Siemens SINUMERIK 840D sl Function Manual page 408

Compensations (K3)
Dynamic feedforward control (following error compensation)
Machine data MD10082 determines the lead time for the output of speed setpoints. The
larger the value entered, the sooner the drive transfers the speed setpoints.
The following meanings apply:
● 0 %: Setpoints are transferred at the beginning of the next position control cycle
● 50 %: Setpoints are already transferred after execution of half of the position control cycle
A reasonable lead time can only be determined by measuring the maximum position control
calculating time. Machine data MD10083 suggests a value measured by the control. As this
is a net value, a security reduction of e.g. 5 % must be undertaken by the user.
Note
If lead times that are input are too high, this can cause output of drive alarm 300506.
The input value is rounded to the next lower speed controller pulse rate in the drive. If the
speed controller pulse rates of the drives are different, changing the value will not
necessarily lead to the same degree of controller improvement for all configured drives.
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Function Manual, 03/2009, 6FC5397-1BP10-4BA0
Extended Functions