Encoder Accuracy And Excentricity - Baumuller b maXX BM3000 Operating Manual

4.4
Configuration

4.4.6.5 Encoder accuracy and excentricity

To increase the absolute accuracy in the drives and to reduce the vibrations at rotational
frequency the encoder angle can be improved by an angular-dependent correction value.
Vibrations may occur in the speed, with the frequency of the present speed, if the encoder
is not exactly aligned centrically towards the motor shaft. The position error, which was
caused by an encoder eccentricity, cannot be corrected by the positioning controller or by
the speed controller. The position error can be approximated by a sinusoidal function.
Thus, the control error is suppressed on the encoder angle by adding an additional angle
with a sinusoidal function.
Encoders providing a low resolution such as resolvers are imprecise in their absolute ac-
curacy. In the controller the basic vibration (1st harmonic vibration) as well as other har-
monic (up to the 4th harmonic vibration) angular displacements can be compensated. For
this purpose the amplitude and the phase of the correction function must be entered in
Z106.71–
monic vibrations). The maximum harmonic vibration to be corrected is specified by
Z106.75–
Z106.3–.
a) a)
b) b)
a) Error of encoder excentricity and its approach
b) Variation of the position value angle
Figure 87:
Determination is carried out in current control. The setpoint frequency (speed) must be
constant. It must lie between 0.1 and 500 Hz.
170 Parameter manual b maXX BM3000
Document no.: 5.12001.07
of 820
Z106.70–
and (basic vibration) and in
whereat 0 is the 1st harmonic vibration. The correction is enabled by bit 6 of
2p
Encoder excentricity
Phase shifting 106.70
0 0
0 0
Approximation
Encoder excentricity
Z106.76–
Encoder excentricity
a mplitude 106.71
Position actual
2p 2p
value 106.10
(angle)
Position actual
value 106.10
(angle)
Z106.77–
and (higher har-
t
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