
B-65150E/04 3. α SERIES PARAMETER ADJUSTMENT
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<6> Position gain adjustment
A specified feedrate is calculated as follows:
Specified feedrate = (position gain) × (positional
deviation) + (feed-forward)
Therefore, if a deviation occurs between the command and
actual position, a higher position gain makes a stronger error
correction, thus making a figure error smaller. When level-
up HRV control is used, the response of the velocity loop is
improved, so that a position gain higher than before can be
set. With a medium-size machining center, a value up to
about 80 to 100 [1/s] can be set. (When a large machine or
closed-loop machine is used, a lower value needs to be set if
the backlash between the motor and machine is large.)
Perform rapid traverse and cutting feed at a maximum
cutting feedrate, and find a position gain limit while
observing the TCMD at the time of acceleration/deceleration.
Then, set a value of about 80% of the limit. A position gain
limit appears where a large swell of about 10 to 30 Hz is
observed in the TCMD waveform.
After determining a position gain value, readjust the position
feed-forward coefficient of <5> above.
[Parameter for position gain setting]
No. 1825 (Series 16, Series 15): 5000 to 10000
(5) Method of resonance frequency measurement using servo adjustment
software
For machine resonance measurement, use the procedure below. It is
assumed that servo adjustment software of a version of October, 1998
and later is used.
<1> Make a preparation to use servo adjustment software (SD). Set
the type of measurement data in Adjustment 2. (When using a
check board of analog/digital integrated type, set 6 as the number
of data digits. When using a digital check board, set the DIP
switch to 12 (for an odd-numbered axis) or 13 (for an even-
numbered axis).
<2> Set bit 7 of the parameter No. 2206 (Series 16) or No. 1746 (Series
15) to 1. Set this bit for both axes controlled by the same DSP.
<3> In this state, a TCMD waveform is output for each current loop
control period.
This means that a torque command for 1 second for 4000 data
items can be acquired when the current control period is 250 µs,
and a torque command for 1 second for 8000 data items can be
acquired when the current control period is 125 µs.