Rockwell Automation 1746-HSRV SLC Servo Control Module User Manual - Manual (Page 127)

Publication 1746-6.1.2 - July 2000
8-10 Programming the SLC Processor to Run the SLC Servo Module
The Incremental Position command is active all the time. It can
execute along with other interpolated moves from the mutually
exclusive interpolated moves described in the next section except for
the blend profile move. This allows you to make offset position
adjustments while an interpolated move (i.e., absolute/incremental
move or speed move) is executing.
Since the Incremental Position command is added directly to the
commanded position in the servo loop, software overtravel limits are
not checked. You must stay within software overtravel limits when
using an Incremental Position command.
Executing Simultaneous Moves
The SLC Servo Module executes a motion block from the move
command set in conjunction with the Incremental Position command
except for the blend profile move. Incremental Position command
cannot be active when the blend move profile is executing.
When executing the Incremental Position command, the resulting
command to the servo is computed as the sum total of the
Incremental Position command from the PLC ladder and the
interpolated move command executing every coarse iteration as
shown in Figure 8.3. The move interpolator is the algorithm residing
in the module that determines position increment commanded for
coarse iteration.
Figure 8.3 SLC Processor/Servo Module Interaction During Simultaneous Move
SLC
LADDER
I/O SCAN
Servo
Command
Every
Coarse Iteration
4.8 to 9.6
Milliseconds
SLC Servo Module Execution Environment
SLC
SERVO
I/O
Image
Table
SLC LADDER
EXECUTION
IPC
Move
Interpolator
ADD