Rockwell Automation 57C422B 2 Axis Servo Module - Manual (Page 59)

PROGRAMMING 4-31
The tune feedforward gain command will self-tune the
feedforward gain. The feedforward gain can be used
whenever the reference to the drive is a current reference or
a velocity reference and the speed loop in the drive is a
proportional-only control. Feedforward gain should not be
used if the drive contains a proportional+ integral velocity
loop.
The feedforward gain is used to compensate for the offset
that occurs in a proportional speed regulator between set
speed and actual speed. The feedforward gain allows you to
null out this offset over the entire speed range for a fixed
motor load. However, overshoot can occur during
incremental and absolute moves. Register 8 is used to define
the maximum allowable following error. Registers 11, 12 and
13, 14 are used to limit the travel. The value chosen should
be such that no mechanical interference will occur. Registers
19, 20 should be set to 80%-90% of maximum velocity.
Registers 21 through 24 should be set to some reasonable
value, i.e., a percentage of the maximum capable by the
machine. The feedback encoder should be in "linear" mode
while this function is being performed. In order for this
command to work properly, the motor must be able to rotate
in both directions for many revolutions. If this is not possible,
this command should not be used.
The results obtained from the "tune feedforward" command
are stored in register 6.
The stop motion command is used to stop the axis. This
command works in conjunction with the “stop action” bit in
register 65.
The do cam profile command is used to execute a cam
profile stored in registers 128-2046. The time cam will be
executed as soon as this command is issued. If position cam
is enabled in register 130, the axis waits for the master
reference position to be exceeded before entering the cam
table. The axis should be less than the master reference
position when this command is issued. The "do cam profile"
command enables the test that determines whether master
position > master reference position.
The change velocity command is used after "velocity control"
mode in register 65 is set to modify the velocity of the axis.
You can also use this command to change the velocity while
making a move.