OpenSafety

Key takeaways

OpenSafety belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect OpenSafety to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of OpenSafety from memory before moving on to harder problems.

Reference excerpt

openSAFETY is a communications protocol used to transmit information that is crucial for the safe operation of machinery in manufacturing lines, process plants, or similar industrial environments. Such information may be e.g. an alert signal triggered when someone or something has breached a light curtain on a factory floor. While traditional safety solutions rely on dedicated communication lines connecting machinery and control systems via special relays, openSAFETY does not need any extra cables reserved for safety-related information. It is a bus-based protocol that allows for passing on safety data over existing Industrial Ethernet connections between end devices and higher-level automation systems – connections principally established and used for regular monitoring and control purposes. Unlike other bus-based safety protocols that are suitable for use only with a single or a few specific Industrial Ethernet implementations and are incompatible with other systems, openSAFETY works with a wide range of different Industrial Ethernet variants.

Certifications, approvals and key functionality openSAFETY is certified according to IEC 61508 and meets the requirements of SIL 3 applications. The protocol has been approved by national IEC committees representing over two dozen countries around the world, and has been released for international standardization in IEC 61784-3 FSCP 13. openSAFETY supports functional features to enable fast data transfer such as direct communication between nodes on a network (cross-traffic) as well as a range of measures needed to ensure data integrity and accuracy, e.g. time stamps, unique data packet identifiers, and others. One particularly notable characteristic is openSAFETY's encapsulation of safety data within an Ethernet frame: two subframes, each being an identical duplicate of the other, are combined to form the full safety frame. Each of the subframes is secured by its own checksum, which in effect provides multiple safeguards and levels of redundancy to ensure any distortions of safety data or other types of faults cannot go unnoticed.

Compatibility and open-source license In contrast to all other bus-based safety solutions on the market, which were created to complement a specific Industrial Ethernet protocol or family of bus systems, openSAFETY was designed for general interoperability. Though openSAFETY was conceived by the Ethernet POWERLINK Standardization Group (EPSG) and originally developed as a safety companion to that organization’s own Industrial Ethernet variant, POWERLINK, the safety protocol is no longer bound to POWERLINK. Instead, it can be used with various major Industrial Ethernet implementations, namely PROFINET, SERCOS III, EtherNet/IP, Modbus-TCP, and POWERLINK. This broad compatibility with about 90% of the installed base of Industrial Ethernet installations in 2010 is achieved because openSAFETY operates only on the topmost (application) layer of the network, where safety data can be trafficked irrespective of specific network characteristics that may differ from one underlying bus system to another. This approach is commonly known as "black channel" operation in communication protocol engineering.

Proof of concept presentation in 2010 A relatively late arrival on the scene, openSAFETY was first released in 2009. It is based on its immediate precursor technology, POWERLINK Safety, which was originally launched in 2007. openSAFETY won broad public attention in April 2010, when a presentation at the Hannover Messe trade show in Germany showcased four different implementations of the safety solution running in SERCOS III, Modbus TCP, EtherNet/IP and POWERLINK environments. The public presentation and open-source release of the protocol was hotly debated, with strong reactions both in favor and against the new solution, which prompted extensive reporting in the trade press. Following the major openSAFETY presentation in Hanover, proponents of the new solution gave lectures at other industry events as well, e.g. at TÜV Rheinland’s 9th International Symposium in Cologne, Germany, on 4–5 May 2010. Speaking at this conference on Functional Safety in Industrial Applications, Stefan Schönegger of Austria’s Bernecker + Rainer Industrie-Elektronik Ges.m.b.H. (B&R), a co-creator and major advocate of openSAFETY, provided an introduction to key characteristics of the new protocol. Reports on later gatherings indicate that the focus of presentations and discussions about the protocol soon shifted to specific implementation and applicability issues.

See also Functional safety IEC 61508 Ethernet Powerlink

Notes and references

External links official website official website of Ethernet POWERLINK Standardization Group Archived 2019-11-25 at the Wayback Machine download openSAFETY specification on EPSG website Archived 2016-08-30 at the Wayback Machine download openSAFETY stack on SourceForge documentation and source of openSAFETY Development Kit on SourceForge

Illustrations

openSAFETY logo

Worked examples

Example 1 — a first encounter with OpenSafety

Start with the simplest possible case. Write down what OpenSafety claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to OpenSafety before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about OpenSafety ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of OpenSafety

In research: OpenSafety appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses OpenSafety in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: OpenSafety is common in secondary-school and first-year university syllabi. It links to neighbouring topics Industrial Ethernet, Safety, so understanding it makes those chapters shorter.
In everyday life: Look for OpenSafety outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study OpenSafety in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what OpenSafety means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain OpenSafety out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is OpenSafety in simple terms?

openSAFETY is a communications protocol used to transmit information that is crucial for the safe operation of machinery in manufacturing lines, process plants, or similar industrial environments. Such information may be e.g. an alert signal triggered when someone or something has breached a light…

Why does OpenSafety matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study OpenSafety?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on OpenSafety.