
User Manual
Chapter 4
GFK-1742F
Jan 2020
Configuration
115
5.10 Command Direction. Allows an axis to be configured for unidirectional or bi-
directional operation. If unidirectional operation is selected (Positive Only or
Negative Only), servo commands in the opposite direction will not be sent to the
servo position loop. Default: Bi- directional
5.11 Axis Direction For all digital servos, a configured axis direction of Normal defines the
positive axis direction as counterclockwise (CCW) motor shaft rotation when viewed
looking into the motor shaft. A configured axis direction of Reverse defines the
positive axis direction as clockwise (CW) shaft rotation.
For analog servos, a configured axis direction of Normal defines the positive axis
direction as encoder channel A leading channel B. A configured axis direction of
reverse defines the positive axis direction as encoder channel B leading channel A. In
practice, the axis direction configuration allows the user to easily reverse the motion
caused by all commands without having to change the motion program. Default:
Normal
5.12 Feedback Source. This configuration item is unused in the present DSM314
firmware. It must be set to Default.
5.13 Feedback Mode. Only used when the Axis Mode is set to Digital Servo. This item
configures Incremental or Absolute feedback type for the serial encoder.
Incremental means the serial encoder is being used as an incremental encoder and
encoder battery alarms will not be reported. Absolute means the serial encoder is
being used as an absolute encoder (encoder backup battery installed), which
maintains position if system power is cycled. In Absolute mode, encoder battery
alarms will be reported. See appendix C, Position Feedback Devices, for more
information. Default: Incremental
5.14 Reversal Compensation. A compensation factor that allows the servo to reverse
direction and still provide accurate positioning in systems exhibiting backlash.
Backlash is exhibited by a servomotor that must move a small amount (lost motion)
before the load begins moving when direction is reversed. For example, consider a
dead bolt door lock. Imagine the servo controls the key in the lock and the feedback
reports bolt movement. When the servo turns the key counterclockwise, the bolt
moves left. However, as the
servo turns the key clockwise, the bolt does not move until the key turns to a certain
point. The Reversal Compensation feature adds in the necessary lost motion to
quickly move
the servo to where motion will begin on the feedback device. The DSM314 removes
the compensation distance when a move in the negative direction is commanded
and adds the compensation distance before a move in the positive direction.
Default: 0.
Note:
Reversal compensation is not available if the Follower Control Loop configuration is set
to Enabled.