新型六自由度服务机器人的结构设计与运动学分析

设计了一种新型六自由度服务机器人机械臂,此机械臂采用部分解耦的结构,能在不明显增加体积的情况下,带来逆运动学求解快速的优点。采用D-H(Denabit-Hartenberg)法建模,获得机械臂正运动学模型,进行正运动学求解,并针对其结构特点,提出一种新的几何法来求解逆运动学问题。通过空间几何关系转换,得到逆解解析表达式和末端位置,该末端位置与正解的末端位置表达式完全相同,印证了几何方法理论上的正确性。经过数值计算验证了正运动学模型和逆解的正确性,为机器人接下来的路径规划和运动控制提供了理论基础。     

一种冗余自由度机械臂逆运动学解析算法

针对7自由度机械臂逆运动学求解问题,在考虑了空间构型的复杂性和冗余自由度机械臂自运动流形的基础上,提出了一种逆运动学的位置解析算法,即参照"自由度模块化"的概念,进而将仿人机械臂的7自由度划分为两个4自由度的模块化单元。通过控制自由度模块化单元,将复杂的空间构型转化为平面构型,减少了计算的复杂性;同时基于"锚点"和"虚拟连杆"的概念,实现冗余自由度机械臂的位姿参数化,从而实现了机械臂逆运动学快速求解。     

一种丝驱连续体手术机械臂的设计及其运动学分析

针对现有的连续体机械臂及其运动学模型无法得到运动学解析解的问题,设计了一种具有两个弯曲自由度的丝驱动连续体机械臂原型,并对其正逆运动问题进行了研究。基于分段常曲率假设,结合D-H法建立了连续体机械臂的正运动学模型,推导出了驱动丝长度到机械臂末端位置的映射关系,得到了正运动学解析解;通过提取机械臂骨干曲线,利用几何分析法建立了连续体机械臂逆运动学模型,推导出了机械臂末端位置到驱动丝长度的映射关系,并得到了部分逆运动学解析解;最后,通过实验对所提出运动学模型的有效性进行了验证。研究结果表明:所提出运动学模型的平均位置误差不超过2.56 mm,约占机械臂总长度的2.57%,能够很好地用于连续体机械臂末端位置控制。     

仿人7自由度机械臂位置层面轨迹规划研究

仿人7自由度机械臂作为一种特殊结构的冗余自由度机器人,具有更好的运动学性能.为了简化仿人机械臂轨迹规划的计算量,从仿人机械臂的逆运动算法入手,讨论了位置层面的仿人机械臂逆运动计算方法,并在轨迹规划中采用定时插补和定距插补的方法,通过位置层面逆解中加入机器人运动的速度和加速度等信息,实现了在位置层面上对仿人7自由度机器人关节空间的全方位运动规划.     

位姿水平的冗余自由度机械臂运动学逆解算法

本文通过分析七自由度机械臂构造特点,用曲面几何理论得到肘关节在笛卡尔空间中的点集,参考各关节角运动范围,可以求出冗余自由度机械臂逆运动学的全部构型解,从而可以方便地实现实现机械臂的全局优化。此方法既提高了解的精度,又减少了运算量,同时为速度解的解算提供了便利条件和新的思路。     

一种五自由度机械臂逆运动学求解的几何法

针对五自由度机械臂自由度不足而导致的基于笛卡尔空间轨迹规划产生的目标末端位姿,可能不存在运动学逆解的情况,提出了一种基于自由度约束的末端位姿描述,并根据该位姿描述得出了一种五自由度机械臂逆运动学求解的几何方法。该方法基于机械臂模型的几何特性,通过将轨迹规划和运动学逆解2个阶段进行一定程度的结合,确保了轨迹规划得到的目标末端位姿的运动学逆解的存在性。通过仿真实验分析,证明了该方法的可行性与精确性。     

六自由度机械臂运动学分析与仿真研究

针对六自由度机械手臂的运动学分析问题及其工作可靠性的探究,设计开发了一套基于OpenGL的六自由度机械臂仿真软件.采用D-H参数法构建机械臂模型,对六自由度机械手臂进行了正、逆运动学分析,求解得到机械臂的正逆解.研究设计了机械臂的空间直线和圆弧插补算法,实现了机械臂在三维空间中按照目标轨迹的可靠运动.在VS2017软件...     

基于BP神经网络的冗余机械臂逆运动学分析

常见的七自由度冗余机械臂逆运动学解法较为繁杂,且对不同构型机械臂的逆运动学解法通用性较差。为了找到一种通用的七自由度机械臂逆运动学求解方法,建立了神经网络模型,选择了合适的激励函数、隐藏层神经元数量、神经网络层数和学习速率等模型参数。设计轨迹跟踪实验对神经网络模型进行验证,实验数据证明该方法有效且精度较高,是一种可行的冗余机械臂逆运动学求解方法。     

七自由度机械臂运动学分析

针对神经网络和梯度投影法求解七自由度机械臂逆运动学存在的可靠性差及累积误差等问题,充分考虑机械臂构型特点和自运动特性,提出一种几何法和解析法相结合的冗余机械臂逆运动学新方法并进行仿真验证,通过位置误差和姿态误差来衡量该方法的可行性。实验结果表明:采用该方法对机械臂逆运动学进行求解,机械臂末端位置最大误差不超过0.015mm,平均运行时间为0.455ms,满足实时控制要求,为具有横滚转动副机械臂关节角度求解提供了一种新的思路。     

结合旋量和代数方法的工业机械臂逆运动学解法

针对工业机械臂逆运动学解算的问题,提出一种结合旋量方法和代数方法的逆运动学新解法。通过旋量的方法将工业机械臂整体逆运动学问题进行分解,利用Paden-kahan逆运动学子问题求解。并在该基础上利用工业机械臂的结构特点,利用代数方法进一步简化末端腕部三个关节的问题求解。以安川公司MH6六自由度工业机械人为例,验证算法正确性。实验表明:该方法可以获得正确的八组逆解并在旋量解逆运动学的基础上有效减少了中间计算步骤,降低了时间复杂度和空间复杂度。     

Knockdown of lncRNA XIST prevents the epithelial-mesenchymal transition of TGF-β2-induced human lens epithelial cells via miR-124/Slug axis

Posterior capsular opacification (PCO) is linked to the pathological process of lens epithelial cells, which includes proliferation, migration, and epithelial-mesenchymal transition (EMT). Our goal was to investigate whether long noncoding RNA (lncRNA) XIST contributes to EMT via targeting miR-124/Slug axis in TGF-β2-induced SRA01/04 cells. EMT was induced by stimulating SRA01/04 cells with 10 ng/mL TGF-β2 for 24 h, and PCO microenvironment was simulated. The expressions levels of lncRNA XIST, miR-124, and Slug were measured by real-time polymerase chain reaction (RT-PCR) and western blot. The role and mechanism of lncRNA XIST in promoting EMT of TGF-β2-treated SRA01/04 cells were investigated by using cell transfection, cell counting kit-8 (CCK-8), immunofluorescence staining, transwell assay, wound-healing assay, RT-PCR, western blot and dual-luciferase reporter assay. The expression of Slug and lncRNA XIST was markedly increased, while miR-124 was downregulated in TGF-β2-treated SRA01/04 cells compared with the control group. Knockdown of lncRNA XIST reduced EMT, migration, and cell viability in TGF-β2-induced SRA01/04 cells; moreover, it adversely modulated miR-124 and adjusted the expression of Slug in SRA01/04 cells, while these effects were diminished by co-transfection with AMO-miR-124. Our data demonstrated that lncRNA XIST functioned as a competitive endogenous RNA (ceRNA) of miR-124 to modulate the expression level of Slug, thereby modulating EMT, migration, and cell viability in SRA01/04 cells. In conclusion, lncRNA XIST has a crucial role in promoting TGF-β2-induced EMT via modulating the miR-124/Slug axis in SRA01/04 cells, and it may provide a novel therapeutic option for PCO treatment.     

硅微谐振式加速度计的实现及性能测试

为了提高硅微谐振式加速度计性能,从一种基于DDSOG(Deep Dry Silicon on Glass)工艺的硅微谐振式加速度计样机入手,介绍了加速度计的结构、加工方法和接口电路。该谐振式加速度计结构包括敏感质量块、谐振器和微杠杆3部分,采用差动结构来减小共模误差的影响。接口电路中采用了自动增益控制电路来稳定谐振器的振幅,成功实现了谐振器的闭环自激振荡和频率检测。分析了谐振式加速度计频率输出与加速度输入的关系,测试了硅微谐振式加速度计样机性能,结果为量程±50g,标度因数143 Hz/g,零偏稳定性1.2 mg,零偏重复性0.88 mg,阈值170μg。文章最后提出,DDSOG工艺中采用的玻璃材料和硅材料温度系数不同,影响了加速度计的温度特性,因此需要进步一改进加工工艺。     

小型化硅微谐振式加速度计的实现与性能测试

设计了一款由微机电系统和专用集成电路构成的小型化硅微谐振式加速度计。该加速度计采用80μm厚SOI工艺加工微机电系统(MEMS)结构,采取真空封装技术降低结构噪声。首先,采用振荡信号作为自动增益控制电路中斩波器的控制信号,降低了闪变噪声且不会引入额外的功耗。其次,使用线性区工作的乘法器取代传统的吉尔伯特单元,通过大幅降低系统总体供电电压来降低功耗。最后,采用复位计数器进行频率数字转换,在所关心的带宽内抑制量化噪声。实验显示:该加速度计在达到±30 g线性量程的前提下,实现了2.5μg/√Hz的分辨率和1μg的零偏不稳定度。此外,为了减小电路自身发热引起的温度漂移,该样机的功耗被控制在3.5mW以内,系统集成后的尺寸约为45mm×30mm×20mm。基于所述技术,系统在体积、功耗和性能方面均有较大的提升。     

Quantitative and qualitative methods using fluorescence microscopy for the study of modified low density lipoproteins uptake

Atherosclerosis and heart disease are the main cause of death in United States. The development of atherosclerosis includes lipid deposition and foam cell formation in the artery wall. Scavenger Receptors A‐I and II (SRA‐I/II) have an important role of in foam cell formation and atherogenesis. Most of the SRA‐I/II studies had been performed using Iodine‐125‐radiolabeled modified low‐density lipoprotein. This report attempts to validate the use of fluorescence microscopy techniques as an alternative to obtain qualitative and quantitative information of the uptake of fluorescence‐labeled acetylated low‐density lipoprotein (AcLDL) in adherent CHO cells expressing SRA‐I/II. After verifying the protein expression of SRA‐I and II, uptake was quantified using a Laser Scan Cytometer, and images of cells containing fluorescent AcLDL were obtained. A significant increase in fluorescence was found in the cells transfected with SRA‐I/II vs. those with empty vector. When SRA‐I/II competitive ligands were used, the uptake of AcLDL was significantly decreased. In conclusion, the use of fluorescence microscopy techniques in obtaining qualitative and quantitative information of the uptake of fluorescence‐labeled AcLDL by adherent cells, such as CHO cells, is an alternative to the traditional use of radiolabeled iodine. SCANNING 31: 167–173, 2009. © 2009 Wiley Periodicals, Inc.     

Tribology applications of surface reflectance analyzers: optical characterization of the head disk interface

In this paper, we will discuss Surface Reflectance Analyzers (SRA) and their applications in tribology. We will show how the SRA instrument can be used to locate and quantify tribological parameters, such as carbon wear and lubricant buildup, at the head/disk interface. This damage can be caused by a variety of head/disk interactions. In one case, we will demonstrate the importance of slider crown on tribological performance by quantitatively comparing the damage to the disk surface during continuous start–stop test in the laser texture zone. In another case we will demonstrate the importance of slider air bearing design in ramp load/unload tests by quantitatively comparing the amount of damage near the OD of the disk. Ramp load/unload damage manifests itself in various forms. In addition to local carbon wear and lubricant effects, there is also debris from the ramp wear and occasional “dings”. We will show how the SRA system can be used to distinguish and quantify these various types of damage.     

硅微谐振式加速度计驱动电路参数优化

将遗传算法与低频模型相结合,提出了一种快捷的驱动电路设计方法,用于提高低功耗硅微谐振式加速度计模拟驱动电路的瞬态性能,并缩短设计周期。该方法通过对闭环驱动电路模型进行高低频解耦,提取闭环驱动电路的低频模型;将提取的低频模型与遗传算法相结合,给出完整的优化方法,得到了满足各项实际约束的最优电路参数。针对某型硅微谐振式加速度计,建立了SIMULINK低频仿真模型,根据实际情况制定了约束条件。应用该方法求出了系统启动速度最快的PI控制器的参数,并对其进行了实验验证。起振实验结果表明,采用优化参数可使超调量小于50%,相位误差小于5°,1%调节时间从优化前的0.42 s减少到优化后的0.19 s,实验与仿真误差小于5%。得到的结果证明提出的方法正确有效,具有可实施性。     

Tribology of X-1P vapor lubricated hard disks

The tribological characteristics of vapor lubricated X-1P films on carbon coated disks were investigated as a function of lubricant thicknesses (0.2–2 nm) and compared with traditionally dip-coated X-1P and PFPE films. Glide and flyablity tests were performed and the lubricant redistribution in the ‘wear track’ was investigated using a surface reflectance analyzer (SRA). A critical lubricant thickness was found to exist for X-1P below which lubricant accumulation was observed, while lubricant loss was found to be present if the thickness of the lubricant film was greater than the critical thickness.     

梳齿结构与振动梁复合的硅微谐振式加速度计非线性振动特性

硅微谐振式加速度计的非线性振动可以导致振动幅度噪声耦合到频率输出进而恶化器件的噪声性能,因此有必要对谐振式加速度计的非线性振动特性进行评估及优化,拓展线性振动范围。本文针对所设计的基于梳齿结构与振动梁复合的硅微谐振式加速度计进行了仿真与实验分析。首先对加速度计结构使用COMSOL仿真软件进行了非线性仿真分析,该方法通过在谐振梁的振动方向上施加一个静力,得到力与位移之间的关系,计算出非线性三次项系数k3,eff和线性系数keff的比值约为2.13×10^10 m^-2。然后,对双端固支音叉(DETF)进行扫频测试,得出DETF的非线性振动频响曲线。根据Duffing方程对实验数据进行拟合,得出器件两个DETF的非线性三次项系数k3,eff和线性系数keff的比值分别为2.24×10^10 m^-2和2.19×10^10 m^-2。仿真值与测试值的误差分别为5.2%和2.8%。实验结果与仿真值吻合得较好,印证了仿真方法的有效性和测试数据的可靠性。最后,对所设计的谐振加速度计进行非线性分析,当振幅小于35.4 nm时,DETF工作在线性区,可为后续谐振式加计的控制电路设计提供参考。     

Investigation of disk damage caused during load/unload using a surface reflectance analyzer

Wear of the carbon layer of a magnetic recording disk is investigated during load/unload using a surface reflectance analyzer (SRA). Wear is determined as a function of the number of the load/unload (L/UL) cycles, the vertical head speed, the disk rotational speed, and the air bearing design. Two types of subambient pressure sliders are used in the experiments, the difference between the two designs being related to the size and position of the subambient pressure region. The load/unload behavior of the two slider types is determined numerically using a finite element air bearing simulator.     

The Effect of Slider Texture on the Tribology of Near Contact Recording Sliders

Island-type texture was fabricated on two types of pico-sliders using plasma etching and ion beam etching. Laser–Doppler interferometry was used to investigate the vibrations of textured and untextured pico-sliders in near-contact situations. Lubricant depletion on the disk surface was investigated in the slider wear tracks using scanning ellipsometry (Surface Reflectance Analyzer (SRA)). The results show that slider in-plane and out-of-plane vibrations were reduced as a consequence of the texture on the slider surface. In addition, lubricant depletion on the disk surface was found to be less severe for textured sliders than for untextured sliders at flying heights below 10 nm.