Safety and control in collaborative robotics
Motoman’s control-based collaborative operation
Yaskawa Motoman’s dual-arm SDA robots and single-arm SIA models use safety-rated monitored stop. In some cases, they also use speed and separation monitoring.
Unlike these other collaborative robots, the Motoman systems maintain the speed and power associated with traditional industrial robots, and their six-figure price tags reflect that performance advantage. Motoman robots are designed to work by themselves the majority of the time, but optional safety features can be added to allow for collaborative operation.
“The decision we made as an industrial OEM is to let the robot go fast when it can, when the people aren’t there, and then let it behave in a safe manner when people are present,” said Erik Nieves, technology director for Yaskawa Motoman Robotics in Miamisburg, Ohio.
The safety-rated monitored stop component of Motoman’s optional functional safety unit is in the robot controller. External safety-rated laser sensors monitor when a person enters the robot’s interactive space, signaling the robot arm to slow down and stop.
“We have signals being processed in the controller that change the behavior and the speed of the manipulator,” said Nieves. “Our robot continues to be a powerful unit, but we slow the arm down through control. We have to assure safe operation, because otherwise our robot would knock you on your can.”
Nieves demonstrated Motoman’s single-arm model in an assisted-assembly application the same day the new safety standard was released. “In that instance we have safety-rated sensors that are cognizant of where I am as the operator. When I enter the robot’s space, the functional safety unit automatically slows the robot down. In that regard, we qualify for collaborative operation under speed and separation monitoring.”
“Safety-rated sensors have built-in fail-safes,” added Nieves. “The signals go to two separate places in the robot controller, and those signals are then processed by separate hardware running different algorithms. Those two pieces of software and hardware are then doing cross-checking between them. And if either one of them drops, the system goes into a safe condition. Robot controllers that are third-party certified for functional safety per the standard have to demonstrate that level of redundancy.”
Similar to Yaskawa, other traditional robot manufacturers with systems that meet the safety standard, such as Kuka and ABB, have hardware or software, or both, that allow their robot systems to operate collaboratively with their human coworkers.
The collaborative robot space is occupied by a wide variety of robots—from Baxter, the human-like, multipurpose tasker, to the Motoman high-speed, high-precision workhorse, and Universal’s nimble six-axis arm with performance specs somewhere in between the two. So what does this mean for end users and their safe implementation of this new breed of fence-free robot?
Implementing collaborative robots
In the case of Rethink’s Baxter and Universal’s UR series robots that require little, if any, integration, the responsibility lies with the user to set up and put the system into production.
“Most of the time the end user is taking on the whole responsibility of unpacking it, bolting it down, and integrating it into their processes themselves,” said Universal’s Mullen. “Usually they bypass the integrator task. That puts the pressure on the end user to make sure they do their due diligence with regard to risk assessment.”
Universal sells its robots through distributors. The Braas Company in Eden Prairie, Minn., has been distributing UR robots since Feb 2013.
“It’s the person who owns the automation, the end user, who has the responsibility to verify that they have a safe work environment,” said Braas president, Matt Gallagher. “This new category of robot exists, but it’s not a panacea for safeguarding. There are unsafe work environments that can be created around a collaborative robot.”
“Something like the gripping mechanism could be deemed hazardous or maybe the machine that the robot is interfacing with,” said Gallagher. “You could have an unsafe situation created by a machine door being opened and closed automatically that the robot is controlling. Just the fact that it’s a collaborative robot doesn’t negate the need to do an evaluation of your work environment.”
Universal claims that 80% of its systems are operating without traditional safety enclosures. Gallagher said this holds true to his experience. “So far, all the Universal robots we’ve sold have operated without guards.”
“Universal Robots offers us the chance to sell robots to customers that may not have bought them before,” said Gallagher. “And safety is really just one component that drives that accessibility, probably one of the smaller components. The key feature that makes it more accessible to our customers and also minimizes the need for that traditional integrator channel is the UR’s ease of use.”
“I think what Universal has really hit on the head is a product that demystifies robots for general-purpose applications and first-time robot users. The interface is very accessible. Anyone who has navigated a Windows environment and can understand a flowchart type of structure can navigate the robot programming pretty quickly. And if it’s a shop that has smaller-run types of products, the ease of use allows them to move the robot around and decouple it from one production area and set it up in another area in a very short time period.”
Applications for the UR series have included material handling, machine tending (injection molding and traditional CNC), and assembly applications.
Rethink’s Baxter is best suited for mundane, repetitive tasks that don’t require a lot of skill or speed, or similar tasks with varying parts. “We’re finding that both small companies and larger companies have parts of their manufacturing that have both of those aspects, either low-value things like packaging and kitting, or parts that vary. So you would not want to invest all the effort in structuring the environment and integrating an industrial robot only to have to redo it three or four days later,” said Williamson.
In the lab at P&G
Larger manufacturing companies often have forward-looking labs that test new technologies before they put them on the line. For Procter & Gamble, this is standard practice. The Cincinnati-based multinational manufacturer of personal care and household cleaning products routinely tests new robotics applications and technology on a small scale before introducing it to the larger organization.
“We’re in the process of evaluating the Universal robot arm (10-kg payload UR10) for potential applications within our manufacturing and our R&D environments,” said Mark Lewandowski, robotics technology network leader at P&G’s Beckett Ridge Technical Center in West Chester, Ohio. “We’re testing a lot of applications right now where we have either highly manual operations, such as material handling custom packs of items, or areas where we have slower speed, repeatable motion.”
“We’re working with our safety personnel to evaluate the safety aspects of the arm and figure out how we want to deploy it in a manufacturing environment in a safe way,” said Lewandowski. “We have the capability in-house to do our own risk assessment. We’re also evaluating the robot’s capabilities in terms of speed, repeatability, accuracy, and types of applications.”
Lewandowski is on the RIA Board of Directors and participates in the R15.06 safety subcommittee. He notes a number of resources available to help collaborative robot users evaluate their own safety practices.
“We’re taking advantage of the ISO 10218 standard out of Europe, which has also been adopted by the RIA as the new 15.06 standard. We’re also using the BGIA (Institute for Occupational Safety and Health of the German Social Accident Insurance) document out of Germany. They have a white paper that addresses how to use risk assessment when applied to collaborative robots.” Lewandowski said they also consult the ISO TS 15066.
“So far, the robot is meeting or exceeding all the claims that Universal has given us for safety performance, speed, and accuracy. Another reason we were looking to apply something like the Universal arm was that it’s very easy for somebody to create and develop an application without having to do a significant amount of programming.”
“I’ve had a summer intern and a mechanical engineer able to create applications and functions with no formal robot training,” he added.
“At P&G, we do a lot of automation. This is just another tool in the toolbox that allows us to do what we call affordable automation for those tasks that we don’t have a good solution for today. This is another tool that will allow us to remain competitive in many of our markets.”
Keeping up to speed
Robotics technology is moving at the speed of light, while the standards process is struggling to keep up. As demonstrated, there are ways to safely implement these new types of human collaborative robots in spite of the many variables that still need to be addressed.
“This puts more pressure on RIA to get things done more rapidly and more frequently,” said Davison. In the interim, he provides some advice. “Conduct a thorough risk assessment, work with experienced suppliers, and get involved with the standards development process.”
- Tanya M. Anandan is a contributing editor for the Robotic Industries Association and Robotics Online. Edited by Mark T. Hoske, content manager, CFE Media, Control Engineering, and Plant Engineering, mhoske(at)cfemedia.com.
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