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5
Safety function
The FORTiS-N FS encoder system shall provide a safe position when requested by the
evaluation unit.
The following restrictions apply to this claim:
•
The system installer must perform a verified commissioning test during installation.
•
The system repairer must perform a verified commissioning test following replacement of a
system part.
•
The maximum request rate supported is 32 kHz and 16 kHz for DRIVE‑CLiQ.
•
Electrical errors for the BiSS Safety serial interface are detected by the evaluation unit
comparing CPW and SPW content. See the data sheet BiSS Safety for RESOLUTE and
FORTiS encoders (Renishaw part no. L-9517-9884) for more information.
•
Electrical errors for the Siemens DRIVE-CLiQ serial interface are detected by the evaluation
unit comparing POS1 and POS2 content. See the relevant Siemens AG evaluation unit manual
for more information.
•
When installed correctly, the FORTiS-N FS encoder, with or without mounting spar, has a
mechanical safe position of ±1 mm.
5.1 Fault exclusions
The following will invalidate the Functional Safety certification of the FORTiS‑N FS encoder system:
•
Faults caused by cutting and reconnecting the cable or the use of a non-Renishaw cable that is
not approved.
•
Incorrect installation.
•
Dismantling.
•
Operating the system outside the limits specified in this installation guide.
5.2 Failure modes effects and diagnostics analysis
All diagnosed failure modes are detected immediately except for a position discrepancy between
the two measurement methods which is detected within 375 μs.
See
section 4
on page
10
for a summary of the FMEDA.
NOTE: For the purposes of the FMEDA calculation the following conditions have been assumed:
Method: SN29500-2005-1
Environment: Ground mobile
5.3 Installation
For the safety function to be valid the instructions detailed in this installation guide must be
followed.
5.4 Commissioning test
The following test MUST be performed when commissioning the FORTiS-N FS encoder system
and after any repair or maintenance of the system.
Resolution check
Move the axis by a known distance and confirm that the position
changes as expected. The tolerance for raising a fault condition is
relative to the safe position determined by the system manufacturer.
Temperature: 60 °C
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11
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