Lost Motion Compensation Function - Mitsubishi Electric MELSERVO-J4 Series Instruction Manual

7.6

Lost motion compensation function

The lost motion compensation function is enabled only in the position mode.
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.
Travel
direction
The locus before compensation
Parameter setting
Setting [Pr. PE44] to [Pr. PE50] enables the lost motion compensation function.
■Lost motion compensation function selection ([Pr. PE48])
Select the lost motion compensation function.
[Pr. PE48]
0 0
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 kpulse unit
■Lost motion compensation ([Pr. PE44]/[Pr. PE45])
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 size 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.
■Torque offset ([Pr. PE47])
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 0.00%.
■Lost motion compensation timing ([Pr. PE49])
You can set the delay time of the lost motion compensation start timing with this parameter. When a protrusion occurs
belatedly, set the lost motion compensation timing corresponding to the protrusion occurrence timing.
■Lost motion compensation non-sensitive band ([Pr. PE50])
When the travel direction reverses frequently around the zero speed, unnecessary lost motion compensation is triggered by
the travel direction switching. By setting the lost motion compensation non-sensitive band, the speed is recognized as 0 when
the fluctuation of the droop pulse is the setting value or less. This prevents unnecessary lost motion compensation.
When the value of this parameter is changed, the compensation timing is changed. Adjust the value of Lost motion
compensation timing ([Pr. PE49]).
7 SPECIAL ADJUSTMENT FUNCTIONS
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7.6 Lost motion compensation function
Compensation
The locus after compensation