Siemens SIMATIC S7-300 Manual page 248

Description of Functions
In all operating modes except Open–loop control mode, the "servo ready"
signal is required for the duration of every traversing movement when the
parameter is active (MD37.2). If the servo ready is not detected or is deacti-
vated during the movement, the "servo not ready" message is triggered (see
Table 11-5, Class 3/No. 62).
Position approach The following diagram shows position approach.
On approach to a position, the monitoring time is activated:
t
t
24
25
9-72
s
Target range (PEH) (MD24)
Set
Actual
a
b
c
t t t
1 2 3
PEH – Position reached, stop
s – path
t – time
Time
t (a) After the interpolator reaches the target position, the monitoring time
1
(MD25) for reaching the target range is started in the CL controller, after
the overtravel in the jolt filter dies down to the target range value (PEH
on setpoint side).
(b) Before the monitoring time expires, the actual position reaches the target
2
range. Positioning is completed. A PEH is signaled, and exact matching
is performed by the CL controller.
(c) After the monitoring time expires, the actual position has not reached the
3
target range (PEH).
Error message: "PEH Target Range Monitoring" (see Troubleshooting,
Table 11-7, Class 3/No. 64)
MD Designation
Target range 0...1 000 000
Monitoring time 0 = no monitoring
1...100,000
Upper range
Position to be approached
Lower limit
Monitoring time (MD25)
Position monitoring
Value/Meaning
[MSR]
[ms], rounded to 2–ms
steps
FM 354 Servo Drive Positioning Module
t
Unit