Mitsubishi Electric MELSERVO-J4 Series Instruction Manual page 557

Friction estimation function
Speed
[Pr. PF31]
Zero speed
Forward
rotation
Servo motor speed 0 r/min
Reverse
rotation
Zero speed
[Pr. PF31]
To perform friction estimation, the servo motor must be rotated at zero speed or higher, and operated for 150 s both in the high
and low-speed sections. High-speed section indicates that the absolute value of the servo motor speed is [Pr. PF31 Machine
diagnosis function - Friction judgment speed] or more. Low-speed section indicates that the absolute value of the servo motor
speed is less than [Pr. PF31]. For the above operation pattern, when (a) + (c) is 150 s or more and (b) is 150 s or more, the
friction in the forward rotation direction is estimated. The friction in the reverse rotation direction is not estimated, even if time
(d) is 150 s or more because the servo motor is not operated in the high-speed section. In this case, decrease the setting
value of [Pr. PF31] to perform friction estimation. When "0" is set in [Pr. PF31], 1/2 of the rated speed will be the threshold.
For the following operation pattern, it takes approximately 20 min. for completing friction estimation.
Speed
1/2 of rated speed
Forward
rotation
0 r/min
Servo motor speed
Reverse
rotation
1/2 of rated speed
The friction estimation function estimates the static friction both at forward rotation and reverse rotation, and the dynamic
friction (at rated speed) both at forward rotation and reverse rotation. To estimate these values, it is unnecessary to perform
to-and-fro positioning operation. By operating the servo motor in acceleration/deceleration for forward rotation, you can only
estimate the static friction and dynamic friction (at rated speed) at forward rotation. By operating the servo motor in
acceleration/deceleration for reverse rotation, you can only estimate the static friction and dynamic friction (at rated speed) at
reverse rotation.
Vibration estimation function
The vibration estimation function monitors torque vibrations to estimate high-frequency minute vibration level and vibration
frequency. Thus, the function enables to monitor a backlash on the guide, ball screw, belt, etc. and the increase in vibration
level and change in vibration frequency due to deterioration.
Torque
Vibration frequency
The vibration estimation function estimates the vibration level and vibration frequency respectively during servo motor
operation and at a servo motor stop. Concretely, the function estimates the vibration level both during servo motor operation
and at a servo motor stop, and vibration frequency both during servo motor operation and at a servo motor stop.
(d)
(a) (b) (c)
3000 r/min
1 s
1 s 1 s 1 s 0.5 s
Vibration level
Time
Zero speed
1 s 1 s 0.5 s
Time
Zero speed
-3000 r/min
17 APPLICATION OF FUNCTIONS
17.5 Machine diagnosis function
17
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