Siemens SINUMERIK 840D sl Function Manual page 363

MD32620 $MA_FFW_MODE (feedforward control mode)
Value Meaning
3
4
Activating and deactivating via the part program
Part programs can be used to activate and deactivate the feedforward control for all axes,
using commands FFWON and FFWOF.
If the feedforward control of the individual axes should not be influenced by FFWON/FFWOF, the
setting in the following machine data must be changed for these axes:
MD32630 $MA_FFW_ACTIVATION_MODE (activate feedforward control from program)
Parameterization
Recommended setting for recommissioning
If recommissioning, or if default values have been loaded (switch position 1 on commissioning
switch and POWER ON), the following machine data default values apply:
● MD32620 $MA_FFW_MODE = 3
● MD32610 $MA_VELO_FFW_WEIGHT (feedforward control factor for the velocity
feedforward control) = 1
The balancing time for the speed feedforward control then just has to be adjusted in the
following machine data:
MD32810 $MA_EQUIV_SPEEDCTRL_TIME (equivalent time constant speed control loop for
feedforward control)
Setting the equivalent time constant of the speed control loop (MD32810)
We recommend that the axis be allowed to move in and out in "AUTOMATIC" mode with a
part program and that travel-in to the target position, i.e. the actual position value of the active
measuring system, be monitored with the servo trace.
The initial value for setting is the time constant of the speed control loop. This can be read
from the reference frequency characteristic of the speed control loop. In the frequent case of
a PI controller with speed setpoint smoothing, an approximate equivalent time can be read
from drive machine data p1414, p1415, p1416 and p1421.
This start value (e.g. 1.5 ms) is now entered:
MD32810 $MA_EQUIV_SPEEDCTRL_TIME = 0.0015
The axis then travels forward and backward and the operator monitors a greatly-magnified
characteristic of the actual position value at the target position.
Basic Functions
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
G2: Velocities, setpoint / actual value systems, closed-loop control
Speed precontrol
Combined torque/speed precontrol
7.6 Optimization of the control
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