Influence of vehicle noise emission directivity on sound level distribution in a canyon street. Part II: Experimental verification

In the paper, predictions of relative sound level distribution on building façades in city-centres obtained by using the simulation PROP11 program are compared with measurements. The simulation involves the geometry of surrounding buildings, road geometry (number of lanes and their positions) and traffic structure (vehicle flow rates and their average speeds). The agreement between measurement and simulation results is tested for different directivity characteristics of an equivalent point source representing the vehicles.     

Validation of a complex urban noise model close to a road

The adequacy of a model for the sound level close to a road is investigated by comparing resulting predictions for the sound level over a building façade with measurements. The road model involves the road geometry (the number and positions of traffic lanes), the traffic structure (vehicle flow rates and their average speeds in each lane) and equivalent omnidirectional point sources representing the vehicles. It is found that the assumed road traffic noise source model is adequate only for predicting levels over the higher part of the façade. However the investigation has allowed definition of what improvements are needed in the road source modelling to enable adequate predictions over the whole of the building façade.     

The experimental validation of a numerical model for the prediction of the vibrations in the free field produced by road traffic

The objective of the present paper is the experimental validation of a numerical model for the prediction of traffic-induced vibrations. The vibrations in the free field, generated by the passage of a vehicle on an uneven road, are predicted in two stages. First, the equations of motion of the vehicle are solved to determine the dynamic axle loads. Next, these axle loads are applied to the road and the free field vibrations are computed. An elaborate measurement campaign has been set up to validate this model. The response of a Volvo FL6 truck and the response in the free field have been measured simultaneously during the passage of the truck over an artificial road unevenness. The parameters related to the vehicle, the road and the soil have been determined experimentally. A comparison of the predicted and the measured response demonstrates the predictive qualities of the numerical model. Furthermore, the results provide a clear insight in the influence of the vehicle speed on the vehicle's and the free field response.     

A GIS based road traffic noise prediction model

A road traffic noise prediction model has been developed suitable for use in China. This model is based on local environmental standards, vehicle types and traffic conditions. The model was accurate to 0.8 dBA at locations near the road carriage way and 2.1 dBA within the housing estate, which is comparable to the FHWA model. An integrated noise-GIS system was developed to provide general functions for noise modeling and an additional tool for noise design, where a new interaction mode in “WHAT IF Question/Explanation” format was used. Application of this system offered improvements in the efficiency and accuracy of traffic noise assessment and noise design.     

信号灯控制下的主道双车道入匝道系统交通流特性研究

采用元胞自动机模型研究了具有信号灯控制的主道为双车道的入匝道系统交通流特性.将信号灯设置在入匝道口处,通过信号灯来引导主道和匝道上的车辆通行.分析了信号灯控制对主道与匝道的车流量、系统通行能力以及入匝道口处的车流平均速度的影响.通过相图比较,说明信号灯控制的双车道入匝道系统能模拟出比信号灯控制的单车道入匝道系统更加符合实际的交通流特性.与姜锐提出的模型［Jiang R 2003 J. Phys. A 36 11713］结果相比,信号灯控制下的匝道系统的交通流状态得到改善并且道路通行能力有所提 关键词： 交通流 元胞自动机 入匝道系统 信号灯     

道路交通的流体物理模型与粒子仿真方法

针对受多种因素影响的复杂道路交通系统问题,基于颗粒动力学理论,结合传统的Lighthill-WhithamRichards物理模型,建立道路交通系统的流体物理模型,采用无网格粒子与网格相结合的方法进行数值仿真,并应用于典型道路交通问题的求解.在新模型中,将车辆比拟为硬颗粒,车辆的跟车比拟为颗粒间的碰撞相互作用,已知道路情况对驾驶员操作车辆的影响比拟为流-粒两相系统中的外部流体驱动力作用,不同车道间车辆的影响比拟为颗粒间的黏性作用,从而在颗粒动力学理论的基础上,推导建立了道路交通系统拟流体模型;引入光滑离散颗粒流体动力学(SDPH)对车辆系统模型进行离散,建立"SDPH车辆"与真实车辆之间的一一对应关系,再结合有限体积方法,对道路交通构建的双流体模型进行求解,建立求解交通流体物理模型的新型仿真方法.最后,采用所建立的模型和方法对车辆汇入以及机非混合对交通系统的影响过程进行了数值仿真,所得结果与实测值符合较好,表明新的模型和方法有效性好、可靠性高,为道路交通问题的解决提供了一条全新的途径.     

Computer simulation model for the prediction of traffic noise levels

This paper describes a computer simulation model capable of predicting the noise levels generated by traffic passing through road intersections controlled by roundabouts where departures from free-flow traffic conditions occur. The model depends for its operation on the acoustical and flow characteristics of single vehicles travelling on a road from which the overall noise generated by traffic streams can be deduced using a sampling/integration technique. Distance effects, ground cover, vehicle type, velocity and headway characteristics, etc. are taken into account in the model and the simplest possible input parameters are used deliberately to facilitate the eventual use of the model by highway and planning authorities. Good agreement has been achieved between measured and predicted L₁₀ values for freely flowing traffic negotiating roundabouts. Further applications of the model involving road intersections controlled by traffic lights and the effect of traffic queues are nearing completion.     

Traffic behavior in the on-ramp system with signal controlling

In this paper, we investigate the on-ramp system on the highway using cellular automaton traffic model. Different from previous work, we introduce traffic signal to control the vehicle flows on the main road and the on-ramp. A method of signal controlling is presented, and the update rule in special road is given in detail according to the stimulation role of signal to the drivers. The simulation results show that, the phase diagram of on-ramp system is divided into three regions. The currents of the on-ramp system are discussed. Under the control role of traffic signal, the vehicle flows of the main road and the on-ramp can become orderly. The capacity of the system may keep a maximum value. In addition, the drastic velocity fluctuation is discussed near the on-ramp. A dangerous condition in Jiang et al. [Phys. Rev. E 66 (2002) 036104] can be effectively avoided.     

Validation method of infrared imaging simulation based on recognition range北大核心CSCD

随着红外成像技术的发展和应用,红外系统成像仿真及验证技术越来越受到重视。现有仿真模型验证方法没有考虑到人眼视觉的影响,可能导致严重后果,为了解决这一问题,提出了基于识别距离的红外系统成像仿真模型验证方法。以识别距离作为红外系统成像仿真模型的准确度评价因子,考评仿真图像与实测图像在灰度分布、信噪比、分辨率、成像大小、人眼视觉等方面的综合差异。     

Sound quality prediction of vehicle interior noise using deep belief networks

The sound quality of vehicle interior noise strongly influences passengers’ psychological and physiological perceptions. To predict the sound quality of interior noise, a vehicle road test with four compact cars has been conducted. All recorded interior noise signals have been denoised via a discrete wavelet transform (DWT) denoising procedure and subsequently evaluated subjectively through the anchor semantic differential (ASD) test by a jury. In addition, a novel prediction method, namely, regression-based deep belief networks (DBNs), which substitute the support vector regression (SVR) layer for the linear softmax classification layer at the top of the general DBN’s structure, has been proposed to predict the interior sound quality. The parameter selection of the DBN model has been compared and studied using a grid search. In addition, four conventional machine-learning-based methods have been introduced to enable a comparison of the performance with the newly developed DBNs. Furthermore, the feature fusion ability of DBNs has been studied by varying the amount of information that the dataset offers. The results show the following: (1) The accuracy and robustness of the proposed DBN-based sound quality prediction approach are better than those of the 4 other referenced methods. (2) The multiple-feature fusing process can strongly affect the prediction performance. (3) Finally, the unsupervised pre-training process of the DBNs can enhance the information fusing ability. Finally, the newly proposed regression-based DBN approach may be extended to address other vehicle noises in the future.     

Adaptive Kalman filter based state of charge estimation algorithm for lithium-ion battery

In order to improve the accuracy of the battery state of charge(SOC) estimation, in this paper we take a lithiumion battery as an example to study the adaptive Kalman filter based SOC estimation algorithm. Firstly, the second-order battery system model is introduced. Meanwhile, the temperature and charge rate are introduced into the model. Then, the temperature and the charge rate are adopted to estimate the battery SOC, with the help of the parameters of an adaptive Kalman filter based estimation algorithm model. Afterwards, it is verified by the numerical simulation that in the ideal case, the accuracy of SOC estimation can be enhanced by adding two elements, namely, the temperature and charge rate.Finally, the actual road conditions are simulated with ADVISOR, and the simulation results show that the proposed method improves the accuracy of battery SOC estimation under actual road conditions. Thus, its application scope in engineering is greatly expanded.     

Commercial road vehicle noise

A survey of the characteristics of the noise emitted by commercial vehicles has been made. The most important single parameter determining the noise of a modern diesel-engined vehicle is the engine speed. All of the other parameters such as load, road speed, etc., have only a secondary effect.The sources of noise on the vehicle are reviewed and it is shown how the characteristics of these sources determine the overall noise characteristics of the vehicle. It has been found that a simple model of the vehicle as a number of coincident point sources predicts the overall noise characteristics of the vehicle to ±2 dB(A). It is shown that there are two extremes of behaviour, the rolling noise controlled vehicle and the power unit noise controlled vehicle; the engine is currently the controlling noise source.Tyre noise has been investigated in some detail as comparatively little has been published previously on this source. Empirical relationships between the tyre noise and speed, tyre size and road surface roughness are given. It is concluded that tyre noise is generated by impacting between elements of the tyre tread and elements of the road surface.Modifications have been made to the engine, exhaust, intake and cooling fan of a 9 ton, 6 litre diesel engined truck which have reduced its ISO test noise level from 88 dB(A) to 80 dB(A). However, it is concluded that 80 dB(A) commercial vehicles are not yet feasible for production. In particular insufficient is known about cooling fan design.Finally cab noise has been investigated and it has been found to originate from the same source as the exterior noise, power unit airborne noise. Therefore any modifications to the power unit to reduce exterior noise will have a similar effect on interior noise. This is confirmed by the vehicle modifications mentioned above which reduced the maximum cab noise from 87 dB(A) to 79 dB(A).     

基于驾驶员行为的元胞自动机模型研究

从研究驾驶员行为入手,分析了驾驶员行为作用机理,并结合元胞自动机(CA)模型,将与车辆自身速度、相对速度、车间距和安全车间距有关的驾驶员行为作用机理引入CA模型(简称ACA).并利用ACA模型进行微观交通仿真观察到亚稳态、相分离和回滞现象,并将ACA模型与只考虑车辆自身速度和车间距的CA模型(简称BCA)的仿真结果进行比较可得:宏观方面,从最大车流量、稳定性和堵塞消溶效率三方面进行对比,ACA模型的仿真结果显示有更高并更接近实测数据的最大流量值,有更强的稳定性,堵塞消溶的效率更高;微观方面,从车辆速度波动和车头间距波动两方面进行对比,ACA模型的仿真结果显示车辆不会骤然加速或减速,车辆能够相对均匀地分布在道路上.这些结果说明相对速度和安全间距对驾驶员行为会产生重要影响,也说明ACA模型与实际情况更符,有一定实际意义.     

Identification of damping in a bridge using a moving instrumented vehicle

In recent years, there has been a significant increase in the number of bridges which are being instrumented and monitored on an ongoing basis. This is in part due to the introduction of bridge management systems designed to provide a high level of protection to the public and early warning if the bridge becomes unsafe. This paper investigates a novel alternative; a low-cost method consisting of the use of a vehicle fitted with accelerometers on its axles to monitor the dynamic behaviour of bridges. A simplified half-car vehicle-bridge interaction model is used in theoretical simulations to test the effectiveness of the approach in identifying the damping ratio of the bridge. The method is tested for a range of bridge spans and vehicle velocities using theoretical simulations and the influences of road roughness, initial vibratory condition of the vehicle, signal noise, modelling errors and frequency matching on the accuracy of the results are investigated.     

Second-order phase transition in two-dimensional cellular automaton model of traffic flow containing road sections

Two-dimensional cellular automaton model has been broadly researched for traffic flow, as it reveals the main characteristics of the traffic networks in cities. Based on the BML models, a first-order phase transition occurs between the low-density moving phase in which all cars move at maximal speed and the high-density jammed phase in which all cars are stopped. However, it is not a physical result of a realistic system. We propose a new traffic rule in a two-dimensional traffic flow model containing road sections, which reflects that a car cannot enter into a road crossing if the road section in front of the crossing is occupied by another car. The simulation results reveal a second-order phase transition that separates the free flow phase from the jammed phase. In this way the system will not be entirely jammed (“don’t block the box” as in New York City).     

Urban road network evolution mechanism based on the ‘direction preferred connection’ and ‘degree constraint’

The urban road network is a complex system that exhibits the properties of self-organization and emergence. Recent theoretical and empirical studies have mainly focused on the structural properties of the urban road networks. This research concentrates on some important parameters such as degree, average degree, meshedness coefficient, betweeness, etc. These parameters of the real road network exhibit specific statistical properties. Some studies show that perhaps these specific statistical properties are caused by a compromise mechanism of the formation of a minimum spanning tree and the greedy triangulation. Inspired by these results, we propose a principle to construct the network (we call it a MG network in this paper) whose structure is located between the minimum spanning tree and the greedy triangulation at first. The structural properties of the MG network are analyzed. We find the formation mechanism of the MG network cannot explain the urban road network evolution well. Then, based on the formation mechanism of the MG network, we add the ‘direction preferred connection’ and ‘degree constraint’ principles to the urban road network evolution simulation process. The result of the simulation network turns out to be a planar network that is in accordance with reality. Compared with the real road network’s structural properties, we find the simulation results are so consistent with it. It indicates the validation of the model and also demonstrates perhaps the ‘direction preferred connection’ and ‘degree constraint’ principle can explain the urban road network evolution better.     

Noise emission of road vehicles: Reconstitution of the acoustic signature

The paper describes a model that can be used to reconstitute the acoustic signature (sound pressure level) of a moving road vehicle. Account is taken of the Doppler and ground effects and of the directional characteristics of the noise emitted by the vehicle. The variations of the usual noise indices (maximum noise level, equivalent noise level due to the passing by of the vehicle) with the different parameters concerned, as determined by the modal, are considered and such variations compared with experimental results. It is shown, on the basis of the assumptions made, how a monopole source provides a good representation of a road vehicle. Finally an evaluation is made of the accuracy with which the apparent acoustic power of a vehicle can be determined.     

系留升空平台光电探测目标的坐标转换误差分析

系留升空平台的目标定位技术在军民领域中具有广泛的应用,定位精度的高低已成为评价无人机、系留升空平台综合性能的一项重要指标。开展了无人升空平台光电探测系统的精度测试研究,对目标高精度定位误差进行分析,推导出光电探测系统误差转换模型,对误差转换坐标进行仿真验证。运用蒙特卡罗思想, 综合分析了升空载荷光电探测系统中各误差参数对定位精度的影响,提出了提高目标高精度定位精度的改进方法,为无人升空平台光电吊舱的目标定位精度、光电吊舱的高精密设计提供了理论基础。     

The modelling of the dynamic behaviour of tyre tread blocks

The interaction between tyre and road constitutes the dominant noise source for road vehicles at speeds above 50 km/h. The understanding and control of tyre/road noise generation mechanisms is still one of the main challenges in the field of acoustics, covering a wide area of topics, such as the structure-borne sound properties of tyres, the non-linear contact between tyre and road and the sound radiation from vibrating tyres. The work presented here only covers a small part of this complex field, the modelling of the tread blocks in order to incorporate the dynamic behaviour into a simulation model for a rolling tyre on a rough road. A finite element model is made for individual blocks in order to investigate their first eigenfrequencies and mode shapes. This information is used to build an equivalent model consisting of a simple mass and springs. The equivalent model has the advantage of being handier when coupling to a model of the tyre structure. The impedance coupling method is used. The results of the driving point mobility in the radial and tangential directions to the surface of the block are compared with measurements on tyres. The results show good agreement for the radial direction, while for the tangential direction, the agreement is poor. This is mainly due to the fact that the model for the tyre structure does not include in-plane motion. The results also show that, for the frequency range up to 3 kHz, the influence of the blocks depends strongly on their geometry. The geometry of the tread blocks determines the contact geometry as a kind of macro roughness. It also determines the eigenfrequencies, which for typical tread blocks are expected to be situated, at least, in the range above 2000 Hz.