超精密大行程麦克斯韦磁阻驱动器磁场建模与推力分析

为了克服大行程麦克斯韦磁阻驱动器在大气隙下漏磁大幅增加、气隙区磁场分布不均匀且非线性强烈等现象导致的磁场和推力解析模型精度较低等问题,利用考虑综合高斯函数的加权漏磁系数的磁路建模方法,改进了磁阻驱动器的三维漏磁分布计算方式,并得到了可准确描述其推力与输入电流函数关系的解析模型,从而为该类驱动器的设计及控制提供重要依据。首先,建立了大行程麦克斯韦磁阻驱动器考虑漏磁前后的工作磁路,分析了永磁偏置磁路的作用及使用永磁偏置结构后仍具有非线性的原因,并利用安培环路定律和磁路的欧姆定律以及磁场的可叠加性,建立了该磁阻驱动器的推力解析模型。然后,为了优化解析模型,提出了基于高斯曲线的加权漏磁系数计算方法,同时利用有限元仿真软件对大行程麦克斯韦磁阻驱动器的三维磁场分布及漏磁系数进行了分析计算,得到了考虑加权漏磁系数的推力解析模型。最后,搭建了大行程麦克斯韦磁阻驱动器推力测试系统,并通过对比优化前后解析模型计算推力与仿真推力和实测推力,验证了解析模型的准确性。结果表明,优化后解析模型的均方根误差仅为优化前的11.1%,其精度得到有效提升;同时,优化后解析模型计算推力与实测推力之间的均方根误差小于0.6 N,精度较高。研究结果对高端微纳制造装备与测量仪器中新型超精密驱动部件的设计有一定意义和参考价值。     

Field-Circuit Hybrid Method for Magnetic Actuator Using a Laminate Composite

The magnetic actuator using a laminate composite of piezoelectric (PZT) and magnetostrictive materials (MM) achieves active control of magnetic force without Joule heat loss. To study its characteristics, the field-circuit hybrid method is proposed based on the equivalent magnetic circuit and the finite element analysis (FEA) of piezoelectric and magnetic fields. The strain of laminate composite under different voltage is obtained through the piezoelectric FEA. On the basis of magnetostrictive equation, the MM branch in the magnetic circuit of the actuator is transformed equivalently, the work point of the actuator is determined, and the corresponding FEA model of magnetic analysis is then set up. The relationships between magnetic force, gap, and voltage are discussed by the hybrid method, which can be expanded into the design and analysis of the magnetostrictive actuator and sensor to improve simulation efficiency and precision.      

一种新型隔振器的设计与分析

针对传统被动隔振器低频振动抑制性差的缺陷,设计了一种新型的电磁-橡胶主被动一体化隔振器,通过研究输出力特性来评估其减振性能,首先,利用等效磁路分析法对其磁路结构进行设计仿真以及动力学分析,并得到其电磁力计算公式。然后,基于COMSOL软件对作动器的输出力进行动态仿真分析,并得到电流及其频率对输出力特性的影响,最后,将特性实验结果与仿真结果进行对比分析。     

Magnetic force control based on the inverse magnetostrictive effect

We describe a novel magnetic force control method. The method employs a mechanical stress applied to a magnetostrictive material to control the attractive force between fixed and movable members of a magnetic circuit that includes a permanent magnet. The method has the advantage over electromagnet control that a constant force can be maintained without energy consumption. We discuss the variation of the magnetic force with compression of several magnetostrictive materials. The experimental results agree with theoretical predictions of magnetic force based on analysis of an equivalent magnetic circuit and the piezomagnetic properties of the magnetostrictive materials.     

Novel high-response electromagnetic actuator for electronic engraving system

We describe a new moving-iron electromagnetic actuator that utilizes cantilever-beam-type springs, /spl pi/ type armature, full-bridge magnetic circuits, and a single driving coil. The actuator is suitable for electromechanical converters with high response and minor displacement for use in electronic engraving systems. We analyzed its static and dynamic characteristics by using a three-dimensional finite-element method. We used a simple and practical measuring method based on light reflection to detect the actuator's real hysteresis loop and amplitude frequency response characteristics. The results show that the actuator has a displacement of /spl plusmn/65 /spl mu/m, hysteresis of less than 5.5%, and amplitude cutoff frequency of 3.1 kHz. We tested the actuator on a real engraving system and confirmed its characteristics by the engraving results.     

Analytic model for a nonlaminated cylindrical magnetic actuator including eddy currents

The eddy currents induced within a nonlaminated cylindrical magnetic actuator by a changing field have a fundamental influence on the actuator's performance. Understanding of these dynamics is essential in designing high-performance actuators and developing control algorithms for them. This paper presents an analytical approach to modeling the relationship between applied magnetomotive force and mechanical force. The approach is based on dividing the actuator into elements according to the flux distribution inside the actuator and finding the frequency-dependent reluctance of the flux paths of each element. An analytic model and its half-order simplification are derived, both of which are explicitly dependent on actuator material and geometric properties. Performance predictions from both analytic models are compared with finite-element analysis, demonstrating the accuracy of the models.     

A Miniature Short Stroke Linear Actuator—Design and Analysis

We report a newly developed miniature short stroke tubular linear permanent-magnet actuator for robotic applications. Compared to a rotary-to-linear mechanism, the linear actuator has the advantages of efficiency, thrust control, and compact size in generating linear motion. We optimized the electromagnetic force of the actuator analytically by selecting appropriate dimensions and then predicted the force produced by the winding currents by the finite-element method under the brushless dc excitation scheme. We analyzed the actuation performance by dynamic modeling of the actuator. We constructed and tested a prototype on a specially designed test bench to verify the design. Finally, we analyzed and measured the end effect on the magnetic force due to the limited length of the stator core and translator.     

Actuator gains for a toothless permanent-magnet self-bearing motor

Permanent-magnet self-bearing motors provide independent bearing and motoring functionality in a single magnetic actuator. Typically, self-bearing motor designs use toothed stators to provide minimum reluctance flux paths that create the magnetic bearing forces necessary to support the rotor. These toothed designs can have significant cogging torque, rendering them ineffective for smooth torque applications such as those found in aerospace. A toothless permanent-magnet self-bearing motor can provide smooth torque production and adequate bearing force for low-gravity environments. Characterization of the open-loop gains for this actuator is necessary for linear controller development. In this paper simple algebraic equations are derived for the motoring and bearing current gains, and an analytical method is presented for computing the negative stiffness. The analytical method solves the Dirichlet boundary value problem (BVP) in the eccentric annulus for the magnetomotive force (MMF) in the air gap subject to harmonic boundary conditions. A conformal transformation to bipolar coordinates is used, yielding a BVP that is solvable by separation of variables. Expressions for the flux density, Maxwell force on the rotor, and the negative stiffness in terms of the MMF are presented. A sample problem is presented that illustrates the flux distribution in the air gap and the operating principals of this actuator type     

Magnetic force control with composite of giant magnetostrictive and piezoelectric materials

We propose a new magnetic force control device, composed of a giant magnetostrictive material (Terfenol-D) and a piezoelectric material (PZT), for coilless magnetic force control. The device uses the inverse magnetostrictive effect, whereby the variation of magnetization of a Terfenol-D rod controlled by PZT is converted to the variation of magnetic force by a magnetic circuit. Because PZT is electrically capacitive, the method has the advantage of low power consumption and low heat generation in static operation. We have fabricated several devices with different geometrical shapes of the rods and magnetic yokes, and we describe their characteristics such as power consumption, heat generation, and response. We discuss a magnetic circuit design strategy that uses the /spl Delta/E effect in magnetostrictive materials to increase the energy conversion efficiency.     

Simplified unipolar, quasisquare wave energy recovery drive circuits for piezoelectric actuators

A simple two-switch circuit for driving piezoelectric actuators with unipolar quasisquare waves is presented. The circuit provides for recovery of the energy stored on the actuator capacitance back to the primary power supply when the actuator is de-energized.     

轮带系统横向振动变结构控制方法

针对由主从动轮、作动器及皮带构成的典型轮带系统模型,皮带横向振动与主、从动轮及作动器振动相耦合,其横向位移受主、从动轮及作动器影响,给出皮带在谐波激励下横向振动位移精确表达式,利用变结构理论,采用指数趋近律设计出有效控制力以控制张紧臂方向,从而抑制皮带横向振动。在初始条件和与激励作用下,利用Matlab进行数值仿真。结果表明：在谐波激励下,皮带横向振动位移得到有效抑制,验证控制力的有效性。     

Frequency Dependent Strain-Field Hysteresis Model for Ferromagnetic Shape Memory Ni–Mn–Ga

We quantify the relationship between magnetic fields and strains in dynamic Ni-Mn-Ga actuators. As a result of magnetic field diffusion and structural actuator dynamics, the strain-field relationship changes significantly relative to the quasistatic response as the magnetic field frequency increases. We model the magnitude and phase of the magnetic field inside a Ni-Mn-Ga sample as a 1-D magnetic diffusion problem with applied dynamic fields known on the surface of the sample, from which we calculate an averaged or effective field. We use a continuum thermodynamics constitutive model to quantify the hysteretic response of the martensite volume fraction due to this effective magnetic field. We postulate that the evolution of volume fractions with effective field exhibits a zero-order response. To quantify the dynamic strain output, we represent the actuator as a lumped-parameter, single-degree-of-freedom resonator with force input dictated by the twin-variant volume fraction. This results in a second-order, linear ordinary differential equation whose periodic force input is expressed as a summation of Fourier series terms. The total dynamic strain output is obtained by superposition of strain solutions due to each harmonic force input. The model accurately describes experimental measurements at frequencies up to 250 Hz.     

超磁致伸缩棒磁场强度建模及线圈优化分析

超磁致伸缩棒上的磁场强度对超磁致伸缩致动器(GMA)至关重要,因其幅值和上升、下降时间直接影响致动器的输出力和响应时间.建立电压到磁场强度的模型,并提出较合理的线圈优化方案.将线圈充、放电过程简化为一阶RL线性电路的暂态过程,计算得到线圈电流,并根据线圈电流建立超磁致伸缩棒上的磁场强度模型.由模型可知,致动器尺寸有限制时,棒上磁场强度的优化应主要考虑线圈匝数;通过分析线圈匝数对磁场强度稳态值、上升时间和下降时间的影响确定匝数的取值范围.向线圈施加不同频率和幅值的方波电压信号,得到的模型曲线与测得的实验结果相吻合,从而验证了模型的正确性.     

Crosslinking Metal Nanoparticles into the Polymer Backbone of Hydrogels Enables Preparation of Soft,Magnetic Field‐Driven Actuators with Muscle‐Like Flexibility

The combination of force and flexibility is at the core of biomechanics and enables virtually all body movements in living organisms. In sharp contrast, presently used machines are based on rigid, linear (cylinders) or circular (rotator in an electrical engine) geometries. As a potential bioinspired alternative, magnetic elastomers can be realized through dispersion of micro‐ or nanoparticles in polymer matrices and have attracted significant interest as soft actuators in artificial organs, implants, and devices for controlled drug delivery. At present, magnetic particle loss and limited actuator strength have restricted the use of such materials to niche applications. We describe the direct incorporation of metal nanoparticles into the backbone of a hydrogel and application as an ultra‐flexible, yet strong magnetic actuator. Covalent bonding of the particles prevents metal loss or leaching. Since metals have a far higher saturation magnetization and higher density than oxides, the resulting increased force/volume ratio afforded significantly stronger magnetic actuators with high mechanical stability, elasticity, and shape memory effect.     

A new algorithm for coupled solutions of electric, magnetic andmechanical systems in dynamic simulation of solenoid actuators

An algorithm is presented for the simultaneous solutions of the coupled electric, magnetic, and mechanical problems in the dynamic simulation of a solenoid actuator. The transient nonlinear field in the coupled problem is analyzed using the finite-element (FE) method, which considers the effects of saturation, eddy current, and armature movement in the actuator. The nonlinear electronic circuit is represented by equivalent circuit equations that are coupled to the FE equations and are solved simultaneously with them in an iterative manner. Dynamic responses of the solenoid actuator predicted by using this algorithm agree closely with experimental results. The advantage of this method is that its principle is applicable to general types of power electronic devices. With suitable modifications, it can be used to simulate the dynamic responses of power-electronic-controlled electric machines     

Design of a permanent magnetic circuit with air gap in a magnetic refrigerator

We calculate the magnetic field distribution of a permanent magnetic circuit with an air gap in a magnetic refrigerator by a finite-element method, and compare the field strengths of different structural parameters of the magnetic circuit. We show how the structure of the magnetic circuit can be optimized and present some approaches to improve the structure for a specific magnetic circuit. The main purpose is to provide basic parameters for the design of a practical magnetic refrigerator.     

Fault tolerance of magnetic bearings by generalized bias currentlinearization

The mathematical basis for bias linearization of quadratic magnetic actuators, as typified by magnetic bearings, is developed. The approach generalizes prior ad hoc methods of linearizing the relationship between actuator force and electromagnet current, obviating the earlier assumptions of stator symmetry. This relationship is fundamentally quadratic in the regime where the magnetic material is unsaturated and flux is essentially proportional to magnet current. Growing from the properties of a fundamental representation for the current-force relationships in magnetic bearings, conditions are determined under which linearization may be possible. A numerical optimization problem is posed whose solution provides a linearization scheme which maximizes the available force capacity of the actuator. A corollary result is a method for obtaining coil-fault tolerance in magnetic bearings without adding coils to existing actuators. Several paper examples are presented to illustrate linearization of asymmetric actuators, actuators with failed coils, and force/moment actuators     

A simple dynamic model for eddy currents in a magnetic actuator

This paper presents a simple dynamic model of eddy currents in a magnetic actuator. The model is based on the application of Maxwell's equations to a homogeneous ferromagnetic conductive material. The resulting diffusion equation is solved in two dimensions for a cross-sectional cut through a rectangular bar; boundary conditions are imposed by a sinusoidally varying actuator coil current. The utility of the new modeling approach is illustrated by predicting the dynamic performance of a magnetic bearing actuator. The predictions are found to be in good agreement with measured values. The model provides a new and convenient method of modeling the relationships among voltage, current, force, and flux in magnetic circuits containing eddy currents     

一种降低微结构瞬态响应的方法

研究了机械结构的动力学快速减振方法。以硬盘读写头动臂为例，分析了其受驱动力激振后的瞬态响应。在其指导下，选择了作用力的作用时间和波形：该作用力的作用时间T应为机械结构一阶固有频率对应周期的2倍，且为关于T／2奇对称的单周期波形。通过实验，证明了这样的作用力可以有效减小系统的残余振动，实现快速减振。此方法可以引申到一般应用场合。     

厚膜永磁阵列微致动器的磁路研究

研究了厚膜永磁阵列微致动器中的磁场分布，并研究了永磁阵列单元几何尺寸对微致动器电磁力的影响。结果表明，厚膜永磁阵列单元高宽比和磁体单元间隔对微致动器电磁力影响较大磁徕单元高宽比为0．7是一个比较合适的尺寸。