Setting
up Compax3
Positioning via digital I/Os
210
192-120101 N11 C3I11T11 November 2007
Example rubbing caused by friction:
In systems subject to a distinct transition between rubbing caused by friction and
sliding friction, the rubbing force will reduce abuptly as soon as the drive is moved
(v>0). With a motor at standstill, the excitation signal will cause a multiple passing
through the range of rubbing friction during measurement. Due to the non-linearity
in the signal range, the resulting measurement will be inexact.
If the drive moves, however, fast enough during the measurement, so that the
speed will not become zero during the measurement, the system remains in sliding
friction and a precise measurement can be obtained.
Optimal measurement with rubbing friction
v
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v
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v
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±
V
sti
m
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v
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st m
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V
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v
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static friction
V
test move
: Speed of the test movement
V
stimulation
: Speed of the excitation signal
Example backlash: (for example in gearboxes)
Here, non-linearities are caused, if the tooth edges will turn from one side to the
other during measurement. The reason for this is a change of the sign of the force
transmitted by the gearbox.
In order to avoid this, you can try to transmit a constant torque by keeping a
constant speed and to avoid a change of the sign during the measurement by
choosing a relatively small excitation amplitude.
