Siemens SINUMERIK 840Di Function Manual page 435

Supplementary condition
1. The functional expansion is available for all control variants,
2. The function can only be used on axes with two encoders:
If these conditions are not met, reset alarm 26016 will acknowledge the function when an
attempt is made to activate machine data:
MD32950 $MA_POSCTRL_DAMPING.
The function remains deactivated internally when this alarm is active.
2.5.2 Position controller position setpoint filter: new balancing filter
For speed and torque feedforward control
Application
With feedforward control active, the position setpoint is sent through a socalled balancing
filter before it reaches the controller itself. It is thus possible to feedforward control the speed
setpoint at 100%, without resulting in overshoots when positioning.
Functionality
Until now, it was possible to compensate the negative effects of the balancing filter (a low
pass with settable time constant), which has remained unchanged since SW 1 and which
has admitted instead of an overshoot also undesired undershoots of some 10 micrometers,
as follows:
• Setting a compromise of overshoots and undershoots
• Setting the positioning slightly overshooting and reducing the amplitude of these
• Setting a speed controller with reference model instead of PI behavior
• Setting the filter time to zero and setting the feedforward control factor to a value less
• Sacrificing the feedforward control and bringing the machine to a very high position
With SW 5 and higher, a second, improved balancing filter is therefore available.
The existing filter is still installed and is active with the same function when transferring
existing archives (e.g. in the case of upgrades).
Velocities, Setpoint/Actual-Value Systems, Closed-Loop Control (G2)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
which use SIMODRIVE 611 digital drives.
MD30200 $MA_NUM_ENCS = 2
One of the encoders must be parameterized as an indirect measuring system and the
other as a direct measuring system.
overshoots by way of position setpoint signal smoothing and jerk limitation
(only possible with 840D)
than 100%
controller gain using dynamic stiffness control.
This measure requires a stiff machine.
Detailed Description
2.5 Optimization of the control
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