Forward Feed Control For Command- And Plc Axes - Siemens SINUMERIK 840D sl Function Manual

Compensations (K3)
5.5 Dynamic feedforward control (following error compensation)
Effect on servo gain factor
When the feedforward control is set correctly, the response to setpoint changes in the
controlled system under speed feedforward control is as dynamic as that of the speed
control loop or, under torque feedforward control, as that of the current control loop, i.e. the
servo gain factor set in machine data
MD32200 $MA_POS_CTRLGAIN (servo gain factor)
has very little influence on the response to setpoint changes (e.g. corner errors, overshoots,
circle/radius errors).
On the other hand, feedforward control does not affect the disturbance characteristic
(synchronism). In this case, the servo gain factor entered in MD32200 is the active factor.
Service display "Servo gain factor"
When a feedforward control is active, the servo gain of the axis (corresponds to servo gain
factor applied to response to setpoint changes) shown in the Service display is very high.
5.5.2

Forward feed control for command- and PLC axes

Function
To prevent the activation/deactivation of the feedforward control at higher speeds you must
set the following machine data:
MD32630 $MA_FFW_ACTIVATION_MODE = 2
In MD32630 = 2, the FFWON/FFWOF- instruction for this axis is effective only below the
stoppage velocity
MD36060 $MA_STANDSTILL_VELO_TOL (threshold velocity/speed of axis/spindle
remains).
If the switchover instruction coincides with an axis motion, the required switchover is
executed only in the next stoppage condition of the axis. This way one can avoid a sudden
impact of the following error.
NOTICE
A stoppage velocity set to a very high value can lead to the changeover of the feedforward
control in the movement. Controls can be activated depending on the existing following
error.
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Function Manual, 01/2008, 6FC5397-1BP10-3BA0
Extended Functions