A.3.2 Accuracy Of Speed Monitoring (Sls, Ssr From The Point Of View Of The Application - Festo CAMC-G-S3 Manual

A Technical appendix
A.3.2 Accuracy of speed monitoring (SLS, SSR)
from the point of view of the application
When the safety function with speed monitoring is requested, e.g. SLS, SSR, the current speed v_act is
detected continuously and monitored for compliance with specific limit values.
The limit values can change dynamically, e.g. on requesting SLS, if the system first brakes to the
safely-limited speed.
Monitoring takes place in a speed window of:
v_min ≤ v_act ≤ v_max
Application-specific requirements for v_max (for SLS) are stated in Section A.3.7, Tab. A.34.
The acceptable filter time constant t_filter_v in the speed monitoring is the result of the quality of the
analogue signal processing on the safety module (for position encoders with analogue signals, such as
resolvers or Hiperface encoders) and the position resolution (number of angle steps for motor revolution).
In addition, on dynamic changes, there is a "swing-in process" until the speed swings into the new
setpoint. The length of time depends on the band width of the rotational speed regulation circuit. To
ensure a high level of system availability, short swing-in processes in the range of the bandwidth of the
rotational speed regulation circuit should not lead to a response of the monitoring system.
An allowable time t_tol_v is provided for that. During the length of time t_tol_v, v_act may move out­
side the speed window before the violation of the safety condition is triggered.
Parameter Name
v_max Speed limit for SLS
n_max Minimum speed limit
on the motor shaft
for SLS
t_filter_v Filter time constant,
speed detection
t_tol_v Allowable time for
v_act outside the ap­
proved speed range
1) The resolution of the speed signal is primarily determined by the quality of the encoders used and the parameterised filter time of
the speed filter. Monitoring for n_typ_min should be possible with common shaft encoders, such as resolvers or SIN/COS encoders,
if the speed filter is parameterised in the range of 20 ms (the axle moves just 0.08 mm at 4 mm/s for 20 ms).
Tab. A.27 Typical values, SLS
262
Min. Typical
4 mm/s 250 mm/s
2.1 rpm 167 rpm
2 ms 8 ms
0 ms 10 ms
Festo – GDCP-CAMC-G-S3-EN – 1406NH – English
Max. Please note
≥ 10 m/s Section A.3.7,
Tab. A.34
­ Sample calculation,
based on a feed of
90 mm/rev
≥ 100 ms Section A.3.7,
Tab. A.33
≥ 100 ms Typical bandwidth of
the speed control
f_gr = 100 Hz