New!
PLCopen 15 years anniversary brochure!
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TC5 - Safety - introduction
PLCopen, together with its members and external
safety related organizations, defined safety related aspects within the IEC
61131-3 development environments. With this, the safety aspects can be supported
by a dedicated software tool, which is integrated into the software development
tools. As such it combines the logic and motion application development with
the related safety aspects. This combination helps developers to integrate
safety related functionality into their systems, even from the beginning of
the development cycle, while contributing to the understanding of safety
aspects.
Basic requirements
The basic requirements for safety application for the machine builders are independent
from the applicable safety standards:
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Separation between safety and non-safety functionality
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Deployment of applicable programming languages and language subsets
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Deployment of validated software blocks
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Usage of applicable programming guidelines
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Usage of the common known error reducing measures for the life-cycle of the safety related software
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Standardization – the way out
For users, these high demanding requirements should be controlled and
reduced. This can be done via standardized solutions with which the normal
functionalities can be easily implemented. Standardization in functionality
and the integration and support from the software tools helps the programmers
to integrate safety in their applications from the beginning, without
inhibiting their functionality and performance, and without adding costs.
This was exactly the target of the PLCopen Technical Committee 5 – Safety.
With support from nearly all relevant safety control suppliers, software
suppliers, and safety related organizations, they produced the first specification.
Included in this specification is:
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Representation of the software architecture
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Definition of the programming languages
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Presentation of safety related datatypes
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Definition of language subsets
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Definition of user levels for safe and fast programming
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Programming guidelines
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Error handling and diagnosis concept |
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Certification guidelines for the function blocks
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The definition of a set of 20 safety related function blocks.
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Overview of the applicable Function Blocks
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Equivalent
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Antivalent
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Mode Selector
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Emergency Stop
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Safe Stop 1
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Safe Stop
2
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Safely Limited Speed
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Electro-Sensitive Protective Equipment
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Safety Guard Monitoring
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Safety Guard Interlocking
with Locking
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Two-Hand Control Type II
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Two-Hand Control Type III
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Sequential
Muting
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Parallel
Muting
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Parallel Muting with 2 Sensors
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Safety Request
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Testable Safety Sensors
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External Device Monitoring
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Out Control
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Enable Switch
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User Benefits
This complete approach provides the user with a harmonized view to the
total application, safety and non-safety related application software
within one environment. And with multiple implementations, this is also
valid across platforms.
This means less educational efforts, and simpler
transfer of knowledge and application software between different controls.
Also, it tackles the ‘not-invented-here syndrome’, which often
is a cause of errors and additional costs. By using tested functionality,
and support in the programming environment, including language definition
with subsets of functionality, one is able to create safety related
application programs for easy commissioning.
Specifications
Part 1 - Concepts and Functions Blocks - is focused to the implementers of the
safety functionalities. With this part 1 the safety aspects can be transferred to a software
tool, which is integrated in the software development.
Part 2 - User Guidelines - is focused to the users of the PLCopen functionalities and
demonstrates the ease of use of the defined function blocks in real life
applications.
Certification
For quick identification of compliant products, PLCopen has developed a logo
for the Safety Specification:
In order to fulfill the requirements set, different levels of certification are applicable:
- Certification of the software tools, often part of the control supplier
- Certification / Conformity of the application at the user and/or machine builder
Ad 1: Certification of the software tool supplier
The development environment, including the safety related function blocks, as well as the underlying hardware, have to be certified by the relevant safety related bodies. In order to be able to be certified, certain rules, like described in IEC 61508 and related standards like IEC 61511, are applicable. The PLCopen specification provides a framework for this; however the overall requirements are beyond the scope of PLCopen, and have to be dealt with by external dedicated organizations.
Ad 2: Certification / Conformity of the application
Within an application, a certification includes the safety related software combined with the infrastructure, like sensors, switches and actuators, connection schemes, etc, like described in standards like IEC 62061. Certification or approvals for the application software are made easier, however the full application have to be dealt with by external dedicated organizations.
The use of the PLCopen logo does not give any guarantee about any compliance or fulfillment. The use of the logo just refers to the inclusion of the ideas and guidelines as described in this document, within the relevant software environment, and the availability of this information in more detail on the relevant section of PLCopen website.
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