by the user in the range of 2
5
through 2
12
points per sinusoidal cycle via AF command. See the AF command in the
command reference for more information.
The unique position within one cycle can be read using the following equation:
a
b
1
-
n
V
V
tan
360
2
Fine
The overall position can be determined using:
Fine
2
les
Coarse_cyc
Position
n
Where:
n is the number of bits of resolution that were used in the conversion.
Coarse_cycles is the whole number of cycles counted.
Fine is the interpolated position within one cycle.
Vb and Va are the two signals as indicated in Figure A11.2.
Calculating Equivalent Counts
The units of distance is counts in DMC code and all feedback types, including sin/cos feedback, is translated into
equivalent counts. Below is a brief example of how a user would calculate sin/cos periods into counts which is
helpful in determining the resolution of the system.
Example:
Assume that a motor has 1000 sin/cos periods per revolution. With
no
interpolation the controller will
interpret a single sin/cos period as 4 equivalent counts. Thus the total counts per revolution would be as
follows:
1000
[
sin
/
cos
period
rev
]
×
4
[
counts
sin
/
cos
period
]
=
4000
[
counts
/
rev
]
Using “AF 5” the user has selected to interpolate the the sin/cos signal to 2
5
counts per sin/cos period. The
following counts/rev would calculated as follows:
1000
[
sin
/
cos
period
rev
]
×
2
[
counts
sin
/
cos
period
]
5
=
32,000
[
counts
/
rev
]
A12 – ICM-42100 (-I100) ▫ 273
DMC-40x0 User Manual