Setting
up Compax3
Positioning via digital I/Os
208
192-120101 N11 C3I11T11 November 2007
Non-linearities and their effects
In this chapter you can read about:
Attenuation of the excitation amplitude............................................................................................209
Shifting the working point into a linear range...................................................................................209
Non-linearities in mechanical systems are for example due to friction, backlash or
position-dependent transmissions (cams and crankshaft drives). In general, the
frequency response is only defined for linear systems (see
Linear Systems 7.2
(see page 224)). What happens in the frequency range in the event of a non-linear
system, is shown below.
Signal amplitude too high => non-linearity in the signal range
Signals
Spectrum
O
utput
S
ign
al
Input Signal
System
Input Signal
Output Signal
Input Signal
Output Signal
Due to the non-linear transmission behavior of the system, many "new" frequencies
were generated in the output signal. In the frequency response, only one change of
the frequency present in the input signal can be displayed meaningfully.
=> The frequencies generated in the spectre of the output signal lead to a
deterioration of the measured frequency response.
There are however two possibilities to make successful measurements of
frequency responses in spite of non-linearities present:
