Siemens SINUMERIK 840D sl Function Manual page 467

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Position controller position setpoint filter: new jerk filter

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

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

The filter available since software version 1, which is set via:

MD32400 $MA_AX_JERK_ENABLE = 1

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.

Basic logic functions: Velocities, Setpoint/Actual Value Systems, Closed-Loop Control (G2)

Function Manual, 11/2006, 6FC5397-0BP10-2BA0

) is displayed.

Detailed description

2.5 Optimization of the control

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