User`s manual

1-10 Motion Mate™ DSM314 for Series 90™-30 PLCs User's Manual – January 2001 GFK-1742A
1
Standard Mode Operation
Figure 1-2 is a simplified diagram of the
Standard
mode Position Loop. An internal motion
Command Generator provides
Commanded Position
and
Commanded Velocity
to the Position
Loop. The Position Loop subtracts
Actual Position
(Position Feedback) from
Commanded
Position
to produce a
Position Error
. The
Position Error
value is multiplied by a Position Loop
Gain constant to produce the Servo Velocity Command. To reduce
Position Error
while the servo
is moving,
Commanded Velocity
from the Command Generator is summed as a Velocity
Feedforward term into the Servo Velocity Command output.
The following items discussed above are included in the data reported by the DSM314 to the PLC:
Commanded Velocity
- the instantaneous velocity generated by the DSM314’s internal
path generator.
Commanded Position
- the instantaneous position generated by the DSM314’s internal
path generator.
Actual Velocity
- the velocity of the axis indicated by the feedback.
Actual Position-
the position of the axis indicated by the feedback.
Position Error
- the difference between the
Commanded Position
and the
Actual
Position
.
The DSM314 allows a
Position Loop Time Constant
(in units of 0.1millisecond) and a
Velocity
Feedforward
(in units of 0.01 percent) to be programmed. The
Position Loop Time Constant
sets the Position Loop Gain and determines the response speed of the closed Position Loop. The
Velocity Feedforward
percentage determines the amount of
Commanded Velocity
that is summed
into the Servo Velocity Command.
POS LOOP
GAIN
COMMAND
GENERATOR
CMD VELOCITY (VELOCITY FEEDFORWARD)
CMD
POSITION
POSITION
FEEDBACK
POS
ERROR
SERVO
VEL
CMD
SERVO
AMPLIFIER
MOTOR
ENCODER
JOG
MOVE
AT VEL
MOTION
PROGRAMS
+
-
+
+
Figure 1-2. Simplified Standard Mode Position Loop with Velocity Feedforward