Speed Feedforward Control - Siemens SINUMERIK 840D sl Function Manual

The feedforward control should only be activated or deactivated while the axis/spindle is
stationary in the axis mode, in order to prevent jerky motion. Hence the switchover is delayed
automatically up to the next standstill through block search stop.
Note
A preprocessing stop has no effect for command or PLC axes traversing asynchronously to
the part program processing. To ensure that FFWON/FFWOF only has an effect on the axis/
spindle when it is next stationary in the axis mode, you must explicitly set MD32630 = 2 for
each axis/spindle in the axis mode (see also "Forward feed control for command- and PLC
axes (Page 319)").
5.5.2

Speed feedforward control

Function
In the case of speed feedforward control, a velocity setpoint is also applied directly to the input
of the speed controller. With this value the following error can be reduced to nearly zero (i.e.
system deviation is 0) when the velocity is constant.
Commissioning
The following axis-specific parameters must be defined for the speed feedforward control
during commissioning:
Equivalent time constant of the speed control loop (MD32810)
The equivalent time constant of the speed control loop must be determined accurately (e.g.
graphically from a speed setpoint step response) and entered into the following machine data
to correctly set the speed feedforward control:
Extended Functions
Function Manual, 10/2015, 6FC5397-1BP40-5BA3
5.5 Dynamic feedforward control (following error compensation)
K3: Compensations
315