林区六足步行机的设计与仿真

针对当前林区移动作业机械存在体积大、油耗高、价格昂贵等问题,基于仿生学原理,模仿人的行走方式,设计了林区六足步行机。应用Denavit-Hartenberg法对六足步行机进行了运动学分析,求解了六足步行机的运动学正问题。利用ADAMS软件对六足步行机进行了运动仿真,验证了六足步行机的各种运动特性。结果表明,六足步行机结构合理、动作稳健,能在林区实现直线行走及爬坡越障,可作为载物平台承担运输等轻型作业。     

非结构环境下六足机器人仿真研究

为了研究六足机器人在不同地形环境下的运动性能,利用CREO三维建模软件生成了一款六足机器人三维实体模型,并导入ADAMS虚拟样机软件获取样机动力学模型.通过建立平地、沟壑以及梅花桩地形虚拟环境对其进行直线行走仿真分析与非结构路面行走步态仿真分析,获取六足机器人在不同运动形式下质心位移、足端受力、各关节转矩等参数随时间的变化曲线,验证了六足机器人结构设计的合理性以及运动的可能性,为六足机器人实物样机的研制提供了理论依据.     

全方位六足步行机的运动设计

本文对六足步行机的全方位运动步态进行了探讨, 提出了基于静态稳定性考虑的最佳步态的选择方案.就横向运动六足步行机的广义三角步态, 分析了其静态稳定裕量、爬坡能力、越沟能力等运动性能, 并给出了采用广义三角步态的横向运动六足步行机总体几何参数CAD的实例.     

六足步行机缩放式腿机构的计算机辅助设计

本文分析了六足步行机圆柱型缩放式腿机构的运动规律及其受力状况,并结合机构的运动空间、六足步行机的最佳机体高度及结构约束等条件,给出了一种合理选择这种机构各设计参数的优化设计方法及计算实例。     

六足机器人多机可达空间协同越障仿真分析

对于小型六足机器人,群体合作是克服单体性能局限的有效措施。为提高六足机器人的越障能力,提出了六足机器人多机协同越障的解决方案。并采用了机器人学D-H参数法,结合足端轨迹规划,对六足机器人多机协同越障情况进行运算,找出六足机器人多机协同时的足端运动范围。再参考求得的运动范围,设定典型障碍,进行虚拟样机仿真。对比三次虚拟样机的仿真结果,展示了多机协同越障的有效性,为提高六足机器人越障能力提供一种新的研究思路。     

少驱动六足机器人结构设计与轨迹优化

设计了一种具有良好稳定性和越障能力的少驱动六足机器人。对少驱动六足机器人的整体结构以及行走步态进行了分析,在此基础上建立了机器人足端点轨迹方程,得到了机器人行走和越障时足端点的运动要求。以六足机器人运动平稳性为目标函数,综合考虑杆长条件、传动性能、几何结构、越障条件和边界条件五类约束,建立了机器人足端轨迹优化模型。利用MATLAB优化工具箱的约束非线性函数fmincon对影响少驱动六足机器人足端轨迹曲线的参数进行优化,得到了满足运动特性要求的机器人腿部机构尺寸。通过对优化后得到的足端轨迹的分析,证明了少驱动六足机器人腿部机构的合理性,为后续六足机器人的研究与开发奠定了基础。     

基于空间曲轴的六足昆虫运动研究

观察现实生活中六足昆虫爬行时各足的运动特征，根据该特征设计了一种创新型3段式空间曲轴，依次与前、中、后足相连，并将与各足相连部分设计成不同的空间连杆机构；为保证各足之间爬行时的运动协调性，分析了空间曲轴和与其有连接关系的各足机构运动参数取值问题；依据协调性运动参数对六足昆虫进行结构建模，并对行走协调性进行了Catia运动仿真。最后，制造出实物进行运动测试，验证了空间曲轴传动结构的可行性。     

新型仿生六足机器人运动控制技术的研究与探索

在仿生学研究的基础上,采用模块化分散递阶控制技术构建了仿生六足机器人控制系统,从结构系统分析、控制系统设计、运动特性分析、运动流程控制等各环节加以研究和探索,并通过M atlab进行了轨迹跟踪仿真试验。仿真结果表明机器人具有较好的运动特性和良好的抗干扰能力,从而为仿生六足机器人运动功能的进一步完善奠定了基础。     

基于3-UPU六足步行机器人的步态规划

提出一种基于非对称3-UPU并联机构的新型六足步行机器人,其具有承载能力大、通过能力强、控制容易等优势。首先,对六足步行机器人进行结构设计,然后,综合考虑机器人的稳定性和腿部干涉两种情况,设计了最大横向移动步幅。还对六足步行机器人进行了步态规划,包括机器人两组腿的占空系数、运动次序、运动步幅、运动轨迹及各分支等效杆长随机器人的移动的变化。     

基于GPS的足轮组合式野外探测机器人设计

针对野外复杂环境,结合腿足式行走和轮式行走机器人的优点,设计了一套足轮组合式探测机器人的控制系统,实现了腿足模式和轮式模式的切换。通过分析"六足纲"昆虫各腿的协调关系,提出了六足机器人的三角步态行走法,并在此基础上对足轮组合运动模式进行了分析,建立了足轮组合式机器人的运动模型和控制理论。设计的机器人能够完成实时环境视频采集,在四轮模式下的前进、后退、左转、右转,六足模式下的前进、后退、左横行、右横行、左转、右转,以及机器人的跟踪定位等功能。     

Air torque position damper hysteresis

The purpose of this paper is to determine the effect of the air torque position (ATP) damper hysteresis on the accuracy of air velocity measurements and the adequacy of the ATP damper mathematical model tested in the present study. A total of three dampers with non-cascading blades were examined: a damper with a single flat blade, a damper with two opposed flat blades, and a damper with two flat blades - one of which is a measuring blade and the other is fixed in the horizontal direction. Furthermore, a total of two damper installation locations in a duct system were examined as well: at the duct exit with a straight duct section preceding the damper and within the duct itself with straight duct sections both preceding and following the damper. The ATP damper hysteresis was found to exert a significant effect on the accuracy of air velocity measurements and the adequacy of the ATP damper mathematical model tested if the ATP damper is more open, i.e. with lower blade angles of attack. Moreover, the ATP damper installed at the duct exit was found to be more susceptible to hysteresis effects than the damper located within the duct.     

Dual-colour microscopy of single fluorophores bound to myosin interacting with fluorescently labelled actin using anti-Stokes fluorescence

We have refined prismless total internal reflection fluorescence microscopy with extremely low background to visualize single fluorophores attached to protein molecules interacting with a filamentous biopolymer labelled with different colour fluorophores. By using Stokes and anti-Stokes fluorescence, two different colour fluorescences from two different colour fluorophores excited with a single wavelength laser can be observed simultaneously. This microscopy was applied to visualize motor proteins, actin and myosin molecules. Single myosin molecules labelled with a tetramethylrhodamine-5-iodoacetamide interacting with a BODIPY FL-labelled actin filament, a filamentous polymer of actin molecules, were observed clearly and simultaneously in aqueous solution. Individual hydrolysis reactions of Cy3-labelled ATP by single myosin molecules and sliding of a BODIPY FL-labelled actin filament along the myosin molecules could also be observed simultaneously. Thus, this technique is useful for observing single molecular processes of proteins interacting with a biological macromolecule such as an actin filament and a DNA.     

涉及空腔制造的最小长度尺寸限制的清晰结构拓扑优化设计

针对以结构柔顺度最小为目标函数,涉及空腔制造的最小长度尺寸限制的结构拓扑优化设计问题,提出了一种新的拓扑优化求解方法。首先,为了消除现有的结构实体相及空洞相的相同的光滑Heaviside映射导致的强烈对立矛盾,引入光滑Heaviside映射和修改的光滑Heaviside映射分别进行实体相及空洞相的设计变量过滤;而后,构建了合理和协同的涉及实体相和空洞相的几何最小长度尺寸限制的结构拓扑优化模型;利用MMA算法,形成了一种新的涉及实体相和空洞相的几何最小长度尺寸限制的结构拓扑优化算法。给出的算例结果表明,与现有方法比,该方法可解决结构实体相和空洞相的几何最小长度尺寸控制问题。且所提方法可获得清晰0/1分布的优化结构拓扑。     

Ni基变形高温合金小孔攻丝扭矩的试验研究

采用修正齿丝锥和标准丝锥对Ni基变形高温合金GH4 1 6 9难加工材料进行了小孔螺纹攻丝对比试验。试验结果表明 ,与标准丝锥相比 ,采用修正齿丝锥可显著减小攻丝扭矩 ,且切削锥角较大的修正齿丝锥加工效果较好     

Multiple-mode structural vibration control using negative capacitive shunt damping

This paper deals with a novel shunt circuit, which is capable of suppressing multimode vibration amplitudes by using a pair of piezoceramic patches. In order to describe the characteristic behaviors of a piezoelectric damper connected with a series and a parallel resistor-negative capacitor branch circuit, the stiffness ratio and loss factor with respect to the non-dimensional frequency are considered. The mechanism of the shunt damper is also described by considering a shunt voltage constrained by shunt impedance. To obtain a guideline model of the piezo/beam system with a negative capacitive shunting, the governing equations of motion are derived through the Hamilton’ s principle and a piezo sensor equation as well as a shunt-damping matrix is developed. The theoretical analysis shows that the piezo/beam system combined with a series and a parallel resistor-negative capacitor branch circuit developed in this study can significantly reduce the multiple-mode vibration amplitudes over the whole structural frequency range.     

Experimental Study of Four-Point Contact Ball Bearing with Deformable Rings

When a ball bearing is designed with thin rings or is mounted in a flexible housing, the assumption of rigid rings is not true anymore. In this article, an experimental study is presented and a comparison with a numerical model is performed. The numerical approach is based on the coupling between a semi-analytical code and a finite element (FE) model that computes the deformation of the rings and housings. The numerical model accounts for ring ovalization, raceway opening, change of conformity, and structural displacements of the whole assembly. The experimental setup allows investigation of the load–displacement behavior of a four-point contact ball bearing submitted to a static thrust loading. Displacements are measured by an optical method (stereo-correlation) that enables comparison of the surface deformation of the two tested bearings and computation of the rigid-body displacement of the inner ring with respect to the outer ring. A comparison between experimental results, numerical results, with and without consideration of ring and housing stiffness, is presented. The numerical results show the importance of the housing stiffness in the modeling, even with standard ball bearings with relatively large and thick rings. Good agreement between measured quantities and numerical results was found. This permits the prediction of the real nonlinear bearing stiffness (load–displacement curve) with a reasonable margin of error.     

Plaster casting process for prototyping of die casting based on rapid tooling

Rapid prototyping (RP) combined with a gravity casting process can provide a suitable substitute with steel tool die casting for prototyping metal casting. Due to differences between die casting and gravity casting, there are several drawbacks in RP simulated die casting. This paper is concerned with the development of a new plaster die casting process that combines pressurization and vibration for prototyping of die castings, and with a plaster die casting machine that has a structure similar to that of a die casting machine. The machine utilizes an oil cylinder for pressurization and a magnetic actuator for vibration. A rapid prototyped pattern is made by the laminated object manufacturing (LOM) process to prepare a plaster mold. In the process, a plunger in the developed machine simultaneously pressurizes and vibrates the molten metal to fill the plaster mold completely and to facilitate the creation of nuclei in the molten metal, respectively. The developed machine has produced a prototype of an end clutch cover with remarkable improvement in mechanical properties.     

超声珩齿的变幅杆设计与有限元分析

推导了不同形状函数变幅杆的四端网络表达式,完成了超声珩齿振动系统的结构设计.利用ANSYS软件进行了动力学分析,验证了设计的变幅杆可满足系统谐振的要求.中空变幅杆可有效地提高变幅杆的放大比,为大孔径齿轮的高效珩齿的变幅杆设计提供了一种新方法.     

Simulation of the Effects of a Plunge Ground Rod on Hydraulic Rod Seal Behavior

A numerical analysis of a reciprocating hydraulic rod seal with a plunge ground rod has been performed. It consists of coupled fluid mechanics, contact mechanics, and deformation analyses. The fluid mechanics analysis consists of a finite volume solution of the Reynolds equation. The deformation is computed with a finite element analysis. The contact of the seal asperities with the rod utilizes the Greenwood-Williamson model and the rod surface geometry is treated deterministically. The fluid transport, friction force, contact pressure distribution, and fluid pressure distribution in the sealing zone have been computed for a polyurethane U-cup seal and for a step seal with a polytetrafluoroethylene (PTFE) sealing element and a nitrile energizer. These have been compared with the results for a smooth rod.     

Direct observation of asperity deformation of specimens with random rough surfaces in upsetting and indentation processes

The trapping behavior of liquid lubricant and contact behavior of asperities at the workpiece-tool interface during upsetting and indentation are observed directly using a compression subpress which consists of a transparent die made of sapphire, a microscope with a CCD camera and a video system. The experiments are carried out without lubricant and with lubricant. Specimens used are commercially pure A1100 aluminum with a random rough surface. From these observations, the change in the fraction of real contact area is measured by an image processor. The real contact area ratios in upsetting experiments without lubricant are in good agreement with numerical ones obtained by Wanheim and Bay and Makinouchi et al. The real contact area ratios in indentation experiments without lubricant increase linearly with increasing normal stress up to 350 MPa. The real contact area ratios after upsetting and indentation experiments with lubricant reached a limiting value of about 60%.