Drive control and features
68
Position correction
Homing
Normally, before first homing, the actual position of the driven machinery does not
correspond to the internal zero position in the drive position control (for example,
with an incremental encoder after each power-up). Homing establishes a
correspondence between these two positions. During homing, the direction can be
changed by an external latch signal or limit switch.
Homing is implemented according to the CANopen Standard Proposal 402 for
Device Profile Drives and Motion Control. The profile includes 35 different homing
sequences (see the following homing method table and Appendix C – Homing
methods). The start direction and used latch signals depend on the selected homing
method (62.01 HOMING METHOD) and the status of the external home switch
signal (62.04 HOME SWITCH TRIG).
A homing sequence (except homing method 35) can be executed only in homing
control mode when the drive is modulating. When homing is activated by the homing
start signal (62.03 HOMING START), the drive accelerates, as defined by homing
acceleration (62.27 HOMING ACC), to homing speed 1 (62.07 HOMING
SPEEDREF1). During homing, the direction can only be changed with homing
methods 1…14. Homing speed 1 is maintained until an external latch signal for
homing speed 2 (62.08 HOMING SPEEDREF2) or for the home position is received.
Homing is stopped with an index pulse/z-pulse or switch signal from an external
latch. The actual position is set as the home position (62.09 HOME POSITION), and
the drive decelerates to zero speed using homing deceleration (62.28 HOMING
DEC). Thereafter, the drive uses the position control mode to return to the exact
received latch position.
Homing is performed in an absolute way. Parameter 62.10 HOME POS OFFSET
can be used to specify an absolute difference between the home position and the
end position after homing; this is useful if the home proximity switch cannot be
located at the physical home position.
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