Yaskawa Large Capacity Sigma II Series - Manual (Page 215)

5 Servo Adjustment
5.4.3 Making Manual Adjustments
5-32
• Position Loop Gain (Pn102)
The responsiveness of the servo system is determined by the position loop gain. The
response speed increases if the position loop gain is set to a high value, so the time
required for positioning will be shortened. In order to set the position loop gain to a high
value, the rigidity and natural frequency of the mechanical system must be high.
The responsiveness of the whole servo system may become unstable if only the position
loop gain is increased, because the speed reference as output from the position loop is
likely to become unstable. Increase the speed loop gain while observing the response.
Adjustment Procedure
1. Set the position loop gain to a comparatively low value. Then increase the speed loop
gain set in Pn100 to within a range where there is no noise or oscillation resulting.
2. Decrease the speed loop gain a little from the value set in step 1. Then increase the posi-
tion loop gain to within a range where there is no overshooting or oscillation resulting.
3. Set the speed loop integral time constant in Pn101 while observing the positioning set-
ting time and the vibration of the mechanical system. If the constant is too large, posi-
tioning setting time will be long.
4. Set the torque reference filter to a small value in Pn401 if the mechanical system does
not have shaft torsion resonance. If the mechanical system generates oscillation noise in
a high-pitched tone, shaft torsion resonance may be resulting. In that case, set Pn401 to
a larger value.
5. Finally, progressively make fine adjustments to parameters such as the position loop
gain, speed loop gain, and integral time constant to find the optimal points.
„ Function to Improve Response Characteristics
The mode switch, feed-forward, and bias functions can improve the response characteristics
of the servo system only if they are used properly. If they are used improperly, they will
worsen the response characteristics. Refer to the following instructions and make adjust-
ments to these functions while observing the change in the actual response characteristics.
Mode Switch
Use the mode switch function in order to improve the saturation characteristics of the servo
system if there is torque reference saturation at the time of acceleration or deceleration of the
servomotor. If an appropriate value is set with this function, the speed loop in PI (propor-
tional and integral) control is switched over to P (proportional) control when the operation
speed exceeds the set value.