How can perceived vertical choppiness in the driver seat be improved in an electric vehicle
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Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Mobility engineering (MPMOB), MSc
Publicerad
2023
Författare
Kunal, Kumaresh
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
It’s essential to understand both the positive and negative implications of the automobile
industry’s transition from traditional internal combustion engine (ICE)
vehicles to electric vehicles (EVs). One such negative impact is the vertical choppiness
levels in an EV. Choppiness, considered a part of ride comfort, is defined as
road-induced uneven pitch and bounce motions of the vehicle. It can be felt between
the frequency ranges of 3 and 8 Hz. Choppiness is more predominant when
the vehicle is driven over an irregular or rough surface. As humans have the lowest
tolerance for vibrations between 3 and 8 Hz, high degrees of choppiness impact the
abdomen region as well as the voice of the occupants. The ICE, together with its
engine mounts, acts as a heavy mass damper, reducing vibration input to the driver
and occupants’ seats at 3-8Hz, whereas the electric motor is not as heavy and has
less potential to reduce choppiness, hence increasing choppiness in a BEV. It is crucial
to think about the impact of choppiness because ride comfort is one of the most
important elements a customer evaluates when buying a new vehicle.
This thesis focuses on finding low cost solutions by examining the interaction of the
driver in the seat with the suspension to reduce the choppiness without having a
negative impact on the shake vibration region (8-20Hz). Air suspensions are one
way to reduce the choppiness, but they cannot be used in every vehicle due to their
high cost. The thesis proposal attempts to validate the potential of altering the seat
characteristics, i.e., the seat spring and damping, in order to lower the levels of choppiness
perceived in the driver’s seat of a BEV, using CAE ride models. The effects
of the driver’s vertical seat bounce frequency on choppiness were investigated using
these ride models, as well as design modifications that have an impact on choppiness
levels. The results obtained from these models were also validated by comparing
them with tests done on the actual vehicle on the shake rig. When these models were
run on different virtual roads, the corresponding responses were recorded and used
for further calculation of RMS acceleration values of the seat, which was the cost
function chosen to quantify the choppiness levels of the ride models in accordance
with the international standards in place for the effect of environmental vibration
on operator health, efficiency, and comfort (ISO 2631).
Beskrivning
Ämne/nyckelord
choppiness , ride comfort , CAE ride models , seat parameters , validation , BEV , ICE , ISO 2631 , efficiency , RMS acceleration