The characteristics of vehicle steering perception are decisive factors concerning vehicle safety and overall pleasure behind the wheel. It is a challenge for vehicle manufacturers to achieve these features and qualities, because usually vehicle tuning almost only relies on subjective evaluation of test drivers, which is costly and time consuming. In order to optimize suspension design and develop a tool that can be used to evaluate steering with objective metrics instead of subjective assessment, links between them must be confirmed. In this master thesis, both objective and subjective testing data of over 20 vehicles across four different segments are introduced in linear and nonlinear analysis. Linear regression analysis is applied to investigate simply positive or negative correlation between a pair of subjective-objective parameters. However, even if certain linear correlations are obtained, it is still hard to define the optimal value for objective metrics. Considering that the general shape of a correlation function can reveal which objective range give higher subjective rating, it is possible to define these preferred ranges with Neural Network (NN). The best data available is adopted from three drivers who tested 15 sedans, and some interesting results are found. The initial results demonstrate that NN is a powerful tool to uncover and graphically illustrate the links between objective metrics and subjective assessments, i.e., the specific range leading to better steering feel. Given a larger sample size, more reliable and optimal links can be defined by following the same method. These confirmed links would enable vehicle dynamics engineers to more effectively develop new vehicles with nearly perfect steering feel.

Comfort is a sensation and state of being that many people seek when they are working in the office, driving in a car, flying on an airplane, or laying in a hospital bed. The literature identifies many definitions and interpretations for comfort and discomfort, and many different ways that researchers have tried to measure comfort and discomfort. de Looze proposed a model to explain the relationship between comfort and discomfort using three key components: (a) the human, (b) the product, and (c) the environment. This dissertation added a measurement component to the model. In a repeated measures design, subjects (n=35) sat in three different office chairs for 60 minutes each on two different dates. Researchers collected subjective survey data and objective electronic data related to perceived sitting comfort and discomfort while participants completed office computer tasks. Data were analyzed to predict and quantify office worker seated comfort and discomfort using linear modeling and neural network modeling. Correlation values from the linear regression model developed in this experiment were R2 < 0.70, while the single hidden-layer neural network model predicted the comfort/discomfort responses with a higher correlation (R2=0.997). The 35 subjects in the study perceived measurable comfort differences between the three chairs tested. Subjective questions that treated comfort and discomfort in a non-linear relationship discriminated chair differences better than questions using a linear relationship. There was no significant difference between male and female comfort/discomfort responses. Comfort ratings decreased over time, while discomfort increased over time; at least 45-minute comfort testing is needed to understand subjects' comfort/discomfort in a particular office chair. Five common factors that were important to the model included: (a) fit of the product to the person, (b) the features of the product itself, (c) the time spent with the product, (d) the subjective questions, and (e) the objective pressure measurements.

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Cette thèse porte sur l'étude des liens entre des mesures électro-physiologiques du système auditif de la cochlée au tronc cérébral, les réglages et les performances auditives d'adultes utilisateurs d'implants cochleaires (IC) MED-EL ®.La majeure partie des travaux s'est intéressée aux ECAP (Electrically-evoked compound action potentials) traduisant l'activité synchrone des neurones auditifs cochléaires en réponse à la stimulation délivrée par l'IC. Ceux-ci ont été enregistrés soit lors de l'implantation, soit chez des utilisateurs expérimentés afin d'évaluer leur intérêt comme prédicteurs des niveaux de perceptions. Nos travaux montrent que malgré de grandes variations interindividuelles, les ECAP sont liés aux niveaux de perception. Cette relation ne permet cependant pas encore une prédiction suffisamment précise des niveaux de perception implémentés dans les réglages. Les IC MED-EL ® présentent la particularité de présenter les données d'impédance brutes sous forme de matrice de voltage pouvant servir à estimer la diffusion du courant autour de chaque électrode, au niveau de l'interface bioélectrique. Une partie des travaux a cherché à évaluer les relations entre diffusion du courant et compréhension de la parole. Les résultats indiquent que la compréhension de la parole ne semble pas liée à cette mesure de diffusion du courant intra-cochléaire.La dernière partie de cette thèse a évalué les relations entre une mesure électro-physiologique de l'intégration binaurale (BIC pour Binaural Interaction Component) et performances binaurales chez des sujets dont l'audition est entièrement médiée par l'IC. Cette étude suggère que les sujets présentant des BIC identifiables semblent tirer un meilleur profit de la binauralité / This thesis investigates the links between electro-physiological responses of the cochlea and the brainstem, the psychoacoustic levels used for CI fitting and the hearing performances of MED-EL® cochlear implant (CI) adult users.The main part focused on the electrically evoked compound action potentials (ECAP), which reflect the synchronous activity of cochlear auditory neurons in response to the electrical stimulation delivered by CI. These were recorded either during implantation surgery or in experienced users to evaluate their usefulness as predictors of the hearing levels. Our work shows that despite broad variations between users, ECAPs can be related to perception levels. This relationship does not allow yet an accurate enough prediction of the perception levels used to program the CI.In MED-EL® CIs impedances raw data are displayed in voltage matrices and can be used to estimate the spread of current around each electrode, at the bioelectric interface level. In a second part, we aimed to evaluate the relationshipss between the current spread and speech recognition. The results indicate that speech understanding does not seem to be related to this measurement of intra-cochlear current diffusion.The last part of this thesis evaluated the relationship between an electro-physiological measurement of binaural interaction (BIC) and binaural hearing performances in subjects using two CI. Our results suggest that subjects with identifiable BICs appear to have better localization scores and make a better benefit from the binaurality as they have to understand speech in noisy environment

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