November/December 2020

32 n SAFETY November/December 2020 www.drivesncontrols.com How do you ensure safety when using cobots? C ollaborative robots (cobots) are a key aspect of Industry 4.0 and the factory of the future. They have various integral safety features, allowing them to work with, or near, people and they can also adapt easily to changing needs. This means that the productivity of many repetitive tasks can be increased significantly, enabling users to obtain a rapid return on their investment. Cobot safety features include lightweight bodies, collision detection technologies and a limited number of pinch points. However, further safety considerations may still be needed for some applications – including the way that end-effectors are used, whether there is other equipment in the collaborative workspace, and the products themselves. For a cobot application to succeed, it must incorporate safety considerations based on comprehensive risk assessments. So, what are the safety standards and solutions that will allow manufacturers to gain the maximum value from cobots used in collaborative workspaces? Safety standards Cobots are usually smaller than conventional robots and incorporate force and speed monitoring capabilities. If linked to safety devices that detect people entering the workspace, they can often work at higher speeds when people aren’t present, helping to increase throughput. Two key safety standards that define the safety functions and performance of cobots are ISO 10218 parts 1 and 2, and ISO TS 15066. The latter sets force and speed monitoring of the cobot based on application data, human contact area and workspace hazards. There are two types of human contact: transient (non-trapping contact); and quasi-static (involving situations that can cause part of a body to become trapped). If you aren’t familiar with the requirements of ISO TS 15066, you can hire a safety assessment provider to do the calculations, take measurements, and recommend improvements to the safety of the application. ISO 10218 and ISO TS 15066 also provide guidance on teaching cobots. Many cobots, such as Omron’s TM series, use“hand guiding” mechanisms to teach them new tasks. This avoids the need to program the movements of the arm. The hand-guiding mode monitors force and speed to ensure that the teaching process complies with safety standards. Before being taught, a robot must be stopped before the operator enters its workspace, even if its force- and speed- limiting functions have been activated. Alternatively, a safety device – such as an area scanner – must perform a protective stop as soon as it detects the operator. If safety force and speed monitoring are in operation, the operator can use a simple trigger, button or mode selector to activate teaching. If not, a three-position safety enable is required. According to the safety standards, the teaching mode transition: must be deliberate; must not lead to any unexpected motion; and must not create additional hazards. At all times, the operator should be aware of surrounding equipment and possible safety issues. To enhance operator safety, it is possible to enforce limits on motion – for example, space and soft axis limits. Before operation, the operator must vacate the safeguarded space. This can be verified by safety sensors or additional operator verification. Intentional mode selection is needed to re-enable the robot for operation. Other equipment Cobots may be operating near other equipment that could be dangerous. It is therefore important to map out all additional equipment in the collaborative workspace. Each device must be assessed for potential hazards and for safety sensors that could prevent human and equipment damage. Types of non-collaborative equipment that might need safety devices include: material handling; tooling; grippers and actuators; and machines. Safety devices can usually be integrated easily into a cobot application. There are several ways to safeguard a collaborative workspace. In open areas and applications with low hazards, these include safety area scanners and mats. In gated or limited areas with more hazardous applications or high-speed operations, safety light curtains and safety switches can be used. In areas with Collaborative robots are designed to operate safely alongside humans, but there are still precautions and procedures that you need to implement to minimise risks. Peter Lange, Omron Europe’s robotics business development manager, explains. For maximum safety, machine-tending applications for cobots require the use of safety-rated grippers to protect operators against injury