Siemens SINUMERIK 840C User Manual
Page 917
12 Functional Descriptions
10.94
12.18.11 GI monitors
12.18.11.1 Monitoring for maximum velocity/speed and maximum
acceleration
The velocity/speed of the following drive is limited to a maximum velocity value (MD 280* or
403*-410*)
1)
. With an unfavourable constellation, the following drive may be influenced by the
leading drives such that it would be forced to exceed this maximum velocity in order to
maintain synchronism. However, since this is not possible, the leading and following drives fall
out of synchronism.
In order to identify and eliminate the risk of this type of disturbance in advance, the velocity of
the following drive is monitored by an additional velocity limit value (prewarning limit) in the
LINK ACTIVE state. When this limit is exceeded, the PLC interface signal VELOCITY/SPEED
WARNING THRESHOLD REACHED is set.
The user is thus able to initiate appropriate measures to reduce the velocity via the PLC. As
an example, the velocity of the leading drives can be reduced via the feed or spindle override.
In view of the reaction time, the velocity warning threshold should not be set too high as this
causes de-synchronization between the leading and following drives.
The following diagram shows the velocity monitoring functions which are available for the
following axis. The monitoring characteristics for following spindles are identical.
Diagram showing velocity monitoring functions for following axis
approx.
10
%
control reserve
NS VELOCITY WARNING
THRESHOLD REACHED
Response of drive error with following
axis (speed setpoint too high)
Limit value for velocity monitor of
following axis in LINK ACTIVE state.
2)
1)
1
Reaction
time
approx. 20 %
n
FD
Speed setpoint FD [VELO]
or [mm/min.] or [degrees/min.]
MD 264*
MD 268*
MD 280*
MD 1448*
IPO STOP with LINK OFF (FD)
Maximum velocity FD
t
[sec.]
0
1 signal =
The FD velocity has
exceeded the velocity
warning threshold
7/8 MD 1448* (percentage value
referred to maximum veloc. FD)
1) Characteristic without reduction in velocity
2) Possible velocity characteristic when F override is reduced by PLC user program
1)
As from SW 4: See functional description for ”Parameter set switchover”
12–142
© Siemens AG 1992 All Rights Reserved 6FC5197- AA50
SINUMERIK 840C (IA)