Thermal behavior modeling and characteristics analysis of electrothermal microactuators

Microsystem Technologies - Electrothermal microactuators possess a number of desirable attributes including ease of fabrication and large force and displacement capabilities relative to other types...     

A nodal analysis method for simulating the behavior of electrothermal microactuators

This paper presents a novel approach to verify and optimize surface micromachined electrothermal microactuators by using a nodal analysis method. The nodal analysis method for the mechanical and electrostatic devices is a schematic-based method which simplifies the design of MEMS devices significantly. A variety of the surface micromachined electrothermal microactuators have been widely applied in various areas due to the high force provided at a relatively low input voltage. These electrothermal microactuators can also be decomposed into essential elements of beams and anchors. This paper presents the nodal analysis method for the electrothermal microactuators. The temperature dependent properties for the thermal conductivity, electrical resistivity and thermal expansion coefficient of polysilicon beams are included. The effect of the effective axial length for the beams due to lateral deflection and large axial stress is also taken into account. This approach is verified by ANSYS and the simulation data agrees well with each other. It extends the general nodal analyses method to simulate the electrothermal microactuators.     

Theoretical modal analysis and parameter study of Z-shaped electrothermal microactuators

Microsystem Technologies - This paper presents a comprehensive modal analysis of Z-shaped beam electrothermal microactuators for the first time. Both longitudinal and lateral vibrations are taken...     

A hybrid surface tension seal for pneumatic and hydraulic microactuators

Recent research revealed that microactuators driven by pressurized fluids are able to generate high power and force densities at microscale. One of the main technological barriers in the development of these actuators is the fabrication low friction seals. This paper presents a novel scalable seal technology, which resists the actuation pressure relying on a combination of a clearance seal and a surface tension seal. This approach allows to seal pressures of more than 800 kPa without leakage. The seal is tested on an actuator with a bore of 0.8 mm2 and a length of 13 mm, which was able to generate forces up to 0.32 N.     

液压控制器辅助控制系统设计

本文介绍了在原有液压控制器的基础上更新设计其辅助控制系统,该系统主要完成输出信号的编辑,信号输入输出的控制,波形显示,信号存储,信号分析及再现.系统通过4通道模拟量输出控制液压泵,8模拟量通道的同步输入采集数据,可采取多种输入输出模式,即可只输出,也可只输入,也可输入输出同步.为了快速可靠的搭建系统,我们选择了NI公司的多功能数据采集卡,连接线缆,及连接端子,在LABVIEW下开发应用软件.系统有简介友好的人机界面,直接在面板上完成各种操作.     

压电折叠梁微执行器的低电压优化设计

采用理论分析和有限元数值模拟相结合的方法,对压电折叠梁微执行器在低电压下工作时的器件结构进行优化设计。首先通过理论分析获得优化的器件结构参数,再通过有限元模拟验证理论分析结果。在器件设计中,通过综合考虑制造工艺、工作条件、器件应用的可靠性,对压电悬臂梁长度、单晶硅层厚度、折叠梁级数,以及工作电压进行折衷优化,获得低电压应用时最佳的器件参数。     

A design methodology for a bulk-micromachined two-dimensional electrostatic torsion micromirror

This paper presents a design methodology for a two-dimensional (2-D) electrostatic torsion micromirror fabricated with bulk-micromachining technology. The theoretical models in mechanical and electrostatic fields presented here provide insights into the influences of different design parameters on micromirror performance. Parametric numerical models built in ANSYS are used to more accurately predict its performance and further refine the design parameter values derived from the theoretical models. By use of the electrical analogy method, an equivalent electrical circuit is built in PSPICE to predict the static and dynamic performance of this micromirror, with the numerical simulation results as the input parameters. The equivalent electrical circuit has been demonstrated to be a simple and powerful approach to characterize the performance of this 2-D torsion micromirror. The test results for this micromirror reveal very good agreement between experimental and numerical results, taking into account fabrication tolerances and experimental accuracies. Incorporating the fabrication tolerances of bulk-micromachining technology, this design methodology can be readily applied to performance characterization and design optimization.     

针对液压检测差动变压器位移传感器的设计

介绍了采用差动变压器作为传感器,通过检测其铁芯在液压和大气压2个相反方向的压力作用下产生的位移来达到检测液压的目的。详细介绍了采用平衡调制解调器芯片实现差动变压器信号检测与处理的原理和方法。由于对差动变压器副边线圈输出的差动信号进行了检相、滤波、积分等处理,经验证明:与其它检测方法相比,该传感器具有更高的灵敏度、更高的准确度、更大的灵活性。     

Spatial-mode analysis of micromachined optical cavities using electrothermal mirror actuation

The performance of optical microcavities is limited by spectral degradation resulting from thermal deformation and fabrication imperfections. In this paper, we study the spatial-mode properties of micromirror optical cavities with respect to commonly seen aberrations. Electrothermal actuation is used to slightly adjust the shape and position of micromirrors and study the effects this has on the spatial-mode structure of the cavity spectrum. The shapes of the micromirrors are changed using Joule heating with thermal expansion deformation. Significant differences in mirror tilt, curvature, and astigmatism are measured, but the tilt has by far the biggest impact on cavity finesse and resolution. We demonstrate that unwanted higher order spatial modes can be suppressed electrically and an amplitude reduction for the higher order modes of over 60% has been obtained with a tuning current of 5.5 mA. A fundamental mode finesse of approximately 60 is maintained throughout tuning. These tunable cavities have great potential in applications using cavity arrays or requiring dynamic mode control.     

Design,closed-form modeling and analysis of SU-8 based electrothermal microgripper for biomedical applications

Microsystem Technologies - This paper presents design analysis of an SU-8 based 2-DoF electrothermal microgripper by developing a closed-form analytical model. The analytical model considers both...     

Electroplated compliant metal microactuators with small feature sizes using a removable SU-8 mould

In the work presented in this article a fabrication process for high aspect ratio metal microstructures has been developed using photoresist EPON SU-8. A smallest feature size of 2 μm with near vertical sidewalls has been achieved on a routine basis. The SU-8 photoresist has been used as mould for electroplating high aspect ratio metal micro actuators. A removal process has also been developed. The removal of the SU-8 mould after plating is done in a plasma asher using an oxygen or oxygen/fluorine plasma with plasma power as low as 200 W. To demonstrate the fabrication process a 10 μm thick nickel, electro-thermal micro actuator has been fabricated.     

Hard and soft magnetic materials for electromagnetic microactuators

An important aspect of the development of electromagnetic microactuators is the search for suitable materials as well as the development of the respective deposition and patterning processes. Within the Collaborative Research Center 516 “Design and Fabrication of Active Microsystems”, it is the task of the subproject B1 “fabrication of magnetic thin films for electromagnetic microactuators” to perform these investigations. The materials of interest can be divided into two groups: hard magnetic materials and soft magnetic materials. Materials with optimized properties and fabrication processes have been developed within both groups. An example is Samarium–Cobalt (SmCo), which can either be deposited using magnetron sputtering as Sm₂Co₁₇ with a very high energy product or in the SmCo₅ phase using gas flow sputtering with very high deposition rates. In the area of soft magnetic materials, investigations on Nickel-Iron (NiFe) especially NiFe81/19 were followed by the evaluation of NiFe45/55, which features a higher saturation flux density B _s and relative permeability μ _r. Furthermore, current investigations focus on Cobalt-Iron (CoFe) and its further increased saturation flux density B _s and relative permeability μ _r. Current tasks include the stabilization of the fabrication processes to achieve good material properties (i.e. electroplating of CoFe) or a shortening (e.g. by using heated substrates during deposition) by using process alternative not used so far. Another topic is the integration into fabrication processes, i.e. the investigation of process stability and compatibility.     

井下液压支架压力在线监测系统设计

针对现有煤矿井下液压支架压力监测系统存在布线困难、组网规模小、传输距离短等问题,采用WaveMesh无线自组网技术,设计了一种井下液压支架压力在线监测系统。该系统通过无线压力传感器采集液压支架的压力数据,压力数据以无线方式传送给无线监测分站,并由无线监测分站通过RS485总线与光纤环网相连上传至地面监测主机。实际应用表明,该系统运行稳定、可靠,可实时、精确监测井下液压支架的压力变化。     

Design and fabrication of an electrothermal microactuator for multi-level conveying

During the past years, a variety of microactuators developed for micro-conveyors have been presented. However, such micro-conveyors can only provide conveying motion in a single plane. Here an electrothermally driven microactuator with a capability of adjustable height is proposed, which may act as a basic unit for multi-level conveyors. This microactuator is based on the principle of thermal bimorph actuation with two long conveying fingers to exert out-of-plane bending motions in the transversal direction, which are connected and lifted by an initially curved height adjuster in the longitudinal direction. The devices can provide conveyance of micro-objects between two plane levels of different heights. The testing results show that the two fingers and a height adjuster can be actuated simultaneously and individually with little thermal crosstalk. The proposed device with a dimension of 900×100×4.5 μm³ can provide 5 μm vertical displacements by the height adjuster at 1 V and 18 μm lateral displacements by the conveying finger at 2 V. Simulations by finite-element program ANSYS 5.7 have been performed and widely match with testing results.     

Design and sensitivity analysis of capacitive MEMS pressure sensor for blood pressure measurement

Microsystem Technologies - This paper presents the design and simulation of a MEMS based clamped capacitive pressure sensor for blood pressure measurement. Normally, Blood pressure for human beings...     

High-speed visualization, a powerful diagnostic tool for microactuators – retrospect and prospect

 A comprehensive testing of microactuators is decisive (i) to prove the workability, (ii) to characterize the output parameters, (iii) to provide kinematic and temperature data for a revaluation of numerical modeling, (iv) to ensure the expected response with the macroscopic world, and (v) to study the mechanism of a premature failure. All this information helps to develop well-aimed strategies for improvements and promote the marketing process of new types of actuators. The most important diagnostic methods encompass high-speed photomicrography, laser interferometry and scanning laser Doppler velocimetry. High-speed thermography and flash microradiography have not yet been fully established for dynamic testing in the microscopic domain because of various technical limitations. The present state of the art of these methods is discussed and illustrated at various microactuator types. By the example of a microrelay it is shown that also material data can be derived from a motion analysis and that the relay operability can be improved by using methods of systems theory and control engineering.     

A study on a hybrid structure flexible electro-rheological microvalve for soft microactuators

In order to realize a fluidic soft microactuator with a built-in control valve, this paper presents a cantilever type flexible electro-rheological microvalve (FERV) with a hybrid flow channel structure made from polydimethylsiloxane (PDMS) and SU-8. The hybrid structure provides high flexibility with the PDMS structure while only slight expansion occurred under high pressure with the SU-8 structure. In addition, its flexible electrodes are realized by UV-curable PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) that is a flexible conductive polymer and can be fabricated by simple and fast fabrication process without high-cost equipment. The proposed FERV can control the flow rate of the electro-rheological fluid (ERF) through the flow channel by changing its apparent viscosity with an applied electric field. FEM simulations were conducted to demonstrate the flexural rigidity of the designed FERV and compare it with the previous FERVs. Developing micro-electro-mechanical systems (MEMS) processes using the photolithography technique, the FERV was successfully fabricated and its characteristics were experimentally clarified. The results showed the feasibility of the proposed FERV in the soft microactuator application.

     

Robustness analysis of a PI controller for a hydraulic actuator

In this work the authors address the problem of robustness of the classic PI controller implemented in a Hydraulic Servo-Actuator (HSA), by presenting a strategy based on the definition of a linear model of the system and the identification of its parameters for different working points. The variation of these parameters is considered as a measure of parametric uncertainty of the linear model. These uncertainties along with the definition of a nominal plant are used to analyze the robustness of the system implementing the Small Gain Theorem. Theoretical and experimental results show that a PI controller can provide robustness to the HSA.     

Comprehensive theoretical digging performance analysis for hydraulic excavator using convex polytope method

This paper proposes a method for analyzing comprehensive theoretical digging performance of an excavator based on the convex polytope. The convex polytope is generated by using Newton–Euler’s equations to establish dynamic relationships between the digging capability of the bucket and the driving capability of hydraulic cylinders with the consideration of the excavator tipping and slipping constraints, and is used to identify the excavator’s output capability for digging forces and moments in the bucket force space. A set of indices for theoretically quantifying the digging capability, digging efficiency, as well as the matchability between the manipulator mechanism and the driving capability of hydraulic cylinders are proposed based on the polytope, and they are used to assess the digging trajectory characteristics and the dynamic digging performance of the entire excavator workspace. Two case studies for the excavator’s digging performance assessment and optimal digging trajectory generation are conducted to test and validate this method. The proposed method contributes to comprehensively and deeply understand the design principles of an excavator, and shows the promising application prospect for guiding the design and development of new excavators.