Parker EME
Setting up Compax3
192-120103 N13 C3I20T11 / C3I32T11 December 2010
259
Example cam drive:
If the drive moves considerably (e.g. 180°) during the measurement, the behavior
of the system will change greatly over this range => caused by non-linearities in the
signal range.
An inexact measurement is the result.
If the excitation is reduced so that the drive will move only by a few degrees, the
behavior of the system at this working point will be approximately constant.
An exact measurement is the result.
Shifting the working point into a linear range
Signal amplitude large with offset => no non-linearity in the signal range
For this, the signal range is shifted so that approximately linear conditions are valid
=> the results of the measurement show the dynamic behavior at the working point.
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 abruptly 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
t
v
tes
t m
o
ve
±
V
s
tim
u
la
ti
o
v
tes
t m
o
ve
±
V
s
tim
u
la
ti
on
v
t
static friction
V
test move
: Speed of the test movement
V
stimulation
: Speed of the excitation signal
static friction: Static friction
