ABB ACSM1 - Page 71

Drive control and features
71
Cyclic position correction
Cyclic position correction functions are used to change or correct the system
position continuously according to data measured by external probe signals, for
example, if there is play in the machinery. The cyclic position correction functions
always need an external probe (or probes) to operate. By means of a programmable
bit pointer, the probes can be configured to use digital inputs DI1 and DI2 of the
encoder interface with different triggering conditions (such as falling or rising edge)
or the digital inputs of the drive control board unit as trigger sources.
The cyclic position correction functions use the probe positions in the correction
calculations in two ways:
• as an actual position latch to correct the drive actual position (1.12 POS ACT)
• as a master reference latch to correct the drive synchron reference position (4.16
SYNC REF GEARED).
To enable cyclic position correction, the following settings must be considered:
• Cyclic correction mode (62.14 CYCLIC CORR MODE)
• Probe positions (62.16 PROBE1 POS, 62.18 PROBE2 POS)
• Triggering conditions (62.15 TRIG PROBE1, 62.17 TRIG PROBE2)
• Maximum allowed correction (62.19 MAX CORRECTION)
• Programmable bit pointer (62.22 TRIG PROBE1 SW, 62.23 TRIG PROBE2 SW)
There are five different cyclic position correction functions available:
• CORR ACT POS: Drive actual position correction (Probe 1 used for actual
position latch).
• CORR MAST REF: Synchronised master drive reference correction (Probe 1
used for master position reference latch).
• CORR M/F DIST: Master and follower distance correction. The drive
synchronised master reference and actual position are both corrected (Probe 1
used for actual position latch and probe 2 for master position reference latch).
• 1 PROBE DIST: Drive actual position correction according to the distance
between two consecutive latches from one probe (Probe 1 used for actual
position latch).
• 2 PROBE DIST: Drive actual position correction according to the distance
between two latches (Probe 1 and probe 2 both used for actual position latch).
When enabled, cyclic correction waits until the triggering conditions of the probes
are fulfilled. The encoder positions are then latched (saved) into 4.03 PROBE1 POS
MEAS and 4.04 PROBE2 POS MEAS. If there is deviation between probe position
and measured position, a correction is carried out. The deviation (shown by 4.05
CYCLIC POS ERR) is added to synchronisation error 4.18
SYNC ERROR and
corrected using the position profile generator and dynamic limiter parameters. The
next correction can be started after the previous correction has been successfully
carried out.
If cyclic correction is configured to use two probes, the correction is done after both
latches have been received. If multiple latches are received from one probe, the last-
received latch is used in the correction calculation.