Guest Contributor: Tom Knauer, Balluff
In a previous blog, we discussed how “Safety Over IO-Link Helps Enable Human-Robot Collaboration”. It was a fairly narrow discussion of collaborative robot modes and how sensors and networks can make it easier to implement these modes and applications. This new blog takes a broader look at the critical role safety plays in the intersection between the machine and the user.
In the past, the machine guarding philosophy was to completely separate the human from the machine or robot. Unfortunately, this resulted in the paradigm of “safety vs. productivity” — you either had safety or productivity, but you couldn’t have both. This paradigm is now shifting to “safety & productivity”, driven by a combination of updated standards and new technologies which allow closer human-machine interaction and new modes of collaborative operation.
The typical machine/robot guarding scheme of the past used fences or hard guards to separate the human from the machine. Doors were controlled with safety interlock switches, which required the machine to stop on access, such as to load/unload parts or to perform maintenance or service, and this reduced productivity. It was also not 100% effective because workers inside a machine area or work cell might not be detected if another worker restarted the stopped machine. Other drawbacks included the cost of space, guarding, installation, and difficultly changing the work cell layout once hard guarding had been installed.
We’ve now come to an era when our technology and standards allow improved human access to the machine and robot cell. We’re starting to think about the human working near or even with the machine/robot. The robot and machinery standards have undergone several changes in recent years and now allow new modes of operation. These have combined with new safety technologies to create a wave of robot and automation suppliers offering new robots, controllers, safety and other accessories.
Machine and robot safety standards have undergone rapid change in recent years. Standard IEC 61508, and the related machinery standards EN/ISO 13849-1 and EN/IEC 62061, take a functional approach to safety and define new safety performance levels. This means they focus more on the functions needed to reduce each risk and the level of performance required for each function, and less on selection of safety components. These standards helped define, and made it simpler and more beneficial, to apply safety PLCs and advanced safety components. There have also been developments in standards related to safe motion (61800-5-2) which now allow more flexible modes of motion under closely controlled conditions. And the robot standards (10218, ANSI RIA 15.06, TS15066) have made major advances to allow safety-rated soft axes, space limiting and collaborative modes of operation.
On the technology side, innovations in sensors, controllers and drives have changed the way humans interact with machines and enabled much closer, more coordinated and safer operation. Advanced sensors, such as safety laser scanners and 3D safety cameras, allow creation of work cells with zones, which makes it possible for an operator to be allowed in one zone while the robot performs tasks in a different zone nearby. Controllers now integrate PLC, safety, motion control and other functions, allowing fast and precise control of the process. And drives/motion systems now operate in various modes which can limit speed, torque, direction, etc. in certain modes or if someone is detected nearby.
Sensors and Networks
The monitoring of these robots, machines and “spaces” requires many standard and safety sensors, both inside and outside the machine or robot. But having a lot of sensors does not necessarily allow the shift from “productivity vs. safety” to “productivity & safety” — this requires a closely coordinated and integrated system, including the ability to monitor and link the “restricted space” and “safeguarded space.” This is where field busses and device-level networks can enable tight integration of devices with the control system. IO-Link masters and Safety Over IO-Link hubs allow the connection of a large number of devices to higher level field busses (ProfiNet/ProfiSafe) with effortless device connection using off-the-shelf, non-shielded cables and connectors.
Balluff offers a wide range of solutions for robot and machine monitoring, including a broad safety device portfolio which includes safety light curtains, safety switches, inductive safety sensors, an emergency stop device and a safety hub. Our sensors and networks support the shift to include safety without sacrificing productivity.
To learn more about Safety over IO-Link, visit www.balluff.com
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