Mitsubishi Electric MELSERVO J5 Series User Manual page 50

Explanation on servo parameter
[Pr. PB10 Speed integral compensation]
This servo parameter determines the time
constant for proportional integral control of
speed control loop. Decreasing the value
improves the responsiveness. If the
moment of inertia ratio is large or the
mechanical system contains vibratory
element, the mechanical system is liable to
vibrate unless the value is increased to
some degree.
Adjustment procedure
Procedure Operation
1 Perform approximate adjustment with the auto tuning. Refer to the following.
Page 37 Auto tuning mode 1
The control gain obtained by the auto tuning is the reference value.
2 Change [Pr. PA08.0 Gain adjustment mode selection] to "3" (Manual mode).
3 Set an estimated value in the load to motor inertia ratio/load to motor mass ratio. (If the estimated
value by auto tuning is correct, setting change is not required.)
4 Set a small value to the model control gain and the position control gain. Set a large value to the
speed integral compensation.
5 Increase the speed control gain within the range where vibration or unusual noise is not generated,
and return slightly if vibration occurs.
6 Decrease the speed integral compensation within the vibration-free range. If vibration occurs,
increase the value until the vibration stops.
7 Increase the position control gain, and return slightly if vibration occurs.
8 Increase the model control gain, and return slightly if an overshoot occurs.
9 If the desired responsiveness cannot be achieved because of mechanical system resonance, or
the like which stops the gains to be increased, suppressing the resonance by the adaptive tuning
mode or the machine resonance suppression filter, followed by steps 3 to 8 may increase the
responsiveness.
10 While checking the settling characteristic and the motor status, fine-adjust each gain.
Servo parameter adjustment method
■[Pr. PB07 Model control gain]
As a guide, this servo parameter can be calculated with the following formula.
Model control gain guideline =
Number of droop pulses at the constant speed can be calculated with the following expression.
Number of droop pulses [pulse] =
Position command frequency differs depending on the operation mode.
• Rotary servo motor and direct drive motor:
Position command frequency =
• Linear servo motor:
Position command frequency = Speed [mm/s] ÷ Encoder resolution (travel distance per pulse)
3 ADJUSTMENT METHOD
48
3.7 Manual mode
Effect when increasing the responsiveness
Command
Droop pulses
Effect on overshoot
Speed control gain
×
(1 + Load to motor inertia ratio)
Position command frequency [pulse/s]
Model control gain setting value
Servo motor speed [r/min]
× Encoder resolution (number of pulses per servo motor revolution)
60
Droop pulses
Time
1 1
to
4 8
Operating status when increase in
responsiveness is excessive
Droop pulses
Command
Occurrence of vibration and unusual noise (low frequency)
Description




Increase the speed control gain.
Decrease the time constant of the speed
integral compensation.
Increase the position control gain.
Increase the model control gain.
Suppression of machine resonance
Refer to the following.
Page 50 Machine resonance
suppression filter
Page 53 Adaptive filter II
Fine adjustment
Time