Standstill Monitoring (Sos, Ss2); Encoder Consistency Check By Small Oscillation During Standstill Monitoring - Mitsubishi Electric MELSEC Q Series Programming Manual

2 SAFETY OBSERVATION FUNCTION

2.7 Standstill Monitoring (SOS, SS2)

2.7.1 Encoder consistency check by small oscillation during standstill monitoring

SOS function is executed by setting the safety speed, safety motor speed and
allowance value of position deviation to approximately "0".
Execute the ON/OFF control of speed monitoring request signal and timer delay
processing for motor deceleration time (SS2) using safety signal in user safety
sequence program.
The command position is also monitored in addition to the speed monitoring for safety
speed "0" during standstill. The load-side machine position is guaranteed to be within
the allowance value of position deviation by feedback position monitoring (Refer to
Section 2.4.8.) and external auxiliary pulse input monitoring (Refer to Section 2.4.10.).
Safety input signal
(Safety door, etc)
V
Motor speed
0
P
Motor position
0
Standstill monitoring
(SOS)request signal
The feedback position validity from the motor encoder (the memory shall not be
internally changed and fixed) must be checked during standstill monitoring which uses
external auxiliary pulse input. Make small oscillation within the allowance range. If the
small oscillation request flag signal does not turn ON after the standstill status
continues for certain time (about one hour), "Safety observation error (error code: 120)"
occurs and the shut-off signal is turned OFF.
The small oscillation executing flag turns ON when the small oscillation request flag is
turned ON, and move the motor so that the external auxiliary pulse both edges are
detected. ("Movement amount: +0.6pulse → -1.2pulse → +0.6pulse", "Command
speed: 1pulse/s" Both are the conversion value of external auxiliary pulse input)
Both edges of external auxiliary pulse input must be defined according to user system.
During standstill monitoring which uses a safety encoder, encoder consistency check
by small oscillation is not necessary.
External pulse input(A/B-phase)
(A-phase)
(B-phase)
Make small oscillation so that the both edge can be detected,
and check the consistency between motor encoder travel amount.
Start of deceleration
The timer delay processed by
user safety sequence program
+0.6pulse +0.6pulse
-1.2pulse
2 - 20
t
Allowance value of
position deviation
t