基于质点动力学模型的三自由度灯体运动控制研究

针对三自由度灯体运动控制系统的多变量、非线性特征,使用拉格朗日函数法对大型灯体运动进行分析建模,得到了描述三自由度灯体运动规律的动力学方程.对于该模型利用多变量非线性系统的逆系统方法通过输入重定义和反馈替代得到伪线性系统,并利用极点配置的方法进行了控制器设计.计算机仿真实验证明,在灯体大角度运动和质心发生漂移的情况下,系统能够快速准确地逼近期望值,动态特性平滑,控制效果较好.     

3-RPS柔性并联定位机构运动学分析与仿真

对具有空间三自由度的3-RPS柔性并联定位机构进行了运动学分析及仿真。首先,以3-RPS并联机构为基础,将机构中的运动副用柔性铰链代替,研制了一台具有三自由度的精密定位机构;其次采用"伪刚体模型"方法将该精密定位工作台等效为伪刚体模型,利用齐次坐标变换方法和矢量闭环方法构建其逆运动学模型;最后,利用软件RecurDyn进行仿真分析,测量出其位移与速度随时间的变化曲线进行验证。结果表明所建立的机构理论模型合理,且机构具有良好的运动学性能。     

三自由度汽车座椅及其振动特性研究

为了解决车辆座椅的多自由度振动和乘坐舒适性等问题,设计了一种三自由度并联机构座椅。利用单开链理论,计算出减振机构的耦合度为1,并用运动输出矩阵验证了三自由度为三平移运动,采用单位力椭球法对椭球圆度的分析为振动特性仿真分析提供了理论依据。通过支链不同刚度、负载和阻尼时的振动传递特性仿真分析,结果表明:系统各轴向共振频段远离乘客不舒适频段4~7 Hz,且在竖直方向上传递率峰值明显优于传统机械式减振座椅;在水平方向上,当激励在1 Hz以上时,传递率趋于零。研究表明该减振座椅能够达到较高的减振标准。     

欧拉动弯曲问题的混沌控制

研究了利用耦合反馈控制法和周期激振力法来控制欧拉动弯曲问题.通过数值仿真的方法,得到系统在不同参数下的各种非线性动力学行为,以此揭示了系统由周期态通向混沌的路径.然后在系统处于混沌态时,通过庞加莱映射法,得到系统的控制参数.通过调节控制参数,对处于混沌态的系统进行控制.通过控制后的全局分岔图,时间相应图和相图来判断控制后的效果.结果表明,通过这两种方法,可以控制系统的混沌运动而得到稳定的周期振动结果.     

基于PC+PMAC的仿人机械臂控制系统的应用研究

针对仿人机械臂及其工作的特点,进行了一个关节型三自由度仿人机械手臂的控制系统的研究,主要对硬件结构、软件结构和控制方法等功能模块进行了设计。该控制系统采用PC机和PMAC多轴运动控制器进行两级控制,保证了系统重量轻、体积小、实时性好、可靠性高的要求,使仿人机械臂工作更具实用性。此项仿人机器臂平台的研究未来前景广阔。     

一种并联多指灵巧手的设计与运动学分析

针对串联灵巧手的不足,利用并联机构的优势,设计并分析了一种新型多指灵巧手。根据构型综合方法,提出了一种三自由度的并联手指机构并对其进行运动学分析;基于手指机构的构型,设计出相适应的手掌,将其组合成多指灵巧手;分析并联多指灵巧手抓取能力和可达工作空间,与串联灵巧手的性能进行对比。结果表明,以并联机构设计的多指灵巧手具有良好的运动性能和工程应用前景。     

边界质量对覆冰输电线舞动的影响分析

基于曲梁理论、Hamilton原理和伽辽金方法,建立同时考虑相邻跨刚度以及绝缘子串质量作用下的覆冰输电线三自由度舞动运动方程。采用Mathematica数学软件编制三自由度曲梁模型对覆冰输电线舞动进行求解分析,分析结果表明,随着边界绝缘子串质量的增大,覆冰输电线竖向的舞动幅值会变大,而侧向和扭转向的舞动幅值则会减小。此外,发生舞动的临界风速也相应增大,整体结构相对更稳定。     

并联机器人的轨迹规划仿真

并联机器人是机器人研究与应用的一个重要部分,并联机构的逆解和轨迹规划比较容易,本文给出了三自由度并联机器人的逆解,描述了轨迹规划的方法,在VC＋＋6．0的环境下利用OpenGL对其运动轨迹进行了实时仿真。     

一个非线性色散-耗散方程新的精确解

利用修正的齐次平衡法,通过计算机代数系统Mathematica 4.0进行验证,得到了用于描述由冷离子和热电子组成的等离子体弱非线性离子声波演化的非线性色散-耗散方程的几类显式精确解,修正和完善了已知的结果.     

谐和与白噪声激励下碰撞振动系统的混沌运动

碰撞振动系统轨线的不连续性使得系统表现出强非线性和奇异性的特性.鉴于此,研究谐和与白噪声激励下非线性单边碰撞振动系统的混沌动力学.利用动力系统稳定性理论和Melnikov方法,分析碰撞振动系统的同宿轨,得到系统出现Smale马蹄混沌的阀值.并通过相图、Poincare截面图和安全盆等数值仿真验证该解析阀值的有效性.研究表明,基于Melnikov方法获得的解析结果是系统出现混沌运动的必要条件,也是系统出现安全盆腐蚀的充要条件.     

女性人体躯干部分体型特征参数探讨

从几何学的角度探讨、分析了女性躯干部分的体型特征,得到13个体型特征参数,并建立了女性躯干部分体型特征参数模型。     

基于三维扫描数据的女性体型特征参数分析

为在不同应用层次上提供一种完善的基于三维人体扫描数据库的体形分析参考标准。提出一种女性体形分析方案,包括体型类别分析方法,局部形态的特征分析和三维特征框架的数据分析,然后对861个18～45岁的女性对象进行体型类别的实例分析,主要包括：基于躯干体积指数(TVI)的体型分类、基于胸腰比-臀腰比的体型分类、及基于胸腰差-臀腰差的体型分类,目的是比较采用不同方法进行体型分类后的各群体体型变化趋势。结果显示,基于TVI指数的分类效果较明显,胸腰比－臀腰比和胸腰差－臀腰差方法同属一种分类方法,分类效果接近。采用我国服装号型标准中的分类方法,能很好反映人体下身围度相对逐渐增肥的趋势。     

Body condition score and body weight effects on dystocia and stillbirths and consequent effects on postcalving performance

The objective of this study was to quantify the effect of periparturient body condition score (BCS) and body weight (BW) related traits on the incidence of calving dystocia and stillbirths, and to determine any consequent effect of dystocia and stillbirths on BCS, BW, milk production, udder health, and fertility in grazing Holstein-Friesian dairy cows. Up to 2,384 lactation records with data on calving dystocia or stillbirths were available from one research herd across 15 yr. Mixed models and generalized estimating equations were used to quantify all effects. Body condition score or BW 8 wk precalving or at calving, or change precalving did not significantly affect the odds of a difficult calving or stillbirth. Cows that experienced dystocia lost, on average, more BCS and BW between calving and nadir and had significantly reduced nadir BCS and BW. Incidence of stillbirths did not affect BCS in early lactation, although BW loss postpartum was greater following a stillbirth. A dystocia or stillbirth event was associated with reduced 60-d milk yield (42 and 52 kg less milk produced following a difficult calving or a stillbirth, respectively). The effect of stillbirth on milk yield was independent of dystocia. Cows that experienced dystocia had reduced milk concentration of fat, protein, and lactose, whereas average somatic cell score (natural logarithm of somatic cell count) in the first 60-d postpartum was elevated. There was no significant effect of dystocia or stillbirth on clinical mastitis, but pregnancy rates to first service and throughout the 12-wk breeding season were compromised in cows that had experienced difficulty at calving. The significance of the effects of stillbirth on somatic cell score and reduced fertility were mediated through its association with dystocia. In conclusion, periparturient BCS and BW within the range observed in the current study did not significantly affect incidence of dystocia and stillbirth, but these events negatively affected cow performance in early lactation.     

A comparison of three strains of Holstein-Friesian cows grazed on pasture: growth, development, and puberty

With the introduction of a protein milk payment system in New Zealand in 1988, there was an influx of North American (NA) Holstein-Friesian (HF) genetics into New Zealand (NZ) dairy herds, leading to an increase in the average percentage of NA genetics in NZ HF cows—from 2% in 1980 to 38% in 1999. Of interest has been the effect this change has had on farm profitability and on the management required for these animals, as well as the phenotypic changes that have occurred within the national herd under the breeding programs operated in NZ from 1970 to 1990. The objective of this study was to quantify differences in body dimensions, body weights, and puberty-related parameters among 3 strains of HF, representing animals of NZ origin representative of the genetics present in 1970 and 1990 and of NA origin with 1990s genetics. A total of 172 animals born in 1999 were compared. The strains were 1) NZ70, a strain of NZ Friesian (average 7% NA genetics) equivalent to high-genetic-merit (high Breeding Worth) cows farmed in the 1970s; 2) NZ90, a strain of HF of NZ origin (average 24% NA genetics) typical of the animals present in the 1990s; and 3) NA90, a strain of HF of NA origin (average of 91% NA genetics) typical of animals present in the 1990s. The differences in BW among all strains were significant at 6 and 12 mo of age. At 15 and 24 mo, the 2 NZ strains were significantly lighter than the NA90 animals. At 24 mo of age (i.e., prior to first calving), the NA90 strain animals (BW = 515 kg) were 22 and 34 kg heavier than the NZ90 and NZ70 strains. The body length of the NA90 strain was greater than either of the 2 NZ strains; the differences among the NA90 strain and the 2 NZ strains varied from 2 to 6 cm, with the differences generally being greater at older ages. The trend in heart girth difference among strains was similar to that observed for body length. The wither height of the NA90 animals was greater than that of the NZ strains by 1 to 7 cm, although there was no significant difference between the NA90 and NZ90 strains at birth. At puberty the NA90 heifers were 20 d older and 20 kg heavier than the NZ90 heifers, which in turn were 25 kg and 25 d older than the NZ70 heifers. The NA90 strain had a heavier mature body weight, and their older age at puberty suggested either that they mature later or that, under pastoral conditions, their growth rate is limited by their inability to consume sufficient metabolizable energy as grazed pasture, with a consequent delay in puberty. Results from this study will be useful in revising target BW in growing heifers of different germplasm.     

Influence of Holstein-Friesian strain and feed system on body weight and body condition score lactation profiles

The objective of the present study was to determine effects of strain of Holstein-Friesian and feed system on body weight (BW) and body condition score (BCS; scale of 1 to 5) lactation profiles in seasonal-calving, grass-based milk production systems. The 3 strains of Holstein-Friesian compared differed in milk production potential and were high-production North American (HP), high-durability North American (HD), and New Zealand (NZ). The 3 feed systems compared were a high grass allowance feed system typical of spring-calving herds in Ireland (MP); an increased stocking rate system (HS); and an increased concentrate supplementation system (HC), each maintained within a separate farmlet. The data comprised 20,611 weekly BW and 7,920 BCS records assessed every 3 wk across 5 yr on 584 lactations. An exponential function was used to model BW and BCS lactation profiles across feed systems. Across feed systems, the NZ strain was significantly lighter (545 kg) but had greater average BCS (3.10 units) compared with the HP (579.3 kg and 2.76 units, respectively) and HD strains (583.2 kg and 2.87 units, respectively). Across feeding systems, the HD and HP strains exhibited a greater loss of BCS in early lactation (0.27 and 0.29 units, respectively) compared with the NZ strain (0.21 units). The HP strain failed to gain BCS over the entire lactation. Concentrate input did not affect the rate of BCS or BW loss in early lactation or BCS at 60 DIM. This study extends previous research outlining the greater suitability of the NZ strain to the low-cost grass-based system of milk production predominantly operated in Ireland.     

从结构看塑身内衣功能性的实现

以塑身内衣为例,从总体结构和细部结构将功能性服装和普通服装做对比,详细论述了塑身内衣塑身美体功能与其结构的密切关系.     

女性体型特征指标的选择及体型细分研究

在人体测量的基础上,利用主成分分析的方法,提取了女性躯干部分的三个特征指标,并根据三个特征指标的不同取值将女性形体分为36种体型。     

基于下装设计的人体建模

下体主要是由腰腹部、臀部、臀沟和腿部组成,提取了这些部位中与下装设计直接相关的18个部位的尺寸,定义了人体的主要特征切面,减少了人体平均形态的计算,同时尽可能地保留了人体躯干的三维体形信息。通过对这些部位特征形状的提取和分析,将控制服装款式变化的关键部位的变化转换为形值点参数的变化,进而进行曲面的拟合,建立了基于下装特征的参数化人体模型。结果可用于指导下装的定制开发。     

基于三维测量的江浙地区50～75岁中老年女性体型细分研究

文章采用德国VITUS SMART XXL三维人体测量系统结合马丁测量仪及体重测量仪,对217名江浙地区50~75岁这一特定年龄层的中老年女性进行人体测量,获得中老年人成衣制作所需要的人体有关尺寸以及体重数据,对中老年人体型有关数据进行分析。     

国内外服装用人体数据库调查与分析

人体体型数据是服装设计开发和生产制造的基础依据。人体体型数据库提供了人体体型的大数据平台,实现了人体体型数据的数字化储存和检索,为人体体型特征研究和成衣设计生产提供了重要的技术支持和数据支撑。通过探讨服装业对人体数据的更新需求及人体数据的获取方法、发展趋势等;并经过多渠道调研,汇总国内外22个人体数据库的研究建立、运行使用以及数据含量等基本情况,基于尚在运行使用中的数据库进行框架特征和功能分析,为人体数据库的查询使用和研究建立提供借鉴。