8.8 Manual Tuning
8.8.1 Tuning the Servo Gains
8-37
8
Tuning
Guidelines for Manually Tuning Servo Gains
When you manually adjust the parameters, make sure that you completely understand the
information in the user’s manual and use the following conditional expressions as guidelines.
The appropriate values of the parameter settings are influenced by the machine specifications,
so they cannot be determined universally. When you adjust the parameters, actually operate
the machine and use the S to monitor operating conditions. Even if the status is sta-
ble while the motor is stopped, an unstable condition may occur when an operation reference
is input. Therefore, input operation references and adjust the servo gains as you operate the
motor.
Stable gain: Settings that provide a good balance between parameters.
However, if the load moment of inertia is large and the machine system contains
elements prone to vibration, you must sometimes use a setting that is somewhat
higher to prevent the machine from vibrating.
Critical gain: Settings for which the parameters affect each other
Depending on the machine conditions, overshooting and vibration may occur and
operation may not be stable. If the critical gain condition expressions are not met,
operation will become more unstable, and there is a risk of abnormal motor shaft
vibration and round-trip operation with a large amplitude. Always stay within the
critical gain conditions.
If you use the torque reference filter and notch filters together, the interference between the fil-
ters and the speed loop gain will be superimposed. Allow leeway in the adjustments.
Guidelines are given below for gain settings 1.
•
Speed Loop Gain (Pn100 [Hz]) and Position Loop Gain (Pn102 [/s])
Stable gain: Pn102 [/s]
≤
2
π
×
Pn100/4 [Hz]
Critical gain: Pn102 [/s] < 2
π
×
Pn100 [Hz]
•
Speed Loop Gain (Pn100 [Hz]) and Speed Loop Integral Time Constant (Pn101 [ms])
Stable gain: Pn101 [ms]
≥
4,000/(2
π
×
Pn100 [Hz])
Critical gain: Pn101 [ms] > 1,000/(2
π
×
Pn100 [Hz])
•
Speed Loop Gain (Pn100 [Hz]) and First Stage First Torque Reference Filter Time Constant
(Pn401 [ms])
Stable gain: Pn401 [ms]
≤
1,000/(2
π
×
Pn100 [Hz]
×
4)
Critical gain: Pn401 [ms] < 1,000/(2
π
×
Pn100 [Hz]
×
1)
•
Speed Loop Gain (Pn100 [Hz]) and First Stage Notch Filter Frequency (Pn409 [Hz]) (or Sec-
ond Stage Notch Filter Frequency (Pn40C [Hz]))
Critical gain: Pn409 [Hz] > 4
×
Pn100 [Hz]
•
Do not set notch filter frequencies (Pn409 and Pn40C) that are close to the speed loop’s
response frequency. Set a frequency that is at least four times the speed loop gain (Pn100).
(However, Pn103 (Moment of Inertia Ratio) must be set correctly. If the setting is not correct,
vibration may occur and the machine may be damaged.
•
Change the notch filter frequencies (Pn409 and Pn40C) only while the Servomotor is stopped.
Vibration may occur if a notch filter frequency is changed during operation.
The following adjusted value guidelines require that the setting of Pn103 (Moment of Inertia Ratio)
is correctly set for the actual machine.
Important
Important