458 research outputs found
Facilitating the driver detection of road surface type by selective manipulation of the steering-wheel acceleration signal
Copyright @ 2012 by Institution of Mechanical Engineers.Previous research has investigated the possibility of facilitating the driver detection of road surface type by means of selective manipulation of the steering-wheel acceleration signal. In previous studies a selective increase in acceleration amplitude has been found to facilitate road-surface-type detection, as has selective manipulation of the individual transient events which are present in the signal. The previous research results have been collected into a first guideline for the optimization of the steering-wheel acceleration signal, and the guideline has been tested in the current study. The test stimuli used in the current study were ten steering-wheel acceleration-time histories which were selected from an extensive database of road test measurements performed by the research group. The time histories, which were all from midsized European automobiles and European roads, were selected such that the widest possible operating envelope could be achieved in terms of the r.m.s. value of the steering acceleration, the kurtosis, the power spectral density function, and the number of transient events present in the signal. The time histories were manipulated by means of the mildly non-stationary mission synthesis algorithm in order to increase, by a factor of 2, both the number and the size of the transient events contained within the frequency interval from 20 Hz to 60Hz. The ensemble, composed of both the unmanipulated and the manipulated time histories, was used to perform a laboratory-based detection task with 15 participants, who were presented the individual stimuli in random order. The participants were asked to state, by answering 'yes' or 'no', whether each stimulus was considered to be from the road surface that was displayed in front of them by means of a large photograph on a board. The results suggest that the selectively manipulated steering-wheel acceleration stimuli produced improved detection for eight of the ten road surface types which were tested, with a maximum improvement of 14 per cent in the case of the broken road surface. The selective manipulation did lead, however, to some degradation in detection for the motorway road stimulus and for the noise road stimulus, thus suggesting that the current guideline is not universally optimal for all road surfaces
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On the need for bump event correction in vibration test profiles representing road excitations in automobiles
This paper presents an approach to the synthesis of compressed vibration test profiles
representing much longer time histories obtained in road testing of ground vehicles. Vibration test
profiles are defined as those related directly to operational testing on specific road surfaces and
which summarise the input to the vehicle in the given conditions. The method extends classical
Fourier transform technique by means of bump event correction in the background Fourier signal
where the bump event term implies a high-amplitude transient event of the shock type. The
orthogonal wavelet decomposition was used as a specific filtering tool facilitating bump event
identification. Examples of seat guide vertical acceleration have been considered. Calculated
probability density functions suggest the ability of the bump correction method to improve the
statistical accuracy of the final vibration test profile with respect to the original road data. Test
profiles obtained by means of Fourier transform synthesis with subsequent reinsertion of bump
events from separated frequency bands were more accurate than those obtained by Fourier synthesis
alone. Further developments led to advanced bump reinsertion with synchronisation of events
occurring in different frequency bands at the same moment of time. Test profiles generated in this
way have provided better accuracy compared to the non-synchronised algorithm
Human emotional response to steering wheel vibration in automobiles
This is the post-print (final draft post-refereeing) version of the final published paper that is available from the link below. Copyright @ 2013 Inderscience Enterprises Ltd.This study investigates what form of correlation may exist between measures of the valence and the arousal dimensions of the human emotional response to steering wheel vibration and the vibration intensity metrics obtained by means of the unweighted and the frequency weighted root mean square (rms). A laboratory experiment was performed with 30 participants who were presented 17 acceleration time histories in random order and asked to rate their emotional feelings of valence and arousal using a self-assessment manikin (SAM) scale. The results suggest a highly linear correlation between the unweighted, Wh weighted and Ws weighted vibration intensity metrics and the arousal measures of the human emotional response. The results also suggest that while vibration intensity plays a significant role in eliciting emotional feelings, there are other factors which influence the human emotional response to steering wheel vibration such as the presence of high peaks or high frequency band amplitudes
A first approach to understanding and measuring naturalness in driver-car interaction
With technology changing the nature of the driving task, qualitative methods can help designers understand and measure driver-car interaction naturalness. Fifteen drivers were interviewed at length in their own parked cars using ethnographically-inspired questions probing issues of interaction salience, expectation, feelings, desires and meanings. Thematic analysis and content analysis found five distinct components relating to 'rich physical' aspects of natural feeling interaction typified by richer physical, analogue, tactile styles of interaction and control. Further components relate to humanlike, intelligent, assistive, socially-aware 'perceived behaviours' of the car. The advantages and challenges of a naturalness-based approach are discussed and ten cognitive component constructs of driver-car naturalness are proposed. These may eventually be applied as a checklist in automotive interaction design.This research was fully funded by a research grant from Jaguar Land Rover, and partially funded by project
n.220050/F11 granted by Research Council of Norway
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Dynamic behavior and damping capacity of auxetic foam pads
A novel set of auxetic (negative Poisson's ratio) open cell polyurethane foam has been developed and tested under dynamic
loading conditions to assess the viscoelastic response under white noise random excitation and compressive cycling. Foam pads
normalized to standard ISO 13753 have been tested at room temperature and frequency bandwidth 10-500 Hz to assess
transmissibility characteristics for possible antivibration glove applications. The results show that the ISO 13753 normalized
transmissibility for these foams falls below 0.6 above 100 Hz, with lower peak maximum stresses under indentation compared to
conventional open cell solids. These results suggest possible use of the auxetic foam for pads or linens against « white fingers«
vibration applications. Further tests have been conducted on cyclic compressive loading up to 3 Hz and loading ratios of 0.95 for
loading histories up to 100000 cycles. The damping capacity of the auxetic foams showed and increase by a factor 10 compared
to the conventional foams used to manufacture the negative Poisson's ratio ones, and stiffness degradation stabilized after few tens on cycles
Phase Segregation Dynamics in Particle Systems with Long Range Interactions I: Macroscopic Limits
We present and discuss the derivation of a nonlinear non-local
integro-differential equation for the macroscopic time evolution of the
conserved order parameter of a binary alloy undergoing phase segregation. Our
model is a d-dimensional lattice gas evolving via Kawasaki exchange dynamics,
i.e. a (Poisson) nearest-neighbor exchange process, reversible with respect to
the Gibbs measure for a Hamiltonian which includes both short range (local) and
long range (nonlocal) interactions. A rigorous derivation is presented in the
case in which there is no local interaction. In a subsequent paper (part II),
we discuss the phase segregation phenomena in the model. In particular we argue
that the phase boundary evolutions, arising as sharp interface limits of the
family of equations derived in this paper, are the same as the ones obtained
from the corresponding limits for the Cahn-Hilliard equation.Comment: amstex with macros (included in the file), tex twice, 20 page
Coronavirus peplomer charge heterogeneity
Recent advancements in viral hydrodynamics afford the calculation of the transport properties of particle suspensions from first principles, namely, from the detailed particle shapes. For coronavirus suspensions, for example, the shape can be approximated by beading (i) the spherical capsid and (ii) the radially protruding peplomers. The general rigid bead-rod theory allows us to assign Stokesian hydrodynamics to each bead. Thus, viral hydrodynamics yields the suspension rotational diffusivity, but not without first arriving at a configuration for the cationic peplomers. Prior work considered identical peplomers charged identically. However, a recent pioneering experiment uncovers remarkable peplomer size and charge heterogeneities. In this work, we use energy minimization to arrange the spikes, charged heterogeneously to obtain the coronavirus spike configuration required for its viral hydrodynamics. For this, we use the measured charge heterogeneity. We consider 20â000 randomly generated possibilities for cationic peplomers with formal charges ranging from 30 to 55. We find the configurations from energy minimization of all of these possibilities to be nearly spherically symmetric, all slightly oblate, and we report the corresponding breadth of the dimensionless rotational diffusivity, the transport property around which coronavirus cell attachment revolves.journal articl
Temperature-induced crossovers in the static roughness of a one-dimensional interface
At finite temperature and in presence of disorder, a one-dimensional elastic
interface displays different scaling regimes at small and large lengthscales.
Using a replica approach and a Gaussian Variational Method (GVM), we explore
the consequences of a finite interface width on the small-lengthscale
fluctuations. We compute analytically the static roughness of the
interface as a function of the distance between two points on the
interface. We focus on the case of short-range elasticity and random-bond
disorder. We show that for a finite width two temperature regimes exist.
At low temperature, the expected thermal and random-manifold regimes,
respectively for small and large scales, connect via an intermediate `modified'
Larkin regime, that we determine. This regime ends at a temperature-independent
characteristic `Larkin' length. Above a certain `critical' temperature that we
identify, this intermediate regime disappears. The thermal and random-manifold
regimes connect at a single crossover lengthscale, that we compute. This is
also the expected behavior for zero width. Using a directed polymer
description, we also study via a second GVM procedure and generic scaling
arguments, a modified toy model that provides further insights on this
crossover. We discuss the relevance of the two GVM procedures for the roughness
at large lengthscale in those regimes. In particular we analyze the scaling of
the temperature-dependent prefactor in the roughness B(r)\sim T^{2
\text{\thorn}} r^{2 \zeta} and its corresponding exponent \text{\thorn}. We
briefly discuss the consequences of those results for the quasistatic creep law
of a driven interface, in connection with previous experimental and numerical
studies
Dewetting, partial wetting and spreading of a two-dimensional monolayer on solid surface
We study the behavior of a semi-infinite monolayer, which is placed initially
on a half of an infinite in both directions, ideal crystalline surface, and
then evolves in time due to random motion of the monolayer particles. Particles
dynamics is modeled as the Kawasaki particle-vacancy exchange process in the
presence of long-range attractive particle-particle interactions. In terms of
an analytically solvable mean-field-type approximation we calculate the mean
displacement X(t) of the monolayer edge and discuss the conditions under which
such a monolayer spreads (X(t) > 0), partially wets (X(t) = 0) or dewets from
the solid surface (X(t) < 0).Comment: 4 pages, 2 figures, to appear in PRE (RC
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