Analytical approach and numerical /spl alpha/-lines method for pull-in hyper-surface extraction of electrostatic actuators with multiple uncoupled voltage sources

This work presents a systematic analysis of electrostatic actuators driven by multiple uncoupled voltage sources. The use of multiple uncoupled voltage sources has the potential of enriching the electromechanical response of electrostatically actuated deformable elements. This in turn may enable novel MEMS devices with improved and even new capabilities. It is therefore important to develop methods for analyzing this class of actuators. Pull-in is an inherent instability phenomenon that emanates from the nonlinear nature of the electromechanical coupling in electrostatic actuators. The character of pull-in in actuators with multiple uncoupled voltage sources is studied, and new insights regarding pull-in are presented. An analytical method for extracting the pull-in hyper-surface by directly solving the voltage-free K-N pull-in equations derived here, is proposed. Solving simple but interesting example problems illustrate these new insights. In addition, a novel /spl alpha/-lines numerical method for extracting the pull-in hyper-surface of general electrostatic actuators is presented and illustrated. This /spl alpha/-lines method is motivated by new features of pull-in, that are exhibited only in electrostatic actuators with multiple uncoupled voltage sources. This numerical method permits the analysis of electrostatic actuators that could not have been analyzed by using current methods.     

Simultaneous On-Chip Sensing and Actuation Using the Thermomechanical In-Plane Microactuator

Many applications in microelectromechanical systems require physical actuation for implementation or operation. On-chip sensors would allow control of these actuators. This paper presents experimental evidence showing that a certain class of thermal actuators can be used simultaneously as an actuator and a sensor to control the actuator's force or displacement output. By measuring the current and voltage supplied to the actuator, a one-to-one correspondence is found between a given voltage and current and a measured displacement or force. This integrated sensor/actuator combination will lead to efficient on-chip control of motion for applications including microsurgery, biological cell handling, and optic positioning.     

Microsized Piston-Cylinder Pneumatic and Hydraulic Actuators Fabricated by Lithography

Future microrobotic applications require actuators that can generate a high actuation force in a limited volume. Up to now, little research has been performed on the development of pneumatic or hydraulic microactuators, although they offer great prospects in achieving high force densities. In addition, large actuation strokes and high actuation speeds can be achieved by these actuators. This paper describes a fabrication process for piston-cylinder pneumatic and hydraulic actuators based on etching techniques, UV-definable polymers, and low-temperature bonding. Prototype actuators with a piston area of 0.15 mm² have been fabricated in order to validate the production process. These actuators achieve actuation forces of more than 0.1 N and strokes of 750 mum using pressurized air or water as driving fluid.     

Graphical determination of heat tolerance limits

This paper describes a simple graphical method for determination of heat tolerance limits (HTL) for any situation in which air movement, metabolic heat production and clothing insulation are specified. HTL are presented as a function of operative temperature (abscissa) and water vapour pressure (ordinate). Comparison of results obtained graphically by this method with experimentally determined limits found in the literature shows good agreement.     

Extending the travel range of analog-tuned electrostatic actuators

The pull-in instability limits the travel distance of elastically suspended parallel-plate electrostatic microactuators to about 1/3 of the undeflected gap distance. In this paper, we examine the “leveraged bending” and “strain-stiffening” methods for extending the travel range of electrostatic actuators. The leveraged bending effect can be used to achieve full gap travel at the cost of increased actuation voltage. The strain-stiffening effect can be used to minimize actuation voltage for a given travel range. An analytical approximation shows that the strain-stiffening effect can be used to achieve a stable travel distance up to about 3/5 of the gap. A tunable reflective diffraction grating known as the polychromator has been designed using these actuation techniques, and selected designs have been fabricated and tested for actuation behavior. Gratings with 1024 flat, closely packed grating-element actuators have been fabricated with over 1-cm-long mirrors, achieving stable vertical travel distances of more than 1.75 μm out of a 2-μm gap     

Lateral MEMS microcontact considerations

A lateral switching relay structure has been developed which provides a double gold contact with as low as 70-mΩ measured contact resistance, 0.45-A current-carrying ability at MEMS compatible force levels, TTL compatible actuation, and air gap isolation when open. The die area used for the relay mechanism itself (distinct from the actuation) is approximately 75 μm by 100 μm and was designed to allow fabrication of the relays in the MCNC MUMP's dual polysilicon foundry process with no assembly. Design analysis shows that substantial characterization is needed to design optimal microrelays. Temperature softening and failure modes have been characterized by current voltage techniques. Polysilicon vernier structures were used to develop force/current/conductance curves. Relays using thermal actuators have been built     

Development of a transformable wheel actuated by soft pneumatic actuators

Small mobile robots with transformable wheels have recently emerged thanks to their increased mobility and maneuverability. When a high payload is applied to these robots, however, wheel transformation becomes difficult because they must directly overcome the payload’s weight. In this paper, we propose a wheel that can be transformed from its starting circular shape (radius, 56 mm) to a wheel with three legs (radius, 99 mm) under a high payload with low operating force. The key design principle of this wheel is to kinematically decoupled legs and passive locking. Its legs are kinematically decoupled but operated by a single air pump using a pneumatic channel connected to soft pneumatic actuators installed at each leg. Application of pressure causes the legs to behave like a coupled system through the pneumatic channel. With pressurization, the two legs that are not in contact with the ground easily emerge from body, and the leg in contact with the ground emerges once the wheel rotates. Once emerged, each leg is supported by a rigid pawl instead of by the soft pneumatic actuators. This setup enables the legs to be transformed independently with low air pressure, even under high payloads. It reduces system weight and the energy required to maintain the transformed shape. This legged wheel can overcome obstacles up to 2.9 times the radius of the wheel in its circular form, and wheel transformation can be accomplished with 85 kPa air pressure for payloads up to 1115 g.     

Effect of plasma chemistry on the simulation of helium atmospheric-pressure plasmas

The effect on the selection of different plasma chemistries for simulating a typical dielectric barrier discharge (DBD) driven by quasi-pulsed power source (20 kHz) is investigated. The numerical simulation was performed by using the one-dimensional self-consistent fluid modeling solver. Our simulation result indicates that the computed temporal current density can be significantly improved by using a complex version of plasma chemistry module rather than the simple one and demonstrates an excellent agreement with the experimental data. The result suggests the metastable, excited and ionic helium related reaction channels, which are important in simulating a DBD, should be taken into account. Furthermore, it also reveals that the power absorption of ions is considerably higher than that of the electron.     

Control of Shape Memory Alloy Actuators with a Neuro-fuzzy Feedforward Model Element

This paper describes development of a motion controller for Shape Memory Alloy (SMA) actuators using a dynamic model generated by a neuro-fuzzy inference system. Using SMA actuators, it would be possible to design miniature mechanisms for a variety of applications including miniature robots for micro manufacturing. Today SMA is used for valves, latches, and locks, which are automatically activated by heat. However it has not been used as a motion control device due to difficulty in the treatment of its highly nonlinear strain-stress hysteresis characteristic. In this paper, a dynamic model of a SMA actuator is developed using ANFIS, a neuro-fuzzy inference system provided in MATLAB environment. Using neuro-fuzzy logic, the system identification of the dynamic system is performed by observing the change of state variables (displacement and velocity) responding to a known input (input voltage to the current amplifier for the SMA actuator). Then, using the dynamic model, the estimated input voltage required to follow a desired trajectory is calculated in an open-loop manner. The actual input voltage supplied to the current amplifier is the sum of this open-loop input voltage and an input voltage calculated from an ordinary PD control scheme. This neuro-fuzzy logic-based control scheme is a very generalized scheme that can be used for a variety of SMA actuators. Experimental results are provided to demonstrate the potential for this type of controller to control the motion of the SMA actuator.     

具有手指外展辅助功能的康复机器人系统

手指外展是改善脑卒中患者手部功能最重要的运动之一,目前国内外柔性手部康复机器人的研究主要聚焦在手指的屈伸上,忽略了手指完全外展的重要性。为实现更好的康复效果,研制了一款具有手指外展辅助功能的康复机器人系统。基于热塑性聚氨酯(TPU)薄膜涂层织物设计了一种新型外展驱动器。推导出外展驱动器一般力学方程,以表征其输出力矩与几何参数和内部气压的函数关系。性能分析结果表明,该驱动器可以在较低的气压下提供足够的外展力,具有辅助手指外展的可行性。招募了10名健康受试者进行日常生活活动(ADL)实验,在肌电信号监测下,验证了外展驱动器的辅助作用。此外,提出的康复系统将手部康复机器人与多功能被动训练模式相结合,通过配套软件,为脑卒中患者提供了更高效的康复训练。     

振荡冲击电压下SF6气体中绝缘子气隙局部放电特性研究

随着GIS设备现场冲击耐压试验的推广实施,冲击电压下的局部放电检测被作为一种新方法,应用于GIS的现场绝缘诊断。冲击电压能够有效限制电晕稳定性作用,相比交流低频电压对局部极不均匀场类缺陷的发现能力更强,因此该方法将具有较好的应用前景。本文建立了冲击电压下的局部放电宽频带电脉冲检测系统,采用标准振荡雷电冲击(OLI)和标准振荡操作冲击(OSL)作为激励源,对绝缘子气隙缺陷在SF₆气体中的局部放电特性及影响因素进行了研究,并在此基础上针对预置人工绝缘气隙缺陷的实际GIS试品进行了模拟试验。研究表明：在振荡冲击下,气隙局部放电脉冲主要包括首次放电、后继放电及反向放电三种放电形式,其中首次放电对其他几种放电形式具有决定作用。且气压、背景场强及气隙尺寸比等对绝缘子气隙局部放电行为具有明显影响。GIS的模拟局部放电检测表明,两种振荡冲击电压(OLI和OSI)均能够有效检测GIS内部的气隙类缺陷。     

Flow control valve for pneumatic actuators using particle excitation by PZT vibrator

This paper reports a new flow control valve for pneumatic actuators that has a lightweight and simple structure and uses particle excitation by PZT vibrator. The flow control valve in this report consists of an orifice plate which has plural orifices, PZT vibrator which is adhered on the orifice plate and iron particles. The valve is normally closed, because air flow carries the particles on to the orifice and particles seal the air flow. Because the orifice plate excitation by the PZT vibrator works to make the particles away from the orifice plate, the air flows through the orifices. It is driven at resonance mode and can be used as a variable speed controller for pneumatic actuators. The new flow control valve avoids the stopping shock of pneumatic actuators at the stroke ends while retaining the advantages of pneumatic actuators.     

Fabrication of microcoils with narrow and high aspect ratio coil lines

Recently, there has been a growing requirement to reduce their size of actuators. However, the miniaturization of actuators has made little progress since this requires micro-fabrication, processing, and other new techniques that are not compatible with traditional machining technologies. We have forcused on the fabrication of electromagnetic type microactuators that could be driven at low voltage and with high efficiency but it is well known that existing technologies for miniaturization of these devices are unsuitable because the allowable current path would be too small in microscopic applications. Therefore, we have proposed the development of a spiral microcoil with narrow width and high aspect ratio lines that can be fabricated using X-ray lithography and metallization techniques. We have fabricated spiral structures consisting of coil lines with widths of 10 μm and with aspect ratios of over 5. We have also succeeded in electroforming copper onto seed layers and have demonstrated isotropic copper etching in order to form narrow width coil lines to act as current paths. In addition, we have estimated the suction forces that can be generated by electromagnetic actuators fabricated using these coils. These results give rise to the expectation that practical high performance spiral microcoils could be manufactured using these techniques, in spite of their miniature size.     

导电聚合物驱动器悬臂梁模型建立及柔性抓取装置设计

基于导电聚合物具有柔韧性好、驱动电压低、能耗小等特性,采用自制的多层弯曲型导电聚合物驱动器搭建实验系统,依据等效悬臂梁理论建立驱动器力学模型。通过测量驱动器的弯曲变形量建立偏转位移与电压、长度的函数关系式,并且计算出等效均布载荷值。实验结果表明,驱动器偏转位移与电压、长度成线性关系;当驱动电压达到1.0 V时,驱动器偏转速度趋于稳定,且偏转效果最佳。为改善普通微操作装置结构复杂、能耗大的缺点,采用导电聚合物智能材料设计并制作出微型手爪制动器,最后验证了手爪可稳定抓起0.0111 g左右的重物。     

Multi-experiment state-space identification of coupled magnetic and kinetic parameters in tokamak plasmas

This paper describes an identification technique for control-oriented linear time-invariant models of the coupled dynamics of the electron temperature and the poloidal magnetic flux for advanced operational tokamak scenarios. The actuators consist of two neutral beam injectors, an electron cyclotron current drive and the ohmic coil that provides the loop voltage at the plasma surface. The model is identified using a combination of subspace and output-error methods for state-space multiple-input and multiple-output system identification. This identification is applied on sets of simulated data from the METIS tokamak simulator with parameters typical of the DIII-D tokamak, and the results of the identification are presented.     

一种基于STM32的气压控制系统

气压作为常见的物理量,在工业生产中经常需要对其进行及时、精确的控制,为此设计一种以STM32F407单片机作为控制单元的气压控制系统。系统由STM32F407、真空箱、气压罐、气泵、电磁阀以及若干气管组成,可以在程序里设置气压控制区间,单片机根据传感器反馈的当前气压值和设定目标气压值之差值做出相应的动作来调控气压,构成一个实时采集实时控制的闭环控制系统。实验表明该气压控制系统具有精度高、稳定性好等特点,能较好地满足工业生产需求。     

High‐frequency drive of high‐Xe‐content PDPs for high efficiency and low‐voltage performance

Abstract— It has been well known that the luminous efficiency of PDPs can be improved by increasing the Xe content in the panel. For instance, the efficiency is improved by a factor 1.7 when the Xe content is increased from 3.5% to 30%. The sustain pulse voltage, however, increases from 180 to 230 V by a factor 1.3. It was found that the increase in the sustain pulse voltage can be suppressed by increasing the sustain pulse frequency. The high‐frequency operation further increases the luminous efficiency. If the Xe content is increased from 3.5% to 30% and the drive pulse frequency is increased from 147 to 313 kHz, the luminous efficiency becomes 2.7 times higher and the luminance 4.5 times higher. Furthermore, the increase in the sustain pulse voltage is suppressed 1.1 times, from 180 to 200 V. A mechanism of attaining high efficiency and low‐voltage performance can be considered as follows. A train of pulses is applied during a sustain period. As the sustain pulse frequency is increased, the pulse repetition rate becomes faster and a percentage of the space charge created by the previous pulse remains until the following pulse is applied. Due to the priming effect of these space charge, the discharge current build‐up becomes faster, the width of the discharge current becomes narrower, ion‐heating loss is reduced, and the effective electron temperature is optimized so that Xe atoms are excited more efficiently. The intensity of Xe 147‐nm radiation, dominant in low‐pressure Xe dis‐charges, saturates with respect to electron density due to plasma saturation. This determines the high end of the sustain pulse frequency.     

Design, fabrication, and operation of submicron gap comb-drivemicroactuators

Making submicron interelectrode gaps is the key to reducing the driving voltage of a micro comb-drive electrostatic actuator. Two new fabrication technologies, oxidation machining and a post-release positioning method, are proposed to realize submicron gaps. Two types of actuator (a resonant type and a nonresonant type) with submicron gaps were successfully fabricated and their operational characteristics were tested experimentally. The drive voltage was found to be lower than that of existing actuators. The stability of comb-drive actuators is discussed     

Effect of electrolyte storage layer on performance of PPy-PVDF-PPy microactuators

Trilayer electroactive conducting polymer actuators comprising of two active polymer layers separated by an electrolyte storage layer in between are capable of working in air. Ions are shuttled between the two active layers via the middle inactive layer during electrochemical switching, which leads to a bending motion like the bending of a cantilever beam under a load. Performance of these types of cantilevered actuators greatly depends on the middle electrolyte storage layer, which holds electrolyte and eliminates the necessity of an external electrolyte reservoir, as required by their predecessors. In this paper, we used different types of poly(vinylidene fluoride) (PVDF) films as an electrolyte reservoir and compared bending displacement performance of the actuators made from such PVDF films. The results indicate that the thickness of the PVDF layer has significant effect on the tip displacement of the actuators. With a reduction in the PVDF thickness, the bending stress generated by the actuator decreases while the free tip displacement increases. Several types of PVDF thin films were also compared. As expected, porous PVDF thin films retained more liquid electrolyte and produced larger actuation than non-porous films of the same thickness. It was also found that addition of the electrolyte salt directly to the PVDF film during its spin casting increased the film conductivity and actuation tip displacement.     

Deep-reactive ion-etched compliant starting zone electrostatic zipping actuators

This paper presents the modeling, design, fabrication and testing of monolithic electrostatic curved-electrode zipping actuators fabricated by deep reactive ion etching (DRIE). In contrast to traditional curved-electrode zipping actuators, the design of the actuators presented here utilizes a compliant starting cantilever to significantly reduce the initial pull-in voltage by closing the gap (kerf) generated by DRIE. Thus, the actuators achieve high actuation force at a relatively low voltage. For example, two actuators each with dimensions of 4.5 mm*100 /spl mu/m*300 /spl mu/m are used to drive a bistable MEMS relay. Together, the two actuators provide up to 10 mN of force over their 80 /spl mu/m stroke at 140 V. Measurements of the force-displacement relation of these actuators confirm theoretical expectations based both on numerical and analytical methods. Finite element analysis is employed to predict the behavior of the complete bistable relay system. [1231].