194 Rockwell Automation Publication 520-UM001A-EN-E - February 2013
Appendix E Encoder/Pulse Train Usage and Position StepLogic Application
overshoot, the filter should be increased and/or the gain should be reduced. In
general, the gain will have a larger effect on most systems than the filter.
Homing Routine
This drive supports incremental encoders only. Therefore, when the drive powers
up it will reset the current position to zero. If this is known to be correct the
position routine can be started without further adjustment. However, in most
applications the drive will need to be “homed” after each power-up and prior to
starting the position routine.
This can be accomplished in one of the following two ways:
1. Manual Homing–Program the following drive parameters:
t062
, t063, t065...t068 [DigIn TermBlk xx] = 37 “Pos Redefine”
Program one of the digital inputs to 37 “Pos Redefine”. Then, move the
system into the home position with a run command, a jog command, or by
manually moving the system into the home position. Then, toggle the “Pos
Redefine” input. This will set the drive to “Home” at its current position
and d388
[Units Traveled H] and d389 [Units Traveled L] are set to zero.
Alternately, the “Pos Redefine” bit in A560
[Enh Control Word] can be
toggled instead of utilizing a digital input.
2. Automatic Homing to Limit Switch–Program the following drive
parameters:
t062
, t063, t065...t068 [DigIn TermBlk xx] = 35 “Find Home”
Program one of the digital inputs to 35 “Find Home”.
t062
, t063, t065...t068 [DigIn TermBlk xx] = 34 “Home Limit”
Program one of the digital inputs to 34 “Home Limit”. Normally, the
“Home Limit” input would be wired to a proximity switch or photo-eye
and will indicate the system is in the home position.
A562
[Find Home Freq] sets the frequency the drive will use while it is
moving to the home position during the automatic homing routine.
A563
[Find Home Dir] sets the direction the drive will use while it is
moving to the home position during the automatic homing routine.
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
The “Pos Redefine” input or bit must be returned to inactive before
starting the position routine. Otherwise the drive will continuously read
a position of “0” (home) and the position routine will not function
correctly.
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