Electricity and Control December 2021-January 2022

SAFETY OF PLANT, EQUIPMENT + PEOPLE

At a glance  In production facilities and warehouses ultrasonic sensors can be used to protect people and AGVs where they are working in the same area.  For safety applications ultrasonic sensors have an advantage over other sensor technologies in that they are unaffected by environmental factors such as dust or vapour.  Compact ultrasonic sensors can be integrated into forklifts, for example, AGVs and machines, to ensure safe operation.

USi-safety offers two independent channels, each of which complies with ISO 13849 Category 3 PL d.

Reliable electronics, intuitive parameterisation Each ultrasonic sensor unit is assigned two fail-safe outputs via the electronics. Two microcontrollers in the control interface monitor both the sensor function and each other. Noticeable deviations of the sensor units or between the controllers automatically trigger the safety circuit. Reliable protection is possible from each of the two independent sensor channels. Thus, the requirements for a safe sensor system are already fulfilled when only one sensor unit is connected. For signal output to a safety controller, one signal output is available for each sensor unit as well as safe OSSD outputs with short-circuit and cross-circuit monitoring. If multiple AGVs are moving through the warehouse and encounter each other, interference between the ultrasonic sensors of the different vehicles is suppressed by dedicated software. Fixed interference variables and reference objects for tamper protection can be hidden. Switching points, output logic, periodic tests, and safety- and ultrasound-specific parameters can all be set intuitively using the parameterisation software. This also automatically generates safety records for plant documentation. Some practical examples illustrate where the USi-safety ultrasonic sensor system can be used for collision avoid- ance, personal safety and machine protection. In automated forklifts For collision avoidance in automated forklifts, for example, in addition to the main direction of travel, the secondary directions – such as travel in the fork direction and the lateral zones – need to be considered for protection as well. The small sensor units of USi-safety can be integrated at any point, directly in the forks of automated forklifts. The decoupled control interface can be located separately in the chassis of the vehicle. The three-dimensional sound field of the sensor units thus secures the hazardous area directly in front of the fork arms. Airborne dust and other environmental influences do not affect detection. In track-guided AGVs In the case of track-guided AGVs, the vehicles follow markings on the ground. The tracks are often located in areas where people also move around and the safety of people needs to be ensured without the transport being interrupted unnecessarily. Optical systems, which are used for free navigation and the protection of personnel, can be supplemented or replaced by alternative protective equipment such as USi-safety systems. The sensor units

USi-safety can be flexibly integrated into AGVs.

can be integrated flexibly into the AGV. The parameterisation software can be used to adapt the detection range of the sensor units quickly and easily to the specific environmental conditions. The signal output can be used to reduce speed or to output a warning signal, for example. And the safety outputs reliably trigger a stop in a hazardous situation. For machine protection In machines, critical areas are usually protected with photoelectric light grids. In some environments, such as the wood industry, such sensors are often falsely triggered due to the inevitable generation of dust or airborne particles. The machine then switches to a safe state, after which the light grid must be cleaned and the system restarted. As an alternative, USi-safety produces a ‘sound curtain’ that is unaffected by wood dust, airborne particles, and adhered contamination. This technology reliably protects the machine without any unnecessary interruptions to the production process. Machine parts that extend into the measurement field can be learned by teach-in, and are also useful as a means of tamper protection. For example, if such a reference target is no longer detected due to tampering, the system will go into a safe state. □

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21 DECEMBER 2021-JANUARY 2022 Electricity + Control