The dynamic safety mats, measuring 1000 mm x 600 mm x 32 mm, combine surface monitoring and machine operation, making new operating concepts possible.

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The expectations placed on safety-related operating concepts are high: today, even complex production plants must be easy to parameterize, intuitive to operate and predictive to maintain. The automation company Pilz also believes that safety requirements in accordance with EN ISO 13849-1 and EN IEC 62061 should always be implemented in such a way that they do not restrict either operability or productivity. A new product meets all these requirements.

Safety mats that switch off a machine or bring a movement to a safe stop are not new: however, the dynamic safety mat 'PSENmat' developed by Pilz is definitely a novelty. Alongside safe area monitoring, it offers flexibly definable switching functions for controlling and operating machinery. Behind this is the integrated spatial resolution: sensors in the mat not only transmit the current location of a person, but are also available as virtual foot switches. The dynamic safety mat therefore supports hands-free working and an obstacle-free workplace.

Connect up to 22 mats together

A dynamic safety mat can be used in combination: Depending on the task, it can consist of any number of units of up to 22 mats, dockable on all sides. This network can in turn be coupled with others. With their integrated spatial resolution, the tactile sensors of a mat network detect where a person is currently located. Based on the underlying position grid, the respective mat module transmits data via a gateway to the computer unit of a higher-level control system. Based on data from the successively activated sensors, the computer determines a movement and its direction in fractions of a second. With a view to operating a system, a wide range of information can be obtained from this.

Movements across the mat field or explicitly pressed buttons trigger predefined actions or reactions. If a group of sensors has been defined as the highest safety zone in accordance with the safety requirements using the intuitive 'PSENmat Assistant' parameterization tool, entering this zone brings a hazardous movement to a safe standstill. As long as the person remains in the danger zone, the safety mat prevents any unintentional restart (e.g. as protection against stepping behind). If the production process is to continue as quickly as possible, the worker returns to the upstream mat area, presses a correspondingly marked button combination with their foot and the machine restarts. The parameterization tool can be used to set up warning and protection areas as required and to set up the desired switching actions in a targeted and logical manner using appropriate button assignments. An internal logic checks the selected parameterization for plausibility against the background of potential access times, among other things, and indicates target conflicts if necessary.

The Safety Device Diagnostics (SDD) gateway provides the mats with a Modbus/TCP output for transmitting standard operating data and two integrated OSSD outputs for transmitting safety data. The safety mats can be flexibly connected in series and require minimal cabling. The new and re-parameterization of the tactile sensors is simple, and with the 'saved recipes' application, entire sensor groups are quickly set up for new tasks. This keeps downtimes short and frequently changing production tasks are easy to handle. Proven parameter sets can be transferred to a second system just as easily.

In MRK use

'PSENmat' from Pilz is able to reliably determine the dynamics and direction of movements by evaluating the tactile sensors involved. In addition to safeguarding surfaces, the safety mat offers a wealth of operating and intervention options in the process - from controlling machine operating processes to quality control. Using appropriate buttons or button combinations 'in the floor', an operator can, for example, feed or discharge parts, change feed units or change the drive speed. In principle, the Safety Mat, sometimes in combination with other safety devices, shows its advantages wherever applications are confusing, full of obstacles or difficult visibility conditions due to dust development are the order of the day.

Even larger applications can be implemented with the dynamic safety mat because up to 22 mats can be connected in series.

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The use of dynamic safety mats offers particular advantages in the context of HRC applications: In the classic case, a 'PSENmat' system forms three zones around a free-standing 6-axis robot that, for example, loads the test stations of a rotary table machine with components fed in by conveyor belt. The worker can operate in the outermost zone without triggering a safety function. Using virtual buttons in the mat area, he can, for example, initiate a container emptying process by stepping on it, tap the robot movement to slow motion for control purposes or report his presence to the system at regular intervals. If it enters the zone defined as a warning area, the robot slows down according to the specifications. If it enters the immediate danger zone, the PSENmat area defined as the safety zone triggers a safe stop.

Hands free for quality control

New application scenarios can also be implemented in conjunction with robots in the field of quality control, for example in automotive engineering: If the worker is already standing on a mat with an integrated switching function for safety reasons, walking distances are generally eliminated. If the worker has to check a component that is held, rotated and turned by a robot gripper and still has testing and measuring instruments in his hand, the advantages become clear: he enters his test results via the variably assignable, virtual foot switches, eliminating the need for a control panel that is only accessible to a limited extent or is even disruptive. If the robot changes its position, for example to pick up a new part or to work at a different location for a certain period of time, the previous safety area is transformed into a freely accessible area. If the component and the associated test routine change, the assignments of the virtual foot switches can be easily adjusted using the parameterization tool.

Insensitive to common stresses

The safety mat, measuring 1000 mm x 600 mm x 32 mm, mainly consists of a bottom shell and a PUR tread surface. In between, there are 40 sensitive areas on a pressure-sensitive tactile sensor that meet the requirements of the EN ISO 13856-1 standard. The safety mat is hard-wearing and resistant to common stresses in industrial environments and offers IP67 protection. The maximum permissible load capacity of the patented safety mat is 800 N/cm², it can be driven over by forklift trucks and can be used at ambient temperatures from 0 °C to +50 °C. It meets the safety requirements SIL 2 according to EN ISO 61508, safety level PL d according to EN ISO 13849. 'PSENmat' completes Pilz's range of sensors for monitoring areas and rooms and can be easily connected to the configurable small controllers PNOZmulti or the automation system PSS 4000 or to the visualization solution PMIvisu. Connection to the respective control unit via the safe OSSD outputs is simple and reliable.

With the combination of safe area monitoring and machine operation, the new safety mats offer great potential for the design of applications - from machine operation and quality control to the safeguarding of HRC applications.

The uses for textile tactile sensors in the form of such sensor mats will be far-reaching in a few years' time: from industrial applications to possible uses in the transport and logistics sector - including the safeguarding of people on internal routes used together with driverless transport systems.

Author:
Stephan Hoffmann is Product Manager Sensors at Pilz.