Gain Factor Change - Siemens SINUMERIK 840C Installation Instructions Manual

11.92

Gain factor change

In the positioning mode it must be possible to drive the spindle to a target position from full
speed under position feedback control. The spindle must be held at the target position even
when there is drift.
To ensure that the spindle is steady at rest, even in the presence of drift, very small set
speeds with very high resolution must be given to the drive actuator via the analog interface.
The speed setpoints are transferred as voltage signals via the analog interface between control
system and drive actuator. Under some circumstances the control behaviour can be improved
by increasing the voltage level (relative to the set speed) because it enables a higher
resolution to be achieved and the analog interference noise can be reduced.
Consequently, with some drive actuators, such as the SIMODRIVE 650, a different scaling for
the set speeds (voltage levels) can be selected by applying a configurable terminal signal.
This changing of the scaling in the drive actuator must be allowed for in the control so that,
overall, the effective gain factor remains the same. The gain factor (dependent on gear ratio,
MD 435* to 442*) must be adapted to the new scaling.
The factor for gain changing is entered as machine data. The value is calculated from:
1
MD 469* =
N
Changing of the gain factor must be initiated by the PLC user program with the interface signal
CHANGE GAIN FACTOR (DW K + 1, bit 15).
The diagram below is intended to illustrate the changeover process using SIMODRIVE 650 as
an example.
IS:CHANGE GAIN FACTOR
a
Following
error
Gain
factor
Simplified block diagram
© Siemens AG 1992 All Rights Reserved
SINUMERIK 840C (IA)
where N = scaling factor in the drive
actuator
SINUMERIK
SIMODRIVE
DAC
MD
469*
6FC5197- AA50
12 Functional Descriptions
12.7.2 Description of the spindle modes
Terminal for M19
b
ADC
P-54
12–47