Launched in 1994, AS-Interface has since become firmly established as a feeder bus from the sensor/actuator level to the higher-level control world in mechanical and plant engineering: To date, more than 37 million ASi nodes have been installed worldwide and around 7 million safety-related switching devices have also been connected via AS-Interface Safety at Work. According to Rolf Becker, Managing Director of the AS-International Association, there is no end in sight to this success story: he says that ASi is still growing at a rate of 15 to 18% per year.

Nevertheless, it was time to bring the ASi-3 generation, which has been in existence since 1999 and has been continuously developed in small steps ever since, into the digital age. Accordingly, a group of development partners - consisting of the automation technology providers Bihl+Wiedemann, ifm electronic, Murrelektronik, Pepperl+Fuchs, Phoenix Contact, Siemens and the chip manufacturer Renesas Electronics - have been working on a completely new generation of ASi since 2013, with the aim of achieving a higher data width and faster transmission times, among other things. After five years of joint development, which according to Becker cost a total of tens of millions of euros, the result - the upcoming ASi-5 - will be presented to the public for the first time at SPS IPC Drives 2018.

Rolf Becker, AS-International Association: "ASi-5 is our shuttle to digitalization!"

© AS-International

What has changed with ASi-5 compared to the previous ASi-3 solution? The number of devices increases from 62 to 96 with a 4-fold increase in data width. At the same time, the cycle time decreases from 5 ms to 1.2 ms with 24 participants and a scalable data width of 16 bits to 32 bytes. In addition, the network length doubles to 200 m per line. As far as safety is concerned, 96x16 safe I/Os can be connected in future - instead of the previous 31x1. Becker comments: "We have told ourselves that in future, it should no longer matter whether they are standard or safe I/Os in terms of the maximum number of devices that can be connected." Last but not least, ASi-5 offers significantly enhanced diagnostics compared to the previous generation. This means that acyclical services are available as well as an additional diagnostic channel parallel to the process data and therefore channel-accurate diagnostics. The data width is also increased accordingly. In short: ASi is now capable of predictive maintenance.

With these features, Becker believes that the AS-Interface is ideally equipped for the transition into the digital age and for integration into connection worlds such as IO-Link downwards and into higher-level, Ethernet-based fieldbus systems or OPC UA: "ASi will be completely universal in this respect in the future!" When asked why the development took quite a long time, the Managing Director of AS-International replies: "A major challenge in the project was that the new ASi5 chip could not be larger or more expensive than the previous one. In other words, we had to fit an extremely large amount of new functionality into the same space. The second major challenge was to ensure that we remained compatible. In other words, the infrastructure - i.e. the familiar yellow cable with the simple pircing technology without connectors and cost-intensive switches - had to be retained 1:1. As a result, this means that AS-i3 and AS-i5 are possible in mixed operation!"

The work on ASi-5 was largely completed with the presentation at SPS IPC Drives 2018. The next step will be the release of the specification for all AS-International members. Becker does not want to commit to an exact date in this regard - only this much: "The final steps are nearing completion." Regardless of this, Becker assumes that the aforementioned development partners will use their head start in the meantime and present the first ASi-5 products at the upcoming Hannover Messe.