Siemens SINUMERIK 840D sl Function Manual page 406

Compensations (K3)
Dynamic feedforward control (following error compensation)
With this value the following error will be reduced to nearly zero (i.e. control deviation is 0)
when speed is constant. This should be checked by making positioning movements based
on the actual "control deviation" shown on the service display.
References:
/FB1/ Function Manual, Basic Functions; Diagnostics Tools (D1)
MD32810 fine adjustment
Minor alterations (fine tuning) to the values in MD32610 and MD32810 can be made to
obtain the required response for the relevant axis/spindle.
This is done by traversing the axis/spindle at a constant velocity and checking the affect of
the changes made in the machine data in the service display 'Control deviation'. The
adjustment criterion for the speed feedforward control is 'control deviation' = 0
● Case 1:
● Case 2:
A small acceleration and a large feedrate should be chosen so that the values can be easily
read on the service display. This produces very long acceleration phases from which it is
easy to read off the control deviation.
References:
/FB1/ Function Manual, Basic Functions; Velocities, Setpoint-Actual Value Systems, Closed-
Loop Control (G2), Chapter "Optimization of Control"
406
When the axis is traveling in a positive direction, the 'control deviation' shows a positive
value,
→ the equivalent time constant of the speed control loop or the feedforward control factor
is too small.
When the axis is traveling in a positive direction, the 'control deviation' shows a negative
value,
→ the equivalent time constant of the speed control loop or the feedforward control factor
is too large.
Function Manual, 03/2009, 6FC5397-1BP10-4BA0
Extended Functions