Design and optimization of carbon nanotube/polymer actuator by using finite element analysis

In recent years,actuators based on carbon nanotube(CNT) or graphene demonstrate great potential applications in the fields of artificial muscles,smart switches,robotics,and so on.The electrothermal and photothermal bending actuators based on CNT/graphene and polymer composites show large bending actuations,which are superior to traditional thermaldriven actuators.However,the influence of material parameters(thickness,temperature change,etc.) on the actuation performance needs to be further studied,because it is a critical point to the design and fabrication of high-performance actuators.In this work,finite element analysis(EEA) is employed to simulate the actuation performance of CNT/polymer actuator,which has a bilayer structure.The main focus of this work is to design and to optimize material parameters by using computational method.FEA simulation results show that each layer thickness of actuator has an important influence on the actuation deformation.A maximum curvature of 2.7 cm~(-1) is obtained by simulation,which is much larger than most of the actuator curvature reported in previous experiments.What is more,larger temperature change and larger difference of coefficient of thermal expansion(CTE) between two layers will result in larger bending actuation.This study is expected to provide valuable theoretical reference for the design and realization of CNT-based thermal actuator with ultra-large actuation performance.     

A built-in force actuator for active control of lateral rotor vibration in cage induction electrical machines

In this paper means of active control of radial rotor vibrations in electrical machines are considered. We examine a built-in force actuator for active generation of force on the machine rotor. The operation of the actuator is based on electromechanical interaction between the rotor and the stator of the machine. The actuator is given a low-order linear state-space model, which is identified by using simulation data obtained from a detailed time-stepping finite element model of the machine. Simulation results obtained by using real machine data and finite element time-stepping method are presented.     

大口径天文薄镜面磨制试验

介绍了采用薄镜面主动支撑技术来加工大口径天文薄镜面的试验情况。试验镜为一弯月型球面反射镜．直径为Ф1035mm,镜面曲率半径为3220mm,径厚比约为40：1。在磨制过程中,有55个分离支撑点支撑存镜子背面。支撑点的位置与支撑力的大小通过有限元分析计算确定,其中3个为固定支撑点．另外52个为主动支撑点。每个支撑点位置设置了力促动器,调节力促动器加力的大小。可以主动改正镜面的低频误差。加工后最后达到的面形精度：λ=632．8nm,面形误差(RMS)小于等于λ／21．5,局部高频误差(RMS)小于等于λ／23。试验证明所采用的方法适合于大口径天文薄镜面的加工。     

Interdigitated electrode design and optimization for dielectrophoresis cell separation actuators

Among all particle separation approaches, dielectrophoresis actuators which use electric properties difference between particles, have turned into strong separating tools. This way, the particles in the fluid within non-uniform electric field experience the dielectrophoresis force. The amount and direction of this force depend on the fluid and particle polarization, particle size and electric field gradient. In this paper after presenting governing equations concerning the dielectrophoresis phenomenon, a microfluidic actuator introduced in which an interdigitated electrode pattern is applied in. Voltage, pitch, and width to pitch ratio of electrode as well as channel height are of the most important geometrical parameters of this actuator whose individual effect on particles separation was investigated using finite element analysis (FEM). The simulation results showed that if the actuator is intended to work in the efficient conditions, channel height and electrodes pitch should be near to each other, height needs to be as minimum as possible while voltage as maximum as possible in order to reach to the least time duration and the highest quantity for particles separation. Then, using theoretical equations and simulation results, a flowchart is introduced to design and optimize dielectrophoresis separation actuators. Finally, experimental results for k562 cell separation, as a biological particle, from Polystyrene, as a standard particle, is presented. In the fabricated actuator recovery and purity efficiency are 93% and about 100% respectively.     

Development and study of novel non-contact ultrasonic motor based on principle of structural asymmetry

The article presents novel design of non-contact rotary ultrasonic motor consisting of ring-shaped stator vibrating in in-plane flexural mode and rotor provided with blades. In contrast to other motors with similar design proposed motor relies on the use of standing ultrasonic waves. This simplifies design and electronic control of motor and becomes possible due to introduction of artificial asymmetry, for example by tilting one or several blades of the rotor relative to the surface normal. Operating principle of the proposed motor is based on acoustic radiation torque exerted on rotor by ultrasonic waves propagating in air or fluid gap between rotor and stator. This torque is calculated using finite element method by means of COMSOL Multiphysics software. Dynamics of rotor is studied using MathCad software and general theory of nonlinear conservative oscillators. Role of asymmetry is explained on the basis of comparative analysis of potential functions and phase trajectories for symmetric and asymmetric cases. It is shown that direction of rotation is determined by structural parameters of motor, particularly tilting direction (clockwise or counter-clockwise) of the blades. Conceptual design of motor with bidirectional rotation is described. Direction and velocity of rotation in the proposed conceptual design can be potentially controlled by changing excitation frequency of stator.     

悬线式力矩器磁路设计中的有限元分析应用

光学头力矩器的空间磁场分布直接决定了力矩器的动态性能,对磁场进行准确分析是力矩器设计的前提。分析了悬线式力矩器的空间磁场产生机理,并采用有限元分析法进行了理论推导。以一款动线圈式二维对称型只读悬线式力矩器为例,采用有限元仿真软件（ANSYS）分析并设计了其空间磁场分布,对影响力矩器空间磁场分布的相关因素进行了分析。将采用有限元法对悬线式力矩器空间磁场仿真计算得出的力矩器动态特性参数与实测力矩器动态特性参数相比,其结果均符合力矩器的设计要求,证明基于有限元分析法的悬线式力矩器空间磁场设计是可行的。     

Modelling and characterization of a piezoceramic inertial actuator

An inertial actuator (also known as a proof mass actuator) applies forces to a structure by reacting them against an “external” mass. This approach to actuation may provide some practical benefits in the active control of vibration and structure-borne noise: system reliability may be improved by removing the actuator from a structural load path; effective discrete point-force actuation permits ready attachment to curved surfaces, and an inherent passive vibration absorber effect can reduce power requirements.This paper describes a class of recently developed inertial actuators that is based on mechanical amplification of displacements of an active piezoceramic element. Important actuator characteristics include resonance frequencies, clamped force, and the drive voltage to output the force frequency response function.The paper addresses one particular approach to motion amplification, the “dual unimorph,” in detail. A model of actuator dynamic behavior is developed using an assumed-modes method, treating the piezoelectrically induced stresses as external forces. Predicted actuator characteristics agree well with experimental data obtained for a prototype actuator. The validated actuator dynamic model provides a tool for design improvement.     

变形镜部分驱动器断电失效对校正性能的影响

变形镜在长期工作的过程中,压电陶瓷驱动器因累积疲劳效应会导致其失效,从而导致校正性能的降低。从变形镜的影响函数出发,将失效驱动器的电压置零,采用有限元方法建立变形镜疲劳失效模型,重点分析畸变波前的形态分布、入射光束的类型和驱动器的排布方式等对校正能力的影响。实验结果表明,在部分驱动器失效的情况下,变形镜应当根据高斯型随机畸变波前的形态分布进行失效分析。从低频部分来看,在第1圈驱动器失效的情况下,变形镜对三种入射光束的校正效果几乎相同,当驱动器失效位置在其他圈数时,变形镜对高斯光束的校正效果最差;从高频部分来看,在不同位置驱动器失效的情况下,变形镜对平顶高斯光束的校正效果最佳。     

Acoustic manipulation of active spherical carriers: Generation of negative radiation force

This paper examines theoretically a novel mechanism of generating negative (pulling) radiation force for acoustic manipulation of spherical carriers equipped with piezoelectric actuators in its inner surface. In this mechanism, the spherical particle is handled by common plane progressive monochromatic acoustic waves instead of zero-/higher- order Bessel beams or standing waves field. The handling strategy is based on applying a spatially uniform harmonic electrical voltage at the piezoelectric actuator with the same frequency of handling acoustic waves, in order to change the radiation force effect from repulsive (away from source) to attractive (toward source). This study may be considered as a start point for development of contact-free precise handling and entrapment technology of active carriers which are essential in many engineering and medicine applications.     

主动光学技术在制造标准大反射镜中的应用

介绍了利用主动光学技术校正大型标准反射镜残余面形误差和重力变形的方法 ,研制了用于施加局部作用力的工具———机械式作动器的结构与性能 ,作用力的测定方法 ;位于不同位置的作用力引起的镜面变形量的测定与分析 ,与镜面最小面形误差对应的作动器作用力控制矩阵的求解等。对一块Φ2 30mm、中心厚 18mm、R880mm、玻璃材料为K 9的标准球面镜进行了面形误差校正实验 ,取得了较明显的校正效果。     

磁悬浮－气囊主被动混合隔振装置理论和实验

为了更有效地控制舰船动力机械宽频和低频线谱振动的传递,提出了一种将磁悬浮作动器与气囊隔振器集成应用的磁悬浮-气囊主被动混合隔振装置。通过对磁悬浮作动器机电耦合特性和混合隔振系统动力学特性的分析研究,确定了满足线谱振动控制要求和满足混合隔振装置性能要求的参数设计方法。针对主动控制时,FxLMS (filtered-x least mean square)算法在小阻尼系统上需用高阶FIR滤波器建模,运算量大的问题,提出了分频段控制的改进FxLMS算法,并有效地解决了作动器的非线性效应问题。样机实验结果表明:理论分析是正确的,该项技术控制力需求小,装置稳定性好,具有优良的宽频隔振和低频线谱振动控制效果。      

Metal nanowires fabricated by means of magnetostrictive actuator

A new method of fabricating nanowires for electric conductance quantization studies is proposed as an alternative to the method based on converse piezoelectric effect. Commonly used for nanowire fabrication, piezoelectric actuators are expensive and require high-level voltage control signal. The method presented in this paper is based on the use of magnetostrictive actuator. Both the actuator structure and the method of the conversion factor measurement are discussed. The results of the tests of the magnetostrictive actuator are also reported. The parameters of the proposed actuator are compared with those of its piezoelectric counterpart used to date. The results of measurement confirm that the proposed actuator can be used for studying electric conductance quantization in nanowires. Presented at the X-th Symposium on Surface Physics, Prague, Czech Republic, July 11–15, 2005     

Design and Optimization of the Electromagnetic Actuator in Active-Passive Hybrid Vibration Isolator

The design and optimization of actuators are difficult and critical for the active-passive hybrid vibration control system. In this paper, an electromagnetic actuator model is established based on Ohm’s Law for magnetic circuit considering the leakage flux. The 600N electromagnetic actuators are designed and optimized based on ANSYS simulation according to the engineering request. Its transient characteristics are studied. The effects of different structural parameters on its output force are analyzed. The experimental results show that the structure parameters and output force characteristics of the designed electromagnetic actuators satisfy the practical requirement.     

变形镜像差拟合能力的有限元仿真

为了研究变形镜对于Zernike多项式像差模式的拟合能力, 利用有限元仿真方法, 建立了两种不同单元排布方式的变形镜有限元模型. 通过给促动器施加理论位移, 进行了仿真分析. 结果指出了不同的促动器排布方式与像差拟合能力之间的关系, 同时表明57点促动器密布的排列方式已经能校正像差到λ/20甚至更小, 验证了促动器对变形镜“印透效应”等的影响.     

Convertible pneumatic actuator for magnetic resonance elastography of the brain

Here we present a novel pneumatic actuator design for brain magnetic resonance elastography (MRE). Magnetic resonance elastography is a phase contrast technique capable of tracing strain wave propagation and utilizing this information for the calculation of mechanical properties of materials and living tissues. In MRE experiments, the acoustic waves are generated in a synchronized way with respect to image acquisition, using various types of mechanical actuators. The unique feature of the design is its simplicity and flexibility, which allows reconfiguration of the actuator for different applications ranging from in vivo brain MRE to experiments with phantoms. Phantom and in vivo data are presented to demonstrate actuator performance.     

A hybrid active noise controller for finite ducts

A hybrid active noise controller (ANC) is proposed to solve some existing problems, which are related to the non-minimum phase (NMP) path models between uncollocated sensors and actuators in many ANC systems. For hybrid ANC schemes, the NMP path causes design difficulties to both feedforward and feedback control. These problems can be solved effectively by adding an extra actuator in the ANC system. A new design procedure is presented to take the greatest advantage of the extra actuator. Theoretical analysis and experimental results are presented to show the improved performance of the proposed ANC.     

Motion planning and actuator specialization in the control of active-flexible link robots

Trajectory planning is a well-known open-loop control strategy to minimize residual vibrations in point-to-point tasks of systems featuring mechanical flexibility. However, the major drawback of open-loop control is its limitation in coping with modeling uncertainty. In this paper a novel approach to trajectory planning based on LQR theory is proposed and applied to a single flexible link robot. To improve performance under parameter uncertainty the strategy is combined with collocated vibration control through piezoelectric actuation of the link. This combination raises the issue of the roles and the contribution of each actuator type to the overall performance of the maneuver. An actuator specialization is proposed where the joint controller is responsible for the gross vibrationless motion of the link, while the link actuators are expected to deal only with residual vibrations that may arise from modeling errors. Simulation and experimental results validate the trajectory planning methodology and the combination of the open-loop strategy with collocated vibration control.     

Discrete time transfer matrix method for dynamics of multibody system with real-time control

By taking the control and feedback parameters into account in state vectors, defining new state vectors and deducing new transfer equations and transfer matrices for actuator, controlled element and feedback element, a new method named as the discrete time transfer matrix method for controlled multibody system (CMS) is developed to study dynamics of CMS with real-time control in this paper. This method does not need the global dynamics equations of system. It has the modeling flexibility, low order of system matrix, high computational efficiency, and is efficient for general CMS. Compared with the ordinary dynamics methods, the proposed method has more advantages for dynamics design and real-time control of a complex CMS. Adopting the PID adaptive controller and modal velocity feedback control on PZT actuators, and applying the proposed method and ordinary dynamics method, respectively, the tip trajectory tracking for a flexible manipulator is carried out. Formulations of the method as well as numerical simulation are given to validate the proposed method.     

Active control of a piezo-composite rotating beam using coupled plant dynamics

Optimal control of a thin-walled rotating beam is considered using a higher-order shear deformation theory (HSDT). The beam is pretwisted, doubly tapered, and carries a tip rotor. It comprises an orthotropic host with surface-embedded transversely isotropic piezoelectric sensor-actuator pairs. Spanwise and thicknesswise variation of the electric field applied to actuators is considered. This yields a coupled electro-mechanical system, wherein all displacement variables are coupled via the electric field. Hence, coupling between bending-transverse shear and extension-twist occurs even when the ply angle configuration has circumferentially uniform stiffness. Optimal LQR control with state feedback is used to obtain the control input, i.e., charge density (hence voltage) applied to actuators. Parametric studies involving ply-angle, rotation speeds of beam and rotor, pretwist, taper, rotor mass, and saturation constraint on actuator voltage, are performed. The HSDT yields lowest coupled natural frequencies (as compared to unshearable and first-order shear models) thus providing conservative data, useful for passive and active control designs. The present plant model, with spanwise varying electric field, yields an order-of-magnitude reduction in settling time and control voltage, and lower response, vis-a-vis the decoupled approach.     

一种电磁直线振动装置的动力学分析

本文介绍一种电磁直线振动装置,并对其进行动力学分析,从而得出它的动力学特性,使其对相关行业的应用具有一定的指导意义