
B-65270EN/05 4.SERVO FUNCTION DETAILS
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(4) Improving overshoot compensation for machines using a 0.1-µm
detection unit
(a) Overview
Conventional overshoot compensation performs imperfect integration
only when the error is 0.
A machine using a 0.1-µm detection unit, however, has a very short
period in which the error is 0, resulting in a very short time for
imperfect integration.
The new function judges whether to execute overshoot compensation
when the error is within a predetermined range.
(b) Setting parameters
1994 (FS15i)
Overshoot compensation enable level
2101 (FS30i, 16i)
[Valid data range] 0 to 32767
[Unit of data] Detection unit
[Recommended value] 1 (detection unit: 1 µm)
10 (detection unit: 0.1 µm)
To set an error range for which overshoot compensation is enabled, set
∆, as indicated below, as the overshoot compensation enable level.
Imperfect
integration enabled
Imperfect integration disabled
Error
Error = +
∆
Error = 0
Error =
− ∆
Imperfect integration disabled
Fig. 4.7 (h) Relationship between error and overshoot compensation
(5) Overshoot compensation type 2
(a) Overview
For a machine using, for example, 0.1-µm detection units, the use of
the conventional overshoot compensation function may generate
minute vibrations when the machine stops, even if the parameter for
the number of incomplete integration is set.
This is caused by the repeated occurrence of the following
phenomena:
• While the machine is in the stopped state, the position error falls
within the compensation valid level, and the integrator is
rewritten. Subsequently, the motor is pushed back by a machine
element such as a machine spring element, causing the position
error to exceed the compensation valid level.
• While the position error is beyond the threshold, a torque
command is output to decrease the position error, then it
decreases to below the threshold again.
In such a case, set the bit indicated below to suppress the minute
vibration.