User`s manual

G-4 Motion Mate™ DSM314 for Series 90™-30 PLCs User's Manual – January 2001 GFK-1742A
G
below represents the effective delay that would be seen across the change in position for
the sampling period in this example.
6.25 10
5
5 10
5
3.75 10
5
2.5 10
5
1.25 10
5
Time (sec)
Position (deg)
0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Figure G-2: Effective response time delay
Therefore, in the example above, the worst case error due to acceleration/deceleration can be
expressed as +/- 0.086 degrees (approximately 2 counts) of position or as 62.5 microseconds of
delay (given that the initial velocity is 0).
Note that the DSM can not deal with fractional
units and therefor the error will be rounded to the nearest count or user unit.
The formulas for determining the strobe error due to acceleration/deceleration on a Digital axis
are as follows:
Counts_of_error =
Effective_delay =
Where:
A = Acceleration/deceleration during the strobe event
T
p
= Position sampling period which is 250 microseconds
V
I
= Velocity just before the strobe
A
T
p
2
8
T
p
(V
I
+ A T
p
)
4
(2 V
I
+ A T
p
)