At first glance, “robotic safety standards” doesn’t seem like a particularly exciting topic. That’s why it’s somewhat surprising to hear Bill Alexander, the packaging business development manager for Beckhoff Automation LLC of Burnsville, Minn., wax enthusiastic about the new ISO 10218-1 robotic safety standard.
“The new ISO 10218-1 standard covers the safety requirements for more complex uses of robotics such as wireless teach pendants, internally-programmed robot safe zones and the use of one controller for the movements of several manipulators,” he notes. “All of these changes will result in the reduction of overall system costs and users of robots should familiarize themselves with the standard to better understand how to reap the benefits.”
This global standard, which is largely based on the previous Robotics Industry Association (RIA) R15.06 standard as well as the Canadian national standard Z434, includes several new wrinkles, including those mentioned by Alexander. Of these, the guidance on internally programmed safe zones may well prove to be the most significant in the short run.
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In a nutshell, internally programmed safe zones are created by controllers that have embedded safety software that limits robot movements without recourse to safety sensors or other external devices. This is a development that is already being implemented by some robotics companies.
Case in point, Fanuc’s Dual Check Safety (DCS) speed and position check software. The main benefit of DCS software comes in applications where the travel of the robot needs to be restricted due to floor space or process limits that are less than the full reach of the robot. This means that the robot can be restrained to exactly the area in which it works; something that is not possible with the current systems that limit robot motion externally using limit switches.
Reduce floor space
By moving some of the safety functions to within the robot, “customers will realize significant savings in floor space, flexibility in system layout, reduced hardware costs, and improved reliability,” says Claude Dinsmoor, general manager, material handling segment, Fanuc Robotics America Inc., Rochester Hills, Mich.
In addition, safe zones can be enabled and disabled from an external source such as a safety programmable logic controller (PLC). Properly designed, such a system can allow an operator to enter and leave the robot’s workspace safely.
“This streamlines the design of robot cells because it prevents the robot from entering the load area when an operator is present,” adds Dinsmoor. “This type of application is possible with existing technology, but it is typically difficult to setup, expensive to implement, and requires more floor space than a system using DCS.”
Kuka Robotics has a similar software offering called SafeOperation. “In the past,” says Yarek Niedbala, Directeur Commercial of Kuka Robotics Canada Ltd., Mississauga, Ontario, Canada, “the work envelope of the robot had to be constrained using hard stops placed on robot joints. This resulted in a somewhat restricted work envelope. However, because the restrictions were angular and not Cartesian, a lot of floor space was still being wasted.”
The software uses a redundant system that monitors the position of the robot at all times. Zones are set up to describe the desired work envelope of the robot using prisms, rather than spheres, that mimic safety fencing. “If the robot were to go outside its zone,” says Niedbala, “the redundant monitoring system would generate an E-stop. Because the zones can be more tightly defined, less fencing is required, thus reducing the cost of the cell. In addition, SafeOperation technology in many cases eliminates the need of a SafetyPLC.”
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