Aerotech UNIDEX 600 Series, Руководство пользователя

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U600 User’s Guide Parameters
Version 1.4
Aerotech, Inc.
C-111
This data is then placed into the Motion Queue, which will feed the commands to the
servo loop. The motion queue interpolates data between the points, by using a splining
algorithm (see Figure C-20).
Figure C-20. UpdateTimeSec Diagram
C.4.145.1. Effects of Decreasing the UpdateTimeSec Task
Parameter
Decreasing the UpdateTimeSec task parameter will result in more points being calculated
within a given time period. However, this is usually not relevant, since the splining
algorithm will approximate the programmed path very well with few points. A linear
move (G1) requires only two points for a perfect fit, and an arc (G2, G3) requires only
three points. All moves will always have at least two points (start and end of move), more
points has no effect on G1 moves. However, for short/fast G2, G3 moves you can end up
with only two calculated profile points on an arc. In this case, if the error is unacceptable
(see the ChordicalToleranceInch parameter) then you can lower this parameter to prevent
two-point arcs. Keep in mind also, that an UpdateTimeSec value that is too low will cause
Motion Queue Starvation during contoured moves. But if you do need a low
UpdateTimeSec to prevent two point arcs, you can raise the UpdateNumEntries parameter
to help prevent starvation. Since the profile points are generated once every polling cycle
by the CNC profiler, a minimum UpdateTimeSec parameter can be established as the
AvgPollTimeSec value that is observed during the contoured motion.
C.4.145.2. Effects of Increasing the UpdateTimeSec Task
Parameter
More typical is the need to increase the UpdateTimeSec task parameter; this may be
necessary to prevent Motion Queue Starvation. However, if the starvation occurs as a
result of contouring through moves whose duration is shorter than the UpdateTimeSec
task parameter, then this will not help eliminate Motion Queue Starvation.
For example, if UpdateTimeSec is 10 (milliseconds), but a particular move lasts only 6
milliseconds, then for that move, the two points generated will be 6 milliseconds apart,
not 10 milliseconds. A minor side effect of increasing the value for the UpdateTimeSec, is
a potential time delay of “Response Time” (see below) between the generation of motion
and its execution. This delay is seen when aborting or changing the speed of a contoured
move. (i.e. using the MFO, Jog/Interrupt or feedhold). Once a target position is passed to
the motion queue, that motion will occur as calculated, regardless of changes to the MFO,
Time
Velocity or
Position
•
•
Where
∆
t is the UpdateTimeSec
value
Profile path
∆
t
∆
t
∆
t
•
•
•