YASKAWA SGD7S

6.13 Absolute Linear Encoders
6.13.6 Calculating the Current Position in Machine Coordinates
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6
Application Functions
6.13.6 Calculating the Current Position in Machine Coordinates
With an absolute linear encoder, you must set the position of the origin (i.e., the origin of the
machine coordinate system).
The host controller reads the coordinate from the origin of the encoder coordinate system. The
host controller must record the value of this coordinate.
The method to calculate the coordinate value of the present position from the origin of the
machine coordinate system is given below.
The position data from the absolute linear encoder is signed 36-bit data, but the upper 16 bits
(with sign) and the lower 20 bits are output separately.
Encoder Divided Pulse Output (PAO and PBO) Signals
For the upper 16-bit data (with sign), the upper bits (16 bits, including the sign) of the current
position after dividing by the setting of Pn281 are output with serial communications according
to the transmission specifications.
For the lower 20-bit data, the lower bits (20 bits) of the current position after dividing by the
setting of Pn281 are output as a pulse train.
Absolute Encoder Position Output (PSO) Signal
For the upper 16-bit data (with sign), the upper bits (16 bits, including the sign) of the current
position in encoder pulses are output with serial communications according to the transmission
specifications.
For the lower 20-bit data, the lower bits (20 bits) of the current position in encoder pulses are
output as a pulse train.
The current position P
M
in the machine coordinate system is calculated as follows:
P
M
= P
E
- P
S
P
E
= M
O
×
R + P
O
P
S
= M
S
×
R + P
S
’
Symbol Meaning
Setting or Unit
Encoder Divided Pulse
Output (PAO and PBO)
Signals
Absolute Encoder
Position Output (PSO)
Signal
P
E
Position data for the current position of the
absolute linear encoder
Encoder Output Resolu-
tion (Pn281)
Encoder pulses
M
O
Upper 16 bits (with sign) of the position data for
the current position of the absolute linear encoder
−−
P
O
Lower 20 bits of the position data for the current
position of the absolute linear encoder
Encoder Output Resolu-
tion (Pn281)
Encoder pulses
P
S
Position data of the origin
M
S
Upper 16 bits (with sign) of the position data of the
origin
−−
Continued on next page.
Machine coordinate
Value of upper
16-bit data
(with sign)
0123 4
0
1
2 3
Origin (reference position) Current position
M
O × R
P
E
PO
PS
PMPS’MS × R