SERVO ADJUSTMENT
A.2.2 Manual Adjustment
— A-6 —
Speed Loop Integration Time Constant (Cn-05)
The speed loop has an integration element to allow response to micro-inputs.
This integration element can produce a delay in the servo system, and the positioning
setting time increases and response becomes slower as the time constant increases.
However, the integration time constant must be increased to prevent machine vibration if
the load moment of inertia is large or the mechanical system includes a element that is
prone to vibration.
The following formula calculates a guideline value.
Ti: Integration Time Constant (s)
Kv: Speed Loop Gain (Hz)
Ti
≥
2.3
×
1
2
π
×
Kv
Torque Reference Filter Time Constant (Cn-17)
When a ball screw is used, torsional resonance may occur which increases the pitch of
the vibration noise.
This vibration can sometimes be overcome by increasing the torque reference filter time
constant.
This filter will, however, produce a delay in the servo system, just like the integration time
constant (Cn-05), and its value should not be increased more than necessary.
Speed Reference Gain (Cn-03)
Changing the speed reference gain (Cn-03) changes the position loop gain an equivalent
amount. That is, reducing the speed reference gain is equivalent to reducing the position
loop gain and increasing it is equivalent to increasing the position loop gain.
Use this parameter (Cn-03) in the following circumstances:
•
No position loop gain adjustment at host controller (including cases where fine ad-
justment not possible by changing number of D/A converter bits)
•
Clamping the speed reference output range to specific speeds
Normally leave at the factory setting.
Note
For a speed-control Servopack, the position loop gain (Cn-1A) is valid in zero-
clamp mode only.
For normal control, change the position loop gain at the host controller or adjust
the speed reference gain (Cn-03) in the Servopack.
Changing Cn-1A does not change the position loop gain.
A
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