ADLINK Technology PCI-8366+, User Manual

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Operation Theory 71
Since the target position is a software recorder for the motion end
position, it doesn’t work under the following conditions:
X Case 1: Velocity motion is applied, because velocity motion
have no end position information.
X Case 2: emg_stop(), tv_stop() and sv_stop() are executed,
because motion stop before motion completed.
Once it is executed, the get_target_position() value is meaning-
less unless a position relatived motion function is executed.
Move ratio control
“Move ratio” means “How many command pulses will let the axes
move 1.0 mm”. Refer to the figure below; a servomotor is used to
drive the moving part through a geared mechanism.
1. If the resolution of the motor is 8000 pulses/round, and,
2. The resolution of the gear mechanism is 10 mm/round.
(i.e., part moves 100 mm if motor turns one round).
Then the “move ratio” will be 8000/10 = 800 pulses/mm.
Figure 4-29: Move Ratio Control
All motion commands issued by the SSCNET board are in units of
mm or mm/sec. Users need to set the “move ratio” value using
set_move_ratio() according to the mechanical design.
If user want to check current “move ratio” value, get_move_ratio()
function is helpful.
Note : If the set_cnt_to_axis() function is called to allow an encoder
counter to work as a position feedback source, then the
move ratio will refer to the pulses from the encoder counter
rather than from the SSCNET motor driver.