Safe Speed Monitor (Ssm) - Siemens Sinamics S110 Function Manual

Safety Integrated Functions
8.5 Extended Functions
8.5.5

Safe Speed Monitor (SSM)

Description
The SSM function is used for reliably detecting when a speed limit value has been undershot
(p9346/p9546) (e.g. for standstill detection) in both directions. A failsafe output signal is
available for further processing.
The function is activated automatically as soon as the Extended Functions are enabled with
p9301.0 = p9501.0 = 1.
NOTICE
The speed limit of the SSM function (p9346/p9546) is also used as shutdown limit for the
SBR function (safe acceleration monitoring). The SBR is deactivated if the speed is below
this limit.
The effect of the SSM safety function is therefore heavily limited if a relatively high
SSM/SBR speed limit is set and the SS1 and SS2 stop functions are activated.
STOP F (indicated by alarm C01711/C30711) only results in a follow-up response (STOP B
/ STOP A) if at least one of the safety-oriented functions (SOS or SLS) is active or has
been selected. If only the SSM function is active, a STOP F crosswise comparison error
does not result in a follow-up response (STOP B/STOP A).
If SSM is used as a safety function, therefore, at least one of the SOS or SLS functions
must be active/selected (e.g. by selecting a high SLS level).
The parameter p9346/p9546 "SI motion SSM (SGA n < nx) velocity limit n_x (CU)" is used to
set the velocity limit (in mm/min). The abbreviation "SGA n < nx" indicates the safety function
required for determining an output signal when a parameterizable velocity limit has been
undershot.
If the velocity limit for the "Safe Speed Monitor" feedback signal (n < n_x) for detecting
standstill is undershot, the "SSM feedback signal active" signal (SGA n < n_x) is set. When
the set threshold value has been undershot, the "Safe Acceleration Monitor" (SBR) function
is also deactivated.
The hysteresis for the SSM output signal is set in parameter p9347/p9547 "SI motion velocity
hysteresis (crosswise)". If the maximum permissible velocity tolerance is overshot (i.e. one
channel displays a velocity less than p9546 - p9547, while the other channel displays a
velocity greater than p9546), a Stop F is issued.
In addition, the output signal for SSM can be smoothed by means of a PT1 filter by setting a
filter time p9345/9545 "SI motion filter time nx".
During safe motion monitoring, both functions (hysteresis and filtering) can be activated or
deactivated jointly by means of an enabling bit (p9301.16 (Power Modules) and p9501.16
(CU)). In the default setting, the functions are deactivated (p9301.16/p9501.16 = 0).
The following diagram shows the characteristic of the safe output signal SSM when the
hysteresis is active:
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WARNING
Function Manual, 10/2008, 6SL3097-4AB10-0BP0
Drive functions