694 HEIDENHAIN Technical Manual iTNC 530 HSCI
6.4.12 Software option 143—Load Adaptive Control (LAC)
The dynamic behavior of machines with rotary tables can vary significantly
depending on the mass moment of inertia of the fixed workpiece. The LAC
option (Load Adaptive Control) enables the control to automatically ascertain
the workpiece’s current mass moment of inertia and the friction forces.
In order to optimize changed control behavior at differing loads, adaptive
feedforward controls can exploit data on acceleration, holding torque, static
friction and friction at high shaft speeds. In this case the parameter values are
adapated using a relatively large time constant in order to ensure high
resistance to disturbances during traverse.
Using LAC in cases where the friction in the system may change considerably
and/or quickly, such as on machines with sliding guides, LAC can be used to
activate an adaptive friction model that adapts the correct parameter for the
friction current. In this case the friction model adapts to the currently effective
conditions that may vary depending on the current traversing speed, aging of
the machine or the lubrication cycles.
Adaptive feedforward control can be activated with TNCopt as of version 6.0.
It is not necessary to save compensation values or tables.
Considerations
before using LAC
Considerations before using LAC:
Is it a moving table? The characteristics of rotary tables, tilting tables or
movable tables change with the load. The mass of the workpiece can vary
significantly during machining.
Can the friction of a tool axis change depending on the load or other
mechanical influences?
Preparation and
activation
Activating LAC:
Activate LAC via TNCopt in the "Expanded compensations" menu item.
Depending on the application, you can activate different feedforward options
for the adaptive feedforward control of LAC:
Holding torque (MP2630):
Should be activated if the holding current changes with the weight of
the
workpiece. This is the case with tables functioning as vertical axes.
Basic friction (MP2610):
Should be activated if the friction changes with the weight of the workpiece.
This occurs frequently with rotary tables.
Friction at high shaft speed (MP2620):
If the friction changes at high shaft speeds, this feedforward control can be
adapted.
Acceleration feedforward control (MP2600):
If the weight of a table changes due to its load, the feedforward control is
adapted accordingly.
LAC must then be enabled for all machining axes via MP2700 bit 2.
This function is described in detail in the Help function of TNCopt 6.0. Available
as of the end of 2011.
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