How do you make a cobot inherently safe?
Increased automation is the price of entry for manufacturing businesses. Automation drives productivity and productivity drives profitability. Robots have been an automation feature of manufacturing plants for decades.
For health and safety reasons, many of these robots have been kept in robust enclosures, adding to the cost and complexity of installing them but providing essential safety for nearby personnel. A more recent trend has been the use of collaborative robots, or cobots, which are designed to work hand-in-robotic-hand with humans. These more compact machines gained recognition in the early 2000s. Designed for use close to people, they don’t need the conventional protective enclosures of their larger counterparts.
The last 10 years saw dramatic growth in cobots and that is set to continue. The analyst, Grand View Research, predicts a 32% compound annual growth rate (CAGR) for the technology between 2023 and 2030, with the global market size rising from $1.58 billion this year to $11.04 billion in 2030.
Are cobots getting smarter?
Launched in 2015 at a trade fair in the Hannover Messe, Germany, ABB's YuMi 14-axis, dual-arm cobot transformed the world of robotics and automation. It was designed for small parts assembly and other delicate operations that require a high level of precision and flexibility.
The robot's arms work together or independently, enabling it to perform complex tasks that would typically require multiple robots or human operators. A seven-axis, single-arm model of the YuMi was unveiled two years later and officially launched in 2018.
In both versions, each arm has a payload of 0.5kG (1.1 pounds) and YuMi’s grippers have integrated vision cameras to enable parts to be picked without the use of a fixture, or for simple inspection applications.
YuMi is designed for production environments. It can be used for machine vision on production lines, but its real strength is in fast and accurate small parts assembly, testing and packaging, and in materials handling. It boasts 0.02mm placement accuracy and is much faster than cobots with higher payloads, which maximizes potential productivity gains.
YuMi is not designed for harsh environments or for handling food, but it has been adopted in a huge range of applications including electronics assembly, automotive electronics, consumer products, toy manufacturing, and medical and cosmetics processing and testing.
What is the ISO/TS 1506 safety specification for cobots?
The first question many people may ask about cobots is this: Are they safe to work alongside human beings? Six years in the making and published in 2016, a year after the launch of the first YuMi, ISO/TS 15066 is the International Standards Organisation (ISO) safety specification developed for cobots. The document details robot power, speed and force limits, the required safety control systems, ergonomics and operator training, and the need for risk assessments.
The force/pressure thresholds were determined following a pain onset level study carried out by the University of Mainz, Germany, as part of the ISO project. It involved 100 participants and established the limits for contact in 29 areas of the human body. The risk assessment helps identify potential hazards and risks associated with cobot operations and guides the implementation of appropriate safety measures.
Although ISO/TS 15066 was written as a comprehensive guide for working with cobots, other legislation may need to be considered when installing and operating them. This may include Operational Safety and Health Administration (OSHA) regulations in the United States, the European Union Machinery Directive, or national regulations such as the Occupational Health and Safety Act in Germany.
How does the design of the ABB YuMi make it safe?
The ABB YuMi is UL Listed for functional safety. The requirements for achieving this listing are available on the UL website. Cobot users must understand what's involved if they are to maintain a safe working environment.
In the example of YuMi, it is equipped with software collision detection and speed supervision that enable it to detect and respond to changes in its environment, ensuring that it can operate safely and efficiently in the presence of humans.
Its compact design and smooth surfaces reduce the risk of injury in the event of a collision. This passive safety approach is facilitated by lightweight magnesium alloy arms designed to avoid pinching between the robot links and the arm edges. Soft rubber pads cover the arms for impact absorption when collisions occur.
However, there is no pressure-sensitive “skin” on the arms to detect impacts. Instead, ABB uses precision Hall sensors to measure changes in the currents in the cobot motors in each joint to initiate protective measures within milliseconds.
Impacts may involve a glancing contact, where there is no collision force after the contact, or an impact where the robot arm becomes static, perhaps trapping a human hand against a worktop. In the case of glancing contact, just touching the robot arm with a single finger is enough to stop its movement. If there’s a static collision, the Hall sensors detect it before any injury can be caused and the robot arm automatically becomes compliant, enabling it to be gently moved away from the point of impact.
Another safety enhancement is that wiring and compressed air are routed inside the robot, reducing the risk of cable or hose damage, or of hands or arms becoming entwined in wires or hoses.
ABB cautions its customers to ensure that accessories such as grippers, fingers and fixtures have smooth surfaces and advises that YuMi should be programmed with the elbows pointing downward and positioned so that the arms cannot come into contact with a human face. The firm also advises the use of safety goggles or a plexiglass screen when working near the cobot.
Certified monitoring of YuMi’s behavior and status is provided by ABB’s optional SafeMove hardware and software, which integrates additional safety features directly into the cobot’s controller. SafeMove enables the creation of more ranges, zones and commissioning tools to further boost productivity.
Perhaps surprisingly, YuMi cannot detect the presence of humans in its vicinity, but this function can be accommodated using external safety sensors.
Why cobots are here to stay
With rising labor costs, labor shortages, and the ever-present need to improve productivity, the future of cobots seems assured. Cobots have proven to be far safer than traditional robots.
Thanks to the introduction of ISO/TS 15066 and the benefit of nearly 20 years of experience using cobots, safety — while always a consideration — does not seem to be holding back adoption of the technology. And, with the growing use of machine learning and other forms of artificial intelligence in automation, cobots capable of continuously improving their performance as they learn on the job are perhaps just around the corner.