
B-65270EN/05 4.SERVO FUNCTION DETAILS
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4.4.4 N Pulses Suppression Function
(1) Overview
Even a very small movement of the motor in the stop state may be
amplified by a proportional element of the velocity loop, thus
resulting in vibration. The N pulse suppression function suppresses
this vibration in the stop state.
When vibration occurs as shown in Fig. 4.4.4 (a), the velocity
feedback at point B generates an upward torque command to cause a
return to point A. A downward torque command, generated by the
velocity feedback at point A is greater than the friction of the machine,
causing another return to point B. This cycle repeats itself, thus
causing the vibration.
Motor position
Stop position
Point A
Point B
Torque by
proportional
element
1 pulse
grid
Time
Fig.4.4.4 (a) N pulse suppression function disabled (Torque due to the
proportional term keeps up, leading to vibration.)
To suppress such vibration, it is necessary to exclude from the
velocity loop proportional term the speed feedback pulses generated
when the motor returns from point B to point A.
If the N pulse suppression function is enabled as shown in Fig. 4.4.4
(b), the feedback pulses generated when the motor returns from point
B to point A are excluded from the velocity loop proportional term.
The standard setting of the grid width at point A is 1 µm. It can be
changed by specifying the level parameter.