21-06-2013, 04:10 PM
Complex eigenvalue analysis of windscreen wiper chatter noise and its suppression through structural modifications
ABSTRACT:
This paper presents an approach to predict automotive windscreen wiper chatter noise using finite element
method. In this study, a 3-dimensional finite element model of a real wiper blade is developed and then
validated using experimental modal analysis. In order to assess stability of the wiper blade assembly,
complex eigenvalue analysis that made available in ABAQUS is performed. The positive real parts of
complex eigenvalue indicate unstable system. The baseline model is first simulated and stability of the
system is examined. Having found a predicted unstable frequency which is chatter noise, various structural
modifications are proposed in order to reduce it.
Introduction
Windscreen wipers are indispensable
components to the maintenance of a safe and
comfortable field of vision when driving on rainy
days. Today, almost all automobile are equipped
with windscreen wiper, often by legal
requirement. Clear vision for the car driver is an
important prerequisite for safety in road traffic. A
conventional wiper as shown in Figure 1
generally consists of an arm, pivoting at one end
and with a long rubber blade attached to the other
[1]. The blade is swung back and forth over the
windscreen, pushing water from its surface. The
mechanical structure of the wiper blades is
attached to the arm tips, holds the rubber blade.
Experimental approaches
This section describes in details experimental
approaches to study vibration of the windscreen
wiper. The first experimental approach is using
experimental modal analysis to validate the
developed 3 dimensional FE model in terms of
natural frequency and its associated mode shape.
The second experiment is carried out to study
vibration of the wiper in the wet condition.
Results and Discussion
The results obtained from the experimental
and FE method is utilized for comparison and
validation. The first section presents the
correlation between EMA and FE modal analysis
results. Then, vibration results from experiment
will be discussed. Next, complex eigenvalue
analysis of baseline model is performed for the
validation with the experimental results. Finally,
complex eigenvalue analysis is performed on the
modified wipers. A good modification should not
produce any positive real parts.
Conclusion
This paper presents an approach to predict
wiper blade chatter noise using FE method.
Complex eigenvalue analysis that made available
in commercial software package, ABAQUS is
used to predict chatter frequencies. From the
experiment, the result shows that the windscreen
wiper produces a low frequency noise called
chatter, at dominant frequency of 11Hz. It is
found that, at different wiper average speeds, the
chattering vibration is generated before and after
the wiper turnover. The complex eigenvalue
analysis has been utilized in a finite element
analysis to study chatter problem. The measured
chatter frequency has been successfully
replicated in the analysis. Initially, there are six
unstable frequencies (chatter) appeared in the
baseline model.