Rockwell Automation 21G PowerFlex 750-Series AC Drives Reference Manual - Manual (Page 65)

Rockwell Automation Publication 750-RM001F-EN-P - February 2012 65
Safe Stop and Safe Stop with Door Monitoring Modes Chapter 6
Standstill Speed and Position Tolerance
For Safe Stop Types that include Standstill Checking, you set the Standstill Speed
and Standstill Position Tolerance.
Standstill Speed is used to declare motion as stopped. The system is at standstill
when the speed detected is less than or equal to the configured Standstill Speed.
The P48 [Standstill Speed] parameter defines the speed limit before the safety
option determines standstill has been reached and the door control logic is set to
Unlock.
The P49 [Standstill Pos] parameter defines the position limit in encoder 1 units
that is tolerated after standstill has been reached. If the position changes by more
than the amount specified by the Standstill Position Tolerance, after standstill has
been reached and the door is unlocked, a Motion After Stopped fault occurs.
This type of fault results in the safety option entering the safe state.
The time required to verify that the Standstill Speed has been reached can be
considerable when a very small Standstill Speed is configured and the encoder
resolution of encoder 1 is very low.
• For rotary systems, the time (in seconds) will exceed
15 / [Standstill Speed (RPM) x Encoder 1 Resolution].
• For linear systems, the time (in seconds) will exceed
0.25 / [Standstill Speed (mm/s) x Encoder 1 Resolution].
Deceleration Monitoring
Deceleration monitoring takes place during the configured Stop Delay P47 [Max
Stop Time], when the Safe Stop Type is configured as Safe Stop 1 or Safe Stop 2.
The deceleration start speed is captured at the beginning of the Stop Delay P47
[Max Stop Time] and used to calculate the deceleration profile.
These parameters define the deceleration profile:
• Deceleration Reference Speed, P50 [Decel Ref Speed]
• Deceleration Tolerance, P51 [Stop Decel Tol]
• Stop Delay, P47 [Max Stop Time]
The Deceleration Reference Speed is relative to encoder 1. The P51 [Stop Decel
Tol] parameter defines the percentage of the Deceleration Reference Speed that
will be tolerated above the calculated deceleration profile.
IMPORTANT The P48 [Standstill Speed] and P49 [Standstill Pos] parameters are not used for
Safe Torque Off without Standstill Checking configurations. Set these
parameters to zero.
IMPORTANT Standstill detection relies on the encoder 1 signal. The encoder 2 signal is used
for fault diagnostics.