SMA驱动丝的建模与仿真

研究SMA动力学优化模型,针对形状记忆合金(SMA)驱动丝具有强非线性、迟滞效应等特性,为设计SMA驱动丝的自适应结构,提出建立SMA驱动丝模型并提供高效的仿真方法。采用有限元软件实现了受轴向载荷的SMA驱动丝的仿真建模。对本构模型是根据自由能的一维热-力学耦合模型,可以同时复现形状记忆效应和超弹性。数值仿真能够引起材料相变的非均匀温度和应变分布。仿真结果表明,建立热-力学耦合模型,可为设计SMA驱动丝的自适应结构计算提供可靠依据。     

Head-positioning control system using thermal actuator in hard disk drives

In this paper, we propose a head-positioning control system with a thermal actuator in hard disk drives (HDDs). The frequency response of the thermal actuator showed that the thermal actuator system has no mechanical resonant mode. Therefore, this head-positioning system with a thermal actuator can control the head-position beyond the major mechanical resonances caused by a voice coil motor (VCM) or suspensions. In this study, the system was a dual-stage actuator system; the first actuator was a VCM, and the second was a thermal actuator. Simulation results for a track-following control in an HDD demonstrated the validity of the proposed method.     

An efficient thermal actuator design for the thermal flying height control slider

In this work, we propose a novel thermal actuator by designing a thermal insulator, a thermal conductor, and their combination to the traditional thermal heater. The thermal-structure simulation coupled with air bearing simulation is used to simulate the actuation by the thermal actuator, as well as the effects on flying performance of slider being actuated. The simulation results show that an additional 0.8–1.1 nm flying height reduction can be obtained by applying the proposed thermal actuator when the flying height of TFC slider is about several nanometers.     

CMOS–MEMS Lateral Electrothermal Actuators

In this paper, a type of lateral electrothermal (ET) actuator fabricated with post-CMOS micromachining is presented. The actuator is a beam with a multimorph structure, composed of CMOS dielectric and metal interconnect. Following structural release, the actuators demonstrate self-assembly under the moments arising from residual stress. Actuation is achieved through the imbalanced thermal expansion of internal interconnect members, whose relative positions and widths determine the magnitude and direction of actuation. Joule heating in discrete polysilicon resistors is used to convert energy from the electrical to thermal domain. For a 1.3-mum-wide 100-mum-long 4.2-mum-thick actuator composed of two driving metal layers, thermal sensitivities up to 18 nm/K are demonstrated with a force of 0.27 muN, given a 112-K temperature change. The analytic model and finite-element-analysis simulation output for thermal sensitivity agree with experiment to within 6%. Increasing thermal isolation is shown to give a diminishing return on thermal sensitivity and to reduce the thermal cutoff frequency of an actuator from 800 to 150 Hz. A figure of merit called the efficiency-volume ratio is presented and used to compare this paper with several actuators taken from the literature. Lateral ET multimorph actuators are shown to provide an advantage in applications where area is constrained and the load is small.     

Paired-wire carrying current actuators and piezoelectric beam sensors for microelectromechanical systems

Microsystem Technologies - An alternative actuator for MEMS/NEMS device is proposed and analyzed. The actuator is based on the paired-wires (PW) carrying current concept, which makes the actuator...     

Feasibility study of thermal positioning control actuator for hard disk drives

We have developed an actuator with a heater embedded in the head slider. This actuator, called the thermal positioning control (TPC) actuator, is integrated next to the read write elements in the head slider. By applying electric power to the TPC actuator, the actuator causes thermal expansion and the read write elements then move in the positioning direction. We demonstrated its feasibility in terms of the stroke and frequency response. We designed and fabricated head sliders that integrated a TPC actuator and a read element. We also conducted an experimental evaluation at the spin-stand. The results of 5?nm stroke and a 5-kHz bandwidth were experimentally demonstrated. These results showed the feasibility of the TPC actuator for future 550?kilo?track per inch class hard disk drives.     

Spatially resolved temperature mapping of electrothermal actuators by surface Raman scattering

In this paper, we report spatially resolved temperature profiles along the legs of working V-shaped electrothermal (ET) actuators using a surface Raman scattering technique. The Raman probe provides nonperturbing optical data with a spatial resolution of 1.2 /spl mu/m, which is required to observe the 3-/spl mu/m-wide actuator beams. A detailed uncertainty analysis reveals that our Raman thermometry of polycrystalline silicon is performed with fidelity of /spl plusmn/10 to 11 K when the peak location of the Stokes-shifted optical phonon signature is used as an indicator of temperature. This level of uncertainty is sufficient for temperature mapping of many working thermal MEMS devices which exhibit characteristic temperature differences of several hundred Kelvins. To our knowledge, these are the first quantitative and spatially resolved temperature data available for thermal actuator structures. This new temperature data set can be used for validation of actuator thermal design models and these new results are compared with finite-difference simulations of actuator thermal performance.     

Design of swing arm type actuators considering thermal and dynamic characteristics

The present state of the design of swing arm actuators for optical disc drives is to obtain the highly efficient dynamic characteristics within a very compact volume. As a necessary consequence, the need of the small form factor (SFF) storage device has arisen as a major interest in the information storage technology. Due to the size constraint, the thermal stability of the optical pick-up head is important: therefore, the actuator is designed to emit the heat, which is generated by the optical pick-up, along the structural body easily. In this paper, we suggest the miniaturized swing arm type actuator that has effective heat emission quality as well as satisfies the dynamic requirements for the SFF optical disk drive (ODD). The actuator is targeted to be installed in CF-II card size drive to be competitive with flash memory or mini hard disk drive used in mobile electric devices; therefore the dimension of the actuator is required as 11.0 mm × 2.5 mm × 25.0 mm (width × height × length). Because of its small size, the dynamic requirements are severe to ensure the enough gain-margin for the system control together with satisfying the DC/AC sensitivity conditions. Moreover, due to the small size, the maximum pick-up temperature is critical in design because the system has high possibility to reach the shut-down temperature. For the operating mechanism, it uses a tracking electromagnetic (EM) circuit for the focusing motion together and the initial model is designed and promoted by the design of experiments (DOE) only considering the dynamic characteristics. New concept design is suggested based on the topology optimization method considering the thermal conductivity. Furthermore, the new design is modified by DOE to maintain the high sensitivity and to have wide control bandwidth and decreasing mass and inertia. The final design of a swing arm type actuator for SFF ODD is suggested and its dynamic characteristics are verified.     

Stacked dielectric elastomer actuator for tensile force transmission

This paper presents a novel approach for active structures driven by soft dielectric electro-active polymers (EAPs), which can perform contractive displacements at external tensile load. The active structure is composed of an array of equal segments, where the dielectric films are arranged in a pile-up configuration. The proposed active structure has the capability of exhibiting uniaxial contractive deformations, while being exposed to external tensile forces. The serial arrangement of active segments has one contracting degree of freedom in the thickness direction of the dielectric EAP film layers.Due to the envisaged tension force transmission capability, special attention is paid to the electrode design which is of paramount importance with regard to functionality of the actuator. A compliant electrode system with anisotropic deformation properties is presented based on nano scale carbon powder. In experiments, the free deformation as well as the contractive motion under external tensile loading of several actuator configurations with different setups is characterized. These involve the study of various sizes and numbers of stacked film layers as well as different electrode designs.     

Continuously tunable terahertz metamaterial employing a thermal actuator

In order to increase the flexibility of the resonance frequency, a widely and continuously tunable terahertz metamaterial structure that employs a thermal actuator for tuning the resonance frequency of a two-cut split-ring resonator is proposed in this paper. The tunable metamaterial device model is designed and simulated based on the MetalMUMPs process. The use of V-shaped thermal actuators enables continuous tuning of the resonance frequency over a large range from 1.374 to 1.574 THz. The transmission curves have a sharp dip in every resonance frequency, which indicates an excellent performance of strong resonance. The geometrical parameters of the V-shaped thermal actuator are optimized by COMSOL Multiphysics 4.2 in order to obtain enough displacement under minimum driven current. The relationship between driven current and slabs’ displacement is also characterized. The reliability of the metamaterial structure array actuated by the thermal actuator is also calculated and discussed.     

Polysilicon micro beams buckling with temperature-dependent properties

The suspended electrothermal polysilicon micro beams generate displacements and forces by thermal buckling effects. In the previous electro-thermal and thermo-elastic models of suspended polysilicon micro beams, the thermo-mechanical properties of polysilicon have been considered constant over a wide rang of temperature (20–900°C). In reality, the thermo-mechanical properties of polysilicon depend on temperature and change significantly at high temperatures. This paper describes the development and validation of theoretical and Finite element model (FEM) including the temperature dependencies of polysilicon properties such as thermal expansion coefficient and Young’s modulus. In the theoretical models, two parts of elastic deflection model and thermal elastic model of micro beams buckling have been established and simulated. Also, temperature dependent buckling of polysilicon micro beam under high temperature has been modeled by Finite element analysis (FEA). Analytical results and numerical results using FEA are compared with experimental data available in literature. Their reasonable agreement validates analytical model and FEM. This validation indicates the importance of including temperature dependencies of polysilicon thermo-mechanical properties such as Coefficient of thermal expansion (CTE) in the previous models.     

Boundary element analysis of cracked homogeneous or bi-material structures under thermo-mechanical cycling

We present a sub-domain boundary element procedure to evaluate the failure capacity of cracked homogeneous and bi-material media under cyclic thermo-mechanical loads. The boundary integral equations of uncoupled, time-dependent thermo-elasticity are employed to account for the time-varying nature of the thermal load. If crack closure due to thermal distortion takes place, then the displacement and traction field may affect the heat flux between the crack faces, and the thermal and mechanical parts of the problem will need to be solved repeatedly until thermo-mechanical convergence is achieved. We present results from cases of pure mode-I fracture in homogeneous materials and for interfacial fracture in bi-materials. Our study discusses the influence of crack closure on quasi-static, sub-critical crack extension. Especially in case of interfacial cracks the type of loading, the thermal resistance between the crack faces, and the coefficient of friction are also taken into account. The results suggest that the above parameters may have a severe impact on the predicted failure capacity of cracked structures and should be considered in the evaluation of fatigue life.     

管道气直驱执行机构在天然气长输管道工程的应用研究

在天然气输气管道工程中,紧急切断阀通常选用气液联动执行机构,但其结构复杂、价格昂贵;紧急放空阀常采用电动执行机构,但其在安全性方面存在不足。因此,有必要为安全仪表系统(SIS)阀寻找满足功能安全、结构简单并节省投资的其他类型执行机构。通过与气液联动执行机构、电液联动执行机构、气动执行机构及电动执行机构的性能和经济性比较,介绍了管道气直驱执行机构和其他类型执行机构的适用场合,并阐述了管道气直驱执行机构的概念、分类和应用情况。通过分析,得出了对于天然气管道工程中口径16英寸(1英寸=25.4 mm)或16英寸以下的紧急切断阀,管道气直驱执行机构更为适用的结论。这为以后的天然气长输管道工程中执行机构类型选择提供了参考和指导。     

Singularity avoidance of CMGs by virtual actuators

An implementable and practical steering law of control moment gyros (CMGs) to avoid singularity is addressed in this paper. The singularity strategy of CMGs revised in this paper is based on a simple but practical virtual actuator methodology. It is known that in a special case of singularity and torque requirement, the virtual CMGs can provide perfect command torque without torque error, which can be proven analytically. In this paper, much extensive analysis is accomplished to provide the performance of the virtual actuator concept, which can avoid the singular configuration of CMGs with possibly smaller control torque error than the conventional singularity robustness method. Finally, the steering law based on the virtual actuator concept is demonstrated by numerical simulations.     

基于SMA的关节驱动器的力学分析及控制

分析了一种用于水下微小型仿生机器人的形状记忆合金(SMA)关节驱动器的力学特性,并通过模糊控制的方法对其进行了实验研究。结果表明:对于物理特性呈非线性、温度滞后、时变和受温度影响很大的SMA驱动器来说,采用模糊控制的方法,能够使驱动器稳定、平滑的工作,尽管产生了轻微的超调现象,但收到了令人较为满意的效果。因此,将模糊控制方法应用于SMA驱动器的控制有一定的理论意义和应用价值。     

Torsional actuator based on mechanically amplified shear piezoelectric response

A torsional actuator, based on the concept of mechanical amplification of piezoelectric shear strain and capable of generating large angular displacement, was proposed and studied experimentally. The actuator is a tube consisting of an even number of the segments poled along the length, which are adhesively bonded together, and the joints act as electrodes to apply the driving voltage. The experimental data measured on the prototype actuators (i) prove the proposed concept of mechanical amplification of small piezoelectric shear strain to generate large torsional motion, (ii) show that the actuator functions well both without load and under the torque load and (iii) demonstrate that the actuator can operate continuously for a long period of time without drop in its performance. Also, the results demonstrated that the proposed torsional actuator is capable of producing both large torque and large angular displacement in a compact package, sufficient to meet many smart structures requirements, and can be tailored for a variety of application requirements. Finally, one of the obvious advantages of the present design of the actuator is its simplicity: the piezoelectric shear strain is transformed directly into the angular displacement, whereas in the previously reported actuators, the conversion mechanism into the torsional motion was rather complicated which thus required a sophisticated design of the whole system.     

Characterization and modeling of the dynamic behavior of a liquid–vapor phase change actuator

The dynamic behavior of a liquid–vapor phase change actuator has been investigated. A modular liquid–vapor phase change actuator was designed and fabricated. The actuator consists of a cavity filled with a two-phase fluid bounded on the bottom by a thin membrane into which heat is added and on the top by a cover slip which is displaced by the expansion of the vapor. A parametric study of geometric and operation parameters was conducted. A lumped parameter mathematical model of the actuator was developed to predict the dynamic behavior of the actuator. The model was validated against measured data. Based on the parameter study, actuators with smaller bubbles experienced higher heat loss. Thicker actuators were associated with higher thermal inertia. Thermal inertia, as well as heat losses, had a major effect on the dynamic behavior of the actuator. The model showed that faster response times and higher sensitivity can be achieved if the thermal inertia and heat loss coefficient values are reduced. Time constants less than 2.5 ms and displacement sensitivity higher than 30 μm/W are feasible.     

Evaluation of thermo-mechanical damage and fatigue life of solar cell solder interconnections

The soldering process of interconnecting crystalline silicon solar cells to form photovoltaic (PV) module is a key manufacturing process. However, during the soldering process, stress is induced in the solar cell solder joints and remains in the joint as residual stress after soldering. Furthermore, during the module service life time, thermo-mechanical degradation of the solder joints occurs due to thermal cycling of the joints which induce stress, creep strain and strain energy. The resultant effect of damage on the solder joint is premature failure, hence shortened fatigue life. This study seeks to determine accumulated thermo-mechanical damage and fatigue life of solder interconnection in solar cell assembly under thermo-mechanical cycling conditions. In this investigation, finite element modelling (FEM) and simulations are carried out in order to determine nonlinear degradation of SnAgCu solder joints. The degradation of the solder material is simulated using Garofalo-Arrhenius creep model. A three dimensional (3D) geometric model is subjected to six accelerated thermal cycles (ATCs) utilising IEC 61215 standard for photovoltaic panels. The results demonstrate that induced stress, strain and strain energy impacts the solder joints during operations. Furthermore, the larger the accumulated creep strain and creep strain energy in the joints, the shorter the fatigue life. This indicates that creep strain and creep strain energy in the solder joints significantly impacts the thermo-mechanical reliability of the assembly joints. Regions of solder joint with critical stress, strain and strain energy values including their distribution are determined. Analysis of results demonstrates that creep energy density is a better parameter than creep strain in predicting interconnection fatigue life. The use of six ATCs yields significant data which enable better understanding of the response of the solder joints to the induced loads. Moreover, information obtained from this study can be used for improved design and better-quality fabrication of solder interconnections in solar cell assembly for enhanced thermo-mechanical reliability.     

Mechanical Characteristics of FIB Deposited Carbon Nanowires Using an Electrostatic Actuated Nano Tensile Testing Device

This research is directed at the development of Electrostatic Actuated NAno Tensile testing devices (EANATs) for measuring mechanical properties of carbon nanowires, deposited by focused ion beam-assisted chemical vapor deposition (FIB-CVD) using phenanthrene gas. The EANATs were composed of the specimen part, actuator part and measurement part. 1000, 3000 and 5000 pairs of comb drive actuators were prepared within the actuator part for stretching the nanowires. The measurement part had a cantilever used as a lever motion amplification system for measuring tensile displacement of the nanowires. A theoretical resolution of 0.17 nm in tensile displacement was achieved using the amplification system and imaging analysis. The uniaxial tensile force was derived from the total spring constant of suspended beams built within the EANATs, with the theoretical resolutions ranging from 108 to 113 nN. This research was therefore successful in obtaining accurate load-displacement curves for carbon nanowires. The Young's modulus observed for the nanowires provided the scatter in absolute values ranging from 42.6 to 80.7 GPa. The fracture stress and strain of the nanowires exhibited larger values of 4.3 GPa and 0.08 strain, respectively. Discussion of the deformation behaviors and failure mechanisms of the nanowires is made from FE-SEM observations of the nanowires before and after tensile failure