Rockwell Automation 1746-HSTP1 Stepper Controller Module/ User Manual - Manual (Page 47)

Publication 999-121 - December 1999
5-12 Configuration and Programming
In an absolute move, the number of pulses generated by the Module
equals the difference between the target position (destination) and the
current position.
In a relative move, the target position defines the distance (in pulses)
that must be traveled relative to the current position.
Normally, both types of move accelerate to the programmed velocity
(slew speed) at the commanded acceleration rate; continue at the
velocity to a predetermined point; and then decelerate to the target
position at the commanded deceleration rate to the starting speed and
stop. This type of move generates a trapezoidal velocity profile, as
illustrated below.
However, if a commanded move is not long enough to attain the
programmed velocity before the deceleration point is reached, a
triangular velocity profile is generated. This profile is shown below.
Blended Moves permit more sophisticated velocity profiles. The figure
below is an example of a move containing 2 segments blended
together.
Upon successful completion of each move, the “move complete” bit
(7) of command mode input word 0 is set, permitting the next move
to proceed. Failure to complete a move generates an error signal,
which sets the appropriate error flag in the command mode input
word image table (bit 11, 12 or 13).
Trapezoidal velocity profiles
with programmable acceleration/
deceleration pulse rates.
Starting
Speed
Velocity
Time
Starting
Speed
Velocity
Time
Blended velocity profiles to
permit high speed traverse and
low speed positioning moves.
Starting
Speed
Velocity
Time