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
87
2.5.6 Expansions for "deceleration axes"
Application
In the case of designconditioned nonlinearities and elasticities, as often occurs in material
handling and highbay racking technology, it is often necessary to sacrifice the position
control due to the unstable position control loop. The axes are, therefore, traversed closed-
loop controlled and not open-loop controlled. To this aim, the WF723 module offers the
special function of the "deceleration axes".
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.
Thus, this axis automatically has all the properties of a normal axis.
• Traversing on the path also becomes possible; exactly which path can be foreseen
considerably earlier, e.g., a highbay racking cage will take at different velocities. A
possible collision can thus be avoided.
• 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.
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