Analysis of the stability of PTW riders in autonomous braking scenarios

While fatalities of car occupants in the EU decreased remarkably over the last decade, Powered Two Wheelers (PTWs) fatalities still increase following the increase of PTW ownership. Autonomous braking systems have been implemented in several types of vehicles and are presently addressed by research in the field of PTWs. A major concern in this context is the rider stability. Experiments with volunteers were performed in order to find out whether autonomous braking for PTWs will produce a greater instability of the rider in comparison to manual braking. The PTW's braking conditions were simulated in a laboratory with a motorcycle mock-up mounted on a sled, which was accelerated with an average of 0.35 g. The motion of the rider was captured in autonomous braking scenarios with and without pre-warning as well as in manual braking scenarios. No significant differences between the scenarios were found with respect to maximum forward displacement of the volunteer's torso and head (p < 0.05). By performing clustering analysis on two kinematic parameters, two different strategies of the volunteers were identified. They were not related to the braking scenarios. A relation of the clusters with the initial posture represented by the elbow angle was revealed (p < 0.05). It is concluded that autonomous braking at low deceleration will not cause significant instabilities of the rider in comparison to manual braking in idealized laboratory conditions. Based on this, further research into the development and implementation of autonomous braking systems for PTWs, e.g. by extensive riding tests, seems valuable.     

Typical pedestrian accident scenarios for the development of autonomous emergency braking test protocols

An increasing proportion of new vehicles are being fitted with autonomous emergency braking systems. It is difficult for consumers to judge the effectiveness of these safety systems for individual models unless their performance is evaluated through track testing under controlled conditions. This paper aimed to contribute to the development of relevant test conditions by describing typical circumstances of pedestrian accidents. Cluster analysis was applied to two large British databases and both highlighted an urban scenario in daylight and fine weather where a small pedestrian walks across the road, especially from the near kerb, in clear view of a driver who is travelling straight ahead. For each dataset a main test configuration was defined to represent the conditions of the most common accident scenario along with test variations to reflect the characteristics of less common accident scenarios. Some of the variations pertaining to less common accident circumstances or to a minority of casualties in these scenarios were proposed as optional or supplementary test elements for an outstanding performance rating. Many considerations are incorporated into the final design and implementation of an actual testing regime, such as cost and the state of development of technology; only the representation of accident data lay within the scope of this paper. It would be desirable to ascertain the wider representativeness of the results by analysing accident data from other countries in a similar manner.     

Pedestrian injury risk and the effect of age

Older adults and pedestrians both represent especially vulnerable groups in traffic. In the literature, hazards are usually described by the corresponding injury risks of a collision. This paper investigates the MAIS3 + F risk (the risk of sustaining at least one injury of AIS 3 severity or higher, or fatal injury) for pedestrians in full-frontal pedestrian-to-passenger car collisions.Using some assumptions, a model-based approach to injury risk, allowing for the specification of individual injury risk parameters for individuals, is presented. To balance model accuracy and sample size, the GIDAS (German In-depth Accident Study) data set is divided into three age groups; children (0–14); adults (15–60); and older adults (older than 60). For each group, individual risk curves are computed. Afterwards, the curves are re-aggregated to the overall risk function.The derived model addresses the influence of age on the outcome of pedestrian-to-car accidents. The results show that older people compared with younger people have a higher MAIS3 + F injury risk at all collision speeds. The injury risk for children behaves surprisingly. Compared to other age groups, their MAIS3 + F injury risk is lower at lower collision speeds, but substantially higher once a threshold has been exceeded. The resulting injury risk curve obtained by re-aggregation looks surprisingly similar to the frequently used logistic regression function computed for the overall injury risk. However, for homogenous subgroups – such as the three age groups – logistic regression describes the typical risk behavior less accurately than the introduced model-based approach.Since the effect of demographic change on traffic safety is greater nowadays, there is a need to incorporate age into established models. Thus far, this is one of the first studies incorporating traffic participant age to an explicit risk function. The presented approach can be especially useful for the modeling and prediction of risks, and for the evaluation of advanced driver assistance systems.     

Integrated assessment of pedestrian head impact protection in testing secondary safety and autonomous emergency braking

Pedestrian impact testing is used to provide information to the public about the relative level of protection provided by different vehicles to a struck pedestrian. Autonomous Emergency Braking (AEB) is a relatively new technology that aims to reduce the impact speed of such crashes. It is expected that vehicles with AEB will pose less harm to pedestrians, and that the benefit will come about through reductions in the number of collisions and a change in the severity of impacts that will still occur. In this paper, an integration of the assessment of AEB performance and impact performance is proposed based on average injury risk. Average injury risk is calculated using the result of an impact test and a previously published distribution of real world crash speeds. A second published speed distribution is used that accounts for the effects of AEB, and reduced average risks are implied. This principle allows the effects of AEB systems and secondary safety performance to be integrated into a single measure of safety. The results are used to examine the effect of AEB on Euro NCAP and ANCAP assessments using previously published results on the likely effect of AEB. The results show that, given certain assumptions about AEB performance, the addition of AEB is approximately the equivalent of increasing Euro NCAP test performance by one band, which corresponds to an increase in the score of 25% of the maximum.     

Analysis of the minimum swerving distance for the development of a motorcycle autonomous braking system

In the recent years the autonomous emergency brake (AEB) was introduced in the automotive field to mitigate the injury severity in case of unavoidable collisions. A crucial element for the activation of the AEB is to establish when the obstacle is no longer avoidable by lateral evasive maneuvers (swerving). In the present paper a model to compute the minimum swerving distance needed by a powered two-wheeler (PTW) to avoid the collision against a fixed obstacle, named last-second swerving model (L_sw), is proposed. The effectiveness of the model was investigated by an experimental campaign involving 12 volunteers riding a scooter equipped with a prototype autonomous emergency braking, named motorcycle autonomous emergency braking system (MAEB). The tests showed the performance of the model in evasive trajectory computation for different riding styles and fixed obstacles.     

Hydrodynamic braking

A viscous fluid lies between two parallel plates. The bottom plate, moving laterally in its own plane, is affected by increasing viscous resistance when the top plate squeezes downward. The problem is solved by a power series expansion in a squeeze number S. Braking characteristics are obtained for several different states: the top plate moves with constant velocity, constant force, or constant power; the bottom moves with constant velocity or when it is free.     

Pedestrian injury analysis with consideration of the selectivity bias in linked police-hospital data

Evaluation of crash-related injuries by medical specialists in hospitals is believed to be more exact than rather a cursory evaluation made at the crash scene. Safety analysts sometimes reach for hospital data and use them in combination with the police crash data. One issue that needs to be addressed is the, so-called, selectivity (or selection) bias possible when data used in analysis are not coming from random sampling. If not properly addressed, this issue can lead to a considerable bias in both the model coefficient estimates and the model predictions. This paper investigates pedestrian injury severity factors using linked police-hospital data.A bivariate ordered probit model with sample selection is used to check for the presence of the selectivity bias and to account for it in the MAIS estimates on the Maximum Abbreviated Injury Scale (MAIS). The presence of the sample selection issue has been confirmed. The selectivity bias is considerable in predictions of low injury levels.The pedestrian injury analysis identified and estimated several severity factors, including pedestrian, road, and vehicle characteristics. Male and older pedestrians were found to be particularly exposed to severe injuries. Rural roads and high-speed urban roads appear to be more dangerous for pedestrians, particularly when crossing such roads. Crossing a road between intersections was found to be particularly dangerous behavior. The size and weight of the vehicle involved in a pedestrian crash were also found to have an effect on the pedestrian injury level. The relevant safety countermeasures that may improve pedestrian safety have been proposed.     

Door velocity and occupant distance affect lateral thoracic injury mitigation with side airbag

The relationship between thoracic injury risk and parameters of door velocity and occupant distance was delineated in blunt lateral impact with side airbag deployment. A sled impact model was exercised with the validated MADYMO fiftieth percentile facet occupant model and a generalized finite element torso side airbag. Impact velocity was incremented from 4.0 to 9.0 m/s; occupant–airbag distance (at time of airbag activation) was incremented from 2.0 to 24.0 cm; simulations without airbag were also examined. Using compression, deflection rate, and the Viscous Criterion, airbag performance was characterized with respect to occupant injury risk at three points of interest: occupant distance of most protection, distance of greatest injury risk, and the newly defined critical distance. The occupant distance which demonstrated the most airbag protection, i.e., lowest injury risk, increased with increasing impact velocity. Greatest injury risk resulted when the occupant was nearest the airbag regardless of impact velocity. The critical distance was defined as the farthest distance at which airbag deployment exacerbated injury risk. This critical distance only varied considering chest compression, between 3 and 10 cm from the airbag, but did not vary when the Viscous Criterion was evaluated. At impact velocities less than or equal to 6 m/s, the most protective occupant location was within 2 cm of the critical distance at which the airbag became harmful. Therefore, injury mitigation with torso airbag may be more difficult to achieve at lower ΔV.     

Cable vibration mitigation by added SMA wires

Summary Limiting the oscillations of suspension or cable-stayed bridges requires a suitable strategy for the cable vibration mitigation. This paper approaches the problem by a campaign of laboratory tests conducted for a suspended steel cable specimen of diameter 2 mm. First the dynamic behaviour of the cable in free vibrations is studied. The main mechanical parameters, such as natural frequencies and damping coefficients, are evaluated by an elaboration of the time histories recorded by two tri-axial accelerometers. A wire of diameter 1 mm, made by shape memory alloy (SMA), is then added to the cable. Several configurations for the system “steel cable–SMA wire” are conceived. The goal is to find how the dynamic behaviour of the steel cable changes, and to assess which configuration could give the best results in terms of cable vibration mitigation and damping increase. Dedicated to Professor Franz Ziegler on the occasion of his 70th birthday     

制动力作用下驾驶室抖动的试验研究

摘 要：为了解决某重型车辆驾驶室抖动问题,通过制动抖动整车道路再现试验研究,分析了抖动现象的特征,确定了制动力作用下驾驶室抖动振动的传递路径,得出了车架悬架系统X、Y方向限位刚度不足是导致驾驶室抖动的主要原因。在上述分析的基础上对车辆抖动问题提出了解决方案,并对原车进行了试验验证,结果表明本文所提出的解决方案很好地解决了驾驶室制动抖动问题,同时验证了本文分析的合理性和可行性。     

An autonomous polymerization motor powered by DNA hybridization

We present a synthetic molecular motor capable of autonomous nanoscale transport in solution. Inspired by bacterial pathogens such as Rickettsia rickettsii, which locomote by inducing the polymerization of the protein actin at their surfaces to form 'comet tails', the motor operates by polymerizing a double-helical DNA tail2. DNA strands are propelled processively at the living end of the growing polymers, demonstrating autonomous locomotion powered by the free energy of DNA hybridization.     

导引概率图与显著特征相结合的行人目标检测

研究了仿生人眼视觉注意机制,采用目标导引概率图作为自上而下的信息,通过调制基于目标显著特征的自下而上信息,实现行人目标检测的方法。首先,对相似场景的目标样本图像提取尺度不变特征变换(SIFT)特征,基于贝叶斯公式,采用高斯混合模型(GMM)建立目标导引概率模型,利用期望最大(EM)算法和狄利克雷过程(DP)自动估计模型参数;进而,对一副待检测图像,采用已估概率模型计算图像中每一像元的目标似然性,形成导引概率图作为自上而下的信息;同时,针对行人目标,模拟中央-外周机制计算多尺度的肤色特征和竖直方向特征,形成基于目标显著特征的自下而上信息;最后,将两者结合得到候选目标区域,再通过提取候选区域的积分梯度直方图和等价的局部二值模式(LBP)特征,输入到级联支持向量机(SVM)分类器,验证并得到目标检测结果。基于实拍数据库和复旦大学-宾夕法尼亚大学行人数据库的大量实验表明,对概率模型的这种改进能显著提升行人目标预测效果,且检测算法在整体上优于传统检测算法。     

Pedestrian fatalities and alcohol

Since the share of alcohol-positive victims has been reported not to show the same reduction in pedestrian fatalities as in other 'road users', this study analysed pedestrian fatalities with special emphasis on the presence of alcohol. Autopsied pedestrian fatalities (286 victims) in northern Sweden from 1977 to 1995 were investigated, using autopsy and police reports. Blood alcohol was detected in 19% of the fatalities, with a median concentration of 1.6 g/l. The proportion of test-positive victims did not change significantly during the period of study. Males more often tested positive for alcohol than females (24 vs. 11%). Further, the test-positive victims had a lower mean age (49 vs. 59 years) and the proportion of test-positive victims was higher during weekends and nights. Pedestrian fatalities testing positive for alcohol differ from those testing negative in several respects. The public should be enlightened of the fact that drinking is a risk not only among users of motor vehicles, but also among pedestrians. Separation of pedestrians from motor vehicles by, e.g. fences, is of greatest importance.     

A new concept of shock mitigation by impedance-graded materials

Over the last several decades, homogenous single-layer armor has been replaced by multi-layer integral armor to improve ballistic penetration resistance. This has led to better attenuation of shock wave energy by multiple interface reflections and transmissions. Efforts have been reported to improve the penetration resistance by providing higher energy dissipation at higher levels of impedance mismatch. However, high stress concentrations and stress reversals have made these interfaces the primary sources of failure. This paper discusses a concept for a new class of blast and penetration resistant (BPRM) materials which are layer-less but designed to have a continuous gradient of impedance that can dissipate the shock energy without material failure. In a simplistic approach by applying the classical theory of uniaxial stress propagation, it has been shown that attenuation of the stress wave energy would be possible by controlling the impedance distribution within the body of such a material. The development of such material to resist blast or impact will overcome the current common difficulty of interfacial delamination failure in any protective barrier system or armors.     

视觉自适应行人计数

基于视觉的行人计数技术因其广阔的应用前景逐步成为智能视觉监控领域的一个研究热点。本文提出了一种基于虚拟门上前景像素点个数的行人计数方法。该方法分为学习和计数两个过程。在学习过程中,本方法采用基于行人检测的方法获取场景中的若干行人模型,并利用线性拟合为虚拟门上的点赋予权重。在计数过程中,本方法在考虑虚拟门上前景像素的权重、运动矢量的大小和方向等信息的基础上,逐帧统计虚拟门上前景点个数,通过特定时间内累计的前景点数量来确定通过虚拟门的行人数量。实验表明,该方法能够在保证计数精度的前提下,有较好的实时性能。     

Glutaraldehyde-fixed biological tissue calcification: effectiveness of mitigation by dimethylsulphoxide

The conditions defining the extent of dimethylsulphoxide (DMSO) effectiveness in mitigating calcification of glutaraldehyde (GA)-fixed tissue have been evaluated. Exposure of GA-fixed tissue porcine aortic valve cusps to low concentrations of DMSO does not impart calcification inhibitory activity. Mitigation in calcification becomes evident only as the DMSO component nears 100% and is best when neat DMSO is used. In all instances, regardless of the DMSO concentration, exposure to DMSO resulted in an increase in the tissue shrinkage temperature, attributed to further cross-linking in the tissue. Histological examination of samples before implantation indicate some deleterious effects to the tissue, the degree dependent on concentration, time and temperature of DMSO exposure. The results of this study suggest that treatment of GA-fixed tissue with high concentrations of DMSO for a short duration at a lowered temperature could give a bioprosthesis that has good mitigating calcification properties with retention of tissue integrity.     

Debiasing overoptimistic beliefs about braking capacity

We investigated, using questionnaires, different strategies for removing drivers’ overoptimism (Svenson et al., 2012a) about how fast their speed could be decreased when they were speeding compared with braking at the speed limit speed. Three different learning groups and a control group made collision speed judgments. The first learning group had the distance a car travels during a driver's reaction time for each problem. The second group had this information and also feedback after each judgment (correct speed). The third group judged collision speed but also braking distance and received correct facts after each problem. The control group had no information at all about reaction time and the distance traveled during that time. The results suggested the following rank order from poor to improved performance: control, group 1, group 3 and group 2 indicating that information about distance driven during a driver's reaction time improved collision speed judgments and that adding stopping distance information did not add to this improvement.     

Molecular autonomous agents

I consider an autonomous agent to be a physical system able to act on its own behalf, such as a bacterium swimming up a glucose gradient. I tentatively define an autonomous agent to be a system capable of self-reproduction and at least capable of performing one thermodynamic work cycle. I give a hypothetical chemical example. I then explore the increasingly odd implications of this definition.     

商用车和挂车气压行车制动反应时间测试研究

行车制动反应时间是评价气压制动系统响应特性的重要指标,决定着行车制动的安全性。该文分析制动管路、部件布置和管路气压3个关键因素对制动反应时间的影响,基于ECE R13法规和GB 12676标准阐述商用车和挂车制动反应时间的测试方法,测试方法体现两者的不同,挂车反应时间测试需要单独额外的模拟装置。该文分别选用商用机动车(牵引汽车)和挂车相关测试样车,重点阐述气压行车制动反应时间的测试流程及注意事项,对数据处理的具体过程做详细解释。测试数据表明:商用车和挂车两测试样车的行车制动反应时间均符合ECE R13法规和GB 12676标准的要求,对进一步完善制动系统测试评价提供基础。