Siemens SIMATIC S7 System Manual page 616

Open loop motion control
12.5 Configuring an Axis of Motion
Configuring reference point and seek parameters
1. Select using a reference point or not using a reference point for your application:
– If your application requires that movements start from or be referenced to an absolute
– If a reference point is used, you will want to define a way to automatically relocate the
2. Enter the Reference Point seek speeds (a fast seek speed and a slow seek speed):
– RP_FAST is the initial speed the module uses when performing an RP seek
– RP_SLOW is the speed of the final approach to the RP. A slower speed is used on
3. Define the initial seek direction and the final reference point approach direction:
– RP_SEEK_DIR is the initial direction for the RP seek operation. Typically, this is the
– RP_APPR_DIR is the direction of the final approach to the RP. To reduce backlash
4. The Motion 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 the
following figure:
– RP_OFFSET: Distance from the RP to the zero position of the physical measuring
– Default = 0
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position, you must establish a reference point (RP) or zero position that fixes the
position measurements to a known point on the physical system.
reference point. The process of automatically locating the reference point is called
Reference Point Seek. Defining the Reference Point Seek process requires two steps
in the wizard.
command. Typically, the RP_FAST value is approximately 2/3 of the MAX_SPEED
value.
approach to the RP, so as not to miss it. Typically, the RP_SLOW value is the
SS_SPEED value.
direction from the work zone to the vicinity of the RP. Limit switches play an important
role in defining the region that is searched for the RP. When performing a RP seek
operation, encountering a limit switch can result in a reversal of the direction, which
allows the search to continue. (Default = Negative)
and provide more accuracy, the reference point should be approached in the same
direction used to move from the RP to the work zone. (Default = Positive)
system.
System Manual, V2.3, 07/2017, A5E03822230-AF
S7-200 SMART