6
Introduction
User Manual
for PMotion
Page 11
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The map shape wraps round. In other words the last segment connects to the first
segment. However the continuity laws across this segment to segment boundary are, by
default, different from those on all other segment to segment boundaries:
Last to first default segment boundary conditions:
Slave Derivative
Last segment to first segment boundary conditions (defaults)
Position
Specified value:
The end position of the last segment and the start
position of the first segment can both be specified. Therefore there can
be a step change in position across this boundary. You can manually
align the end position of the last segment to match the start position of
the first segment if required (linear slave axis).
Velocity
Match with previous:
Normally the start velocity of the first segment
will be automatically adjusted to match the end velocity of the last
segment.
The one exception to this rule is when all segments inherit their
velocity from the previous segment: the first segment will then start
with zero velocity. In this case use a constant velocity segment to
create any required velocity offset.
Acceleration
No value specified:
For all segment types excluding polynomial and
cubic spline the acceleration at the beginning of the first segment is
determined by the segment type.
Match with previous:
If the first segment is either a polynomial or
cubic spline segment then it automatically matches it's start
acceleration with the last segment's end acceleration. For the
polynomial segment alone this matching can be broken.
Jerk
No value specified:
The jerk value at the beginning of the first
segment is determined by the segment type. For the polynomial
segment alone this can be changed to matching or start jerk specified.
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At no instance does a map shape or map table contain any time dependent information.
The velocity and acceleration of the slave axis at any point will depend upon the velocity of
the master axis.
For the PC based Motion Generator PMotion only: to enable you to develop a map shape
that is within the physical constraints of your machinery it is possible to enter the number of
cycles per minute required. This sets the master velocity at a constant value and allows the
motion generator to put figures on the slave velocity and acceleration shapes.
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The default segment type is polynomial. This segment type is the most configurable of all
the available types and should be used in preference to another type whenever possible.
With the exception of the start of segment position parameter (which must always match
the end of the previous segment) it is possible to modify the boundary constraints for all the
derivatives at both the start and end of the segment. This means that it can be configured
to provide a smooth transition between known points.
