Instruction Manual PSx3xxEC
24
3
Sequence of positioning
3.1
Positioning run (with loop)
By default, the PSx3xx always approaches each setpoint from the same direction. If a
destination is in the opposite direction to the loop direction, the setpoint is first
traversed by the value of the loop length (SDO #201F) and then finally approached.
This can, for example, eliminate the backlash of a driven spindle.
The PSx3xx thus distinguishes the following cases during a positioning process:
Assumption: Each target position is approached in forward direction, i.e. the loop
length is -250 = 5/8 rpm.
1. New setpoint position is greater than the current actual position: The target is
approached directly.
2. New setpoint position is smaller than the current actual position: The device is
moved further back by the loop length (2a) and the final destination is then
approached in forward motion (2b).
3. New setpoint position is only slightly larger than the current actual position and
previously there was no positioning movement with loop (e.g. a manual
movement):
In all cases, the drive approaches the target with a forward movement whose
length corresponds at least to the loop length. In order to achieve this, the drive
first moves in reverse direction (3a), i.e. against the actually desired direction of
travel, and then forwards the actual destination (3b).
The maximum length of this distance is the loop length. If the setpoint differs from
the current actual value by more than the loop length, it is approached directly.
