Omron NJ501-1300, User Manual

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8 Homing
8-12
NJ-series CPU Unit Motion Control User’s Manual (W507)
8-4 Homing with an Absolute Encoder
This section describes how to use the absolute encoder of the G5-series Servo Drive with built-in Ether-
Cat communications.
Servo Drives that use EtherCAT communications have their own position control loop. Therefore, the
actual position from the encoder is not used in the MC Function Module for control. Actual position infor-
mation is received via EtherCAT communications. This means that you can access the actual position
in the user program and/or monitor it from the Sysmac Studio.
If you use an absolute encoder, the absolute data can be retained by the battery backup in the encoder
even when the power supply to the CPU Unit is turned OFF. When you execute the MC_Power (Power
Servo) instruction, the position is determined by reading the actual position from the absolute encoder.
Unlike when using an incremental encoder, after home is defined, you do not need to perform the hom-
ing operation again.
Precautions for Correct Use Precautions for Correct Use
• If you use an absolute encoder, connect a battery to the CPU Unit and an absolute encoder
backup battery to the Servo Drive.
• Always execute the MC_Home instruction to define home when you use the absolute encoder
for the first time, after you replace the motor, when the battery in the absolute encoder expires,
or at any other time when the absolute value data is lost.
• If there is an error for the Battery in the CPU Unit when the power supply to the Controller is
turned ON, an Absolute Encoder Home Offset Read Error (event code:14600000 hex) occurs.
You can use the ResetMCError instruction to reset the error and turn ON the Servo. When the
Servo is turned ON, home is defined with an absolute encoder home offset of 0. To move to
correct positions, execute the MC_Home instruction to define the correct home position. If the
power supply to the Controller is turned OFF, home will become undefined.
• After home is defined, cycle the power to the Servo Drive. After you complete these steps, the
position is defined by MC_Power alone.
Battery backup
Motor (absolute encoder)
Servo Drive
Battery
Absolute data
MC_Power executed.
CPU Unit
M
Battery