Technology
Application scenarios for Time Sensitive Networking (TSN) TIME SENSITIVE NETWORKING (TSN) has become well established in the vocabulary of the automation industry. All leading companies in this market have started activities for evaluation or even for the introduction of TSN. But what are the goals for application of TSN technology in industrial and process automation and what has already been achieved today that can be used concretely by customers? What is still missing? Many manufacturers, consortia and TSN testbeds are exhibiting TSN demonstrators showing concrete applications of this new technology with components already available today. For example, Renesas is demonstrating a Profinet PLC with IO-Link master connection via TSN based on a current chip. Depending on the requirements to be fulfilled, the implementation of such TSN-based solutions based on available hardware is rather simple. Protocols such as Profinet or Ethernet/IP can utilize TSN just by extending the Ethernet Layer 2 and without interfering with the higher protocol layers. Scheduled traffic is the most common method here, because this mechanism has already been sufficiently tested and widespread in industrial automation. Well-known systems such as EtherCAT, Profinet IRT or SERCOS III are successfully using this method, which was generalised in the course of TSN development, for years. However, TSN-based solutions have not yet really arrived in the portfolio of automation companies. The reason for this lies in the current discrepancy between the actual goals of TSN introduction and those currently achieved.
The goals
TSN is an important building block in meeting the targets set for Industry 4.0. The technology has the potential to break down the boundaries that currently exist between proprietary real-time solutions by establishing a unified standard. This makes data sharing within individual sections of a production facility simpler and transparent. Different domains can share information directly via a uniform network infrastructure, without the need for gateways or other adaptations (horizontal communication). As an example, machines from different manufacturers can be flexibly combined into production lines or exchanged between
28
SOURCE: RENESAS
TSN is an important building block in meeting the targets set for Industry 4.0. But TSN-based solutions have not yet really arrived in the portfolio of automation companies. The reason for this lies in the current discrepancy between the actual goals of TSN introduction and those currently achieved.
Automation pyramid and consistency.
different domains without having to consider communication standards that are still incompatible today. In addition, customers can implement the complete continuity of the information flow in the vertical direction, in a "Sensor to the Cloud" manner that enables new business models. A further objective is the standardisation of automation equipment and its components, which will reduce the cost of developing, manufacturing and stocking spare parts, as well as the maintenance of the production facility. Specialists personnel in design and maintenance can be deployed more flexibly, warehousing for spare parts is limited to one device type and standardised hardware components become cheaper due to the resulting higher quantities.
Requirements
This abstract goal allows for several possible solutions, which differ particularly in the
lowest level of the automation pyramid. Basically, we can distinguish between coexistence and compatibility. Coexistence or convergence means that devices can share a common network segment and communicate over it without affecting each other. Compatibility means that in addition devices can "understand" each other, i.e. share information among themselves. The real-time networks available today are predominantly neither coexistent nor compatible with each other. TSN as a uniform network standard can meet the demand for coexistence. In fact, IEEE only develops horizontal network standards that describe basic functions. For example, for "Scheduled Traffic" (IEEE802.1Qbv-2015, now adopted in IEEE802.1Q-2018), only the principle and mechanisms are defined for controlling the transmission times of Ethernet packets. However, a concrete application requires
in d u s t r ial et h er ne t b o o k
2.2020
