Developing a load case for analysis of Squeak and Rattle events in passenger cars
Typ
Examensarbete för masterexamen
Program
Product development (MPPDE), MSc
Publicerad
2020
Författare
Blom, Rasmus
Nilsson, Jonatan
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
A part of Volvo Cars strategy is shifting engineering activities to the early phases
of the product development, without the need for complete vehicle prototypes. An
important early phase activity in the product development of passenger cars is to
evaluate Squeak & Rattle emitted from subsystems in the car. The subsystem studied
in this project is the instrument panel (IP). Today’s excitation signals applied
onto the IP is longer than necessary and not optimized for Squeak & Rattle evaluation.
The aim of this thesis is consequently to develop effective excitation signals
and provide the method of how this is achieved for further improvements and the
possibility to develop new excitation signals for future product development of passenger
cars.
The thesis describes the process of recording excitation- and response signals, for
the car as a whole and the IP subsystem. Nine different road tracks are recorded
for two cars. A methodology for creating shortened excitation signals is explained,
with crucial steps of identifying Squeak & Rattle events, grouping these into parts
and concatenating them sequentially in time domain. The frequency content of the
shortened excitation signals is examined to avoid significant deviations from the unshortened
excitation signals.
Eleven different concepts for the development of an excitation signal is created. The
synthesized signals performance is verified with two test rigs. With regards to the
Squeak & Rattle causing properties of the signal and the time compression ability, an
optimal concept is presented. This concept proved to have favourable characteristics
although further optimization could generate an even better concept. The methodology
is not flawless, whilst nevertheless having the capability to compress the total
excitation signal time by up to 95% and maintaining decent quality. Possible error
sources and further methodology improvements is finally discussed.
Beskrivning
Ämne/nyckelord
squeak, rattle, excitation signal, signal compression, product development , relative displacement, instrument panel, FFT, testing, accelerometers, CAE, optimization