体内微型诊疗装置磁定位简化模型的实验研究

无创定位技术是MEMS器械用于人体内诊疗过程的重要研究环节之一。这里在分析永磁体空间磁场分布规律的基础上,讨论了体内微型诊疗装置的磁定位技术;同时,通过实验研究和曲线拟和,对磁定位模型进行了简化,使磁定位的计算更快,检测传感器的放置更简单。实验结果表明,在一定误差范围内,该简化模型可以用于体内微型诊疗装置无创实时定位。     

Frequency characteristics of non-contact ultrasonic motor with motion error correction

The purpose of this research is to achieve real time motion error correction of the rotor in a non-contact ultrasonic motor (non-contact USM). The rotor is installed in a cylindrical stator with a small gap and designed so that it has a resonant frequency of 22.2 kHz, the 8th flexural mode of vibration. The multi-layered piezoelectric actuators excite the flexural wave traveling in the circumference direction. The ultrasonic vibration produces a sound field that levitates the rotor, and the traveling wave induces a near-boundary streaming to rotate the rotor by viscous force. In this paper, we describe an experimental test of the performance of a non-contact USM. When the flexural vibration amplitude was 0.3 μm, the rotational speed was 4 rpm. The rotational speed and starting torque was proportional to the vibration amplitude. The starting performance to attain rotational speed had a time constant of 2 s for several different amplitudes hence the rotational torque is independent of the rotational speed and the resistance force on the rotor is governed by viscosity. In addition, the non-contact USM has the capability of contact-free micro positioning of the rotor by controlling the deformation of the piezoelectric actuators. The PI controller was constructed to correct the detected motion error of the rotor in the radial direction. As a consequence, a motion error of 0.8 μm for one rotor revolution was reduced to 0.1 μm.     

微细电火花加工中电极材料的蚀除机理研究

在微细电火花加工过程中 ,由于放电时间极短 ,使得其阴阳两极的电极材料蚀除过程产生较大的差异。本文应用传热学和电场的基本理论 ,分别对微细电火花加工阴阳两极的材料蚀除机理进行了理论研究 ,得出了在窄脉宽微细电火花加工中 ,尽量缩短脉宽可提高阳极材料的去除效率 ,同时又不会明显增加阴极材料损耗的结论。为微细电火花加工脉冲电源设计及加工工艺的改进提供了理论依据     

镀液温度的自动测控

介绍一种应用微机技术,通过过零调功方式进行温度调节的镀液温度自动测控方法,对其实现电路进行了分析。     

A study on critical depth of cuts in micro grooving

Ultra precision diamond cutting is a very efficient manufacturing method for optical parts such as HOE, Fresnel lenses, diffraction lenses, and others. During micro cutting, the rake angle is likely to become negative because the tool edge radius is considerably large compared to the sub-micrometer-order depth of cut. Depending on the ratio of the tool edge radius to the depth of cut, different micro-cutting mechanism modes appear. Therefore, the tool edge sharpness is the most important factor which affects the qualities of machined parts. That is why diamond, especially monocrystal diamond which has the sharpest edge among all other materials, is widely used in micro-cutting. The majar issue is regarding the minimum (critical) depth of cut needed to obtain continuous chips during the cutting process. In this paper, the micro machinability near the critical depth of cut is investigated in micro grooving with a diamond tool. The experimental results show the characteristics of micro-cutting in terms of cutting force ratio (Fx/Fy), chip shape, surface roughness, and surface hardening near the critical depth of cut.     

Possibility of surface force effect in slider air bearings of 100 Gbit/in hard disks

The recording density has been increasing in a high rate of 60% per year in the last 10 years. In the next several years it is expected that the recording density will be 100 Gbit/in² and then 1000 Gbit/in². It is said that a spacing of about 5 nm will be necessary for 100 Gbit/in². For two solid surfaces with such a small spacing, it is expected reasonably that the surface force will come into action. In this paper, numerical analysis was conducted to explore the possibility of the surface force for the slider air bearing working with respect to the glide avalanche. The numerical results show that surface force reduces the stiffness of the slider air bearing and the load carrying capacity as well. It is worth noting that, although the decrease in the load carrying capacity may not be significant, the reduction in the stiffness may be critical for many cases. The reduction in the stiffness of slider air bearings due to the surface force may be one of the most important mechanisms of the glide avalanche. The predicted take-off height to overcome the surface force is about several nano-meters. Increasing the pitch angle tends to decreases the take-off height. A lubricant film of about 1 nm will reduce the risk of the glide avalanche in some extent, but increasing the film thickness has little effect.     

栅结构微机械陀螺运动特性的研究

对一种新型微机振动陀螺原型的运动特性进行了理论分析。采用差分电容信号调制解调方法测量了微机械陀螺驱动和检测模态的幅频特性。理论计算和实验结果表明,在大气状态下,该微机械陀螺驱动模态和检测模态的品质因子具有相近数值,在100左右。测量了驱动模态民激励驱动下,微机械陀螺检测模态的幅频特性,实验结果表明,在无角速度输入的情况下,微机械陀螺在驱动模态和检测模态的谐振模态的谐振频率处发生谐振。     

用于微量化学分析芯片的微型无阀泵流动特性分析与测试

从理论计算、流场仿真和试验三方面研究了用于微流控化学分析芯片的微型无阀泵流动特性 ,初步建立了微型无阀泵流道结构的数学模型 ,重点讨论了结构参数的选取原则及相应的流动阻尼系数的计算方法 ,采用 Matlab针对该数学模型进行了数值计算 ,并进行了 CFD仿真对计算结果进行对比及修正 ,最后通过试验验证了数值计算与仿真的可靠性 ,为微型无阀泵参数化设计及优化提供了理论依据及经验曲线。     

Micro electro discharge machine with an inchworm type of micro feed mechanism

A micro electro discharge machine with an inchworm type of micro feed mechanism has been developed. The prototype of micro electro discharge machine is comprised of a wire electro discharge grinding unit, a rotating unit of electrode, RC circuitry for micro electro discharge generation and a subsystem detecting and controlling machining process, in addition to the inchworm mechanism. In the design of the inchworm mechanism, a novel clamp mechanism with force magnifying structure is devised to increase its thrust capability and a pair of guide sleeves together with the clamps are used to decrease yawing error. The inchworm mechanism prototype has 60 mm stroke only limited by the length of the shaft, less than 2 μm yawing error and reaches to 30N output thrust force. The machining experiments carried out on the micro EDM prototype are also described. The techniques to machine micro electrode, micro holes with high aspect ratio, micro structures on stainless steel and silicon materials are discussed. Micro electrode diameter as small as 25 μm and micro holes with minimum size of less than 50 μm are obtained. And the maximum aspect ratios of micro electrodes and micro holes exceed 20 and 10 respectively.     

The structural origin of the complex rheology in thin dodecane films: Three routes to low friction

The effective viscosity of confined lubricant films less than 6–7 molecular layers is usually enhanced by many orders of magnitude. For dodecane the high friction film has a strong in-plane order with “mosaic-like” structures that extend across the film and effectively form “crystalline bridges” [Jabbarzadeh A, Harrowell P, Tanner RI. Crystal bridge formation marks the transition to rigidity in a thin lubrication film. Phys Rev Lett 2006; 96: 206102-1/4] resulting in high friction. Using molecular dynamics simulations, we have identified three routes to lower the friction. We show that the structure of confined films and their response to shearing are affected by atomic in-plane order and smoothness of the confining surfaces, the relative orientation of two crystalline surfaces and the direction of shear. We show a small increase in surface roughness in going from crystalline to amorphous surfaces can lead to a much lower friction. We demonstrate that misaligning (twisting) one surface with respect to the other by 45° results in a much lower effective viscosity. Application of shear for extended times induces alignment of lubricant molecules into a nematic-like order with ultra-low effective viscosity. The magnitude of reduction in the friction and the physical process through which it happens varies for each of these three routes. Depending on the method used, destruction of crystalline bridges, multilayer or fault plane slip provides a route for dramatic reduction in friction.