Siemens SINUMERIK 840C - Manual (Page 890)

10.94 12 Functional Descriptions
12.14.1 Feedforward control
Setpoint smoothing
A position overshoot may occur even when the dynamic feedforward control setting is correct.
In this case, an additional PT1 element (setpoint smoothing filter) can be used to slightly flatten
the position setpoint ramps or to smooth the setpoint peaks so that the position control has
enough time to correct the setpoint changes.
Note:
From software version 3 of the SINUMERIK 840C onwards, the machine data dialog includes
an optimization menu which allows settings to be optimized on the basis of measuring curves.
See Section MACHINE DATA DIALOG for further details.
12.14.2 Setpoint filter in drive (SW 4 and higher)
In conjunction with 611D feed drives or main spindle drive DSP, it is possible to activate
preliminary filters in the speed setpoint channel to allow utilization of the feedforward control
function and a high servo gain, even with high natural resonance values. This filter is
calculated in the drive and parameterized by means of drive MDs. Low-pass, band-stop and
compensation filters are available.
It may be necessary to adjust the balancing time constant (MD 392*/MD 467*/MD 4657*) in the
control when the preliminary filter function is used. With SW 4 and higher, please note
description of "Parameter set switchover" function.
The filtering effect can be checked by means of the servo drive start-up application. The filter
functionality is available only for digital drives.
Fig. Position controller structure with filters
Setpoint smoothing filter
MD 1272* or 486*
Balancing filter
MD 392* or 467*
MD 1324*
P gain
MD 252* or 435* ff.
MD 1320* /Filter:/Low pass/Band-stop
MD 1500-1519
NC/SERVO end
Controlled system with
speed controller
D feedforward control factor
MD 1124*/ –
Speed
setpoint
Drive end
Position
setpoint
Differentiator
Differentiator Feedforward control factor
MD 312* or
MD 465*
MD 1260*
Position actual value
+
+
+
+ +
–
© Siemens AG 1992 All Rights Reserved 6FC5197- AA50 12–115
SINUMERIK 840C (IA)