the R15.08 committee. "There are several companies coming out with products in this area. RIA wants to get on top of it and make sure we serve the membership well by developing pertinent standards for how to do things safely."

Gerstenberger has an interesting challenge with this committee. R15.08 is tasked with bringing together two worlds: the mobile platform community and the industrial robot community. Each has its own safety standards.

For mobile platforms, the closest existing standard is ANSI/ITSDF B56.5-2012, Safety Standard for Driverless, Automatic Guided Industrial Vehicles and Automated Functions of Manned Industrial Vehicles.

For industrial robots, the standard is ANSI/RIA R15.06-2012, Industrial Robots and Robot Systems - Safety Requirements.

"Many of the new mobile robots, however, possess a greater degree of autonomy than the traditional AGV, enabling them to operate safely in a more dynamic environment where real-time path re-planning is crucial," said Carole Franklin, RIA director of standards development. "This is not an area currently addressed in the existing AGV standard (B56.5)."

She explained that while the industrial robot safety standard (R15.06) allows for the possibility of a mobile robot system in an industrial environment, most of its guidance assumes a fixed, stationary robotic installation.

Together, committee members must develop this new ANSI/RIA R15.08 standard that will bridge gaps between the two existing standards, B56.5 and R15.06, and provide guidelines for safety considerations unique to mobile robots. In the end, they may decide to fold the newly assembled guidelines into an existing standard, but that remains to be seen.

"One of the most important things that I've been trying to do is to make sure that all the voices on the committee are heard," Gerstenberger said. "I want to make sure that everyone can express their opinions. We have pretty good representation on the committee."

The 75-plus committee members represent most of the traditional robot manufacturers, established mobile robot suppliers and startups, collaborative robot suppliers, traditional AGV manufacturers, robot integrators, safety systems suppliers and integrators, and major end users in the automotive, electronics, consumer goods, and logistics industries.

Also represented are key industry standards and safety organizations such as TÜV Rheinland North America Group, Underwriters Laboratories, the National Institute for Occupational Safety and Health (NIOSH), and the National Institute of Standards and Technology (NIST).

Gaps in existing standards

Hybrid forklift AGV mounted with a collaborative robot arm is developed in the lab to test safety principles. Courtesy: National Institute of Standards and Technology/RIANIST develops test methods and metrics to evaluate the performance of new technologies. Occasionally NIST will lead the efforts toward standards development, as they did in this case with R15.08. For several years, NIST has conducted research in its labs on traditional AGVs, mobile robots, and collaborative robots, and the hybrid integration of these machines.

"We're interested in taking robot models from all different manufacturers and integrating them into one workcell," said Jeremy Marvel, a computer scientist at NIST and member of the R15.08 committee. "That also encompasses mobile industrial robots, particularly the ad hoc integration of the robot arm with mobile platforms from different manufacturers."

Marvel and his NIST colleague Roger Bostelman, who is also on the R15.08 committee, studied the existing safety standards for AGVs and industrial robots while they were conducting their research on hybrid systems. In some cases they found sufficient overlaps, but in other cases they found gaps and conflicts.

Gerstenberger said the committee continues to use NIST's findings as a basis for making sure they have the gaps and conflicts covered as they draft the R15.08 standard. He noted one of the conflicts.

"In the R15.06 standard (published in 2012), it says the robot can be fixed in place or mobile, but shortly after that it also says that the standard only covers the manipulating portion of the mobile robot. So it doesn't cover when this robot can run around, when it's no longer caged in an area."

He also addressed one of the gaps.

"How do the controllers communicate safety information? Should an emergency stop button that's on the mobile platform also cause an emergency stop action on the arm? What about the other way around? If there's an emergency stop that's clearly part of the robot controller, should it stop the mobile platform?"

The R15.08 committee will have to tackle these questions and many others as they draft the document.

"That was the basis for R15.08," Marvel said. "We want to be able to address those gaps and conflicts, and provide guidance and requirements for the provision of a safety-rated solution."

He noted an example with teach pendants. "If you're considering an ad hoc installation or integration of a mobile platform with an industrial arm, both of these will have their own teach pendants. How do you rectify or remedy the control issues so that you only have a single point of control? Do we specify a way to accomplish that? Do we specify that the mobile platform has to relinquish control to the industrial robot, or vice versa? Or do we specify generically that there be a single point of control and then let the integrator or manufacturer figure out how to do that?"

Marvel said right now the committee is leaning toward the latter, meaning it will be up to the manufacturer to determine the single point of control when adding a manipulator to its platform. It's up to the integrator to decide when the two need to be integrated.

"It's a significant challenge to integrate two disparate manufacturers' systems," Marvel said. "In most cases, these are closed systems (with proprietary technology). These are not systems that are meant to be controlled with someone else's software."

Marvel said it's still not easy, but easier to use a common open language like the ROS operating system.

"It took us several months to do our first integration with a closed AGV system, and we're still not sure if we did it correctly. Versus less than three weeks for an open platform we just integrated this summer."

NIST took a conventional forklift AGV and mounted a collaborative robot arm on top of the mobile platform, making it into a hybrid.

"The hybrid does not use guided wires, magnets, or line-following (like traditional AGVs)," Marvel said. "Instead, it uses a laser-based triangulation system to figure out where it is within an open environment, allowing the control software to tell it where to go and generate paths dynamically. Once it's been told where to go it will not deviate from that path. We're working with the manufacturer of the AGV platform as well as the control software to make it more agile and more adaptive, so it can respond in safe ways to any potential collisions or safety hazards."

They also have a mobile platform, which is compatible with ROS. They are comparing closed systems with open systems.

"It's really hard to get safety signals integrated. Same thing with any kind of control. The robot controller is used to being in charge of everything. So now when you're trying to integrate two intelligent systems, it becomes a little bit of a negotiation. Trying to negotiate with two systems that don't want to negotiate is tricky. You end up with a left hand-right hand situation, where the robot arm and the mobile robot are doing their own things, but they are more or less oblivious to each other. That intersection starts to get a little dicey in terms of safety and reliability."



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