Preview-based techniques for vehicle suspension control: a state-of-the-art review

Abstract Automotive suspension systems are key to ride comfort and handling performance enhancement. In the last decades semi-active and active suspension configurations have been the focus of intensive automotive engineering research, and have been implemented by the industry. The recent advances in road profile measurement and estimation systems make road-preview-based suspension control a viable solution for production vehicles. Despite the availability of a significant body of papers on the topic, the literature lacks a comprehensive and up-to-date survey on the variety of proposed techniques for suspension control with road preview, and the comparison of their effectiveness. To cover the gap, this literature review deals with the research conducted over the past decades on the topic of semi-active and active suspension controllers with road preview. The main formulations are reported for each control category, and the respective features are critically analysed, together with the most relevant performance indicators. The paper also discusses the effect of the road preview time on the resulting system performance, and identifies control development trends

Chlamydia trachomatis infection during pregnancy associated with preterm delivery: A population-based prospective cohort study

Chlamydia trachomatis infection is the most prevalent bacterial sexually transmitted infection and may influence pregnancy outcome. This study was conducted to assess the effect of chlamydial infection during pregnancy on premature delivery and birthweight. Pregnant women attending a participating midwifery practice or antenatal clinic between February 2003 and January 2005 were eligible for the study. From 4,055 women self-administered questionnaires and urine samples, tested by PCR, were analysed for C. trachomatis infection. Pregnancy outcomes were obtained from midwives and hospital registries. Gestational ages and birthweights were analysed for 3,913 newborns. The C. trachomatis prevalence was 3.9%, but varied by age and socio-economic background. Chlamydial infection was, after adjustment for potential confounders, associated with preterm delivery before 32 weeks (OR 4.35 [95% CI 1.3, 15.2]) and 35 weeks gestation (OR 2.66 [95% CI 1.1, 6.5]), but not with low birthweight. Of all deliveries before 32 weeks and 35 weeks gestation 14.9% [95% CI 4.5, 39.5] and 7.4% [95% CI 2.5, 20.1] was attributable to C. trachomatis infection. Chlamydia trachomatis infection contributes significantly to early premature delivery and should be considered a public health problem, especially in young women and others at increased risk of C. trachomatis infection

Prenatal parental tobacco smoking, gene specific DNA methylation, and newborns size: the Generation R study

Background: Deleterious effects of prenatal tobacco smoking on fetal growth and newborn weight are well-established. One of the proposed mechanisms underlying this relationship is alterations in epigenetic programming. We selected 506 newborns from a population-based prospective birth cohort in the Netherlands. Prenatal parental tobacco smoking was assessed using self-reporting questionnaires. Information on birth outcomes was obtained from medical records. The deoxyribonucleic acid (DNA) methylation of the growth genes IGF2DMR and H19 was measured in newborn umbilical cord white blood cells. Associations were assessed between parental tobacco smoking and DNA methylation using linear mixed models and adjusted for potential confounders. Results: The DNA methylation levels of IGF2DMR and H19 in the non-smoking group were median (90 % range), 54.0 % (44.6–62.0), and 30.0 % (25.5–34.0), in the first trimester only smoking group 52.2 % (44.5–61.1) and 30.8 % (27.1–34.1), and in the continued smoking group 51.6 % (43.9–61.3) and 30.2 % (23.7–34.8), respectively. Continued prenatal maternal smoking was inversely associated with IGF2DMR methylation (β = −1.03, 95 % CI −1.76; −0.30) in a dose-dependent manner (P-trend = 0.030). This association seemed to be slightly more profound among newborn girls (β = −1.38, 95 % CI −2.63; −0.14) than boys (β = −0.72, 95 % CI −1.68; 0.24). H19 methylation was also inversely associated continued smoking <5 cigarettes/day (β = −0.96, 95 % CI −1.78; −0.14). Moreover, the association between maternal smoking and newborns small for gestational age seems to be partially explained by IGF2DMR methylation (β = −0.095, 95 % CI −0.249; −0.018). Among non-smoking mothers, paternal tobacco smoking was not associated with IGF2DMR or H19 methylation. Conclusions: Maternal smoking is inversely associated with IGF2DMR methylation in newborns, which can be one of the underlying mechanisms through which smoking affects fetal growth

Functional MRI of Auditory Responses in the Zebra Finch Forebrain Reveals a Hierarchical Organisation Based on Signal Strength but Not Selectivity

BACKGROUND: Male songbirds learn their songs from an adult tutor when they are young. A network of brain nuclei known as the 'song system' is the likely neural substrate for sensorimotor learning and production of song, but the neural networks involved in processing the auditory feedback signals necessary for song learning and maintenance remain unknown. Determining which regions show preferential responsiveness to the bird's own song (BOS) is of great importance because neurons sensitive to self-generated vocalisations could mediate this auditory feedback process. Neurons in the song nuclei and in a secondary auditory area, the caudal medial mesopallium (CMM), show selective responses to the BOS. The aim of the present study is to investigate the emergence of BOS selectivity within the network of primary auditory sub-regions in the avian pallium. METHODS AND FINDINGS: Using blood oxygen level-dependent (BOLD) fMRI, we investigated neural responsiveness to natural and manipulated self-generated vocalisations and compared the selectivity for BOS and conspecific song in different sub-regions of the thalamo-recipient area Field L. Zebra finch males were exposed to conspecific song, BOS and to synthetic variations on BOS that differed in spectro-temporal and/or modulation phase structure. We found significant differences in the strength of BOLD responses between regions L2a, L2b and CMM, but no inter-stimuli differences within regions. In particular, we have shown that the overall signal strength to song and synthetic variations thereof was different within two sub-regions of Field L2: zone L2a was significantly more activated compared to the adjacent sub-region L2b. CONCLUSIONS: Based on our results we suggest that unlike nuclei in the song system, sub-regions in the primary auditory pallium do not show selectivity for the BOS, but appear to show different levels of activity with exposure to any sound according to their place in the auditory processing stream

Individual accumulation of heterogeneous risks explains perinatal inequalities within deprived neighbourhoods

Dutch' figures on perinatal mortality and morbidity are poor compared to EU-standards. Considerable within-country differences have been reported too, with decreased perinatal health in deprived urban areas. We investigated associations between perinatal risk factors and adverse perinatal outcomes in 7,359 pregnant women participating in population-based prospective cohort study, to establish the independent role, if any, for living within a deprived urban neighbourhood. Main outcome measures included perinatal death, intrauterine growth restriction (IUGR), prematurity, congenital malformations, Apgar at 5 min < 7, and pre-eclampsia. Information regarding individual risk factors was obtained from questionnaires, physical examinations, ultrasounds, biological samples, and medical records. The dichotomous Dutch deprivation indicator was additionally used to test for unexplained deprived urban area effects. Pregnancies from a deprived neighbourhood had an increased risk for perinatal death (RR 1.8, 95% CI [1.1; 3.1]). IUGR, prematurity, Apgar at 5 min < 7, and pre-eclampsia also showed higher prevalences (P < 0.05). Residing within a deprived neighbourhood was associated with increased prevalence of all measured risk factors. Regression analysis showed that the observed neighbourhood related differences in perinatal outcomes could be attributed to the increased risk factor prevalence only, without a separated role for living within a deprived neighbourhood. Women from a deprived neighbourhood had significantly more 'possibly avoidable' risk factors. To conclude, women from a socioeconomically deprived neighbourhood are at an increased risk for adverse pregnancy outcomes. Differences regarding possibly avoidable risk factors imply that preventive strategies may prove effective

Multimodal design : the semiotic resources of children's graphic representation

In asking how children's graphic representation can be understood as multimodal design, I argue that meaning-making is a complex process of semiotic interweaving. My definition of graphic representation for this thesis embraces the full range of marks made on any graphic surface. Multimodal design is the socioculturally shaped process of transformation where existing semiotic (meaning-making) resources are chosen, shaped and combined according to the individual's interest and his or her perception of the particular representational or communicational need. I propose that graphic representation might be thought about as multimodal compounds (co-present writing and image) and multimodal composites (an integration of the modes that make up the self-contained entities of writing and image). I explore how texts can be understood multimodally by examining what the semiotic resources of children's graphic representation are, how they carry meaning and how they interrelate. Through in-depth analysis of writing and drawing both discretely and appearing together in the same graphic text, I analyse paper-based and electronic texts produced at home and school for different purposes. I take my interpretations of the signs children have made and my theorization always to be hypotheses. Language-as-writing and drawing-as-image offer potentialities for different ways of making meaning but common and particularized semiotic modes such as presentation, layout and punctuation operate across graphic representation. These modes work together in a semiotic partnership. I suggest that semiotic principles across modes of communication including and going beyond the graphic might include criteriality, connectivity and salience. This implies the notion of a multimodal disposition. The multimodality of children's graphic representational design has implications for pedagogy, curriculum policy, professional development and the research community.

Explicit model predictive control for active suspension systems with preview.

Latest advances in road profile sensors make the implementation of pre-emptive suspension control a viable option for production vehicles. From the control side, model predictive control (MPC) in combination with preview is a powerful solution for this application. However, the significant computational load associated with conventional implicit model predictive controllers (i-MPCs) is one of the limiting factors to the widespread industrial adoption of MPC. As an alternative, the authors of this study propose an explicit model predictive controller (e-MPC) for an active suspension system with preview. The MPC optimization problem is an mp-QP problem and is run offline. The online controller is reduced to a function evaluation. To overcome the increased memory requirements of e-MPC, the presented controller uses the recently developed regionless e-MPC approach. The controller was assessed through simulations and experiments on a sport utility vehicle (SUV) demonstrator with controllable hydraulic suspension actuators. For frequencies <4 Hz, the experimental results with the regionless e-MPC without preview show a ~10% reduction of the root mean square (RMS) value of the vertical acceleration of the sprung mass with respect to the same vehicle with a skyhook controller. The addition of preview improves the performance by a further 8% to 21% depending on the test

Use of flexible models in extended Kalman filtering for vehicle body force estimation

The forces acting on a vehicle are an important area in vehicle dynamics research. A direct measurement of these forces, however, is not feasible for mass-produced vehicles. This has motivated the use of model-based estimation techniques such as the Kalman filter. In this work the discrete-time augmented extended Kalman filter is employed to perform a combined estimation of the current vehicle state and the input forces, such as the tyre forces. Currently, the general approach is to use simplified ad-hoc models for the Kalman filter. In vehicle dynamics applications this can lead to an unobservable system which makes it impossible to estimate the individual tyre forces. In order to solve this issue, this work proposes to take the flexibility of the vehicle body into account in the model for the Kalman filter. This adds an effect to the model that allows to differentiate between the contributions of all the different input forces. The model is derived according to the floating frame of reference formulation and a reduced order finite element model is used to describe the flexibility of the vehicle body. An exponential integrator is applied to time-discretize the equations of motion. An observability analysis is performed and the observability conditions for the unknown input forces are derived. Furthermore, it is shown that no position-level measurements are required if only the forces are of interest. The proposed approach is numerically validated and compared to the current general approach. The validation demonstrates that the proposed approach provides superior estimation results.status: publishe

Use of flexible models in extended Kalman filtering applied to vehicle body force estimation

Accurate knowledge of wheel loads is of great value in vehicle design and control. However, a direct measurement of these forces is generally not feasible. This motivates the use of model-based estimation techniques, such as the Kalman filter to obtain operational wheel forces. The general approach in literature is to use simple ad-hoc models (like the bicycle model) in the Kalman filter. In many applications however, including vehicle dynamics, this results in a system that is not observable for all the variables of interest, e.g. the individual tyre forces. In this light, this work proposes the use of general flexible multibody models for Kalman filtering. The introduction of flexible deformations in the model enables the observation of variables which cannot be obtained from a rigid model. This allows the filter to differentiate between the contributions of different input forces. This approach is demonstrated by employing an augmented extended Kalman filter to perform a combined estimation of the current vehicle state and wheel forces of a 2D vehicle model. The system is modeled in a floating-frame-of-reference (FFR) approach and the vehicle body is described by a reduced order finite element model. An observability analysis is performed and the observability conditions for the unknown input forces are derived. The proposed approach is validated numerically and compared to an estimator with a rigid assumption.status: publishe