Omron trajexia CJ1W-MCH72 Operation Manual page 159

All BASIC commands
4-2-89 ENCODER_RATIO
148
/i
Type Axis parameter
Syntax ENCODER_RATIO(denominator, numerator)
Description This command allows the incoming encoder count to be scaled by a non
integer number, using the equation:
MPOS = (numerator / demoninator) x encoder_edges_input
Unlike the UNITS parameters, ENCODER_RATIO affects commands
like MOVECIRC and CAMBOX, since it affects the number of encoder
edges within the servo loop at the low level. It is necessary to change
the position loop gains after changing encoder ratio in order to maintain
performance and stability.
Note: Large ratios should be avoided as they will lead to either loss of
resolution or much reduced smoothness in the motion. The actual phys-
ical encoder count is the basic resolution of the axis and the use of this
command may reduce the ability of the Motion Controller to accurately
achieve all positions.
Note: ENCODER_RATIO does not replace UNITS. Only use
ENCODER_RATIO where absolutely necessary. For all other axis scal-
ing use UNITS.
Arguments • denominator
A number between 0 and 16777215 that is used to define the
denominator in the above equation.
• numerator
A number between 0 and 16777215 that is used to define the
numerator in the above equation.
Example ' 7200 is the closest to the encoder resolution that can be devided
by an
' integer to give degrees. (7200/20=360)
ENCODER_RATIO(8192,7200)
UNITS=20 ' axis calibrated in degrees, resolution is 0.05 deg.
A rotary table has a servo motor connected directly to its centre of rota-
tion. An encoder is mounted to the rear of the servo motor and returns a
value of 8192 counts per revolution. The application requires the table
to be calibrated in degrees, but so that one degree is an integer number
of counts.
See also N/A
Section 4-2