电动助力转向系统简介

汽车电动助力转向系统是汽车助力转向方式之一,近年来在汽车特别是在乘用车上得到越来越广泛的应用,其工作性能优劣直接影响到汽车的操纵稳定性和安全性。文章首先介绍了电动助力转向系统的发展历程,其次阐述了电动助力转向系统是如何分类的,最后对电动助力转向系统研发过程中的一些关键技术进行了说明。     

汽车电动助力转向系统发展综述

综述了国内外汽车电动助力转向(EPS)系统的发展现状,介绍了电动助力转向系统的结构、类型及其特点。分析对比了国内外电动助力转向系统建模及控制策略,展望了电动助力转向系统的发展趋势,指出电动助力转向技术代表未来汽车动力转向技术的发展方向之一,并将在动力转向领域占据主导地位。     

汽车电动助力转向系统路感特性分析

讨论了汽车转向路感的形成及定义,对电动助力转向系统的路感特性进行了分析,研究了电动助力转向系统路感的影响因素,提出了改善电动助力转向系统路感的方法,并对电动助力转向系统进行仿真分析,结果表明所提出的方法是正确有效的.     

汽车动力转向系统的发展

综述了汽车动力转向技术的发展,分别叙述了液压助力转向系统、电控液压转向系统及电动助力转向系统,主要叙述了液压助力转向系统的结构、工作原理和主要控制策略,探讨了汽车动力转向系统的发展趋势.     

汽车线控转向系统路感模拟方法

线控转向系统取消了传统转向系统方向盘到转向车轮的机械连接,因而转向路感无法直接反馈给驾驶员,为此通过对汽车转向系统路感的理论分析,建立了线控转向系统动力学模型。采用卡尔曼滤波技术对汽车转向系统齿条受力进行估计,并引入电动助力转向系统的助力特性,设计复制电动助力转向系统路感的线控转向系统路感模拟方法。试验结果表明,路感模拟方法可以使驾驶员获得有效的路感信息,提高了汽车的操纵性和舒适性。     

电动助力转向系统转向性能的客观评价

针对电动助力转向的结构特点，分析了电动助力转向对汽车转向性能的影响，提出从转向轻便性、转向回正性、转向盘中间位置区域性能、转向盘振动、随动灵敏度和助力特性等方面进行电动助力转向系统转向性能的客观评价，并探讨了相应的评价指标，对电动助力转向助力控制规律、基本设计参数以及相关试验标准的确定有指导意义。     

基于Freescale的汽车电动助力转向控制器研究

介绍了电动助力转向系统的结构原理和系统组成。在研究助力转向控制原理的基础上,设计了基于Freescale 9 s12Xdp512的汽车电动助力转向的控制器,通过方向控制电路、电机驱动电路和PWM脉宽调制技术实现对电机的控制,并对EPS转向助力特性进行了仿真分析。     

新型电动轮转向系统控制策略及性能分析

在现有电动轮汽车的基础上,提出了一种实现主动转向和助力转向功能的方案。介绍了新型电动轮转向系统的结构和基本工作原理,并建立了新型电动轮转向系统与整车机电耦合的动力学模型。提出了主动转向与助力转向的控制策略,并进行了不同车速工况下新型电动轮转向系统的性能分析。仿真结果表明,所提出的实现主动转向和助力转向功能的系统结构方案是可行的,所设计的主动转向与助力转向的控制策略是有效的。     

电动助力转向系统助力特性分析

在建立电动助力转向系统的动力学模型和整车参数的基础上,分析影响转向系统助力特性的参数并分析电动转向系统的稳定性,得到助力特性曲线图,验证了助力特性的准确性,为电动助力转向系统的设计和改造提供依据。实验结果表明,电动助力转向系统的实际助力特性与理想助力特性基本一致。     

汽车转向系统发展趋势

介绍了汽车机械转向系统、液压动力转向系统、电控液压动力转向系统、电动助力转向系统、四轮转向系统、主动前轮转向系统以及线控转向系统,并介绍了转向系统的发展趋势,指出转向系统与其他系统的集成控制是未来的发展方向。     

Overland water and salt flows in a set of rice paddies

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.     

瓦房店市水果生产标准化发展研究

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。     

金谷子耐旱TG118引种试种及推广应用

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。     

对《种子法》存在问题的探讨

《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。     

Review of the Egyptian experience in implementing land drainage projects

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.     

和谐社会理论建设的几点哲学思考

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。     

A European irrigation map for spatially distributed agricultural modelling

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.     

粉质仪和拉伸仪在面粉生产中的应用

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。     

农村信息化服务的现状及建设措施

分析当前我国农村信息化服务的现状,提出加强农村信息化服务的新举措。     

车辆ABS控制算法的研究及探讨

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。