Part 4 of the PLCopen
suite of specifications is focused to the coordinated multi-axes motion in 3D
space, to serve the majority of user's application needs in this area.
Part 1 and Part 2 of the PLCopen Motion Control suite deal with master / slave motion control, a type of coordinated motion control where the master axis position is used to generate one or more slave axis position commands. For multi dimensional movements, one goes beyond this point via a grouping of a set of axes, without a master axis.This is done via the definition of a set of Function Blocks with related coordinated motion functionality as well as a higher level state diagram, linking the single axis state diagrams in the group. In this way a better trajectory planning is possible. Also, the current Master/Slave axes can have the problem that if an error occurs, the other axes have no knowledge about this, 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.
The following function
blocks deal with a master/ slave relationship between a single or group of axes
and a single or group of axes for coordination purposes. There are two kinds of
coordinated motion that have to be distinguished from a programming point of
view and in the realization of the motion control itself. These two modes are
identified here through their names: Synchronization and Tracking. The
differences and related FBs are shown in the next figure:
Then there are other
FBs defines, most without motion:
Part 1 and Part 2 of the PLCopen Motion Control suite deal with master / slave motion control, a type of coordinated motion control where the master axis position is used to generate one or more slave axis position commands. For multi dimensional movements, one goes beyond this point via a grouping of a set of axes, without a master axis.This is done via the definition of a set of Function Blocks with related coordinated motion functionality as well as a higher level state diagram, linking the single axis state diagrams in the group. In this way a better trajectory planning is possible. Also, the current Master/Slave axes can have the problem that if an error occurs, the other axes have no knowledge about this, 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.
The
level of the PLCopen Motion Control Function Blocks are specified at such a
level that the user quickly recognizes the functionality of the function block
and what happens if it is activated or connected to other blocks in a sequence
of motion commands. This PLCopen initiative transforms the functionalities as
known in the CNC and Robotic world to the PLC world.
Overall
there are a number of sets of function blocks defined to do this, as shown below.
without going into details.
The
first step is to group axes. The following FBs are defined for this:
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The
next step is to link the transformations:
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Overview
of the coordinate systems and transformations
- ACS Axis related
- MCS Machine related
- PCS
Product or Workpiece related
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Axes
Group Synchronized Motion
The following function
blocks deal with a master/ slave relationship between a single or group of axes
and a single or group of axes for coordination purposes. There are two kinds of
coordinated motion that have to be distinguished from a programming point of
view and in the realization of the motion control itself. These two modes are
identified here through their names: Synchronization and Tracking. The
differences and related FBs are shown in the next figure:
Graphical explanation of coordination
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