Mitsubishi Electric MR-J4 Instruction Manual page 557

17. APPLICATION OF FUNCTIONS
(9) Lost motion compensation function
The lost motion compensation function corrects response delays (caused by a non-sensitive band due
to friction, twist, expansion, and backlash) caused when the machine travel direction is reversed. This
function contributes to improvement for protrusions that occur at a quadrant change and streaks that
occur at a quadrant change during circular cutting.
This function is effective when a high follow-up performance is required such as drawing an arc with an
X-Y table.
(a) Parameter setting
Setting [Pr. PX36] to [Pr. PX42] enables the lost motion compensation function.
1) Lost motion compensation function selection ([Pr. PX40])
Select the lost motion compensation function.
2) Lost motion compensation ([Pr. PX36]/[Pr. PX37])
Set the same value for the lost motion compensation for each of when the forward rotation
switches to the reverse rotation and when the reverse rotation switches to the forward rotation.
When the heights of protrusions differ depending on the travel direction, set the different
compensation for each travel direction. Set a value twice the usual friction torque and adjust the
value while checking protrusions.
3) Torque offset ([Pr. PX39])
For a vertical axis, unbalanced torque occurs due to the gravity. Although setting the torque offset
is usually unnecessary, setting unbalanced torque of a machine as a torque offset cancels the
unbalanced torque. The torque offset does not need to be set for a machine not generating
unbalanced torque. The torque offset cannot be used for linear servo motors and direct drive
motors. Set "0".
POINT
The lost motion compensation function is enabled only in the position control
mode.
The locus before compensation
[Pr. PX40]
0 0
Compensation
Travel
direction
The locus after compensation
Lost motion compensation selection
0: Lost motion compensation disabled
1: Lost motion compensation enabled
Unit setting of lost motion compensation non-sensitive band
0: 1 pulse unit
1: 1 kplulse unit
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