A virtual yaw rate sensor for articulated vehicles featuring novel electro-hydraulic steer-by-wire technology

Steer-by-wire technologies remain under rigorous research and development given the advantages that they offer over their traditional counterparts. The spectrum of steering systems encompasses applications in the automotive, construction, agricultural, and aerospace industries, to name a few.An original electro-hydraulic steer-by-wire technology based on pump displacement control actuation, an energy efficient alternative to conventional valve control, has been previously proposed by the authors. The new concept was validated and implemented on an articulated steering prototype test vehicle, and resulted in significant fuel savings and machine efficiency increase. This paper investigates the notion of virtual sensing relative to estimating the vehicle׳s yaw rate by only measuring the articulation angle and vehicle speed. Virtual sensing is a promising concept for yaw stability control and is an attractive option for vehicle manufactures as it reduces sensor cost, maintenance, and machine downtime. The designed yaw rate sensor is validated in simulation as well as on a test vehicle by devising appropriate steering maneuvers.     

稀土草酸盐直接制备氟化物的试验研究

稀土草酸盐中直接加氢氟酸置换生成氟化稀土,选择加入１２０％理论量的氢氟酸有较高的转化率和回收率。置换后草酸溶液循环使用,降低了成本。     

液压拉力试验机微机改造及网络应用系统

介绍了液压拉力试验机的微机改造,对改造后自动拉伸测试系统的组成、操作使用及测量精度作了详细的分析研究,结果表明液压拉力试验机的微机改造可使非电拉试验机测试能力提高一个水平,值得推广。该系统完全能满足GB228—87《金属拉伸试验方法》标准要求。     

基于最大长度序列的绝对位移精密检测方法

为了检测精密机构的微小位移,根据位移编码与机器视觉技术,提出一种基于最大长度序列(Maximum Length Sequence—MLS)的绝对位移检测方法;该方法设计了基于MLS的绝对位移检测的视觉靶标方案,采用基于灰度叠加及二值化方法进行图像处理和靶标绝对位置识别;研究了基于拟合相位的精密定位方法,实现一维绝对位移的精密检测,并进行实验验证;实验结果表明,该方法可有效实现一维绝对位移检测,定位精度在±2 μm范围内,具有良好的重复性和鲁棒性,且无须视觉标定。     

基于相位测量的微波位移测量方法

为满足建筑结构全天候、高精度及低成本的位移监测要求,提出了基于相位测量的微波位移测量方法。该方法以微波作为全天候测量信号,利用高精度相位测量实现高精度位移监测,并采用低成本的标准频率器件搭建位移测量系统。实验结果表明:系统位移测量精度可达0.12 mm,并验证了系统具有全天候、高精度、低成本的位移监测特性。     

Effects of military load carriage on kinematics of gait

Manual load carriage is a universal activity and an inevitable part of the daily schedule of a soldier. Indian Infantry soldiers carry loads on the waist, back, shoulders and in the hands for a marching order. There is no reported study on the effects of load on gait in this population. It is important to evaluate their kinematic responses to existing load carriage operations and to provide guidelines towards the future design of heavy military backpacks (BPs) for optimising soldiers' performance. Kinematic changes of gait parameters in healthy male infantry soldiers whilst carrying no load (NL) and military loads of 4.2–17.5 kg (6.5–27.2% body weight) were investigated. All comparisons were conducted at a self-selected speed. Soldier characteristics were: mean (SD) age 23.3 (2.6) years; height 172.0 (3.8) cm; weight 64.3 (7.4) kg. Walk trials were collected using a 3-D Motion Analysis System. Results were subjected to one-way ANOVA followed by Dunnett post hoc test. There were increases in step length, stride length, cadence and midstance with the addition of a load compared to NL. These findings were resultant of an adaptive phenomenon within the individual to counterbalance load effect along with changes in speed. Ankle and hip ranges of motion (ROM) were significant. The ankle was more dorsiflexed, the knee and hip were more flexed during foot strike and helped in absorption of the load. The trunk showed more forward leaning with the addition of a load to adjust the centre of mass of the body and BP system back to the NL condition. Significant increases in ankle and hip ROM and trunk forward inclination (≥10°) with lighter loads, such as a BP (10.7 kg), BP with rifle (14.9 kg) and BP with a light machine gun (17.5 kg), may cause joint injuries. It is concluded that the existing BP needs design improvisation specifically for use in low intensity conflict environments.

Statement of Relevance:The present study evaluates spatial, temporal and angular changes at trunk and limb joints during military load carriage of relatively lighter magnitude. Studies on similar aspects on the specific population are limited. These data can be used for optimising load carriage and designing ensembles, especially a heavy BP, for military operations.     

地基土上水工建筑物的抗滑动稳定研究

研究地基土上水工建筑物滑动设计和计算中存在的问题。利用基坑内压板抗滑动试验成果,确定地基土包括回弹影响后的抗滑动承载能力。采用地基土承受偏心荷载的最大压应力σmax控制地基土与压板的位移和抗滑动形式,可以发生不同的3种最大位移面,形成6种抗滑动形式。根据地基土承受的最大压应力,提出设计抗滑动的计算方法:定量确定地基土与压板抗滑动的摩擦系数计算值,地基土的抗滑动安全系数由指标安全系数控制,修正在地基土上建筑物整体滑动的计算公式,计算预测可能发生的多种最大位移面和抗滑动形式及绘制地基土滑动区轮廓,限定地基土发生平面抗滑动形式时承受的最大压应力值。按拟定方法,回顾分析3座已建水工建筑物,分析计算成果符合实物工况。     

波浪作用下二维海床土体位移分布研究

海洋建筑物设计包括结构和基础两个部分,波浪力的计算对结构部分的设计十分关键,而在基础设计中,海床稳定性的评价工作,也是十分必要的。波浪在海床上传播,会在海床上施加波压力和剪切力,引起孔隙水压力及有效应力的变化,使海床出现变形、软化及液化等现象。正确的评价波浪对海床稳定性的影响,对海洋建筑物基础乃至上部结构的设计,都具有重要的指导意义。该文拟从海床的宏观力学性能出发,提出一简化的力学模型,推导了波浪作用下二维海床的土体位移分布。另外,建立二维有限元模型,将有限元计算结果与力学模型结果进行对比,两种计算结果吻合的较好。基于此简化模型,可以开展海床稳定性评价及海洋环境下被动受荷桩的响应分析方面的工作。     

Fatigue growth prediction of center slant crack in rectangular plate

This paper presents a numerical prediction model of mixed‐mode crack fatigue growth in a plane elastic plate. It involves a formulations of fatigue growth of multiple crack tips under mixed‐mode loading and a displacement discontinuity method with crack‐tip elements (a boundary element method) proposed recently by Yan is extended to analyse the fatigue growth process of multiple crack tips. Due to an intrinsic feature of the boundary element method, a general growth problem of multiple cracks can be solved in a single‐region formulation. In the numerical simulation, for each increment of crack extension, remeshing of existing boundaries is not necessary. Crack extension is conveniently modelled by adding new boundary elements on the incremental crack extension to the previous crack boundaries. At the same time, the element characters of some related elements are adjusted according to the manner in which the boundary element method is implemented. As an example, the present numerical approach is used to analyse the fatigue growth of a centre slant crack in a rectangular plate. The numerical results illustrate the validation of the numerical prediction model and can reveal the effect of the geometry of the cracked plate on the fatigue growth.     

一维单原子纳米颗粒晶格振动性质的理论研究

根据一维单原子纳米颗粒晶格振动量子化的结论 ,推导了一维单原子纳米颗粒晶格振动的内能、比热、原子均方位移和原子均方速度公式 ,并进行了数值计算。数值计算结果表明 ,单位质量的一维单原子纳米颗粒的晶格振动内能与比热随纳米颗粒尺寸的增加而增加 ,一维单原子纳米颗粒的表面原子的均方位移大于内部原子的均方位移 ,而表面原子的均方速度小于内部原子的均方速度