Synchronizing The Stepper Motor Axis - Siemens SIMATIC FM 353 Manual

Description of Functions
9.6.1

Synchronizing the stepper motor axis

Overview
When stepper motors are used, there is an unknown offset between the internal
position value and the mechanical position of the axis after the FM is switched on.
To establish the position reference, the value internal to the FM must be synchro-
nized with the real position value of the axis. Synchronization is performed by tak-
ing over a position value at a known point of the axis.
Reference point approach
is an operating mode used to position the axis at the reference point.
Reference point
is a fixed point on the axis. It is:
S The target coordinate in the Reference-Point Approach mode
S Removed from the synchronization point by the amount of the reference-point
shift, in axes with incremental encoders.
Reference point offset
Difference in distance between the synchronization point and the reference point.
The reference-point shift serves:
S for numeric adjustment of stepper motor.
S as a displacement reserve to brake the drive if the synchronization point is
overshot.
Reference point switch (RPS)
The reference point switch selects the synchronizing zero marker on the traversing
path of the axis.
S It is also the signal encoder for a speed reduction before the synchronization
point is reached.
S It is connected to a digital input of the FM 353.
Synchronization point
is a defined point on the traversing path of the axis. It is defined by the mechanical
position of a reference-point switch or in association with a cyclic zero mark of an
incremental encoder.
9-64
FM 353 Stepper Drive Positioning Module
6ES7 353-1AH01-8BG0