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

6.9.6

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 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.
Machine coordinate
Value of upper
16-bit data
(with sign)
The current position P
P = P - P
M E S
×
P = M R + P
E O
×
P = M R + P
S S
Symbol
Position data for the current position of the
P
E
absolute linear encoder
Upper 16 bits (with sign) of the position data for
M
O
the current position of the absolute linear encoder
Lower 20 bits of the position data for the current
P
O
position of the absolute linear encoder
P
Position data of the origin
S
Upper 16 bits (with sign) of the position data of the
M
S
origin
Origin (reference position)
0 1
0
1
P
S
M × R P '
S S
in the machine coordinate system is calculated as follows:
M
O
'
S
Meaning

6.9.6 Calculating the Current Position in Machine Coordinates

Current position
2 3
2
M × R P
O O
P
E
P
M
Encoder Divided Pulse
Output (PAO and PBO)
Signals
Encoder Output Resolu-
tion (Pn281)
−
Encoder Output Resolu-
tion (Pn281)
−
6.9 Absolute Linear Encoders
4
3
Setting or Unit
Absolute Encoder
Position Output (PSO)
Signal
Encoder pulses
−
Encoder pulses
−
Continued on next page.
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