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

6.13 Absolute Linear Encoders

6.13.6 Calculating the Current Position in Machine Coordinates

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 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 ign)
The current position P
P = P
M
P = M
E
P = M
S
Symbol
P
E
M
O
P
O
P
S
M
S
6-94
0
0
P
M × R
in the machine coordinate system is calculated as follows:
M
- P
E S
×
R + P
O O
×
R + P '
S S
Meaning
Position data for the current position of the
absolute linear encoder
Upper 16 bits (with sign) of the position data for
the current position of the absolute linear encoder
Lower 20 bits of the position data for the current
position of the absolute linear encoder
Position data of the origin
Upper 16 bits (with sign) of the position data of the
origin
Origin (reference po ition)
1 2
1 2
M × R
O
P
E
P ' P
M
Encoder Divided Pulse
Output (PAO and PBO)
Current po ition
4
P
O
Setting or Unit
Absolute Encoder
Position Output (PSO)
Signals
Encoder Output Resolu-
tion (Pn281)
−
Encoder Output Resolu-
tion (Pn281)
−
Continued on next page.
Signal
Encoder pulses
−
Encoder pulses
−