Siemens SINUMERIK 840Di Function Manual page 449

Functionality
This "deceleration axes" function blocks any path movements, but allows positioning with
approach to the target position by reducing the velocity step by step. The response
corresponds to that of a multipoint controller.
For reasons relating to position control loop stability, the position controller algorithm is
extended instead of the special positioning function "deceleration axes". It is thus also
possible to operate drives that might cause problems using the position control.
Advantages
Compared with the existing method "deceleration axes", the expansion of the position
controller algorithm provides the following advantages:
• The structure of the interpolation and control is extended only slightly.
• Traversing on the path also becomes possible; exactly which path can be foreseen
• It is much easier to configure the function.
• In particular, with feedforward control enabled, the positioning processes are faster.
Low-pass filter for analog drives
A lowpass filter connected at the position controller output now also allows the position
controller gain to be reduced quickly with increasing frequency for analog drives (axes). This
suppresses the effect of strong natural frequencies in the form of settable speed setpoint
filters.
This functionality is provided as standard for digital drives.
MD32930/MD32940
The low-pass filter is activated via setting:
MD32930 $MA_POSCTRL_OUT_FILTER_ENABLE = 1.
The filter time constant is input via machine data:
MD32940 $MA_POSCTRL_OUT_FILTER_TIME.
MD32960 "dead zone"
Non-linearities close to zero speed, such as those, which can occur when simple frequency
converters are used, are inhibited by a "dead zone" in the controller.
The threshold for system deviation, under which a speed setpoint of "zero" is output, can be
set via machine data:
MD32960 $MA_POSCTRL_ZERO_ZONE.
The "dead zone" is input in MD32960 for each individual encoder.
Velocities, Setpoint/Actual-Value Systems, Closed-Loop Control (G2)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
Thus, this axis automatically has all the properties of a normal axis.
considerably earlier, e.g. a highbay racking cage will take at different velocities. A
possible collision can thus be avoided.
Detailed Description
2.5 Optimization of the control
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