Structure Of The Absolute Position Detection Function; Outline Of The Function; Basic Terminology - YASKAWA MP2100 Series User Manual

10 Absolute Position Detection

10.1.1 Outline of the Function

10.1 Structure of the Absolute Position Detection Function

This section explains the Absolute Position Detection Function in the MP2100/MP2100M.
10.1.1 Outline of the Function
The Absolute Position Detection Function detects the position of the machine even if 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.
The following are features of the absolute position detection system.
• Eliminates the need to execute the zero point return after power is turned ON.
• Eliminates the need for a zero point dog and overtravel limit switch.

10.1.2 Basic Terminology

The following explanation for basic terminology used in this chapter is provided to ensure basic understanding.
(1) Absolute Encoder
Absolute position detection is generally performed in a semi-closed loop using an absolute encoder built into a
Servomotor. The 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.
(2) Absolute Data
Absolute data that is stored in an absolute encoder is comprised of the number of rotations (N) from the absolute
reference position and position (PO) in a one Servomotor rotation. This absolute data is read as serial data when
the power is turned ON.
All other operations are the same as that for ordinary incremental encoders.
In other words, we can determine the absolute value P from the following equation.
• Absolute value (P) = N × RP + PO
• Number of rotations from the absolute reference position: N
• Number of pulses per one Servomotor rotation: RP
• Position in one Servomotor rotation: PO
(3) Holding Absolute Data
An 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 data if there is a change.
(4) Reading Absolute Data
When power is turned ON, absolute data is read to the SERVOPACK as well as to the MP2100/MP2100M,
where it is used to automatically calculate the absolute position and set the machine coordinate system. This way
the absolute machine position can be detected and automatic operation can begin immediately after power is
turned ON.
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