Target Approach - Siemens SIMATIC FM 351 Installation Manual

2.3

Target Approach

Definition
During a target approach the FM 351 makes various monitoring features and
signals available.
This achieves the following:
Target Approach The target approach, which we are going to examine in the following, begins
when the switch-off point is reached.
The following sequence should be noted.
1. The FM 351 starts the target-approach monitoring on reaching the switch-
2. The actual value must have reached the target range within the monitor-
3. The actual value reaches the target range.
4. When the velocity becomes slower or equal to the value of the standstill
Note
The undercutting of the standstill velocity is only monitored once per target
approach.
5. The monitoring period for the target approach is switched off.
6. The standstill monitoring is switched on. The standstill range is posi-
FM 351 Positioning Function Module
EWA 4NEB 720 6001-02
The target approach is monitored.
The signal Position reached is generated. You obtain the signal on the
parameter POS_RCD of the FC INC_MOD (see Chapter 6.2.1).
The standstill condition in the standstill range is monitored.
off point.
ing period.
velocity within the target range, the FM 351 signals with the signal
POS_RCD (Position reached) that it has detected the reaching of the tar-
get position.
tioned symmetrically about the target position and monitored.
If the actual value leaves the standstill range without a new start request
being issued, the FM 351 signals an error.
Principles of Positioning
2
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