09.2008 Functions
Siemens AG 6SE7087-6QX70 (Version AK)
SIMOVERT MASTERDRIVES Compendium Motion Control 7-25
AVWF = actual-value weighting factor as conversion constant/factor.
For example, if 1 LU = 1 µm, a decimal setpoint of 1000 LU represents
a travel distance of 1000 µm, or 1 mm.
Without the AVWF factor, the length information always refers to the
encoder pulses depending on the resolution of parameter P171 (motor
encoder) 2
P171
.
e.g. P171 = 12 → 4096 LU/revolution
The AVWF is calculated from this as follows:
revolution motor per LU
revolution motor per distance Path
AVWF =
or
(i) factorgearbox revolution motor per LU
ncecircumfere Roller
AVWF
×
=
The aim should be to have a resolution of about 1 µm / encoder
increment. Table 7-5 shows how large the factors are and hence how
high a resolution is to be selected.
In the example, the AVWF factors result from a roller diameter of
300.00 mm (circumference = 942477 µm). This must then be multiplied
by the gearbox factor (AVWF*).
P171 Resolution AVWF AVWF*
12 4096 230.096924 23.0096924
13 8192 115.048462 11.5048462
14 16384 57.524231 5.7524231
15 32768 28.7621155 2.87621155
16 65536 14.3810577 1.43810577
17 131072 7.19052887 0.719052887
18 262144 3.59526443 0.359526443
19 524288 1.79763222 0.179763222
20 1048576 0.89881611 0.089881611
21 2097152 0.44940805 0.044940805
Table 7-5 AVWF factors resulting from a roller diameter of 942477 µm
This results in an AVWF factor (which should be less than 1) of
0.71905288 or, as a fraction
71905288.0
0131072
942477
atorminDeno
Numerator
==
as gearbox factor or factor for the AVWF.
More encoder increments per revolution should therefore be specified
(P171) than there are LUs per revolution.
Actual-value
weighting factor
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