
3. α SERIES PARAMETER ADJUSTMENT B-65150E/04
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3.3 PROCEDURES FOR GAIN ADJUSTMENT AND
VIBRATION-DAMPING CONTROL
3.3.1 Gain Adjustment Procedure
Adjusting the position gain and velocity loop gain to the optimum state
leads to improvements in control performance and disturbance
suppression performance. Therefore, gain adjustment is the item to be
adjusted first in every machine. Setting a higher velocity loop gain is
effective not only in improvement in surface precision and figure
precision in machining at normal speed but also in improvement in
high-speed high-precision machining and high-speed positioning
performance. The extent to which the velocity loop gain can be
increased almost determines the degree of servo adjustment.
Understanding the gain adjustment procedure that aims at the
improvement of the oscillation limit helps to determine the action to be
taken when vibration occurs. Therefore, it is necessary to understand
the gain adjustment procedure thoroughly.
<3> Preparation for gain adjustment 3:
Set an auxiliary function to increase the vibration limit. First, set the
velocity loop proportional high-speed processing function(*1).
For a machine with low rigidity, however, setting the acceleration
feedback function instead of the velocity loop proportional high-speed
processing function may produce better results. For a large machine that
can easily be vibrated, it is sometimes undesirable that an auxiliary
function is used. Therefore, follow the procedure explained below to
select a suitable auxiliary function.
(Procedure for selecting an auxiliary function)
First, set the velocity loop proportional high-speed processing function,
and performs steps up to step <6>, "Determining the velocity loop gain
oscillation limit." If the velocity loop gain cannot attain 300%, set the
acceleration feedback function, and perform step <6> again. If a better
result is obtained than with the velocity loop proportional high-speed
processing function, this procedure terminates. If the result is worse,
disable the auxiliary function, and perform step <6> again. Select the
settings with which the highest velocity loop gain is obtained.
<1> Preparation for gain adjustment 1:
Check that the servo parameters are set to standard values. The
position gain and velocity loop gain are set to levels that do not generate
vibration (normally, the position gain and velocity loop gain are set to
about 3000 and 150%, respectively).
<2> Preparation for gain adjustment 2:
Select the velocity control method. With high-speed high-precision
machines, PI control should be selected. With high-speed positioning
machines such as a punch press, I-P control should be selected.