Siemens SINUMERIK 840D sl Function Manual page 84

Basics on the Safety Functions Integrated in the System/Drive
5.4 Actual value conditioning
1-encoder system
For a 1-encoder system, the incremental or absolute encoder of the motor is used
for the safety-relevant actual values of the NC and drive.
The actual values are generated in a safety-relevant fashion either directly in the
encoder or in the Sensor Module and are provided – with no-reaction – to the NCK
and the drive using safety-relevant communications via DRIVE-CLiQ.
Special feature regarding linear motors:
For linear motors, the motor encoder (linear scale) is also the measuring system at
the load. IMS and DMS are one measuring system. The connection is made at the
IMS input of the Sensor Module or directly via DRIVE-CLiQ.
Significance of the coarse encoder position:
For a 1-encoder system, for all position monitoring functions, the accuracy of the
redundant actual value must be assumed to apply. This accuracy depends on the
encoder evaluation. For all encoder evaluation functions that can be used with Sa-
fety Integrated (SME, SMC, motor with DRIVE-CLiQ), the coarse encoder pulses
are redundantly counted including the quadrupling (coarse encoder position). The
machinery construction OEM must select the appropriate encoder with the neces-
sary encoder pulse number for his particular requirements. To do this, the encoder
resolution must be converted to the accuracy on the load side. This conversion is
dependent on the type of encoder mounting and the type of axis. Further, gearbox
factors, the spindle pitch for linear axes and the radius of the rotary table for rotary
axes must also be taken into account.
Sensor Module cabinet mounted (not used
for encoders with DRIVE-CLiQ interface)
Fig. 5-1 1-encoder system for a feed drive (FD)
2-encoder system
In this case, the safety-relevant actual values for an axis are supplied from 2 sepa-
rate encoders. In standard applications, the drive evaluates the motor encoder
(IMS) and the NC, the measuring system (DMS).
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SINUMERIK 840D sl/SINAMICS S120 SINUMERIK Safety Integrated (FBSI sl) – 03.2006 Edition
DRIVE-CLiQ
Encoders
Gear
Motor
(FD)
Machine table
Back–
lash
© Siemens AG, 2006. All rights reserved
03.06