How safety laser scanners can protect people and machines
protection. If a person crosses the perimeter, a stop signal can be sent, and the machine is stopped. While both light curtains and scanners can be used in perimeter protection, safety light curtains are used more often in perimeter protection, and scanners are used more often in area protection. Access control and area protection, which can be implemented with a light curtain or scanner depending on the specific application needs. Light curtains are suitable when there's a single point of entry. For example, individually monitoring
Figure 1: A safety laser scanner like this can monitor a 275° area to create a two- dimensional protected zone and send an alarm if any unexpected person or object enters that area (red lines). (Image source: Banner Engineering)
and evaluating each beam of light enables a light curtain to
differentiate between a "tall" person and a "short" material carrier, like a pallet crossing a threshold, and modify its response accordingly. Scanners can be set up to monitor a 275° area to create a user-defined two-dimensional protected zone (Figure 1). They can also establish multiple protection zones based on the distance between a person and the protected machine and slow or stop it as appropriate. Mobile systems like autonomous mobile robots (AMRs) and automatic guided vehicles (AGVs) can benefit from using multiple scanners. Those scanners can be battery-powered and installed to work cooperatively, simultaneously monitoring dozens of safety zones
For example, ISO 13849-1 defines the reliability of safe control functions using performance levels (PLs) from "a" to "e", with PLe representing the highest level. Safety laser scanners meet the criteria of PLd and are suitable for use in applications where safety is a major priority. A PLd rating is granted to systems with the probability of a dangerous failure every 1 to 10 million hours (141 to 1,141 years based on continuous operation). Light curtains are available with a wider range of options from PLc to PLe. IEC 62061, Safety of machinery: Functional safety of electrical, electronic, and programmable
around the vehicle. Different zones can be activated based on vehicle speed, position, and anticipated changes in direction. The data from the scanners can be supplemented with encoders on the wheels and other sensor inputs to support AMR navigation. What level of safety? Once the physical space being protected has been defined, the next consideration is the needed level of safety. In addition to having different application benefits, light curtains and safety laser scanners support different levels of safety as defined by various international standards.
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