AS-Interface: Predestined for functional safety

Power supply and communication via one single yellow profile cable, simple and reverse polarity protected wiring using piercing technology, no plugs or pre-assembled cables, no special connection technology, no special switches – no other wiring technology makes it possible to integrate large numbers of individual components or devices in machines and plants as cost effectively and efficiently as AS-Interface. And this applies not only to standard signals, but for safe signals as well, both of which can be transmitted over the same cable. Implementing machine safety efficiently and with technical convenience is one of the central issues for users today. With ASi Safety at Work and the new standard ASi-5 Safety this can be accomplished as simply, cost effectively and individually as never before, because these two safety generations of AS-Interface are ideal complements to each other. Wherever applications are less complex and only one or just a few two-channel safe signals need to be transmitted, ASi Safety at Work is the ideal solution. But when the need is to collect both safe and non-safe signals in the field, connect safe high-end sensors, solve more complex safety applications, send a large amount of safe bits from various modules or use diagnostic and additional information, then ASi-5 Safety is the right supplement to ASi-3 Safety. Not only because it offers significantly greater transmission speeds and data bandwidths, but also because ASi-5 Safety enables much more efficient addressing of the devices.

Fine granularity means extraordinary scalability

The underlying technology advantages are an essential aspect of the success of ASi Safety in making machines and systems safe. In addition, Bihl+Wiedemann as a complete ASi provider offers a product range whose fine granularity opens up many possibilities. This can be seen for example in the connection modules for safe inputs in the field, where the modules provide one, two, four or eight safe signals. This means that the design can be planned according to the needs and thus also optimized in terms of costs. And should changes be required later, these can also be incorporated just as needed, which in total can significantly reduce the costs for unused safe inputs or outputs. Another example is the Safety Basic Monitor from Bihl+Wiedemann. Configured using the ASIMON360 PC software, it can either replace special safety relays for standard applications and thereby act as an autonomous compact safety controller implementing more complex logic connections, or process in the Safe Link environment – together with Safety Gateways – many safe signals in highly complex systems. Here again the Bihl+Wiedemann product range offers the right products for any plant and application size, while at the same time Safe Link enables safe coupling of safe ASi networks of any generation. The system architecture on the I/O level is completely independent from the later subsequent fieldbus connection – the safety application is essentially implemented in the machine and then integrated as a solution into the respective machine controller using the corresponding safe fieldbus gateways from Bihl+Wiedemann. This allows a PLC independent safety technology to be implemented.

ASi Safety: Open for individual applications

In the context of safe machine monitoring, the Bihl+Wiedemann solutions allow you to implement individualized safety-related tasks. One of these is safe speed monitoring. With the company’s speed monitors you can combine and solve at the same time safe motion control functions according to EN 61800-5-2:2017 such as rotation speed, standstill, direction of rotation or speed up to SIL3/PLe together in an application. Another task for safety-related speed monitoring is the detection of machine defects such as shaft break, misalignment, slippage or overspeed. And there is yet another safety application that is widely used in storage and material handling technology: the muting function. Muting is the brief suppression of a non-contacting safety device such as a light barrier or light curtain for allowing permitted objects or persons to pass. A special component in the ASi safety monitor ensures that the settings of this intrinsically complex procedure is reduced to just a few entries, making implementation and operation as convenient as possible.

More efficient addressing and documenting with ASi-5 Safety

It’s not only the significantly better transmission characteristics and diagnostic possibilities as well as technology security with respect to the expected connection of IO-Link Safety that makes ASi-5 Safety an ideal complement to ASi Safety at Work – also key is the ability to address the devices in the network more efficiently. Whereas ASi-3 Safety allows a maximum of 31 safe in- or outputs per ASi network, with ASi-5 Safety a single ASi node number (ASi address) can be used to exchange up to 16 safe in- and outputs as well as further non-safe signals at the same time. In summary, ASi-5 Safety thereby significantly expands the number of connectable safe and non-safe signals per master while reducing effort and overhead costs compared with ASi Safety at Work through more efficient addressing of the ASi modules. The Overhead costs can even be further reduced if single-channel safety according to SIL2/PLc is sufficient in the application. In this case, two-channel safe inputs can also be used separately.

Bihl+Wiedemann is already using many of these technological innovations in their first ASi-5 Safety I/O modules, which have two two-channel safe inputs and 12 standard I/Os. Another advantage of ASi-5 Safety: you can read out all the data from the project planning – safety and hardware configuration, parameter settings, user comments, etc. – at a later time from the new ASi-5/ASi-3 Safety Gateways. These data are then always available in situ as a representation of the specific plant situation, and no longer needed to be searched for in the IT system when for example service is required. 

Cyber security: ASi-5 Safety ensures the highest level of data security

Because of its great significance in process and production stability, the subject of data security has great relevance in industrial environments. Here ASi-5 Safety – like ASi-5 – offers for two reasons the greatest degree of data security,: One, data transmission uses OFDM (Orthogonal Frequency-Division Multiplexing). This method of dynamic frequency assignment makes recording of the sent messages highly difficult and only possible if the entire context of the connection establishment between ASi master and ASi device is known. In practice this makes ASi-5 and ASi-5 Safety virtually safe from eavesdropping. Two, the ASi-5/ASi-3 Safety Gateway provides decoupling between TCP/IP and ASi-5 as well as ASi-5 Safety, i.e. the fieldbus and field levels. The fact that the gateway is the only connection to TCP/IP means that it is the sole cyber security component, while much lesser safety requirements need to be placed on the modules and devices in the ASi circuit. This represents a significant simplification when it comes to continuous network security.

User-friendly software helps to implement safety projects

To be able to use ASi Safety at Work and ASi-5 Safety just as easily both for small projects and for large machines, for simple tasks as well as for more complex or individual applications, Bihl+Wiedemann has placed great emphasis on a user-friendly software suite. This primary goal in the development of this intuitive ASIMON360 software program was to provide the user of both ASi Safety at Work and ASi-5 Safety with the same user experience and maximum operating convenience in planning, parameterization, commissioning, diagnostics and maintenance of the safe devices of the ASi network as well as the entire plant. To this end the software includes an integrated hardware catalog for facilitating the planning and configuration of ASi networks as well as the parameterization of ASi modules from a PC. The necessary safe ASi-3 and ASi-5 modules are inserted into a virtual control cabinet using drag-and-drop. During offline configuration the software continuously performs plausibility checks, for example with respect to the number of devices in the ASi circuit, the presumed current draw or the expected data quantities. The commissioning wizard then – depending on the module preparation – supports fully automated addressing, parameterization and commissioning of all the ASi modules. Following commissioning the online bus information in ASIMON360 can be used to simulate, diagnose and monitor the behavior of the in- and outputs. All the devices can be selected and accessed individually and their parameters modified live by the user. Possible errors in the ASi network are directly viewable and help settings for problem solving are displayed.

Solution space continues to expand

Speed, data bandwidth, addressing efficiency and diagnostic capabilities – but also new gateways and modules from Bihl+Wiedemann – are allowing the solution space in safety technology using ASi-5 to become ever larger. Definite contributors to this will be the development and realization of more complex modules with more safe in- and outputs – a feature already on the agenda.

And so the success story continues…

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