Mitsubishi Q173DSXY Manual page 8

(2) Speed monitoring function (SLS)
• Under the condition that the failure rate of the additional pulse encoder components
does not exceed 195FIT/395FIT the resulting PFD/PFH will be less than 195FIT/395FIT.
(See below diagram.)
Common Comp.
Common
(PSU)
• Avoid the continuous use (about 8 hours) of the same Speed Monitor parameter block
to prevent the accumulation of errors.
• Speed monitoring function guarantees the motor control (the motor rotation speed), but
it does not guarantee the actual machine safety speed. Make sure to set parameters so
that the safe speed of the machine is the same as the safety speed of the motor.
• When SLS function of speed zero (stop) does not have command data from a controller,
please switch to SOS function or must use external sensor (PLG) together.
• The accuracy of safety speed observation depends on the external auxiliary pulses
which is external input pulse. Therefore, the number of the external input pulses for
safety speed must be determined considering the external auxiliary pulses resolution
and the allowance input pulse frequency.
• Check if the rotation speed of the monitored servo axis is the same as the actual speed
by using a tachometer, etc. considering the speed includes an error caused by the
encoder resolution of the external auxiliary input pulses.
• The defect of the mechanical section such as slid of shaft and wanting of a timing belt,
etc is not covered. Be sure to eliminate the risk of mechanical section before operation.
• Speed monitoring error detection time is set to 10ms, but the time resolution in the
actual operation is 25ms. Error in shorter than this time are not detected.
• Create sequence program so that Scan time is within 25ms to make sure that PLC CPU
performs the safety monitoring function within a certain process time. If scan time is
25ms or longer, PLC CPU should be added to distribute the load of the process.
• Safety observation error (shutdown signal OFF) does not occur during the time set by
the speed monitoring parameters after speed is over the limit. Make sure that safety can
be ensured during this period.
• The error occurs when detected speed is different between the motor encoder and the
external auxiliary input pulse, and the time required to detect the error depends on the
frequency of the external auxiliary pulse. Determine the number of external input pulse
considering the error detection risk.
(3) Safe Speed Monitor (SSM)
• If the safety output condition of SSM is used as a restart trigger, incidental start-up
cannot be prevented. A restart interlock must comply with EN60204-1. However, using it
as the operation ready signal is possible.
Encoder MR-J4- B
Additional Pulse
Encoder Comp.
PG2
7
Q17 DSCPU Q173DSXY
Motion
Motion
I/O
QnUDHCPU
and Q3nDB
PLC
PLC
I/O
ch A
ch B