Siemens SINUMERIK 840D sl, Function Manual

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Detailed description
2.5 Optimization of the control
Basic logic functions: Velocities, Setpoint/Actual Value Systems, Closed-Loop Control (G2)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
79
2.5.3 Position controller position setpoint filter: new jerk filter
Application
In some applications, such as when milling sculptured surfaces, it can be advantageous to
smooth the position setpoint curves to obtain better surfaces, due to reduced excitations of
machine vibrations.
Functionality
The filter effect of the position setpoints must be as strong as possible without impermissibly
affecting contour accuracy.
The smoothing behavior of the filter must also be as "symmetrical" as possible, i.e., if the
same contour was to be traveled in both forward and reverse, the characteristic rounded by
the filter should be as similar as possible in both directions.
The effect of the filter can be monitored by means of the effective servo gain factor (K
V
),
which is displayed on the Axis service screen form. The filtering effect rounds the position
setpoints slightly, thus reducing the path accuracy so that with increasing filter time a smaller
effective servo gain factor (K
V
) is displayed.
Advantages
The filter available since software version 1, which is set via:
MD32400 $MA_AX_JERK_ENABLE = 1
and
MD32410 $MA_AX_JERK_TIME = filter time,
meets the requirements for a strong filter effect with smoothing behavior that is as
symmetrical as possible for small time constants of up to approximately 10 ms.
A considerably better result is achieved using this new filter type for axial jerk limitation with
floating averaging. In this case, filter time constants of approx. 20 to 40 ms can be used,
depending on the particular machine.
Thanks to the floating averaging, the new filter achieves lower contour errors with the same
smoothing effect, compared with the previous 2nd degree filter type. The contour of the
smoothing behavior is to a large degree balanced.