224 Rockwell Automation Publication 520-UM001I-EN-E - July 2016
Appendix E Encoder/Pulse Train Usage and Position StepLogic Application
To begin the automatic homing routine, activate the “Find Home” input and
then initiate a valid start command. The drive will then ramp to the speed set in
A562
[Find Home Freq] and in the direction set in A563 [Find Home Dir] until
the digital input defined as “Home Limit” is activated. If the drive passes this
point too quickly it will then reverse direction at 1/10th A562
[Find Home Freq]
to the point where the Home Limit switch reactivates. Approximately one second
after the routine finds home the drive will stop. Alternately, the “Find Home
Freq” and/or “Home Limit” bits in A560
[Enh Control Word] can be activated
instead of utilizing a digital input. The inputs or bits should be returned to
inactive after the routine is complete.
Encoder and Position
Feedback
d376 [Speed Feedback] indicates the measured speed feedback or the calculated
speed feedback when no feedback device is selected. Parameter d376 [Speed
Feedback] is the number value to the left of the decimal (whole number) and
d377 [Speed Feedback F] is the value to the right of the decimal (the portion less
than 1).
d378
[Encoder Speed] indicates the measured speed of the feedback device. This
is useful if the encoder is not used for motor speed control. However, the encoder
must be used for some purpose in order for d378 [Encoder Speed] to indicate a
value. Parameter d378 [Encoder Speed] is the number value to the left of the
decimal (whole number) and d379 [Encoder Speed F] is the number to the right
of the decimal (the portion less than 1).
d388
, d389 [Units Traveled x] indicate the current position of the system in
terms of units away from Home. Parameter d388 [Units Traveled H] is the
number value to the left of the decimal (whole number) and d389 [Units
Traveled L] is the number to the right of the decimal (the portion less than 1).
d387
[Position Status] indicates the status of the positioning functions. The
indication bits are:
Bit 0 “Dir Positive” indicates the current direction the drive has moved
from Home.
Bit 1 “At Position” indicates whether the drive is at its commanded
position. If the drive is within A564
[Encoder Pos Tol] of the commanded
position, this bit will be active.
Bit 2 “At Home” indicates whether the drive is at Home. If the drive is
within A564
[Encoder Pos Tol] of “Home”, this bit will be active.
After the position is reached the drive will stop. If the Find Home is removed
before the homing is complete, the drive will begin running the position
routine without the proper home. In this case Home will not be reset and the
position will be in relation to the power up position.
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