基于牛顿迭代法的显微视觉控制方法研究

在建立显微立体视觉模型的基础上,提出一种仿牛顿迭代法的视觉控制方法,通过遮代逼近的方法控制机械手运动到指定住置,同时还对迭代逼近的收敛条件及近似线性显微视觉系统的迭代误差上限进行分析推导.实验证明,本方法避免了系统的精确标定和高频率采样,具有精确度高、收敛速度快、鲁棒性好等特点,平均迭代3.5次就可以以一个像素的精度逼近目标位置.     

具有力感知功能的四臂式MEMS微夹持器研制

为了解决夹持器小型集成化、夹持力可控的问题，本文采用体硅加工技术成功的研制了一种基于单晶硅的、具有微力检测功能的新型四臂式MEMS微夹持器。以压阻检测技术为基础，利用MEMS侧面压阻刻蚀工艺将力传感器集成在微夹持器的夹持臂末端，实现夹持力的微力检测。采用有限元软件对微夹持器机构和传感器弹性体进行分析。S型柔性梁结构的设计将梳齿驱动的直线运动转化为夹持臂末段的转动，结合四臂式的末段结构，有效的扩展了夹持器的夹持范围。利用硅玻璃键合技术实现夹持臂的电隔离，通过施加80V电压，夹持臂的单臂运动范围为25靘，夹持器的夹持范围30-130靘。实验标定出传感器的最大量程在1mN以上，分辨率为3霳，可以实现夹持力的有效反馈。     

复合式MEMS微夹持器的研制

为实现对亚毫米微小构件稳定夹取及可靠释放等操作,研制了一种复合式微夹持器.采用有限元软件分析了微夹持器的机构及动力特性.应用MEMS体硅工艺将静电梳齿驱动与气动吸放集成构成复合式驱动,气动吸放的引入改善了微夹持器的操作性能,S形柔性梁结构的设计将梳齿驱动的直线运动转化成末端夹爪的转动实现了夹持操作.两种不同尺寸的微夹持器,有效扩展了微夹持器的夹持范围.根据微夹持器的操作控制需求,设计了微夹持器静电驱动控制系统以及气压控制系统.在80 V的驱动电压下,微夹持器末端夹爪位移可达25 μm.针对100～200 μm的小球进行了微操作实验,实验结果表明,静电梳齿驱动结合真空吸附能够使夹取操作更加稳定,基于闭环控制的气路正压力能有效克服小球与夹爪之间的粘附力,实现可靠的释放操作.微夹持器基本满足100～200 μm微小构件的操作需求.     

用于功能热流体的相变材料微胶囊力学性能研究进展

相变材料微胶囊悬浮液用作传热流体时, 具有传热温差小、载热密度高、储放热时间短等突出优点, 但在研究和应用实践中常发现微胶囊经若干次泵送循环后严重变形、塌陷甚至破损, 引起相变物质泄漏、聚结、黏壁、堵塞管路等后果, 使体系性能显著恶化。为使这种悬浮液性能更稳定、循环寿命更长, 本文综述了从微胶囊自身力学性能和循环流动稳定性两方面开展的实验和理论研究工作进展, 认为微胶囊自身力学性能是影响其循环稳定性的内因, 泵送作用是导致微胶囊破裂的主要外因。总结了两方面研究存在的问题, 指出相关研究应朝规范测试表征方法、拓展研究客体范围、充分利用数值模拟技术等方向发展, 使该领域的研究更加深入。     

光镊中轴向光阱力的研究

基于几何光学原理,对微粒直径远大于激光波长的米氏球状微粒所受的轴向力进行了计算,根据计算结果讨论了轴向力与激光光束波长、束腰半径、光束功率、微粒半径、折射率等参数的关系.     

Micromanipulation of chloroplasts using optical tweezers

This paper describes experiments using optical tweezers to probe chloroplast arrangement, shape and consistency in cells of living leaf tissue and in suspension. Dual optical tweezers provided two-point contact on a single chloroplast or two-point contact on two adhered chloroplasts for manipulation in suspension. Alternatively, a microstirrer consisting of a birefringent particle trapped in an elliptically polarized laser trap was used to induce motion and tumbling of a selected chloroplast suspended in a solution. We demonstrate that displacement of chloroplasts inside the cell is extremely difficult, presumably due to chloroplast adhesion to the cytoskeleton and connections between organelles.  The study also confirms that the chloroplasts are very thin and extremely cup-shaped with a concave inner surface and a convex outer surface.     

Application of mass micromanipulations to submillimeter-scale particles in multiple containers on a laterally oscillated stage

The present study proposes a simple mass-micromanipulation method for tiny particles by expanding our previous finding that submillimeter-scale particles scattered at the bottom of a water-filled rectangular container align at specific positions when the particles are subject to standing waves induced by lateral oscillations of the container at specific frequencies. First, this unique phenomenon (termed as the particle alignment phenomenon in the present study) was examined, focusing on the distance from the bottom of the container, oscillation amplitude, and liquid height in order to further reveal the underlying mechanism. The main findings obtained through several simulations and experiments were that the modulation of oscillation amplitude affected the behavior of particles at the bottom of the container related to the alignment precision and that the proper control of liquid height allowed the production of different particle alignment phenomena even if the same lateral oscillation was applied to the container. Additionally, using these new findings, we succeeded in forming different numbers of particle lines in multiple containers, which were set at different liquid heights, placed on an oscillation stage. Based on the results, this paper discusses possible mass micromanipulations using the particle alignment phenomenon.     

Design,modeling, and control of a monolithic compliant x-y-θ microstage using a double-rocker mechanism

This paper reports the design, modeling, and control of a novel three-degrees-of-freedom piezoelectric compliant microstage by introducing a new double-rocker mechanism. The double-rocker mechanism combines a first (leverage) amplifier and a second (rocker) amplifier for double-stage displacement amplification and parasitic motion reduction. An analytical model is established to calculate the deformation behavior of the microstage, and the model is verified using finite-element analysis (FEA). An improved Prandtl-Ishlinskii (PI) model is proposed to describe piezoelectric hysteresis characteristics by optimizing the threshold selection. Then, a composite control strategy is designed to achieve precision trajectory control. The control strategy consists of a hysteresis-based feedforward controller and a proportional-integral feedback controller. A prototype of the microstage is manufactured, and an experimental system is established. Several open-loop and closed-loop experiments are conducted, and the experimental results validate the effectiveness of the proposed microstage and the designed control strategy.     

Correlation analysis of couple optical paths for microstereovision with stereo light microscope

A micro stereovision system with a stereo light microscope (SLM) has been applied in micromanipulation systems. There is a coupling connection between two optical paths of a stereo light microscope. The coupling intension corresponds with two factors: the structure of an SLM and the position of an object point in the view of an SLM. In this paper, a correlation function is proposed to describe the coupling intension between the couple optical paths of an SLM. The quantified results are applied to the error analysis of the imaging model. Experiments show that the correlation of the optical paths of a common main objective of stereo light microscope (CMO-SLM) is little more than that of a G-SLM, and the error must be considered when a pinhole imaging model is used to analyze its correlation. __________ Translated from Journal of Beijing University of Technology, 2006, 32(8): 724–729 [译自: 北京工业大学学报]