Yaskawa MP2000 Series: Built-in SVB or SVB-01 Motion Module - Manual (Page 339)

9.1 Absolute Position Detection Function
9.1.1 Outline of the Function
9-2
9.1 Absolute Position Detection Function
This section explains the Absolute Position Detection Function in the MP2000-series Machine Controller.
Refer to Appendix E Fixed Parameter Setting According to Encoder Type and Axis Type together with this section.
9.1.1 Outline of the Function
The Absolute Position Detection Function detects the position of the machine (axis) even if the power is turned OFF.
This allows it to establish the machine coordinate system automatically and to begin operating automatically without
having to execute the zero point return (ZRET) command after power is turned ON.
Absolute position detection is performed using an absolute encoder built into a Servomotor.
The following are features of the system for detection of the absolute position.
• If eliminates the need for a zero point return after the power is turned ON.
• If eliminates the need for a zero point dog and overtravel limit switch.
Terminology: Absolute Encoder
There are two types of encoders available. An incremental encoder detects position by calculating the zero point difference. An
absolute encoder detects the absolute position relative to a reference position.
The absolute encoder uses a battery connected to the battery terminals of the SERVOPACK to maintain absolute data at all
times even though power is turned OFF. It also updates absolute data if the position changes while the power is OFF.
The absolute encoder is comprised of a detector that is used to detect absolute position within one rotation and a counter that is
used to count the number of rotations.
After the automatic operation starts, the absolute encoder operates in the same way as an incremental
encoder.
9.1.2 Reading Absolute Data
Turn ON the Machine Controller and the SERVOPACK at the same time or turn ON the SERVOPACK first to read the
absolute data loaded from the absolute encoder to the Machine Controller.
The following diagram shows an overview of the absolute data read operation.
* Refer to 9.3.2 ( 1 ) Calculating the Zero Point of the Machine Coordinate System for information on how to cal-
culate the zero point of machine coordinate system.
This way the absolute machine position can be detected and automatic operation can begin immediately after power is
turned ON with an automatic position detection system.
(1) Machine Controller requests SERVOPACK to initialize the sensor when MECHATROLINK communication is estab-
lished.
(2) SERVOPACK obtains the multiturn data (N) and initial incremental pulses (PO) at reception of the sensor initialization
request from Machine Controller.
(3) SERVOPACK creates the position data according to the obtained multiturn data and initial incremental pulses.
(4) Machine Controller reads out the position data or absolute data from SERVOPACK.
(5)
Machine Controller automatically sets a machine coordinate system * according to the electronic gear ratio converted from
the absolute value calculated on the base of the read information and the data of Zero Point Position in Machine Coordinate
System Offset (OL
48).
Position
monitoring
(IL 0E to
IL 16)
Motion monitoring
parameters
(5)
Electronic gear
calculation
CPF
machine
coordinate
system
calculation
MP2000-series Machine Controller
SERVOPACK
MECHATROLINK
Servomotor
Encoder
(4)  Reads position information or
absolute data.
(3) Creates position information.
(2)  Sends absolute data (N and PO).
(1)Requests sensor initialization.
㧨 Motion Section㧪