
16. DIGITAL SERVO
825
NOTE When Ns or Np is greater than 32767, make a setting by using the
method below.
Servo software
series
Setting method
90B0 series
Set the number of position pulses by using the product
of the two parameters including the position feedback
pulse conversion coefficient (PRM2185).
9096 series
Reduce the number of velocity pulses (PRM2023) and
the number of position pulses (PRM2024) by a factor of
10 by setting the initialization bit (PRM2000#0) to 1.
D Setting the number of position pulses by using the position feedback
pulse conversion coefficient
When the number of position feedback pulses = A × B, select B so that A is
within 32767.
A: Number of position feedback pulses (= PRM2024)
Set a value not greater than 32767.
B: Position feedback pulse conversion coefficient (= PRM2185)
Set a value as small as possible not exceeding about 100 as a
guideline. (When 0 is set, 1 is assumed.)
2185
Position feedback pulse conversion coefficient
PRM
NOTE When the detector of the motor is an αi pulse coder (number of ve-
locity pulses = 8192), set a 2 raised to a power (such as 2, 4, 8, and
so forth) in this parameter.
(The position gain value used in the servo control software be-
comes more accurate.)
(Example of setting)
When a linear scale with a minimum resolution of 0.1 µm is used, and
the travel distance per motor revolution is 16 mm
Ns = travel distance per motor revolution (mm)/minimum
resolution of detector (mm)
= 16 mm/0.0001 mm = 160000 (> 32767)
Suppose that you consider two sets of A and B values that satisfy A ×
B = 160000 and A < 32767:
<1> A = 16000, B = 10
<2> A = 10000, B = 16
In <1>, B = 10. This means that this value is not 2 raised to a power.
In <2>, B = 16 = 2^4. This means that this value is 2 raised to the forth
power.
So, by using the setting of <2>, set the following:
A (PRM2024) = 10000
B (PRM2185) = 16
When servo control software of the 9096 series is used, the position
feedback pulse conversion coefficient cannot be used.
(8) Reference counter
1821
Reference counter capacity for each axis (0 – 99999999)
PRM
Specify the grid interval for the reference position return in the grid method.
Size of the reference counter =
grid interval
detection unit
Grid interval = the amount of travel per rotation of the pulse coder