Calculating The Current Position In Machine Coordinates; Encoder - YASKAWA SGD7S Product Manual

6.12 Absolute Encoders

6.12.6 Calculating the Current Position in Machine Coordinates

6.12.6 Calculating the Current Position in Machine Coordinates

When you reset the absolute encoder, the reset position becomes the reference position.
The host controller reads the coordinate Ps from the origin of the encoder coordinate system. The host
controller must record the value of coordinate Ps.
This section describes the reference position in the machine coordinate system.
The method to calculate the coordinate value of the present position from the origin of the machine
coordinate system is given below.
Machine coordinate
Value of
multiturn data
The current position P
P = P
M
P = M
E
P = M
S
Symbol
P
E
M
P
O
P
S
M
S
P '
S
P
M
R
Calculations for Reverse Rotation Mode (Pn000 = n.1)
Information
6-80
-1
-1
in the machine coordinate system is calculated as follows:
M
- P
E S
×
R + P
O
×
R + P '
S S
Meaning
Position data for the current position of the
absolute encoder
Current position of the multiturn data of the
absolute encoder
Position of the current position within one rotation
Position data of the absolute encoder when
absolute encoder was reset
Multiturn data of the absolute encoder when
absolute encoder was reset
Position of the absolute encoder within one
rotation when absolute encoder was reset
Current position in machine coordinate system
Number of encoder pulses per revolution
If you are using a Rotary Servomotor, you must reset the absolute encoder. Refer to the following
section for information on resetting the absolute encoder.
5.17
Resetting the Absolute Encoder
Origin (reference position)
0 +1
±0 +1
M × R
P
E
P P
S M
on page 5-52
Current position
+2 +3
+2
P
O
Setting or Unit
Encoder Divided Pulse Absolute Encoder
Output (PAO and PBO) Position Output (PSO)
Signals
Encoder output pulses
(encoder pulses x setting
of Pn212)
−
Encoder output pulses
(encoder pulses x setting
of Pn212)
−
Encoder output pulses
(encoder pulses x setting
of Pn212)
Setting of Pn212
PM = PE - PS PM = PE - PS
PE = -M × R + PO PE = -M × R - PO
PS = MS × R + PS PS = MS × R - PS'
Signal
Encoder pulses
−
Encoder pulses
−
Encoder pulses
Encoder resolution