Delta Tau GEO BRICK LV Manuale Utente
Turbo PMAC User Manual
308
Writing and Executing Motion Programs
Because of the nature of the lookahead calculations – trajectory calculations are done well in advance of
the actual move execution, and moves are kept within machine limits by the automatic adjustment of
move speeds and times – they are not appropriate for some applications. Any application requiring quick
reaction to external conditions should not use lookahead. Also, also any application requiring precise
synchronization to external motion, such as those using PMAC’s external time base feature, should not
use lookahead.
the actual move execution, and moves are kept within machine limits by the automatic adjustment of
move speeds and times – they are not appropriate for some applications. Any application requiring quick
reaction to external conditions should not use lookahead. Also, also any application requiring precise
synchronization to external motion, such as those using PMAC’s external time base feature, should not
use lookahead.
When the lookahead function is enabled, Turbo PMAC will scan ahead in the programmed trajectories,
looking for potential violations of its position, velocity, and acceleration limits. If it sees a violation, it
will then work backward through the pre-computed buffered trajectories, slowing down the parts of these
trajectories necessary to keep the moves within limits. These calculations are completed before these
sections of the trajectory are actually executed.
looking for potential violations of its position, velocity, and acceleration limits. If it sees a violation, it
will then work backward through the pre-computed buffered trajectories, slowing down the parts of these
trajectories necessary to keep the moves within limits. These calculations are completed before these
sections of the trajectory are actually executed.
Turbo PMAC can perform these lookahead calculations on LINEAR and CIRCLE mode moves. The
coordinate system must be put in segmentation mode (Isx13 > 0) to enable lookahead calculations, even if
only LINEAR mode moves are used. (The coordinate system must be in segmentation mode anyway to
execute CIRCLE mode moves or cutter radius compensation.) In segmentation mode, Turbo PMAC
automatically splits the moves into small segments, which are executed as a series of smooth splines to re-
create the programmed moves.
coordinate system must be put in segmentation mode (Isx13 > 0) to enable lookahead calculations, even if
only LINEAR mode moves are used. (The coordinate system must be in segmentation mode anyway to
execute CIRCLE mode moves or cutter radius compensation.) In segmentation mode, Turbo PMAC
automatically splits the moves into small segments, which are executed as a series of smooth splines to re-
create the programmed moves.
Turbo PMAC stores data on these segments in a specially defined lookahead buffer for the coordinate
system. Each segment takes Isx13 milliseconds when it is put into the buffer, but this time can be
extended if it or some other segment in the buffer violates a velocity or acceleration limit.
system. Each segment takes Isx13 milliseconds when it is put into the buffer, but this time can be
extended if it or some other segment in the buffer violates a velocity or acceleration limit.
This technique permits Turbo PMAC to create deceleration slopes in the middle of programmed moves, at
the boundaries of programmed move, or over multiple programmed moves, whichever is required to
create the fastest possible move that does not violate constraints. All of this is done automatically and
invisibly inside the Turbo PMAC; the part programmer and operator do not need to understand the
workings of the algorithm.
the boundaries of programmed move, or over multiple programmed moves, whichever is required to
create the fastest possible move that does not violate constraints. All of this is done automatically and
invisibly inside the Turbo PMAC; the part programmer and operator do not need to understand the
workings of the algorithm.
The following diagram shows the principle of how the lookahead function can create acceleration and
deceleration profiles automatically over multiple programmed moves. In this case, the programmed
moves are too short to permit the full acceleration to and from programmed speed in a single programmed
move. Without any change to the motion program, the lookahead function will create a profile that does
not violate acceleration constraints.
deceleration profiles automatically over multiple programmed moves. In this case, the programmed
moves are too short to permit the full acceleration to and from programmed speed in a single programmed
move. Without any change to the motion program, the lookahead function will create a profile that does
not violate acceleration constraints.
Lookahead for Multi-Block Accel / Decel
ACCEL & DECEL TIME MUST BE EQUAL TO
OR SHORTER THAN BLOCK MOVE TIME
ACCEL & DECEL ARE CONTROLLED BY
SPECIFIED ACCEL LIMIT (G’s)
Before Lookahead
F100
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DWELL50
X1
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DWELL50
After Lookahead
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