PLCopen’s Function Blocks add order to motion control

Zaltbommel, Netherlands – Applying various, often incompatible motion control systems can be complex, confusing, and costly to users. PLCopen has announced some sorely needed progress in standards development for this arena with the release of ‘Function Blocks for Motion Control’ specification version 1.0, at the SPS/IPC/Drives show in Nuremberg, Germany, at the end of November 2001.

PLCopen is a vendor- and product-independent worldwide association supporting IEC 61131-3 programming standard.

The Function Blocks library – covering single-axis control and coordinated multi-axis control, among other items – has been in the works for years by PLCopen’s Task Force Motion Control, according to the organization’s managing director, Eelco van der Wal. Also included in the specs are examples on how to use the Function Blocks, along with timing diagram and error handling examples. Actually, ‘version 0.99’ of the spec was released for comment at last year’s SPS/IPC/Drives event (CE, Dec. 1, 2000, Daily News at www.controleng.com ). This was the source of ‘several hundred changes,’ which make the new version 1.0 of the document more useful, explains Mr. van der Wal.

Although based on IEC 61131-3 standard, Function Blocks for Motion Control go beyond the programming language. They focus, as well, on standardizing interfaces among different motion control solutions and promote more reuse of application software. PLCopen sees the result as less hardware dependent and less costly for training and support.

Mr. van der Wal refers to the new standardization tool as a way ‘to harmonize access of motion control functionality across platforms, ranging from centralized or integrated control to distributed control.’ The function blocks’ standardized interfaces and their derivation from IEC 61131-3 promote wide support by industry. Moreover, Function Blocks for Motion Control are ‘open to existing and future technologies.’

Further function block libraries focused on specific application areas may be added later. A .pdf file of the specification can be downloaded from www.plcopen.org free of charge.

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