Changing the Face of Automation with TSN

In these types of highly automated systems, real-time communication is essential and sometimes vital. Imagine a self-driving car hesitating to brake for a pedestrian in its path or robots on an assembly line receiving delayed instructions from the computer that is synchronizing their movements.

Several real-time communication technologies, including EtherCAT, PROFINET IRT and Sercos III, are used to ensure timely communications. However, they also have compatibility issues and offer limited (if any) support for directly leveraging ongoing and future enhancements of basic IEEE 802 Ethernet technology, such as increased bandwidth.

3 Essentials Time-Sensitive Networking (TSN) Provides

1. Dependable real-time communication and feedback-free transmission of critical and non-critical traffic on the same network.
2. High bandwidth to accommodate the vast amount of sensor and background data that flows across automation networks that scales as Ethernet develops further.
3. Backward compatibility to standard Ethernet device.
   
   

What is TSN?

TSN allows networks to transmit lower-priority background traffic in a way that does not impact the time-critical traffic.

One example of time-critical traffic is used in closed-loop control: sensors react based on the control data received from the PLCs and afterward return their feedback toward the PLCs, closing the loop. At the same time, sensor-generated data on the field level that isn’t time-sensitive is transmitted on the same network infrastructure and is aggregated in the local automation cloud and subjected to big-data analysis.

This process is the implementation of the sensor to the cloud vision. Automation networks start at the sensor that’s directly connected to the primary manufacturing process and, in its most complex variant, end within a cloud infrastructure service at the factory backbone or even in a remote cloud for global optimization or analysis. Messages on these networks vary in importance: They range from mission-critical through less urgent to pure background traffic. The mission-critical control traffic is used to control the manufacturing process and often has strict requirements for delivery timeliness and robustness. Less urgent sensor data is used to analyze and optimize the processes and usually does not come with timing or delivery guarantee requirements.

With TSN, all data travels the same information superhighway with urgent data given high priority. It’s sort of like an emergency vehicle lane or a bus lane on a highway except that TSN doesn’t reserve distinct traffic lanes because doing so would create inefficiencies when no critical traffic is present. TSN directs traffic to maximize use of the available bandwidth and strictly controls access to the network medium.

4 Common Network Options:

When building a network to carry both urgent and non-urgent traffic, you have four options:

1. Use TSN to strictly control network access for urgent and non-urgent traffic
2. Build completely separate networks for urgent and non-urgent traffic, a high cost option.
3. Massively oversize the network infrastructure bandwidth, a widely used but extremely expensive approach called bandwidth overprovisioning. In addition this will provide you with a statistical solution, but not one that is 100% deterministic.
4. Accept possible traffic delays in urgent mission-critical data, which usually isn't a viable option.

Of these options, the clear option of choice is the first: use TSN.

TSN is the best option not only because it works but also because it has lower costs due to only requiring one single network.

Putting TSN to Work in Automation Networks

Due to its ability to separate traffic in automation networks, TSN enables the convergence of numerous small, disconnected networks into one unified network structure. This new network can accommodate the requirements for real-time communication on a larger scale, while providing the benefits of network convergence: asset and data visibility. This is true for many different automation network markets:

Factory Automation

In factory automation, network convergence enables distributed real-time control; large machinery and numerous robots can interact with each other more precisely and flexibly than previously possible. Organizations can enable applications, such as predictive maintenance, that require the analysis of substantial amounts of sensor data. A converged network from cloud to sensor also allows secure remote access from the Internet to the production machinery to perform maintenance and other tasks remotely.

Energy Automation

In energy automation—for example, in electrical substations—TSN can be used to allow for mission-critical data, such as sampled values from voltage and current, to travel through the network to the electrical protection equipment. TSN can also be used to improve the performance of important event notifications, Generic Object-Oriented Substation Events (GOOSE), when the GOOSE protocol uses the same network infrastructure used, for example, for sensor data or network surveillance through a SCADA system.

Transportation Applications

In transportation—for example, on train networks—convenience applications such as passenger entertainment can share a network with other applications such as passenger information or control functions that are not safety relevant. In turn, safety functions can be combined with other less-critical control functions on dedicated control networks.

Automotive In-Vehicle Networks

TSN enables the convergence and replacement of many different in-vehicle communication busses to form a unified connectivity layer. TSN, with its capability to merge traffic of different priorities, feedback-free, to a single cable, is ideally suited as an in-vehicle car backbone communication technology. Car makers can use TSN in different ways depending on their architecture. For some, TSN connects only the different application domains inside the vehicle, such as drive train, body control and passenger entertainment. In other cases, TSN is also used within the individual application domains and replaces the in-vehicle car bus network altogether.

The key takeaway is that TSN enables urgent and less urgent data to share the same network infrastructure, while preventing less urgent traffic from hindering the flow of the more urgent traffic. For more information, check out this white paper on Time Sensitive Networking & Signaling Systems.