09.95
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SINUMERIK 840C (IA)
9.5 Quadrant error compensation9.5.1 General comments
Technical reasons why If an axis is accelerated from a negative to a positive velocity (or vice versa), it
quadrant error compen- sticks when passing through zero speed because of the changing friction
sation is necessary conditions. this action causes contour errors with interpolating axes. This action
seriously effects machining of circular contours, where one axis moves at the
maximum path velocity whereas the second axis is still at the quadrant transition
point. Measurements on machines have shown that this disturbing friction mo-
ment can be compensated for by applying an additional speed setpoint impulse
(with a high enough amplitude and correct sign).
Other measurements shows that the compensating amplitude of the friction feed-
forward value does not remain constant across the whole acceleration range.
Where the acceleration is higher, feedforward control must be applied with a
smaller compensation value than for smaller acceleration. For this reason, a fric-
tion compensation with adapted amplitude has been developed.
Installation The compensation value for the quadrant error compensation essentially de-
pends on the machine configuration.
The easiest way to install the quadrant error compensation is to carry out a circu-
larity test. With a circularity test, deviations from the programmed radius when a
circle is described can be measured and displayed graphically, must especially at
the quadrant transition points. To obtain an optimum compensation in the whole
working range of the friction feedforward control, the compensation dependancy
on the acceleration must also be considered. This is done by measuring this de-
pendancy at various points in the range between acceleration 0 and set maxi-
mum acceleration.
9.5.2 Circularity test (option – SW 4)
Explanation The circularity test is provided as a means of testing the contour accuracy
achieved. It is implemented on a level above axial start-up since the functions
involved are applied generally rather than to one specific axis.
This circularity test can be used to check the neuronal as well as the conven-
tional quadrant error compensation. Since this test function displays a number of
important guide quantities, it also facilitates setting of the conventional QEC.
Notes At least 2 axes must be defined or else activation of the circularity test function is
disabled with error message 160107 “Axes not configured”.
The circle must be specified by means of an NC part program, i.e. the circularity
test is a pure measurement function.
Selection The circularity test display can be called by means of softkeys Diagnosis,
Start-up and Drive servo startup.
9 Drive Servo Start-Up Application (as from SW 3)
9.5 Quadrant error compensation