Gravity Compensation - YASKAWA SGD7S series Product Manual

Operating Procedure for Friction Compensation
Use the following procedure to perform friction compensation.
 Before you execute friction compensation, set the moment of inertia ratio (Pn103) as accu-
rately as possible. If the setting greatly differs from the actual moment of inertia, vibration
may occur.
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 friction com-
pensation 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
Pn121: Friction Compensation Gain and Pn122: Second Friction Compensation Gain
2
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
8.12.3

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.
ervomotor
Holding brake
When the brake i relea ed, the gravity
compen ation torque prevent the
moving part from moving due to gravity.
Moving part of machine
CAUTION
Incon i tent re pon e
becau e of friction
Low friction
Po ition deviation
High friction
Po ition reference peed
Before Friction Compen ation
8.12 Additional Adjustment Functions
Operation
table re pon e due to
friction compen ation
Po ition deviation
Po ition reference peed
After Friction Compen ation

8.12.3 Gravity Compensation

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