共查询到20条相似文献，搜索用时 156 毫秒
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以拖拉机减振为目的,建立了二自由度拖拉机油气悬架系统的数学模型,分析了油气悬架系统数学模型的非线性特性。运用AMEsim仿真软件,采用阶跃信号、谐波信号和随机信号模拟拖拉机典型行驶路况,对比分析了被动悬架和油气悬架的振动特性,验证了数学模型的正确性。通过比较两种悬架的振动特性、非线性特性和车身高度偏离静平衡状态的程度等3项指标可知:采用油气悬架可明显改善拖拉机悬架的振动性能,提高行驶平顺性和乘坐舒适性。 相似文献
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结合某型工程车辆,建立其双气室油气悬架的物理模型和非线性阻尼数学模型,基于MATLAB/Simulink模块建立了相应的仿真模型。利用该模型研究了激振信号对油气悬架阻尼特性的影响。结果表明,该油气悬架具有非线性变阻尼特性,对高频、大振幅激振信号减振效果优越,适用于恶劣环境下高速行驶的车辆。 相似文献
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建立了单气室油气悬架的非线性数学模型和二自由度汽车振动模型,利用蒙特卡洛法构造了路面不平度时间函数,利用MATLAB/SIMULINK进行了时域仿真。分析了油气悬架主要参数包括蓄能室初始体积、主活塞杆面积、阻尼孔面积变化对车辆平顺性、安全性的影响,得出了某型油气悬架结构参数的可行设计范围。 相似文献
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为研究双蓄能器油气悬架在农用车辆行驶过程中的输出特性规律,笔者以某农用车辆的油气悬架为研究对象,分析了双蓄能器油气悬架结构及工作原理,建立了系统非弹力数学模型、阻尼力数学模型。利用AMESim软件建立了油气悬架系统模型,分析了阻尼孔直径、单向阀直径对悬架振动特性的影响。结果表明：改变悬架结构参数会影响其振幅衰减程度以及振动衰减周期;在允许范围内相应增大阻尼孔和单向阀直径时,相对位移峰值、相对速度峰值得到提升的同时,车身垂直加速度峰值、油缸压力也会相应提升。所以可以根据实际情况适当调整阻尼孔直径以及单向阀直径。 相似文献
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建立了某型工程车辆油气悬架的运动微分方程,基于油气悬架的多相介质力学特点,引入了分数阶微积分理论,建立其分数阶Bagley-Torvik方程。通过Oustaloup算法设计低通滤波器进行数值运算,求得非线性分数阶微分方程数值解,探讨分数阶模型下悬架的振动特性。通过搭建等比例试验台和建立仿真模型,将分数阶、整数阶仿真和试验数据进行对比。结果表明当分数阶次取0.9时能更好地反映油气悬架运动特性,系统的分数阶模型与实测数据能够更好地吻合,验证了分数阶模型在油气悬架系统模型上的有效性。 相似文献
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多轴越野车辆油气悬架系统参数仿真 总被引：3，自引：2，他引：1
建立了多轴越野车辆的平面力学模型,对其参数进行了计算机仿真,仿真参数包括悬架弹簧变刚度和变阻尼,分析涉及的车辆模型有弹簧悬置的车体和4个车桥.研究了车辆系统的6个自由度的运动方程及动态特性.分析了车辆在粗糙路面上的油气弹簧刚度和阻尼特性的非线性变化规律,获得了多轴车辆悬架系统在路面激励下的响应特性,提出提高车辆平顺性的途径. 相似文献
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2级串联式ISD悬架非线性建模与参数优化 总被引：1，自引：0，他引：1
基于非线性因素对滚珠丝杠式惯容器实际力学性能的影响机理分析,建立了考虑摩擦以及丝杠弹性效应的惯容器非线性力学模型,进行了惯容器实际力学性能试验,根据试验数据对惯容器非线性力学模型中的参数进行了识别。在此基础上,建立了包含惯容器非线性的两级串联式惯容器-弹簧-阻尼器(ISD)悬架半车5自由度数学模型,通过对悬架参数的灵敏度分析,确定了ISD悬架参数的优化变量。根据车辆行驶平顺性性能评价指标,建立了ISD悬架参数优化模型,并采用粒子群优化算法对两级串联式ISD悬架的参数进行了优化。结果表明,该优化方法在满足车辆行驶安全性和控制悬架撞击限位概率的要求下,座椅处垂向加权加速度均方根降低了24.12%,车辆行驶平顺性得到了显著改善。 相似文献
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Overland water and salt flows in a set of rice paddies 总被引：1，自引：0，他引：1
E. Playn O. Prez-Coveta A. Martínez-Cob J. Herrero P. García-Navarro B. Latorre P. Brufau J. Garcs 《Agricultural Water Management》2008,95(6):645-658
Cultivation of paddy rice in semiarid areas of the world faces problems related to water scarcity. This paper aims at characterizing water use in a set of paddies located in the central Ebro basin of Spain using experimentation and computer simulation. A commercial field with six interconnected paddies, with a total area of 5.31 ha, was instrumented to measure discharge and water quality at the inflow and at the runoff outlet. The soil was classified as a Typic Calcixerept, and was characterized by a mild salinity (2.5 dS m−1) and an infiltration rate of 5.8 mm day−1. The evolution of flow depth at all paddies was recorded. Data from the 2002 rice-growing season was elaborated using a mass balance approach to estimate the infiltration rate and the evolution of discharge between paddies. Seasonal crop evapotranspiration, estimated with the surface renewal method, was 731 mm (5.1 mm day−1), very similar to that of other summer cereals grown in the area, like corn. The irrigation input was 1874 mm, deep percolation was 830 mm and surface runoff was 372 mm. Irrigation efficiency was estimated as 41%. The quality of surface runoff water was slightly degraded due to evapoconcentration and to the contact with the soil. During the period 2001–2003, the electrical conductivity of surface runoff water was 54% higher than that of irrigation water. However, the runoff water was suitable for irrigation. A mechanistic mass balance model of inter-paddy water flow permitted to conclude that improvements in irrigation efficiency cannot be easily obtained in the experimental conditions. Since deep percolation losses more than double surface runoff losses, a reduction in irrigation discharge would not have much room for efficiency improvement. Simulations also showed that rice irrigation performance was not negatively affected by the fluctuating inflow hydrograph. These hydrographs are typical of turnouts located at the tail end of tertiary irrigation ditches. In fact, these are the sites where rice has been historically cultivated in the study area, since local soils are often saline-sodic and can only grow paddy rice taking advantage of the low salinity of the irrigation water. The low infiltration rate characteristic of these saline-sodic soils (an experimental value of 3.2 mm day−1 was obtained) combined with a reduced irrigation discharge resulted in a simulated irrigation efficiency of 60%. Paddy rice irrigation efficiency can attain reasonable values in the local saline-sodic soils, where the infiltration rate is clearly smaller than the average daily rice evapotranspiration. 相似文献
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瓦房店市是我国重要的水果生产基地,在国内水果生产领域占有重要地位。随着水果市场化的不断深入,如何满足和适应国内外市场需求成为瓦房店市水果生产的关键问题。从瓦房店市水果生产实际出发,阐述了实施水果生产标准化的必要性,提出了发展水果生产标准化的具体措施。 相似文献
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对引进的谷子新品种金谷子耐旱TG118进行品种比较试验和多点试种。结果表明：该品种抗旱、耐瘠、适应性强,稳产、高产、抗病抗风抗倒伏强,品质优良,粮草兼用,种植简单,省工易管;一般产量在6000kg/hm2以上,比当地主栽品种增产20%以上。最高产量达9450kg/hm2,适于在辽西北地区推广应用。 相似文献
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对《种子法》存在问题的探讨 总被引：1，自引：0，他引：1
李鹏 《农业机械化与电气化》2011,(6):129-130
《种子法》是我国种植业第一部法律。自实施以来,为依法加强种子管理提供了有力的法律支撑,促进我国种子产业发生翻天覆地的变化。但随着依法管理工作的深入和种子产业的快速发展,《种子法》及配套规章的一些问题逐步显现出来。对《种子法》及配套规章存在的问题进行深入分析,对需要进一步补充的章节以及需要调整的内容进行深入探讨,以求更加完善和明确。 相似文献
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About 30 years have passed since the Government of Egypt embarked on implementing a series of large scale drainage projects. At present, about 3.8 million acres have been provided with drainage systems on the basis of systematic pre-drainage investigations and designs. The target is to provide drains in approximately 6.4 million acres in the Nile Valley and Delta.The implementation of the subsurface drainage system is carried out by the public sector and private contractors under direct supervision of governmental regional departments. The implementation process depends on many factors related to the drainage material, machinery, manpower, site requirements, farmers and organizations involved. Problems and constraints are sometimes challenging, however, the annual rate of implementation has gradually increased to 170,000 acre/year.This paper discusses the different aspects involved in the implementation process of drainage systems. The development in materials, machinery and construction technologies will be reviewed. Institutional and management factors are going to be also considered. 相似文献
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在新世纪,面对机遇和挑战,党的十六大把“社会更加和谐”作为全面建设更高水平的小康社会的一个重要目标。中国人素有社会和谐的理想;西方人自古也向往社会和谐;借鉴东西方两种和谐社会思想的经验、教训,构建社会主义和谐社会理论。 相似文献
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Gunter Wriedt Marijn van der Velde Alberto Aloe Fayçal Bouraoui 《Agricultural Water Management》2009,96(5):771-789
We present a pan-European irrigation map based on regional European statistics, a European land use map and a global irrigation map. The map provides spatial information on the distribution of irrigated areas per crop type which allows determining irrigated areas at the level of spatial modelling units. The map is a requirement for a European scale assessment of the impacts of irrigated agriculture on water resources based on spatially distributed modelling of crop growth and water balance. The irrigation map was compiled in a two step procedure. First, irrigated areas were distributed to potentially irrigated crops at a regional level (European statistical regions NUTS3), combining Farm Structure Survey (FSS) data on irrigated area, crop-specific irrigated area for crops whenever available, and total crop area. Second, crop-specific irrigated area was distributed within each statistical region based on the crop distribution given in our land use map. A global map of irrigated areas with a 5′ resolution was used to further constrain the distribution within each NUTS3 based on the density of irrigated areas. The constrained distribution of irrigated areas as taken from statistics to a high resolution dataset enables us to estimate irrigated areas for various spatial entities, including administrative, natural and artificial units, providing a reasonable input scenario for large-scale distributed modelling applications. The dataset bridges a gap between global datasets and detailed regional data on the distribution of irrigated areas and provides information for various assessments and modelling applications. 相似文献
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在介绍粉质仪和拉伸仪结构和原理的基础上,探讨了粉质曲线中吸水率、形成时间、稳定时间、弱化度和评价值等指标与面粉品质的关系,以及如何根据拉伸曲线中面团最大拉伸阻力、延伸度和拉伸曲线面积等指标来评价面团品质,并结合生产实际,概述了粉质仪和拉伸仪在面粉生产中的作用。 相似文献
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车辆ABS控制算法的研究及探讨 总被引：1，自引：0，他引：1
对现代汽车的ABS控制算法作了一些简单的介绍,同时指出了它们的一些缺陷,相应地提出了几种对ABS的其它控制方法并加以探讨,其中着重论述了ABS门限值控制算法中参考车速的确定方法和基于附着系数的控制算法。 相似文献