Analysis of Fresh Air Volume of Air-conditioning System for Railway Vehicles

The relevant standard requirements both in domestic and abroad provide the basis for designing air-conditioning system of railway vehicles present. However, there are great differences in the fresh air volume indicators among different standards requirements, and the requirements of each vehicle procurement contracts are also different. The design of air-conditioning become difficult above these. In this paper, the fresh air volume of different type railway vehicles is analyzed from health and equipment electricity consumption according to the railway vehicles air-conditioning system standard requirements in domestic and abroad. Some advises for designing air-conditioning system of railway vehicles through the fresh air volume calculation and comparison for domestic air-conditioning system of railway vehicles was provided.

Estimation and Prediction of the Condition of the Vehicle Engine Based on the Correlation Dimension

This paper applies the fractal dimension as a characteristic to describe the engine抯 operating condition and its developmental trend. A correlation dimension is one of the quantities that are usually used to characterize a strange attractor. With the operation of the phase space reconstruction, respective correlation dimensions of a series of vibration signals obtained under different conditions are calculated to find the intrinsic relationship between the indicator and the operating condition. The experiment result shows that the correlation dimension is sensitive to the condition evolution and convenient for the identification of abnormal operational states. In advanced prognostic algorithm based on the BP neural network is then applied on the correlation dimensions to predict the short-term running conditions in order to avoid severe faults and realize in-time maintenance. Experimental results are presented to illustrate the proposed methodology.

Nonlinear trajectory tracking control of a new autonomous underwater vehicle in complex sea conditions

Autonomous underwater vehicles (AUVs) navigating in complex sea conditions usually require a strong control system to keep the fastness and stability. The nonlinear trajectory tracking control system of a new AUV in complex sea conditions was presented. According to the theory of submarines,the six-DOF kinematic and dynamic models were decomposed into two mutually non-coupled vertical and horizontal plane subsystems. Then,different sliding mode control algorithms were used to study the trajectory tracking control. Because the yaw angle and yaw angle rate rather than the displacement of the new AUV can be measured directly on the horizontal plane,the sliding mode control algorithm combining cross track error method and line of sight method was used to fulfill its high-precision trajectory tracking control in the complex sea conditions. As the vertical displacement of the new AUV can be measured,in order to achieve the tracking of time-varying depth signal,a stable sliding mode controller was designed based on the single-input multi-state system,which took into account the characteristic of the hydroplane and the amplitude and rate constraints of the hydroplane angle. Moreover,the application of dynamic boundary layer can improve the robustness and control accuracy of the system. The computational results show that the designed sliding mode control systems of the horizontal and vertical planes can ensure the trajectory tracking performance and accuracy of the new AUV in complex sea conditions. The impacts of currents and waves on the sliding mode controller of the new AUV were analyzed qualitatively and quantitatively by comparing the trajectory tracking performance of the new AUV in different sea conditions,which provides an effective theoretical guidance and technical support for the control system design of the new AUV in real complex environment.

Regenerative braking control for hybrid electric vehicles under decelerating condition

The operating mode of a single shaft hybrid electric vehicle （SSHEV） in which the electric motor exerts negative torque on the shaft to imitate engine braking is analyzed. The method of determining the quantity of regenerative braking torque is proposed with the premise that the braking intensity required by the driver is satisfied. On this basis, factors that affect torque generated by the motor are listed, and how the battery＇ s temperature and state of charge （ SOC ） restrict and correct the braking torque is expounded. Finally, road test results show that the motor＇ s constant power or constant torque control is an effective way to recover the mechanical energy during decelerating.

PermissibleWind Conditions for Optimal Dynamic Soaring with a Small Unmanned Aerial Vehicle

Dynamic soaring is a flight maneuver to exploit gradient wind field to extend endurance and traveling distance.Optimal trajectories for permissible wind conditions are generated for loitering dynamic soaring as well as for traveling patterns with a small unmanned aerial vehicle.The efficient direct collection approach based on the Runge-Kutta integrator is used to solve the optimization problem.The fast convergence of the optimization process leads to the potential for real-time applications.Based on the results of trajectory optimizations,the general permissible wind conditions which involve the allowable power law exponents and feasible reference wind strengths supporting dynamic soaring are proposed.Increasing the smallest allowable wingtip clearance to trade for robustness and safety of the vehicle system and improving the maximum traveling speed results in shrunken permissible domain of wind conditions for loitering and traveling dynamic soaring respectively.Sensitivity analyses of vehicle model parameters show that properly reducing the wingspan and increasing the maximum lift-to-drag ratio and the wing loading can enlarge the permissible domain.Permissible domains for different traveling directions show that the downwind dynamic soaring benefitting from the drift is more efficient than the upwind traveling pattern in terms of permissible domain size and net traveling speed.

Measurement of in-vehicle volatile organic compounds under static conditions

The types and quantities of volatile organic compounds （VOCs） inside vehicles have been determined in one new vehicle and two old vehicles under static conditions using the Thermodesorber-Gas Chromatograph/Mass Spectrometer （TD-GC/MS）. Air sampling and analysis was conducted under the requirement of USEPA Method TO-17. A room-size, environment test chamber was utilized to provide stable and accurate control of the required environmental conditions （temperature, humidity, horizontal and vertical airflow velocity, and background VOCs concentration）. Static vehicle testing demonstrated that although the amount of total volatile organic compounds （TVOC） detected within each vehicle was relatively distinct （4940 μg/m^3 in the new vehicle A, 1240 μg/m^3 in used vehicle B, and 132 μg/m^3 in used vehicle C）, toluene, xylene, some aromatic compounds, and various C7-C12 alkanes were among the predominant VOC species in all three vehicles tested. In addition, tetramethyl succinonitrile, possibly derived from foam cushions was detected in vehicle B. The types and quantities of VOCs varied considerably according to various kinds of factors, such as, vehicle age, vehicle model, temperature, air exchange rate, and environment airflow velocity. For example, if the airflow velocity increases from 0.1 m/s to 0.7 m/s, the vehicle＇s air exchange rate increases from 0.15 h^-1 to 0.67 h^-1, and in-vehicle TVOC concentration decreases from 1780 to 1201 μg/m^3.

Hydrodynamic Efficiency Improvement of the High Skew Propeller for the Underwater Vehicle Under Surface and Submerged Conditions

An algorithm based on the Boundary Element Method(BEM)is presented for designing the High Skew Propeller(HSP)used in an Underwater Vehicle(UV).Since UVs operate under two different kinds of working conditions(i.e.surface and submerged conditions),the design of such a propeller is an unwieldy task.This is mainly due to the fact that the resistance forces as well as the vessel efficiency under these conditions are significantly different.Therefore,some factors are necessary for the design of the opti-mum propeller to utilize the power under the mentioned conditions.The design objectives of the optimum propeller are to obtain the highest possible thrust and efficiency with the minimum torque.For the current UV,the main dimensions of the propeller are pre-dicted based on the given required thrust and the defined operating conditions.These dimensions(number of blades,pitch,diameter,expanded area ratio,thickness and camber)are determined through iterative procedure.Because the propeller operates at the stern of the UV where the inflow velocity to the propeller is non-uniform,a 5-blade HSP is preferred for running the UV.Finally,the propel-ler is designed based on the numerical calculations to acquire the improved hydrodynamic efficiency.

Analysis and innovation of key technologies for autonomous underwater vehicles

As the mission needs of the autonomous underwater vehicles(AUV) have become increasingly varied and complex,the AUVs are developing in the direction of systematism, multifunction, and clustering technology, which promotes the progress of key technologies and proposes a series of technical problems. Therefore, it is necessary to make systemic analysis and in-depth study for the progress of AUV's key technologies and innovative applications. The multi-functional mission needs and its key technologies involved in complex sea conditions are pointed out through analyzing the domestic and foreign technical programs, functional characteristics and future development plans. Furthermore, the overall design of a multi-moving state AUV is proposed. Then, technical innovations of the key technologies, such as thrust vector, propeller design, kinematics and dynamics, navigation control, and ambient flow field characteristics, are made, combining with the structural characteristics and motion characteristics of the new multi-moving state AUV. The results verify the good performance of the multi-moving state AUV and provide a theoretical guidance and technical support for the design of new AUV in real complex sea conditions.

Vibration Severity Monitoring and Evaluation of Armored Vehicle Transmission

Vibration monitoring and vibration severity evaluation of armored vehicle transmission are realized by additional sensors. An algorithm of vibration severity in frequency domain is presented. The algorithm has powerful applicability for signal type and flexible selectivity for frequency range,and avoids the processing of signal conversion used calculus and filtering compared to the algorithm of vibration severity in time domain. An applied example is given in company with attentive proceedings and measures for improving evaluation effect.

Thermal Management of Vehicle Cabins,External Surfaces,and Onboard Electronics:An Overview

Reducing heat accumulation within vehicles and ensuring appropriate vehicular temperature levels can lead to enhanced vehicle fuel economy,range,reliability,longevity,passenger comfort,and safety.Advancements in vehicle thermal management remain key as new technologies,consumer demand,societal concerns,and government regulations emerge and evolve.This study summarizes several recent advances in vehicle thermal management technology and modeling,with a focus on three key areas:the cabin,electronics,and exterior components of vehicles.Cabin-related topics covered include methods for reducing thermal loads and improving heating,ventilation,and air-conditioning(HVAC)systems;and advancements in window glazing/tinting and vehicle surface treatments.For the thermal management of electronics,including batteries and insulated-gate bipolar transistors(IGBTs),active and passive cooling methods that employ heat pipes,heat sinks,jet impingement,forced convection,and phase-change materials are discussed.Finally,efforts to model and enhance the heat transfer of exterior vehicular components are reviewed while considering drag/friction forces and environmental effects.Despite advances in the field of vehicle thermal management,challenges still exist;this article provides a broad summary of the major issues,with recommendations for further study.

Investigation on the Influence of Refrigerant Charge Amount on the Cooling Performance of Air Conditioning Heat Pump System for Electric Vehicles

The application of air conditioning heat pump(ACHP) in electric vehicles could lead to significant electrical power saving effect. As for an air conditioning heat pump system for electric vehicles, the influence of refrigerant charge amount should be investigated during the design phase. In this study, experimental method was employed to investigate the influence of the refrigerant charge amount on the performance of the ACHP system. The results showed that the refrigerant charge amount had different influence on the refrigerant properties at various locations within the system. The coefficient of performance and pressure-enthalpy diagram were calculated, and showed a close relationship with refrigerant charge amount under different compressor speeds. The degree of subcooling and the degree of superheating were recorded and the critical charge amount was determined by a typical practical test method. In addition, the critical refrigerant charge amount determined by the experimental method was also compared with two typical void fraction correlation models, and the model with consideration of two phase stream reaction of the refrigerant showed a good estimation accuracy on the critical charge amount.

Nonlinear Dynamic Characteristics of the Vectored Thruster AUV in Complex Sea Conditions

The mobility of the vectored thruster AUV in different environment is the important premise of control system design. The new type of autonomous underwater vehicle (AUV) equipped with rudders and vectored thrusters which are combined to control the course is studied. Firstly, Euler angles representation and quaternion method are applied to establish six-DOF kinematic model respectively, then Newton second law and Lagrangian approach are used to deduce the vectored thruster AUV’s nonlinear dynamic equations with six degrees of freedom (DOF) respectively in complex sea conditions based on the random wave theory according to the structural and kinetic characteristics of the vectored thruster AUV in this paper. The kinematic models and dynamic models based on different theories have the same expression and conclusion, which shows that the kinematic models and dynamic models of the vectored thruster AUV are accurate. The Runge-Kutta arithmetic is used to solve the dynamic equations, which not only can simulate the motions such as cruise and hover but also can describe the vehicle’s low-frequency and high-frequency motion. The results of computation show that the mobility of the vectored thruster AUV in interference-free environment and the integrated signals including low-frequency motion signal and high-frequency motion signal in environmental disturbance accord with practical situation, which not only solve the problem of especial singularities when the pitch angle θ = ±90° but also clears up the difficulties of computation and display of the coupled nonlinear motion equations in complex sea conditions. Moreover, the high maneuverability of the vectored thruster AUV equipped with rudders and vectored thrusters is validated, which lays a foundation for the control system design.

Centralized control of parallel connected power conditioning system in electric vehicle charge-discharge and storage integration station

This study presents a centralized control scheme that coordinates parallel operations of power conditioning system(PCS)for the grid interactions of electric vehicles(EVs)in EV charge-discharge and storage integration station.Key issues for the control and operation of PCS under various operation modes are discussed,including vehicle to grid(V2G)mode,stand-alone mode and seamless transfer mode.The intelligent multi-mode charge-discharge method is utilized for the V2G mode,and the parallel control method based on communication network is adopted for the standalone mode.In addition,a novel seamless transfer strategy is proposed,which is able to implement PCS transition between V2G mode and stand-alone mode.The detailed process of the seamless transfer between the two modes is illustrated.Experimental results are presented to show the performance and feasibility of this strategy.

Study of Fuzzy Neural Networks Model for System Condition Monitoring of AUV

A structure equivalent model of fuzzy-neural networks for system condition monitoring is proposed, whose outputs are the condition or the degree of fault occurring in some parts of the system. This network is composed of six layers of neurons,which represent the membership functions, fuzzy rules and outputs respectively. The structure parameters and weights are obtained by processing off-line learning, and the fuzzy rules are derived from the experience. The results of the computer simulation for the autonomous underwater vehicle condition monitoring based on this fuzzy-neural networks show that the network is efficient and feasible in gaining the condition information or the degree of fault of the two main propellers.

大功率履带越野车用液力变矩器循环工况构建

为解决液力变矩器的传统稳态试验工况同实车工况契合度不高、无法反应实车上运行状态的问题,提出了一种大功率履带越野车用液力变矩器循环工况。在某型履带车辆实车工况数据基础上,统计分析液力变矩器在实车运行中的工况特征,选取了12个统计特征参数和10个比例特征参数,利用主成分分析法对工况数据进行了降维处理,通过无监督学习中的K均值聚类算法完成了数据片段的聚类分析,使用动态规划方法整合闭锁工况,获取典型工况片段用于循环工况重构,利用汉宁窗对片段进行平滑连接。以循环工况与总体数据主要特征值平均误差、连接处转速差值总和及斜率差值总和为目标,借助模拟退火和多目标粒子群算法进行优化,构建基于实车数据、契合液力变矩器实车运行特征的循环工况。结果表明,最终所得工况由叶轮转速——时间和闭锁信号——时间组成,主要特征参数平均相对误差为2.92%,与实车数据的工况特征表现一致。本研究成果为设计液力变矩器的可靠性试验工况提供了一种新的思路和途径。

基于光纤光栅“活塞式”封装的军用车辆振动传感研究

提出一种基于光纤光栅(fiber bragg grating,FBG)“活塞式”封装的军用车辆高可靠性振动传感器。FBG和圆柱体振子连接,并固定于圆柱体外壳的上下底面。圆柱体振子直径略小于圆柱体外壳内径,在外界振动信号激励下,振子带动FBG在圆柱体外壳内做“活塞式”往复运动,进而对FBG轴向应变产生调制。基于“活塞式”封装方式,振子被约束于外壳内,提高了传感器机械稳定性,避免了其他方向振动导致的测量误差。实验结果显示,传感器在0.1~0.7 g的振动加速度范围内的灵敏度为48.2 pm/g。公路路况车载试验下的振动信号较为平稳,最大加速度为±0.2g。河床路况车载试验下的振动信号成分更为复杂,最大振动加速度约为±0.4g,不同路况车载试验及模拟射击冲击下的实验结果与路况环境相符。

城市道路网联混驾车辆分阶段动态轨迹控制方法

随着城市的进步和不断发展,智能驾驶车辆逐渐代替路段中的部分人工驾驶车辆,但在未来较长时间内人工驾驶车辆并不会被完全取代,此时出现网联车与人工驾驶车辆的混驾环境,即目前以及未来时间内我们面临的驾驶环境。网联车与人工驾驶车辆驾驶行为在路段内相互干扰,造成混合车流行驶效率低下。为减弱2种车辆间的相互作用,提出一种分离混驾环境下网联车和人工驾驶车辆的分阶段动态车道引导算法(dynamic lane guidance algorithm for separating CAVs and HDVs in mixed traffic environment,SCHME)。通过该算法分离在交叉口上游路段的混合流车辆集合,调整智能驾驶车辆的行驶路线并进行实时动态更新,在满足运动学约束收敛的条件下,人工驾驶车辆根据网联车的动态路线进行相应调整,实现在每辆车广义安全损失成本最小的情况下提高路段内混驾环境下车辆运行效率。通过MATLAB模拟车辆在进入交叉口前的车辆运行状态,结果表明,SCHME算法可在广义安全损失成本最小的情况下提高路段内平均车辆通行效率(17.29%),同时当车辆优化数组越大,车辆集合距离交叉口越远时,智能驾驶车辆渗透率越低,每辆车的道路广义安全损失成本越低。

水下航行体极限大机动流动分离大涡模拟研究

针对大机动极限工况下水下航行体流动分离带来的机动性不足问题,本文以Suboff标模为研究对象,采用大涡模拟数值计算方法开展大机动工况下水下航行体的流体动力性能评估,并完成水下航行体尾部及舵面流动分离涡旋结构的精细捕捉。本文研究成果可为后续极限机动工况下水下航行体流动控制提供技术支撑。

混合工质电动汽车空调全生命周期气候性能分析

空调作为整车系统中环境调控的关键子系统,其全生命周期的碳排放对于电动汽车的环保和排放要求至关重要。本文结合汽车空调系统全生命周期气候性能LCCP模型及相关数据,对全国各省份电动汽车空调系统的LCCP情况进行分析,同时对两种不同制热方案以及不同电力碳强度下的LCCP进行了比较分析。结果表明,RE170/R134a低GWP混合工质(二甲醚与R134a质量分数比90∶10)替换后电动汽车空调LCCP值降低了11.2%~28.1%,而采用热泵替换PTC电加热器后电动汽车空调LCCP值降低了0~33.1%,此外,随着未来我国电力碳强度与电动汽车保有量的变化,至2035年单辆车的LCCP值将会下降31.7%~39.3%,而全国整体电动汽车LCCP值将大幅上升。