Siemens SIMATIC S7-200 System Manual page 285

The Position Control wizard provides advanced reference point options that allow you to
-
specify an RP offset (RP_OFFSET), which is the distance from the RP to the zero position.
See Figure 9-15.
RP_OFFSET: Distance from the
RP to the zero position of the
physical measuring system.
Default = 0
Backlash compensation:
Distance that the motor must move
to eliminate the slack (backlash) in
the system on a direction change. y
Backlash compensation is always B kl h
a positive value. Default = 0
Choose a Reference Point search sequence.
The Position module provides a reference point switch (RPS) input that is used when
-
seeking the RP. The RP is identified by a method of locating an exact position with respect
to the RPS. The RP can be centered in the RPS Active zone, the RP can be located on the
edge of the RPS Active zone, or the RP can be located a specified number of zero pulse
(ZP) input transitions from the edge of the RPS Active zone.
You can configure the sequence that the Position module uses to search for the reference
point. Figure 9-16 shows a simplified diagram of the default RP search sequence. You can
select the following options for the RP search sequence:
RP Seek mode 0: Does not perform a RP seek sequence
RP Seek mode 1: The RP is where the RPS input goes active on the approach from the
work zone side. (Default)
RP Seek mode 2: The RP is
centered within the active region of
the RPS input.
RP Seek mode 3: The RP is
located outside the active region of
the RPS input. RP_Z_CNT
specifies how many ZP (Zero
Pulse) input counts should be
received after the RPS becomes
inactive.
RP Seek mode 4: The RP is
generally within the active region
of the RPS input. RP_Z_CNT
specifies how many ZP (Zero specifies how many ZP (Zero
Pulse) input counts should be
received after the RPS becomes
active.
Tip
The RPS Active region (which is the distance that the RPS input remains active) must be
greater than the distance required to decelerate from the RP_FAST speed to the RP_SLOW
speed. If the distance is too short, the Position module generates an error.
Open Loop Motion Control with the S7-200
g
ti i l
Figure 9-15 Relationship Between RP and Zero Position
RP Seek Mode 1
LMT- -
Active
Figure 9-16 Default RP Search Sequence (Simplified)
RP Zero Position
RP_OFFSET
RP Seek Direction
RPS
RP Approach Direction
Active
Work Zone
Chapter 9
Work
Zone
271