Chapter 8 Motion Control Function
Chapter 8 Motion Control Function
In case the position control function of motion controller is used, the origin must be determined first to execute commands based on
the absolute coordinate position. The position value of absolute coordinates is the distance based on the predetermined origin(0
position). The origin determination means setting the origin of the machine for position control using absolute coordinates.
8.1.1 Origin Determination
1. Methods to determine the origin
There are two methods to determine the origin of the machine as below.
(1) Homing
It is a method to determine the origin of the machine by moving the machine using a sensor connected to servo drive with
homing (MC_Home) motion function block.
When homing command is executed, the origin determination becomes the origin indetermination status, and homing is
successfully completed, it becomes the origin determination status.
(2) Current position setting
After moving the machine to a certain position by using JOG operation (LS_Jog) or relative coordinate position control
(MC_MoveRelative) motion function block, the position can be set to the specific position with the current position location
setting (MC_Setposition) motion function block. In this case, the position is recognized as an absolute coordinate and
becomes origin determination status.
The origin determination status of axis can be identified with motion axis flag AXxx_HOME_CMPL. (xx: axis number)
2. Origin determination when using absolute encoders
In case of using absolute encoder in servo drive, absolute data value is maintained by battery backup even if the power is
off. Motion control module can continue to maintain the origin determination status by reading the current position from the
value of absolute encoder and calculating absolute coordinate position when it is connected to servo drive.
To this end, the encoder selection of basic parameters among operating parameters should be set to ‘1: Absolute encoder’
in case of using absolute encoder. Even though the power of motion control module and servo drive is off after the
establishment of origin determination status, the previous origin determination status is maintained by calculating absolute
coordinate position when servo drive is connected in case encoder selection parameter is ‘1: Absolute encoder’ when the
power is re-applied.
In absolute coordinate system using absolute encoder as above, the absolute coordinate position can be controlled without
the origin determination even after power off/on.
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