Operation & Software Manual
202
Direct Drives & Systems
Chapter C: System functions
ETEL Doc. - Operation & Software Manual # DSC2P 903 / Ver. F / 3/6/05
13.10 Analog encoder interpolation
A period is divided into four equal parts and each of them is interpolated. Parameter
K77
determines this
interpolation for
analog encoders
(1Vptp and EnDat 2.1). As the encoder signals are coded on 13 bits (16 bits
for the DSCDL), it is possible to choose an interpolation included between 8 and 12 bits (8 and 15 bits for the
DCSDL) corresponding to an interpolation factor between 0 and 4 (0 and 7 for the DSCDL).
Example:
We have an analog encoder with a period equal to 40
µ
m. If the maximum interpolation factor of the sine and
the cosine (K77=4 for all controllers and K77=7 for the DSCDL) is used, there are 4
⋅
2
12
= 16384 (4
⋅
2
15
=
131072 for the DSCDL) increments on one period of encoder signals. The encoder resolution is:
Parameter K77 directly influences the motor position, speed, acceleration and jerk values (refer to
It also directly influences units scales (refer to
). Refer to
for more information about the position
encoder.
Parameter
K69
has a similar effect as parameter K77, but for
digital TTL encoders
.
Remark:
With an analog encoder (1 Vptp and EnDat 2.1), the minimum position reading resolution is 1 [dpi].
With a TTL encoder (no interpolation), the minimum position reading resolution is 16 [dpi],
corresponding to the 4 bits (= 16) default shift value. Refer also to formulas in
, to see the
effect of this factor 16 value.
Available on
DSC2P
DSC2V
DSCDP
DSCDL
DSCDM
DSC2P / DSC2V / DSCDP / DSCDM
DSCDL
Formulas
K
Name
Controller
Value
Comment
K77
Encoder
Interpolation
shift value for
analog encoder
(1Vptp and
EnDat 2.1)
DSC2P
DSC2V
DSCDP
DSCDM
0
1
2
3
4
Interpolation of signals on 8 bits
Interpolation of signals on 9 bits
Interpolation of signals on 10 bits
Interpolation of signals on 11 bits
Interpolation of signals on 12 bits
5
6
7
...
12
Signals shift of 1 bit
Signals shift of 2 bits
Signals shift of 3 bits
Signals shift of ... bits
Signals shift of 8 bits
DSCDL
0
1
2
3
4
5
6
7
Interpolation of signals on 8 bits
Interpolation of signals on 9 bits
Interpolation of signals on 10 bits
Interpolation of signals on 11 bits
Interpolation of signals on 12 bits
Interpolation of signals on 13 bits
Interpolation of signals on 14 bits
Interpolation of signals on 15 bits
8
...
12
Signals shift of 1 bits
Signals shift of ... bits
Signals shift of 5 bits
K
Name
Value
Comment
K69
Encoder shift value
for TTL encoder
0
1
2
3
4
...
Signals shift of 4 bits (= 16 [dpi] min. resolution)
Signals shift of 5 bits (= 32 [dpi] min. resolution)
Signals shift of 6 bits (= 64 [dpi] min. resolution)
Signals shift of 7 bits (= 128 [dpi] min. resolution)
Signals shift of 8 bits (= 256 [dpi] min. resolution)
(values above 4 are normally not used)
40 10
6
–
⋅
16384
----------------------
2.44 10
9
–
m
⋅
=
40 10
6
–
⋅
131072
----------------------
0.3 10
9
–
m
⋅
=
