sh030106u.pdf - 第264页
7. SPEC IAL ADJUSTMEN T FUNCT IONS 7 - 35 (d) Lost mo tion c ompensa tion t iming ([ Pr. PE4 9]) You can s et the delay time of the l ost motio n com pensatio n star t tim ing wit h this p arameter. When a protrusion occ…
7. SPECIAL ADJUSTMENT FUNCTIONS
7 - 34
7.6 Lost motion compensation function
POINT
The lost motion compensation function is enabled only in the position control
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.
The locus before compensation The locus after compensation
Compensation
Travel
direction
(1) Parameter setting
Setting [Pr. PE44] to [Pr. PE50] enables the lost motion compensation function.
(a) Lost motion compensation function selection ([Pr. PE48])
Select the lost motion compensation function.
Lost motion compensation selection
0: Lost motion compensation disabled
1: Lost motion compensation enabled
0
Unit setting of lost motion compensation non-sensitive band
0: 1 pulse unit
1: 1 kpulse unit
[Pr. PE48]
0
(b) 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
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.
(c) 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%.
7. SPECIAL ADJUSTMENT FUNCTIONS
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(d) 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.
(e) 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]).
(f) Lost motion filter setting ([Pr. PE46])
Changing the value of this parameter is usually unnecessary. When a value other than 0.0 ms is set
in this parameter, the high-pass filter output value of the set time constant is applied to the
compensation and lost motion compensation continues.
(2) Adjustment procedure of the lost motion compensation function
(a) Measuring the load current
Measure the load currents during the forward direction feed and reverse direction feed with MR
Configurator2.
(b) Setting the lost motion compensation
Calculate the friction torque from the measurement result of (2) (a) in this section and set a value
twice the friction torque in [Pr. PE44] and [Pr. PE45] as lost motion compensation.
Friction torque [%] =
2
|(load current during feed in the forward rotation direction [%]) -
(load current during feed in the reverse rotation direction [%])|
(c) Checking protrusions
Drive the servo motor and check that the protrusions are corrected.
7. SPECIAL ADJUSTMENT FUNCTIONS
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(d) Adjusting the lost motion compensation
When protrusions still occur, the compensation is insufficient. Increase the lost motion compensation
by approximately 0.5% until the protrusions are eliminated. When notches occur, the compensation
is excessive. Decrease the lost motion compensation by approximately 0.5% until the notches are
eliminated. Different values can be set as the compensation for each of when the forward rotation
(CCW) switches to the reverse rotation (CW) and when the reverse rotation (CW) switches to the
forward rotation (CCW).
The locus before compensation The locus after compensation
Compensation
Travel
direction
(e) Adjusting the lost motion compensation timing
When the machine has low rigidity, the speed loop gain is set lower than the standard setting value,
or the servo motor is rotating at high speed, quadrant projections may occur behind the quadrant
change points. In this case, you can suppress the quadrant projections by delaying the lost motion
compensation timing with [Pr. PE49 Lost motion compensation timing]. Increase the setting value of
[Pr. PE49] from 0 ms (Initial value) by approximately 0.5 ms to adjust the compensation timing.
Before timing delay compensation After timing delay compensation
Compensation
Travel
direction
(f) Adjusting the lost motion compensation non-sensitive band
When the lost motion is compensated twice around a quadrant change point, set [Pr. PE50 Lost
motion compensation non-sensitive band]. Increase the setting value so that the lost motion is not
compensated twice. Setting [Pr. PE50] may change the compensation timing. Adjust the lost motion
compensation timing of (2) (e) in this section.
Before timing delay compensation After timing delay compensation
Compensation
Travel
direction