Technology Option F01 08.2012
6SE7087-6QX70 (Version AN) Siemens AG
9-170 Compendium Motion Control SIMOVERT MASTERDRIVES
9.8.18 Configuring and testing the virtual master axis
Commissioning step:
Commission the virtual master axis:
(you can skip this step if you only want to use the positioning functions)
The virtual master axis [832] generates a path setpoint KK817 and a
velocity setpoint KK816 [832.8] for drives that are to be operated in
synchronism. These setpoints are normally distributed to the drives
over the SIMOLINK drive interface. The common velocity ramp-function
generator for all drives should be calculated on the drive on which the
virtual master axis is activated. The velocity setpoint that the ramp-
function generator is to reach can be transmitted via a field bus
(PROFIBUS-DP etc.) or as an analog signal.
The velocity ramp-function generator [832.5] integrated in the virtual
master axis can be used as a ramp-function generator for simple
applications and extremely short cycle times (of several 100 ms). For
more demanding technical conditions, you should use the "comfort
ramp-function generator" [790], which operates with rounded ramps
and provides a large variety of control features and selection of
acceleration/deceleration times. You can connect the output of the
comfort ramp-function generator to the virtual master axis with
U681 = 571 [832.1] and U683 = 0 [U832.3].
The virtual master axis is a separate free block (it can be used
independent of positioning and synchronization). It is activated with the
following parameter settings and should be nested in the same
sampling time as the synchronization function, e.g.:
U953.34=4 ; Nest virtual master axis in sampling time T4
;(=2
4
*T0=16*200µs=3.2 ms with converter frequency 5 kHz)
Connect the desired enable commands to the virtual master axis with
U684 and U689 [832.2].
If you use the percentage-weighted input setpoint (U683 = 0), you must
enter the maximum machine velocity in U682 [832.2]. In many cases,
this will be the value already entered in MD23 (see section 16 and
[836.7] [804]; N.B.: MD23 is entered in [1000 LU/min.] but U682 is
entered in [10 LU/min]!)
Select the master axis cycle length with U687. In many cases this will
be the number of LUs per encoder revolution or per revolution of the
gearbox output shaft, e.g.:
U687=4096 ; Example: axis cycle length[832.6] for the virtual
; master = 4096 LU equals 1 encoder revolution with
; P171=12 [330.3]
Setting the
parameters for the
virtual master axis
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