A study of the human ability to detect road surface type based on steering wheel vibration feedback

A study was performed to investigate the human ability to detect road surface type based on the associated steering wheel vibration feedback. Tangential direction acceleration time histories measured during road testing of a single mid-sized European automobile were used as the basis for the study. Scaled and frequency filtered copies of two base stimuli were presented to test subjects in a laboratory setting during two experiments which each involved 25 participants. Theory of signal detection (TSD) was adopted as the analytical framework and the results were summarised by means of the detectability index d’ and as receiver operating curve (ROC) points. The results of the experiment to investigate the effect of scaling suggested monotonic relationships between stimulus level and detection for both road surfaces. Detection of the tarmac surface improved with reductions in acceleration level while the opposite was true of the cobblestone surface. The ROC points for both surfaces were characterised by gradual increases in detection as a function of acceleration level, obtaining hit rates of nearly 100% at optimum. The results of the experiment to investigate the effect of frequency bandwidth suggested a monotonically increasing relationship between detectability and the bandwi\dth of the vibration stimuli. Detection of both road surfaces improved with increases in bandwidth. Average hit rates exceeded 80% for stimuli covering the frequency range from 0 to 80 Hz. Human detection of road surface type appears to depend on the long term memory model, or cognitive interpretation mechanism, associated with each surface. The complexity of the measured response suggests the need to categorise and classify incoming data before an optimal choice of feedback stimuli can be made in automotive steering systems

The role of the scale and the frequency bandwidth of steering wheel vibration on road surface recognition

Automobile drivers are regularly exposed to vibrational stimuli in their vehicle. Of the automobile subsystems, the steering wheel is one of the most important due to its role in controlling the vehicle. In particular, the steering wheel plays an important role in transmitting information about the road and about the vehicle to the driver. This paper investigates the effect of steering system feedback gain and steering system feedback bandwidth on the human interpretation of the driving information transmitted by the steering wheel. Human recognition of road surface type was found to be highly dependent on the feedback gain and the feedback bandwidth of the steering wheel vibration. The results provide some basic guidelines for designing the control logic of steer by wire systems

Steering System Vibration : Information and Perception Enhancement

Automobile drivers are regularly exposed to vibrational and acoustic stimuli. These stimuli cause discomfort, and methods for analysing the noise, vibration and harshness (NVH) properties of automobiles are in regular use. Most manufacturers currently dedicate significant attention to the NVH characteristics of their products. NVH criteria are regularly applied to the design of the steering system, whose vibration spectra can reach frequencies as high as 300 Hz. The design of steering components has been the subject of several studies (Pak et al., 1991) and the human subjective response to steering vibration has also been investigated, in terms of perceived intensity (Giacomin et. al., 2004) and induced fatigue (Giacomin and Abrahams, 2000). While further research is required, much is known about the discomfort produced by steering vibration. A less well understood topic is the information transmitted to the driver. With electronically assisted and by-wire steering technologies (Jurgen, 1999) the question of what stimuli should reach the driver has become important. All current methods for estimating vibrational discomfort, whether hand-arm or whole-body, and whether based on frequency weightings (ISO 5349-1, 2001) or customer correlations (Schoeggl, 2001), are defined in such a way as to suggest that a uniform reduction in vibration level brings a uniform reduction in discomfort. Less vibration is considered better. This may not be appropriate in the case of information, however, since situations can be imagined in which an increase in vibration might prove useful towards understanding the nature of the road surface or of the vehicle dynamic state. The question of what information the steering should transmit to the driver is not a simple one. Vibrational stimuli help the driver to interpret many things including the type of road surface, the presence of water or snow, tyre slip (both longitudinal and lateral) and the dynamic state of subsystems such as the engine, the steering and the brakes. The stimuli are perceived, compared to models from long term memory and interpreted. A possible approach is the measurement of statistical information. Since the work of Shannon (1949), numerous researchers have applied the concept of information entropy to problems in human behaviour and control (Corning, 2001; Bea and Marijuan, 2003). In Shannon’s terminology information refers to the capacity to reduce statistical uncertainty, while entropy is the degree of uncertainty. The basic premise is that a communication channel can be analysed in terms of the symbols used, and that the probability of occurrence of the symbols can be used as a metric of information flow. In recent years information measures have occasionally been applied to automotive problems, one example being the measure of steering wheel entropy defined by Nakayama et. al. (1999). The availability of a metric for quantifying the information transmitted to the driver provides an important new type of evaluation. As shown in figure 1, stimuli can then be judged in terms of the two, often opposing, criteria of discomfort and information. Further, optimisation of the information transmitting elements of the steering system by the automobile designer leads to a perception enhancing interface, or, more specifically, a Perception Enhancement System (PES). A possible PES for a by-wire steering system is shown in figure 2, where movements at the tyre or wheel hub are returned to the driver through a perception enhancing electronic controller unit, which identifies significant features which are then amplified and transmitted. Research to define information metrics and perception enhancement systems for automobile steering systems is being performed as part of a collaboration between the Perception Enhancement Systems research group of Sheffield University and the Hyundai Motor Company central research laboratory. This article describes the results of two experiments which have measured the effect of the amplitude and the frequency bandwidth of steering vibration on the human ability to identify road surface type

Isolation, phenotype, and allostimulatory activity of mouse liver dendritic cells

Donor liver-derived dendritic cells (DC) have recently been identified within various lymphoid and nonlymphoid tissues of organ allograft recipients, including nonimmunosuppressed mice transplanted with and permanently accepting major histocompatibility complex (MHC)-disparate hepatic allografts. These findings have raised questions about the basis of the tolerogenicity of the liver—and, in particular, about the properties of liver-derived DC. To study further the structure, immunophenotype and allostimu-latory activity of leukocytes resident in normal mouse (B10.BR; H-2k, I-Ek) liver, a procedure was developed to maximize the yield of viable, nonparenchymal cells (NPC) obtained following collagenase digestion of perfused liver fragments and density centrifugation (Per-coll). These cells comprised populations expressing lymphoid and myeloid cell surface antigens. As compared with spleen cells, they proved good allostimula-tors of naive (BIO; H-2b, I-E") splenic T cells when tested in primary mixed leukocyte reactions (MLR). After overnight (18-hr) incubation of the NPC, enrichment for transiently adherent, low-density (LD) cells on metrizamide gradients permitted the recovery of low numbers of cells (approx. 2-5 × 105 per liver), many of which displayed distinct DC morphology. Flow cytometric analysis revealed that these cells were CD3-, CD4-, CD8-, and B220-, but strongly expressed CD45 (leukocyte-common antigen), and mild-to-moderate levels of CD lib, heat-stable antigen, and CD44. The cells also expressed moderate intensity of NLDC 145 but not 33D1, DC restricted markers which have been shown to be differentially expressed on mouse DC isolated from various organs. This DC-enriched population was more strongly MHC class II(I-Ek)+ than NPC, as determined by immunocytochemistry and flow cytometry and exhibited much more potent allo-stimulatory activity for naive T cells. These findings demonstrate that freshly isolated murine liver NPC, and perhaps their counterparts in situ, exhibit allo-stimulatory activity that is enhanced in the nonadherent, low-density (DC-enriched) fraction after overnight culture. They further suggest that the © 1994 by Williams and Wilkins

Inverted polymer fullerene solar cells exceeding 10% efficiency with poly(2-ethyl-2-oxazoline) nanodots on electron-collecting buffer layers

Polymer solar cells have been spotlighted due to their potential for low-cost manufacturing but their efficiency is still less than required for commercial application as lightweight/flexible modules. Forming a dipole layer at the electron-collecting interface has been suggested as one of the more attractive approaches for efficiency enhancement. However, only a few dipole layer material types have been reported so far, including only one non-ionic (charge neutral) polymer. Here we show that a further neutral polymer, namely poly(2-ethyl-2-oxazoline) (PEOz) can be successfully used as a dipole layer. Inclusion of a PEOz layer, in particular with a nanodot morphology, increases the effective work function at the electron-collecting interface within inverted solar cells and thermal annealing of PEOz layer leads to a state-of-the-art 10.74% efficiency for single-stack bulk heterojunction blend structures comprising poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-alt-3-fluorothieno[3,4-b]thiophene-2-carboxylate] as donor and [6,6]-phenyl-C71-butyric acid methyl ester as acceptor

Can Emergency Physicians Perform Carotid Artery Point-of-Care Ultrasound to Detect Stenosis in Patients with TIA and Stroke? A Pilot Study

Introduction: Patients with severe, symptomatic carotid stenosis can have their subsequent stroke risk reduced by surgical intervention if performed soon after a transient ischemic attack (TIA) or stroke. Patients presenting to an emergency department (ED) without computed tomography angiography (CTA) with TIA/stroke, may require transfer to another hospital for imaging to rule out carotid artery stenosis. The objective of this study was to determine the test characteristics of carotid artery point-of-care ultrasound (POCUS) in detecting greater than 50% stenosis in patients presenting with TIA/stroke.Methods: We conducted a prospective cohort study on a convenience sample of adult patients presenting to a comprehensive stroke centre with TIA or stroke between June–October 2017. Carotid POCUS was performed. Primary outcome measure, stenosis ≥ 50%, was determined by the final radiology report of CTA. A blinded POCUS expert separately reviewed the archived carotid POCUS scans. We calculated sensitivity and specificity for stenosis ≥ 50%.Results: We conducted POCUS on 75 patients, of which 70 were included in our analyses. Of those 70, 14.3% were diagnosed with greater than 50% stenosis. Carotid POCUS performed as follows: sensitivity 70.0% (95% confidence interval [CI], 34.8%-93.3%); specificity 86.7% (95% CI, 75.4%-94.1%); positive likelihood ratio (LR +) 5.3 (95% CI, 1.2-9.3); negative likelihood ratio (LR -) 0.4 (95% CI, 0.0-0.7). The inter-rater reliability between POCUS performer interpretation and expert interpretation had moderate agreement (k = 0.68). Scans took a mean 6.2 ± 2.2 minutes to complete.Conclusion: Carotid POCUS has low to moderate association with CTA for detection of carotid artery stenosis ≥ 50%. Further research and investigation is needed prior to widespread use of carotid POCUS in patients with acute cerebral ischemia. Additionally, external validity is likely affected by availability of training, maintenance of competency, and experience in more rural centres