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PLCopen releases safe motion specification to plug a gap
Published:  27 July, 2017

PLCopen has released version 1.0 of its PLCopen Safe Motion specification which fills a gap in specifications released earlier by PLCopen’s motion and safety activities, which only partially described the safety aspects involving motion.

The introduction of safety-approved networks makes the control of drives and motion increasingly software-based, with hard-wired systems being replaced by software commands over networked systems. This trend is also being driven by initiatives such as Industry 4.0 which are attempting to create more flexibility, ideally while maintaining quality and price levels. However, the different networks come with different solutions, which creates problems for users especially in production environments employing combinations of networks.

To harmonise this, PLCopen started a working group on Safe Motion, which created a generic proposal to solve the motion control safety aspects over networks such as ProfiSafe, Safety-over-EtherCat, CIP-Safety-over-Sercos, OpenSafety, CC-Link IE and Mechatrolink, as well as user areas described in Omac.

There are also many commands related to safe motion, and it makes no sense that to create function blocks for all of them if the functions are largely the same.

The new system-independent specification is based on existing functions already specified in PLCopen Safety: SF_SafetyRequest. With this, most drive safety functions can be mapped easily, especially by providing a “guideline” with defined naming conventions, containing a generic scheme on how to name signals related to the functions supported by safety drives.

A grouped overview of the PLCopen safe motion functions

Combined with an I/O or drive configurator, these names can be generated automatically for the bits in the drive’s status / control word, matching the drive’s profile (symbolic names). This proposal is based on the safety functions, including all relevant parameters, being in the drive.

The new specification can be downloaded from PLCopen’s Web site.