
4. SERVO FUNCTION DETAILS B-65150E/04
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4.4.4 N Pulse 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.
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.
Motor position
Stop position
Point A
Point B
Torque by
proportional
element
1 pulse
grid
Time