B9: Zero Servo - YASKAWA U1000 Series Technical Manual

◆ b9: Zero Servo

The Zero Servo function is a position loop that can be used to lock the motor at a certain position against external power
to the motor.
It must be activated using a digital input set for H1- = 72. Once this input is closed and the motor speed falls below
the level set in parameter b2-01, the drive will enter Zero Servo mode and maintain the current position. Even if the
motor speed exceeds the level set in parameter b2-01 in Zero Servo mode, the drive will continue to maintain the current
position. When the input assigned to trigger the Zero Servo function is released and the Run command is still present, the
drive reaccelerates according to the speed reference.
Figure 5.30
When Zero Servo is active, the deviation between the rotor position and the zero position is displayed in monitor U6-22
(monitor value must be divided by 4 to get the deviation in actual encoder pulses).
A digital output programmed for "Zero Servo complete" (H2- = 33) is turned on when the rotor position is within the
zero position, plus or minus the Zero Servo completion width set in parameter b9-02.
Note: 1. The Run command must remain on when using the Zero Servo function. If the Run command is switched off, then Zero Servo will no
longer be able to hold the load in place.
2. When the Zero Servo command has shut off, the Zero Servo Completion digital output width also shuts off.
3. Avoid using Zero Servo to lock 100% load for long periods, as this can trigger a fault. If such loads need to be held in place for long
periods, either make sure the current is less than 50% of the drive rated current during Zero Servo, or use a larger capacity drive.
4. If the load rotates the motor when using CLV/PM, a dv4 fault may occur. To prevent this, either increase the Zero Servo gain (b9-01)
or increase the number of pulses set to F1-19 that are required to trigger dv4.
■ b9-01: Zero Servo Gain
Parameter b9-01 adjusts the responsiveness of the Zero Servo position loop. Increase the value if the response is too slow
and the deviation from the zero position rises too high when load is applied. Decrease the value if vibrations occur during
Zero Servo operation.
Note: Before adjusting the Zero Servo gain, make sure the ASR parameters (C5-) are set up properly and vibration or hunting does
not occur when running with a zero speed reference.
No.
b9-01
b9-02: Zero Servo Completion Width
■
Sets the output range of the Zero Servo completion signal. Enter the amount of deviation allowable from the desired
position to trigger Zero Servo. An output terminal set for Zero Servo Complete (H2- = 33) will be triggered when the
motor reaches the position Zero Servo position plus or minus b9-02.
No.
b9-02
YASKAWA ELECTRIC SIEP C710636 02B YASKAWA U1000 Technical Manual
Run command
Zero Servo command
Motor Speed
b2-01
DC Injection Braking
start frequency
Figure 5.30 Zero Servo Operation
Name
Zero Servo Gain
Name
Zero Servo Completion Width
ON
ON
Zero Servo
Operation
5.2 b: Application
OFF
OFF
Setting Range Default
0 to 100
Setting Range Default
0 to 16383
5
5
10
215