Siemens SINUMERIK 840C - Manual (Page 893)

12 Functional Descriptions 04.96
12.16 Quadrant error compensation (SW 2 and higher)
12.16 Quadrant error compensation (SW 2 and higher)
12.16.1 Corresponding data
MD 1232* Compensation value in range 2
1236* Comensation time constant
1240* Compensation value in range 4
1244* Upper limit range 1 (a
1
)
1248* Upper limit range 2 (a
2
)
1252* Upper limit range 3 (a
3
)
1256* Smoothing time constant
MD 1804, bit 6 Quadrant error compensation
1804, bit 7 Adaptation
Technical reasons for quadrant error compensation
If an axis is accelerated from a negative to a positive velocity (or vice versa), it sticks when
passing through zero speed because of the changing friction 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 moment can be compensated for by applying an additional speed setpoint pulse (with a
high enough amplitude and correct sign).
Other measurements have shown that the compensating amplitude of the friction feedforward
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 quadrant error compensation (QEC) with adapted amplitude
has been developed.
12.16.2 Parameterization
Quadrant error compensation is activated axis-specifically via MD 1804*, bit 6. If MD 1804*, bit
7 is set, the adaptation characteristic (see Fig. 1) also becomes active.
The following machine data are available for parameterization:
MD 1232* Compensation value in range 2 [0.1 mV] [0.01 %] 1)
MD 1236* Compensation time constant [0.1 ms]
MD 1240* Compensation value in range 4 [0.1 mV] [0.01 %] 1)
MD 1244* Upper limit range 1 (a
1
) [100 units MS/s 2 ]
MD 1248* Upper limit range 2 (a
2
) [100 units MS/s 2 ]
MD 1252* Upper limit range 3 (a
3
) [10000 units MS/s 2 ]
QEC is the abbreviation for Quadrant Error Compensation
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SINUMERIK 840C (IA)