Rockwell Automation 1771-QA Stepper Positioning Assembly User Manual - Manual (Page 74)

3–52 Programming and Operation
Publication 1771-UM002A–EN–P – May 2000
If ORT
Prog
in equation 3a is zero, then ORT
Act
will be instantaneous
(<10ms).
The equation parameters (ORT
Act
, ORT
Prog
, OFR, and IR) and a
sketch of the move are shown in Figure 3.24.
Example Problem 1:
An override ramp time is programmed for 6.2 seconds. What will be
the actual override ramp time if the override is enabled while a rate
(IR) of 8k pulses per second is being executed? The final rate of the
override move is 10k.
Solution: Write down the known facts.
IR = 8k pulses per second
OFR = 10k pulses per second
ORT
Act
= 6.2 seconds
ORT
Act
+ ORT
Prog
x
|OFR–IR|
OFR
ORT
Act
+ 6.2 x
|10k–8k|
10K
+ 6.2x 2k
10k
ORT
Act
+ 1.24seconds
This is the range of 0-9.99 seconds and is therefore acceptable. If
the initial rate had been greater than 10k, then the absolute value of
|OFR-IR| (negative difference considered as if positive) would have
been used.