PLCopen Motion Control specs, Part 4, underway

By Control Engineering Staff September 22, 2005
First public draft of PLCopen’s Motion Control specifications, Part 4–Interpolation—is planned for April 2006.

Part 4 of PLCopen ’s evolving suite of Motion Control specifications reportedly got off to a good start at a kick-off meeting held at Siemens AG in Nuremberg, Germany, on July 13-14, 2005. Goal of Part 4, “Interpolation,” is to define a set of extensions to “Part 1-PLCopen Function Blocks for Motion Control” and “Part 2-Extensions,” which focus on coordinated multi-axis motion in 3-D space, according to PLCopen’s managing director, Eelco van der Wal.

Specification Part 1 and 2 deal with single axis and a master/slave type of coordinated motion control, such as electronic camming and gearing. “For three-dimensional movements, one goes beyond this point via the grouping of a set of axes, without a master,” said van der Wal. Grouping the axes provides a user-friendly interface and solves specific problems associated with multi-axis systems. As an example, van der Wal cited that in case of an error with existing master/slave axes, other coupled axes are not made aware of the error and continue their movement. “By combining axes in a group one knows upfront which axes are involved and has the basis for a better error behavior,” he adds. “Interpolation brings working in motion control to a new level.”

Illustrating the added complexity of working in 3-D space, several coordinate systems are applicable (axes system, machine system, and product-related system), along with a kinematic model of the associated system mechanics. Moreover, the kinematic model normally resides in a separate software tool, such as a CAD or simulation system, explains van der Wal, “An interface is provided to incorporate such a model in the application program.”

With Part 4 underway, the current suite of PLCopen’s Motion Control specifications comprises:

  • Part 1 – PLCopen Function Blocks for Motion Control

  • Part 2 – Extensions

  • Part 3 – User Guidelines

  • Part 4 – Interpolation

  • Part 5 – Homing Extensions

Frank J. Bartos, executive editor