Time-sensitive networking (TSN) is not a protocol but an update to improve the IEEE Ethernet standard … and let engineers use general-purpose Ethernet for increasingly fast and sophisticated control and automation. It includes IEEE802.1AS defining its time-synchronization scheme and IEEE802.1Qbv defining its timesharing scheme. These make for punctual and reliable data and signal transmission to get synchronized and deterministic communications over Ethernet.
In a recent conversation about TSN, Design World asked CC-Link Partner Association for the Americas director Timothy Lomax as well as CLPA-Americas manager John F. Wozniak, P.E. several questions about CC-Link IE Time Sensitive Networking (TSN) — a new network offering based on CC-Link IE. CC-Link IE TSN supports integration of Operational Technology (OT) and IT while boosting the performance and functionality automated system communications.
Here’s what Lomax and Wozniak had to say when specifically asked about how CC-Link IE TSN supports motion designs.
How does time-sensitive networking (TSN) help motion applications?
Lomax: Over the last few decades, motion control has shown incredible advancement. Today’s designs include internal processing of motion-control commands and related functions … and other hardware driving ever-increasing performance. Consider high-resolution encoders: Now these are to 24 and 25-bit resolution … and we’re constantly seeing higher resolutions from encoders for motion applications. Here and elsewhere, the trend towards higher performance continues unabated for servo motion … and these benefit from components and networking (TSN in particular) to synchronize disparate motion axes.
What are networking challenges specific to motion control?
Wozniak: For motion applications, the biggest concern isn’t necessarily network speed. Rather, it’s jitter. So an engineer can have a slow motion control … but if it exhibits absolutely zero jitter (which means that latency is always the same amount of time) it’s an acceptable motion network. Unfortunately, traffic over standard general-purpose internet protocol (IP) Transmission Control Protocol and User Datagram Protocol (TCP and UDP) networks always exhibit jitter … and signals on that network can come nanoseconds (or more) sooner or later than expected.
TSN prioritizes signals and dedicates a lane and portion of the cycle time for prioritized messages. During a blockout time preceding the reserved cycle time, messages that threaten the prioritized messages’ timing are prevented from entering the TSN switch. CC-Link IE TSN also divides messages to ensure reliability. Set timeframes for set motion signals dramatically reduce latency (jitter time) and make the system predictable and deterministic.
What other functions can CC-Link IE TSN support?
Lomax: TSN supports motion, sequence control, and safety functions and their related hardware offerings — including those for traditional I/O and safety, servo motion, CNC, and process functions. TSN even supports the challenging application of machine vision. As mentioned, the use of common Ethernet connectivity also means this TSN network supports IoT functionality.
How does CC-Link IE accommodate devices communicating at disparate speeds?
Wozniak: CC-Link IE Field runs off an ASIC and is fixed at 1 Gbps. CC-Link IE Field Basic (the general-purpose CC-Link IE) accommodates 100 Mbps or 1 Gbps networking such as TSN. But we recognize that not everybody needs 1 Gbps … and these engineers can execute slower software implementations while maintaining a path to motion and TSN. They can put lower-level software devices on TSN that may transmit messages once every five seconds, but that’s not going to affect devices sending messages once every millisecond. Other networks wait for the former to transmit; in contrast, TSN (and CC-Link IE-implemented TSN) proceeds with handling the every-millisecond signals and “works in” the every-five-second messages.
It’s a network that satisfies an array of applications, including those that have cost constraints … because it’s a software-based network that accepts slower devices … and it’s not expensive. In fact, CC-Link IE TSN lets engineers use hardware or software for masters or slaves (and not just ASICs) for one or the other or both. This is one of the few networks that lets engineers employ software-software, hardware-hardware, or any mixture of hardware and software to get a complete network.
How does CC-Link IE TSN enable IIoT functionality?
Lomax: CC-Link IE TSN supports IT systems and where edge processing and computing executes — acting as one network to bridge all systems together. Key here of course is having hardware architecture to enable that — with intelligence for diagnostics, safety, and security.
Consider the automotive industry, which requires capacity and bandwidth. Many of this industry’s operations already have diagnostics to make troubleshooting machinery across vast facilities easier — because remember, these are operations so big that employees literally ride bicycles from one end of the plant to the other. So it’s helpful to know whether a problem is next door or all the way on the other side of the plant. The semiconductor industry — including teams developing the smartphone hardware of tomorrow — also needs built-in connection and connectivity from the machines in its facilities … as does the packaging industry.
Look for manufacturers developing TSN-compatible products in this realm — for sequence control, safety, robotic applications, and HMIs, and the rest of it — with not just talk about TSN but actual hardware for engineers to connect and try.
Filed Under: Motion Control Tips
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