A.3.5 Vector Length Monitoring Of Analogue Encoder Signals (Resolver, Sin/Cos Encoder - Festo CAMC-G-S3 Manual

A Technical appendix
A.3.5 Vector length monitoring of analogue encoder signals (resolver, SIN/COS encoder)
The safety module monitors the analogue encoder signals of a SIN/COS encoder or resolver:
– the tracking signals ex (corresponds to COS signal of a SINCOS encoder / resolver) and ey (corres­
ponds to SIN signal of a SINCOS encoder / resolver) are measured.
– each individual signal is monitored (compliance with the approved signal range). Short circuits of
individual signals against GND / VCC and impermissibly high signal levels are detected.
– In addition, the vector length is calculated:
e + e ) e
2 2
x y
– the currently measured vector length e is checked for compliance with parameterisable limit val­
ues:
t e t e
e
max
min
– if an individual signal (e
triggered and the error response is evoked (error of group 55-x).
Vector length monitoring is used to detect various errors of the encoder and for detection of errors in
the analogue signal detection è Section A.2.3:
– failure of a signal through short circuit, interruption, etc.
– amplitude and phase errors
– Stuck-At errors
– drift and oscillation
The maximum error angle up to the response of the vector length monitoring is calculated based on
the nominal vector length e
e
min
Då + acos ) acos
e
rated
Diagnostic coverage of vector length monitoring:
The diagnostic coverage can be calculated from the ratio of the voltage surfaces in the x-y coordinate
space as follows, assuming a homogeneous distribution list of the voltage errors:
Value
Voltage range of the encoder
signals e , e
x y
Total area of the voltage range
F
total
Proportion of the "permitted"
voltage range F
valid
= ð(e
F ² – e
valid max min
Diagnostic cover DC
vl
DC =1 – F / F
vl valid total
1) Factory setting
2) Setting with reduced tolerance
Tab. A.30 Calculation of diagnostic coverage
The diagnostic coverage of the vector length monitoring DC
coder errors into the total diagnostic coverage DC
higher than DC .
VL
Festo – GDCP-CAMC-G-S3-EN – 1406NH – English
(parameters P06.0F, P06.10, P06.1A, P06.1B)
, e ) or the vector (e) is outside the permitted range, an encoder error is
x y
, taking the limit values into account as follows:
rated
e
min
e
max
SIN/COS encoder
0.5 V  e
x
F = (4.50 V – 0.50 V)²
total
= ð(0.70 V² – 0.21 V²)
F
valid
= ð(0.60 V² – 0.40 V²)
F
valid
²)
DC =91%
vl
DC =95 %
vl
 4.5 V
, e
y
1)
2)
1)
2)
goes through the FMEA of possible en­
VL
for the encoder system. DC
AV
Resolver
–6.7 V  e  6.7 V
, e
x y
F = (6.7 V – (-6.7 V))²
total
Fvalid = ð(2.20 V² – 6.40 V²)
Fvalid = ð(5.20 V² – 6.40 V²)
1)
DCvl =37 %
2)
DC =76 %
vl
is mostly markedly
AV
1)
2)
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