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

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 - P
M E S
×
P = M R + P
E
×
P = M R + P
S S
Symbol
Position data for the current position of the
P
E
absolute encoder
Current position of the multiturn data of the
M
absolute encoder
P
Position of the current position within one rotation
O
Position data of the absolute encoder when
P
S
absolute encoder was reset
Multiturn data of the absolute encoder when
M
S
absolute encoder was reset
Position of the absolute encoder within one
P '
S
rotation when absolute encoder was reset
P
Current position in machine coordinate system
M
R Number of encoder pulses per revolution
Calculations for Reverse Rotation Mode (Pn000 = n.1)
If you are using a Rotary Servomotor, you must reset the absolute encoder. Refer to the following
Information
section for information on resetting the absolute encoder.
Origin (reference po ition)
-1 0
-1 ±0
P
in the machine coordinate system is calculated as follows:
M
O
'
S
Meaning
5.17
Resetting the Absolute Encoder

6.12.6 Calculating the Current Position in Machine Coordinates

Current po ition
+1 +2
+1
M × R P
O
P
E
P
M
Encoder Divided Pulse
Output (PAO and PBO)
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
PE = -M × R + PO
PS = MS × R + PS
on page 5-51
6.12 Absolute Encoders
+
+2
Setting or Unit
Absolute Encoder
Position Output (PSO)
Signal
Encoder pulses
−
Encoder pulses
−
Encoder pulses
Encoder resolution
PM = PE - PS
PE = -M × R - PO
PS = MS × R - PS'
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