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The efficiency of transmissions is related directly to the energy consumption in vehicle systems. Hence, it is worth a lot researching the overall power losses inside the transmission, in order to modify the transmission performance or optimize the transmission. In most research works, only how to model the component power losses is considered. It is then necessary to put forward a general or standard method to calculate the overall power losses in the transmissions. In this paper, a general model of overall power losses in transmissions is built up, based on the selection of the submodels of component power losses from literature. With the help of the experimental data from the test bench, the methodology of parameter identification is introduced. As a result, more accurate power loss distribution of the transmission is possible to be obtained, through combining the overall efficiency experimental data and the model of overall power losses. In order to validate the methodology, it is applied into two study cases of different transmissions. Through the results of the two study cases, it is concluded that the methodology of modelling of power losses in transmissions with parameter identification is ready to be extended to other transmission study cases. It is expected that with the help of the methodology in this paper, a platform can be built up to benchmark different production transmissions in the future. 相似文献
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Energy efficiency represents one of the most relevant trends in many fields, including the sector of power transmissions and gears, which are involved whenever power has to transmitted and transformed. For instance, in the automotive industry, gearboxes can contribute to the overall efficiency of the system and promote lower fuel consumption and emissions, both allowing an optimization of the whole system and reducing their own power losses. In many circumstances a better efficiency corresponds to lower operating temperatures and to a higher reliability of the systems, which can be related to the final profit, like in industrial applications, or even to the success, like for instance in motorsport racing. Improving the efficiency is therefore a main issue also for the gearbox manufacturers, and the availability of methods and tools to forecast the behavior with respect to lubrication and power losses since the beginning of the design phase strongly contributes to the goal. 相似文献
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An approach to analyze the power flow and efficiency of multi-speed automatic transmission is proposed. The kinematic and torque equations in each shift are established based on three types of relations in hypergraphs. Load dependent/load independent power losses of each component and idle power losses caused by idle components are taken into consideration. The efficiencies of each component and the whole system are predicted by following the power flow in different shifts. The method presented is suitable for computer programming and beneficial for accurate efficiency calculation. A nine-speed automatic transmission is taken as an example to highlight the method. 相似文献
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M. Hofstetter D. Lechleitner M. Hirz M. Gintzel A. Schmidhofer 《Forschung im Ingenieurwesen》2018,82(4):361-370
In the design process of electric powertrains, consisting of electric machine, gearbox and power electronics, the requirements regarding performance, package and costs are typically set on system level. This imposes that deduction of component requirements is not unique and component properties interfere with each other. As a component of the powertrain system, the gearbox represents a linking element between the electric machine and drive shafts to the wheels. Through this the available installation space of the gearbox shows manifold characteristics due to multiple possible motor- and power electronics variants as also versatile system installation positions and angles. This space can be utilized by different gearbox variants, which are characterized by gearbox-internal design parameters. They affect gear ratio, configuration of gear wheels, outer shape of the gearbox and therefore the package as well as efficiency and production costs. The high variability of gearbox design parameters and packaging-related aspects lead to a complex problem in the design process.In this context, the present contribution introduces a gearbox design optimization process to support decision-making in the early development phase. For given load-, lifetime- and package-requirements, the introduced differential-evolution-based process delivers design parameters for shafts, gears, bearings and their arrangement to handle efficiency, package and costs in a multi-objective manner. The results are represented by a Pareto front of gearbox designs variants, from which decision makers are able to choose the best and most suitable trade-off. The new approach is exemplarily demonstrated on a single-speed, two-stage helical gearbox with an integrated differential drive, which represents a common gearbox topology for xEV-axle drives. 相似文献
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The IEEE 802.11 distributed coordination function (DCF) employs a carrier sensing mechanism, a simple and effective mechanism to mitigate collisions in wireless networks. But the carrier sensing mechanism is inefficient in terms of shared channel use because an overcautious channel assessment approach is used to estimate interference at a receiver. A DCF node simply blocks its transmission when it senses that the channel is busy. However, in many cases this channel assessing node?s own transmission may not generate enough interference to disrupt the ongoing transmission at the receiver. This overcautious channel assessment unnecessarily blocks transmission attempts, and thus degrades the overall network throughput. To avoid this unnecessary blocking, the authors propose a spatial reuse DCF (SRDCF), which utilises location information and transmission parameters to make accurate channel assessments and to permit concurrent transmissions by adjusting the transmission power. SRDCF also resolves the contention between opportunistic concurrent transmissions with a secondary backoff counter. Consequently, the proposed scheme improves the overall network throughput because of more concurrent transmissions. The authors theoretically analyse the performance enhancement of SRDCF over the original IEEE 802.11 DCF by using a Markov chain model and verify it through simulations. 相似文献
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本文以船用人字齿轮减速器为研究对象,依据人字齿轮传动结构特点,综合考虑齿轮时变啮合刚度、误差等激励以及人字齿轮轴向定位与滑动轴承支撑等因素,建立了传动系统弯-扭-轴耦合动力学模型,通过求解得到了传动系统轴承动载荷。以轴承动载荷为激励,采用FEM/BEM方法计算了齿轮箱噪声辐射,得到了齿轮箱声场声压分布云图与各场点噪声谱。系统讨论了人字齿轮基本参数(包括齿顶高系数、顶隙系数、齿宽、螺旋角及压力角)以及减速器结构特征(人字齿轮中间连接刚度、轴向定位刚度)对减速器振动噪声的影响,为减速器的减振降噪设计提供了理论基础。 相似文献
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Amanda M. Wilson Mark H. Weir Marco-Felipe King Rachael M. Jones 《Journal of the Royal Society Interface》2021,18(182)
Mathematical models describing indirect contact transmission are an important component of infectious disease mitigation and risk assessment. A model that tracks microorganisms between compartments by coupled ordinary differential equations or a Markov chain is benchmarked against a mechanistic interpretation of the physical transfer of microorganisms from surfaces to fingers and subsequently to a susceptible person''s facial mucosal membranes. The primary objective was to compare these models in their estimates of doses and changes in microorganism concentrations on hands and fomites over time. The abilities of the models to capture the impact of episodic events, such as hand hygiene, and of contact patterns were also explored. For both models, greater doses were estimated for the asymmetrical scenarios in which a more contaminated fomite was touched more often. Differing representations of hand hygiene in the Markov model did not notably impact estimated doses but affected pathogen concentration dynamics on hands. When using the Markov model, losses due to hand hygiene should be handled as separate events as opposed to time-averaging expected losses. The discrete event model demonstrated the effect of hand-to-mouth contact timing on the dose. Understanding how model design influences estimated doses is important for advancing models as reliable risk assessment tools. 相似文献
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本文以某三轴五档手动变速箱作为研究对象,运用LMS.VirtualLab多体动力学软件对箱体建立动力学模型,进行动力学分析以此获得轴承座动态反支力。再以轴承座动态反支力作为激励,分别建立综合考虑变速箱内部润滑液和空气影响与不考虑变速箱内部润滑油和空气影响的变速箱振动响应分析模型,并分析对比箱体的振动响应结果,然后运用声学边界元法预估了箱体辐射噪声并通过试验进行验证,最后通过箱体结构优化使该变速箱得到了降噪,对提前规避变速器的振动噪声问题具有重要的工程实际意义。 相似文献
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综合考虑轮齿啮合时变刚度、齿轮传递误差、齿轮啮合冲击以及风载变化等因素影响,建立具有多级齿轮传动的大型风电齿轮箱的齿轮-传动轴-轴承-箱体系统耦合非线性动力学模型。对风电齿轮箱系统有限元模型进行耦合模态分析,运用模态叠加法对齿轮箱系统在内部激励与外部激励综合作用下的振动响应进行求解。将仿真结果与实验数据对比,进而得到齿轮箱各点振动位移、速度、加速度及结构噪声等系统动态评价指标,为大型风电齿轮箱动态特性的准确评价及齿轮系统动态性能优化设计提供理论依据。 相似文献
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由于大功率船用齿轮箱的特殊使用工况,其性能要求远远高于其他齿轮箱。论文对某大功率船用齿轮箱结构和传动原理进行分析,根据试验模态分析的基本原理和方法,利用最小二乘法对频响函数进行优化,并利用单模态识别法对大功率船用齿轮箱进行模态参数识别,得出系统的前20阶固有频率和阻尼,结果表明该船用齿轮箱系统的转频、啮合频率远离固有频率,系统不存在共振现象。但考虑齿轮箱实际工作的复杂性,在系统转速变化达到临界转速时存在较为剧烈的共振现象。试验结果可为进一步系统研究动态特性提供分析依据。 相似文献
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针对某车型进气系统在高转速时的宽频带进气噪声问题,提出了一种多腔微穿孔管消声器结构。根据传递矩阵法,建立了有流条件下多腔微穿孔管消声器传递损失计算模型;针对研究车型进气口噪声的频谱特性,采用多种群遗传算法对多腔微穿孔管消声器的结构参数进行优化设计,通过阻抗管台架和实车测试验证了消声器消声效果。结果表明,优化的多腔微穿孔管消声器能够有效拓宽降噪频带,消声器传递损失预测结果与实验测试结果一致,验证了所提出的传递损失计算模型的准确性及优化算法的有效性;在实车进气系统中采用该微穿孔管消声器后,进气噪声在600~1800 Hz中高宽频段以及200~400 Hz低频段均有明显降低,证实了所提出的多腔微穿孔管消声器的实际宽频消声特性。 相似文献
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Design and optimization of gear transmissions have been intensively studied, but surprisingly the robustness of the resulting optimal design to uncertain loads has never been considered. Active Robust (AR) optimization is a methodology to design products that attain robustness to uncertain or changing environmental conditions through adaptation. In this study the AR methodology is utilized to optimize the number of transmissions, as well as their gearing ratios, for an uncertain load demand. The problem is formulated as a bi-objective optimization problem where the objectives are to satisfy the load demand in the most energy efficient manner and to minimize production cost. The results show that this approach can find a set of robust designs, revealing a trade-off between energy efficiency and production cost. This can serve as a useful decision-making tool for the gearbox design process, as well as for other applications. 相似文献
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为提高传动轴空间布置的合理性和适应性, 优化设计需要结合悬架的空间运动特性.从板簧汽车实际行驶的动态工况出发,对汽车板簧进行了运动学分析,建立基于悬架空间运动模型的传动轴运动模型,并提出了传动轴动态空间的优化目标,利用线性加权的方法,将多目标优化问题转化为单目标优化问题,选择小种群遗传算法作为优化算法.实例计算得到了平均当量夹角更小的传动布置方案,有效减小了振动和噪声.优化结果表明:基于板簧运动的传动轴空间动态设计,比传统的单一载荷下的优化设计更为合理,优化效率更高,并且优化结果的适应性更好. 相似文献
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通过波动方程建立了多分支赫歇尔-昆克(Herschel-Quincke,HQ)管的传声损失模型,该模型可计算包含任意数量、不同管径和不同管长组合的HQ管模型。通过与前人的计算结果进行比较,验证了该方法的有效性。并通过数值计算,分析讨论了不同参数(如HQ管的长度和直径、HQ管分支数量)对多分支HQ管传声损失的影响。结果表明:在总横截面积相等的情况下,多分支HQ管吸声性能与单分支HQ管相同;改变管道的长度可以改变共振频率;比较频率平均传声损失,HQ管长度不统一的结构的声学特性优于长度统一的结构。 相似文献
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