Diagnostic possibilities for as-i from bihl+wiedemann

Higher, faster, further – the performance of machines and systems has increased in recent years, also thanks to increasingly clever components. .

The BWU2828 is an AS-i-3.0-Profinet gateway with integrated safety monitor in stainless steel housing. With the AS-i Gateways from Bihl+Wiedemann digital and analog data, which have been read in decentrally via AS-i slaves, can be passed on to the higher-level control system via the respective bus system, and output signals of the control system can be transmitted to the AS-i actuators.

Higher, faster, further – the performance of machines and systems has also increased in recent years thanks to increasingly clever components. But in addition to sheer performance, another factor has emerged as a competitive criterion: availability. It helps to detect errors before they lead to failures.

Do you know this? One of your dipped headlights on the car is not working. But until the workshop appointment, everything lights up again and you drive home without having achieved anything. Wobbly contacts are something stupid… Modern cars are one step ahead: More and more frequently, the mouse cinema of the dashboard displays a warning message in the event of a fault. You learn about your defective low beam before oncoming traffic notifies you at night by flashing their headlights. And thanks to the readable fault memory, the culprit can be found in the workshop, even if everything is working again. Practical.

The safety unit of the device provides 16 terminals, 12 of which can be optionally configured as standard I/Os, as six safe outputs and three safe two-channel inputs, or as six safe inputs. The status and error messages of the connected slaves can be shown on the displays of the gateways on site.

To ensure that this can be implemented just as well in machines and systems, modern field devices and bus systems are available that can create, store and report diagnostic data. The AS-Interface (Actuator-Sensor-Interface, abbreviated AS-i) is one of these possibilities. AS-i is a standard for fieldbus communication that was developed to replace the parallel cabling that was common in the past. The interface has been a manufacturer-neutral international standard in accordance with EN 50295 and IEC 62026-2 since 1999. AS-i allows devices at the lowest field level to be connected to the higher-level controller. This makes it a cost-effective and intelligent feeder for the fieldbuses and Ethernet-based communication systems at the control level. With "AS-i Safety at Work" a certified standard has been developed, which allows the use of safety-related components in the AS-Interface network. These include safety monitors, emergency stop actuators, door interlocks, light curtains and light grids or optical scanners. Safety at Work achieves the highest performance level e according to EN ISO 13849-1 (IEC 61508 / SIL 3) and can therefore be used for emergency stop applications with stop category 0 or 1.

Large selection of safe components

The company Bihl+Wiedemann from Mannheim has established itself as a specialist for AS-i. The product portfolio is very diverse: If the plant is large or widely branched, the manufacturer offers safety gateways with safe cross-communication via Ethernet-based bus systems. In the maximum configuration, these enable almost 2000 safe two-channel input signals to be collected cost-effectively and efficiently and safe outputs to be controlled centrally or decentrally.

For small plants the Safety Basis Monitor – with and without AS-i master – is available, which is a cost-efficient alternative to the traditional parallel wiring for three or more safe signals. For medium-sized plants with ten to 100 safe inputs and outputs, Mann-heimer offers AS-i gateways with integrated safety monitor, which comply with AS-i-3.0 standard can evaluate up to 62 safe signals per device. With little wiring effort, the lower field level can be connected to common automation systems, no matter if it is Profibus, Profinet, Profisafe, Ethercat, Sercos, CC-Link, Can-open, Ethernet/IP or Modbus over Ethernet.

A PC software allows the comfortable reading of the AS-i states as well as the logging and tracing of sporadic errors. It thus helps the plant engineer, the maintenance engineer and the technical support engineer.

Diagnostics and display on board as standard

The special focus of the Mannheim-based company is on AS-i-based safety technology. At Bihl+ Wiedemann, for example, the safety monitor required for AS-i Safety at Work is integrated in the AS-i master instead of being plugged in as a separate component next to the master, as is the case with many other manufacturers. The AS-i Master devices serve as head station of the AS-i network and are at the same time gateways to the higher-level fieldbuses. "A special feature at our company is the display available on all these devices for fast on-site diagnostics," explains Sven Meister, Key Account Manager at Bihl+Wiedemann. " The user can see at a glance when he opens the control cabinet, if there is anything wrong in the AS-i network. In addition, he can make settings relatively comfortably on the device without having to use external tools."
The diagnostic functions in these safe small controllers are very important to the developers at Bihl+Wiedemann and are correspondingly extensive. Therefore they have implemented a lot of capabilities in the devices, so that the user does not need any further tools or sensors to be able to comprehensively diagnose the network. This starts with the AS-i-typical symmetry measurement of the symmetrical bus system, goes over voltage and current measurements including interference voltage detection up to the double address detection in order to detect problems with bus participants.

In the diagnostic software, general device data can be read out as well as system errors. The user interface is clear and uncluttered.

In addition, there is a complete shutdown history including detailed, uninterrupted status information about all AS-i components. In this way, the higher-level control system can react more quickly to faults and thus, under certain circumstances, considerably reduce downtimes.

Diagnosis and troubleshooting from outside

In order to make the possibilities of the devices even easier to handle, the engineers of Bihl+Wiedemann have now developed a new PC software, which can be used to make the extensive diagnostic data available on a standard laptop, for example. Behind the program with the somewhat unwieldy name "Software for diagnosis, service and release measurements" lies a useful helper that puts complex functionality into a simple and user-friendly interface.

Extensive safety portfolio: On the left the AS-i Safety 4E/2A Module BWU2314, in the middle the AS-i Safety Input Module BWU2631 in IP67 with four M12 inputs. Right the safe small controller with integrated fieldbus interface and connected expansion modules.

Especially the simplicity of operation was the focus of the developers. The program gets by with few buttons, there are only a manageable number of options and parameters. "It was important to us that basically anyone can operate the program," explains Meister. "AS-i is mostly only a small part of a plant. Understandably, hardly any user has the time or interest to get into all the details. We take this complexity from the users. You have to enter the interface or IP address and press start, that’s it."The software works with all devices of the Mannheim manufacturer, it accesses the measurement technology and log files directly in the devices. It shows all the information that the AS-i master also sees and logs it – practical for sporadically occurring errors.

If necessary, the program can be easily updated via the Internet at the push of a button. This gives the possibility to include new know-how or even new methods, e.g. if a new AS-i device is able to measure or display something different than the ones available so far. This makes the software a future-proof investment in several ways.

Wolfgang Kraublich
Chief Editor
Design media

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