End Of Positioning - Siemens SIMATIC FM 351 Manual

Modes and Jobs
9.1

End of Positioning

Definition
The end of a positioning operation is indicated by the return signal WORKING = 0.
This can be achieved in three different ways:
Final target approach
Terminating
Aborting
Monitoring Functions
In the last phase of a positioning operation, the following monitoring functions are
active:
Monitoring time
The monitoring time is retriggered for the last time at the switch-off point and
ceases to be valid at the end of the positioning operation.
During this time, the end of the positioning operation must be reached,
otherwise the outputs are deactivated and the operating error "error in target
approach" (error number 5) is signaled.
Monitoring of the target range
The FM 351 places a symmetrical range either side of a target which defines
the positioning accuracy of your application. The axis must become stationary
during a target approach within this range. Setting a value of "0" cancels the
tolerance during target approach.
Monitoring of the stationary speed
The stationary speed is used to check that the drive becomes stationary within
the target range. After reaching the switch-off point, the drive is monitored to
detect when the speed falls below this setting.
The drive speed must fall below the stationary speed within the target range,
otherwise the FM 351 signals the operating error "target range passed" (error
number 10).
The speed falling below the stationary speed is monitored only once per target
approach.
Note that the speed can fall below the stationary speed used by the module to
detect the speed when the axis moves at an extremely slow positioning speed
(less than 2 pulses per 8 ms).
Monitoring of the stationary range
On completion of a positioning operation, a monitoring function detects whether
the drive remains stationary at the target position or whether it drifts away from
this position.
The stationary range is monitored
9-2
FM 351 Positioning Module
C79000-G7076-C351-02