Gravity Compensation - YASKAWA SGD7S-xxxDA0 series Product Manual

Step
Set the following parameters related to friction compensation to their default settings.
Friction compensation gain (Pn121): 100
Second friction compensation gain (Pn122): 100
Friction compensation coefficient (Pn123): 0
1 Friction compensation frequency correction (Pn124): 0
Friction compensation gain correction (Pn125): 100
Note:
Always use the default settings for the friction compensation frequency correction (Pn124) and fric-
tion compensation gain correction (Pn125).
Gradually increase the friction compensation coefficient (Pn123) to check the effect of friction com-
pensation.
Note:
Usually, set the friction compensation coefficient (Pn123) to 95% or less.
If the effect is insufficient, increase the friction compensation gain (Pn121) by 10% increments until
vibration stops.
Effect of Adjusted Parameters
2
Pn121: Friction Compensation Gain and Pn122: Second Friction Compensation Gain
These parameters set the response to external disturbances. The higher the setting is, the better
the response will be. If the machine has a resonance frequency, however, vibration may occur if the
setting is too high.
Pn123: Friction Compensation Coefficient
This parameter sets the effect of friction compensation. The higher the setting is, the more effective
friction compensation will be. If the setting is too high, however, vibration will occur more easily.
Usually, set the value to 95% or less.
Effect of Adjustments
The following graphs show the response with and without adjustment.
3
9.12.3

Gravity Compensation

When the Servomotor is used with a vertical axis, gravity compensation prevents the moving
part from falling due to the machine's own weight when the brake is released.
SERVOPACKs with software version 0023 or higher support gravity compensation.
Servomotor
Holding brake
When the brake is released, the gravity
compensation torque prevents the
moving part from moving due to gravity.
Moving part of machine
A timing chart for when the moving part is raised then lowered is provided below.
Refer to the following section for details on brake operation timing.
6.11.1
Brake Operating Sequence
Poor response
because of friction
Low friction
Position deviation
High friction
Position reference speed
Before Friction Compensation
on page 6-32
9.12 Additional Adjustment Functions

9.12.3 Gravity Compensation

Operation
Response improved by
friction compensation
Position deviation
Position reference speed
After Friction Compensation
9
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