A variable reluctance stepping microdynamometer

 A magnetic variable reluctance stepping micromotor fabricated using LIGA processing is described which is integrated with an external planar coupled gear train and electromagnetic brake. Variable mechanical loading of the micromotor through the electrically controlled brake allows dynamometry measurements to be performed. All components are fabricated from electroplated 78 Permalloy. A planar gear coupling is achieved by using involute gear teeth as the salient elements in the rotor. The rotor used for testing has a pitch radius near 500 μm with 180 μm thickness and is complemented with a stator which provides for a step rotation of 2.4°. Coil windings are implemented with assembled spring clip coil forms with 400 turns of 50 AWG magnet wire. Improved coil efficiency is responsible for decreasing the minimum power required for rotor rotation to 52 microWatts. Maximum speeds near 8000 rpm are achieved although stepping action is affected by stepping instabilities which are a function of excitation magnitude and frequency. Calibration of the electromagnetic brake is accomplished with static beam bending measurements and indicates a maximum peripheral rotor output force of 0.6 milliNewton corresponding to an output torque near 0.3 microNewton-meter. Dynamometry measurements indicate a maximum mechanical power output of 20 microWatts. Received: 30 October 1995 / Accepted: 25 January 1996     

A variable reluctance stepping microdynamometer

A magnetic variable reluctance stepping micromotor fabricated using LIGA processing is described which is integrated with an external planar coupled gear train and electromagnetic brake. Variable mechanical loading of the micromotor through the electrically controlled brake allows dynamometry measurements to be performed. All components are fabricated from electroplated 78 Permalloy. A planar gear coupling is achieved by using involute gear teeth as the salient elements in the rotor. The rotor used for testing has a pitch radius near 500 μm with 180 μm thickness and is complemented with a stator which provides for a step rotation of 2.4°. Coil windings are implemented with assembled spring clip coil forms with 400 turns of 50 AWG magnet wire. Improved coil efficiency is responsible for decreasing the minimum power required for rotor rotation to 52 micro Watts. Maximum speeds near 8000 rpm are achieved although stepping action is affected by stepping instabilities which are a function of excitation magnitude and frequency. Calibration of the electromagnetic brake is accomplished with static beam bending measurements and indicates a maximum peripheral rotor output force of 0.6 milliNewton corresponding to an output torque near 0.3 microNewton-meter. Dynamometry measurements indicate a maximum mechanical power output of 20 microWatts. This work was supported in part by the National Science Foundation under grant #ECS-9116566 and additionally by ARPA-DALP contract ONR N00014-93-1-0911. Beamline support at the Synchrotron Radiation Center in Madison, WI was provided by P. Mangat and was funded under the HI-MEMS Alliance TRP/ARPA Technology Development Agreement contract MDA972-94-3-0043. The Synchrotron Radiation Center is supported by the National Science Foundation under grant number DMR-88-21625. Work at Sandia National Laboratories is supported by the United States Department of Energy under contract DE-AC04-94AL85000.     

A new process to fabricate the electromagnetic stepping micromotor using LIGA process and surface sacrificial layer technology

 In this paper, a new process to fabricate an electromagnetic stepping micromotor using surface sacrificial layer technology (SSLT) is illustrated, and the SEM photo of the stepping micromotor is showed. The torque of the stepping micromotor with maximum torque of 60 μNm is directly calculated by using electromagnetics laws and the law of conservation of energy. The stator and the shaft and the rotor of the micromotor with the material of nickel are first all fabricated by normal LIGA process at the same time. The sacrificial layer structure with the material of AZ resist is made on the surface of the rotor by using SSLT. The stator and the shaft are fixed together with copper substrate instead of the old Ti substrate by electroplating. After removing the Ti substrate, PMMA resist and the sacrificial layer structure, the rotor is separated from the stator and new copper substrate, and can rotate on the new substrate driven by magnetic force. The four coils with 300 turns each are wound on iron bars by hand using microscope and stepping motor. The bars are assembled by hand into the stator holes from rear of new copper substrate to form a magnetic circuit with the stator and the rotor. A power supply with four consecutive pulses provides the current for the coils wound on the iron bars and produces the magnetic force to drive the rotor to run with the speed of 60 rpm.     

A fully integrated surface micromachined magnetic microactuatorwith a multilevel meander magnetic core

A fully integrated magnetic microactuator using surface micromachining techniques is presented. To achieve this device, low-resistance meander conductors located in a single plane were interwoven with multilevel meander magnetic cores. This `wrapped' solenoid (with the core wrapped around the conductor) was fabricated in a fully integrated fashion. A magnetic microactuator was realized by incorporating a surface micromachined nickel-iron cantilever beam as part of the magnetic circuit of the core. The nickel-iron cantilever beam was 2.5 μm thick, 25 μm wide, and 780 μm long, and the magnetic circuit contained seventeen turns of meander-type solenoid coils. Cantilever beam tip deflection of 6 μm in the vertical direction was achieved when a DC voltage less than 1 V (and resulting drive current of 800 mA) was applied to the coils. This fully integrated multilevel topology offers advantages in a variety of micromagnetic applications, where actuators can be fabricated on the same substrate with an integrated circuit and actuated with low voltages     

Analytical calculation of the flux density distribution in a superconducting reluctance machine with HTS bulks rotor

This paper deals with the analytical computation of the magnetic field distribution in a wholly superconducting reluctance motor. The rotor is made with high temperature superconductor bulks which nearly present a diamagnetic behavior under zero-field cooling. The stator consists of superconducting armature windings fed by AC currents of high amplitude. The superconducting stator winding can generate a high rotating magnetic field without the need of ferromagnetic material in the rotor. The electromagnetic torque is obtained by the interaction between the rotating magnetic field created by the superconducting stator windings and the variable reluctance due to the superconducting bulks. The proposed analytical method is based on the resolution of Laplace's equation (by the separation of variables method) for each sub-domain, i.e. rotor shaft, holes between superconducting bulks and air-gap. The global solution is obtained using boundary and continuity conditions. Magnetic field distribution and electromagnetic torque obtained by the analytical method are compared with those obtained from finite element analyses.     

实心转子感应电动机高速运转性能分析

分析了实心转子感应电动机的磁路及M-S曲线;采用Ansoft有限元软件对电动机变频启动的动态过程进行仿真,得到了空载启动的磁场分布、定转子电流、启动转矩等动态数据;测试了电动机在高频高速状态下的性能,论证了实心转子感应电动机高速运行的可行性。     

A novel rotor position estimation approach for an 8/6 solid rotor switched reluctance motor

Switched reluctance motor (SRM) is becoming popular due to its simple construction, low manufacturing cost, ruggedness and fault-tolerant capability. In conventional switched reluctance motor (SRM), rotor is laminated. But in solid rotor switched reluctance motor (SRM), rotor is not laminated, and it is suitable for applications where rotors are immersed in water environment. A stationary can arrangement is introduced between stator and rotor. In this research, an 8/6 solid rotor switched reluctance motor which is used in reactivity control mechanisms of nuclear reactors is considered as test motor. As solid rotor switched reluctance motor is suitable for working in water environments in nuclear reactors, rotor position estimation is the topic of interest. A new approach which adopts two-phase excitation method is presented for rotor position estimation. Four different artificial neural networks (ANNs) with 2-5-5-1 structure are trained to estimate rotor position. The main advantage of this approach is to minimize the required number of voltage and current sensors. The validity of the new approach is verified through online comparison of estimated and actual rotor position.     

Advanced LIGA technology for the integration of anelectrostatically controlled bearing in a wobble micromotor

This work concerns the alleviation of friction in a novel design of multistator electrostatic wobble motor. The output torque and the kinematic accuracy of this device are limited by the sliding friction between the rotor and the top surface of the bearing. A solution for an axial bearing has been developed using an advanced LIGA technique to integrate polymethylmethacrylate (PMMA) cylinders into nickel micro structures. A new version of the micromotor has been fabricated, utilizing an axial electrostatic field to hold the rotor against an engineered sliding surface. The integrated bearing stabilizes the rotor and potentially permits operation in liquid environments by sealing the stator electrodes     

Modeling of a synchronous reluctance machine accounting for space harmonics in view of torque ripple minimization

The paper deals with modeling of synchronous reluctance motor (SynRM) accounting for all phenomena responsible for torque ripple. Based on winding function approach, the proposed model consists in computing self and mutual inductances considering no sinusoidal distribution of stator windings, slotting effect and no sinusoidal reluctance variation caused by the rotor saliency. Then, optimal current waveforms are determined for each rotor position by solving a second order equation to reduce torque ripple. These currents are used within a vector control scheme. Satisfactory agreement between simulation and experimental results is obtained.     

六相感应电动机定子间互感电压研究

对六相感应电动机通入梯形波相电流时的定子间瞬时自感、互感系数及互感电压进行了理论计算和有限元分析。计算及分析结果表明:定子侧通入梯形波的六相感应电动机可以模拟直流电动机控制模式;转矩电流对定子每相的感应电压影响非常小,验证了建模与仿真时忽略定子转矩电流和转子感应电流产生的磁效应是合理的。     

Magnetic induction micromachine-part II: fabrication and testing

This paper presents the realization of a magnetic induction machine. The development of this machine is part of an ongoing project to create high-power density electric microgenerators for use in portable-power applications. The results reported here focus on testing a first-generation nonlaminated electromagnetic actuator, a metrology device designed for exploring and characterizing the fabrication process and the operating behavior of the magnetic induction micromachine. Achieving high power density requires large electrical currents and magnetic fluxes, which necessitate thick, multilayered microstructures that are difficult to fabricate. The batch-fabrication schemes developed as part of this work are based on low-temperature micromolding that makes extensive use of various ultra-thick photoresists and electroplating of electrical conductors (Cu) and ferromagnetic materials (Ni-Fe 80%-20%), resulting in the successful fabrication of a multilayer two-phase planar stator and a planar rotor. To evaluate the performance of the complete machine (stator plus rotor), a 4-mm-diameter, 500-/spl mu/m-thick electroplated Ni-Fe rotor is tethered to a series of flexible structures that prevent it from making a complete revolution, but allow accurate torque performance extraction. The tethered induction micromotor studied here exhibits torque production as high as 4.8 /spl mu/N/spl middot/m.     

一种用于异步电机矢量控制的新型滑模转子磁链观测器研究

针对异步电机矢量控制需要实现定、转子电路解耦的一个关键问题是准确地观测转子磁链.提出了一种以异步电机在两相同步旋转坐标系下的定子电流和转子磁链为状态变量的基于滑模变结构思想的转子磁链观测器,对滑模变结构输入控制信号的设计使得滑模运动速度与轨迹和滑模面的距离相关联,并利用李亚普诺夫理论证明了算法的收敛性.通过仿真表明,该方法具有较高的转子磁链观测准确度,对转子电阻的变化具有很强的鲁棒性,能够改善异步电机矢量控制调速系统的动静态性能.     

开关磁阻电机转子位置软测量建模与仿真

位置检测是开关磁阻电机调速系统中的重要环节。实时、准确的位置信息是开关磁阻电机正确运行的关键。由于其转子位置角是各相磁链与电流的高度非线性函数,传统线性及解析的方法难以精确求得。提出了基于BP神经网络的位置检测方法,采用BP神经网络建立软测量模型,通过离线和在线相结合的方法对网络进行训练,建立开关磁阻电机的电流、磁链与转子位置之间的非线性映射,从而实现SRM转子无位置传感器的检测。仿真及实验结果表明,方法能够实现电机转子位置的准确估计,进而实现开关磁阻电机的无位置传感器控制。     

三维多层仿形织造过程多机协同智能控制技术

三维多层仿形织造过程多机同步协同控制是其关键技术之一。本文通过对三维多层仿形织造工艺技术的研究,依据磁场磁链定向控制作用机理,提出了一种对磁场磁链定向和变力矩控制的方法,来分别对多个感应电动机进行速度和力矩跟踪智能控制。依据控制方法,通过建立全维转子状态估计器,来辨识感应电动机的转子速度、定子和转子电阻、瞬时外负载等参数。由外负载辨识结果与速度、力矩PID控制器来确定感应电动机的转矩电流,实现感应电动机速度与力矩控制。仿真实验与三维多层仿形织造工程试验结果表明了该智能控制方法的先进性和实用性。     

A high-power MEMS electric induction motor

An electric induction micromotor with a 4-mm-diameter rotor was designed and built for high-power operation. Operated at partial actuating voltage, the motor has demonstrated an air gap power in excess of 20 mW and torque of 3.5 /spl mu/Nm at speeds in excess of 55 000 rpm. Operation at higher power and speed was limited by bearing stability at higher rotational speeds. The device builds on an earlier micromotor demonstrated by Frechette et al. The high power of the present motor is enabled by its low-loss, high-voltage electric stator, which also offers improved efficiency. The development of this electromechanical device is an important enabling step not only for watt-scale micromotors, but also for the development of microelectric generators. This paper presents the motor's design, the fabrication process that was created to meet its stringent design requirements, and its performance to date.     

双变量交交变频双馈电动机功率因数控制研究

分析了双馈电动机的数学模型,推导出电动机定子侧电流与转子侧电流的关系;采用双变量交交变频器为双馈电动机提供变频励磁电源,并通过控制变频器输出电压的幅值、频率来控制转子侧电流;通过实验研究转子侧电流对双馈电动机定子侧功率因数的影响,得出可以通过控制转子侧电流来调节电动机功率因数的结论。     

变频器非正弦供电对异步电机的影响

介绍变频器非正弦供电对异步电机的影响,分析谐波电压和电流对电机磁路、定子和转子功率因数、电机损耗与效率、谐波转矩、电应力、轴电流产生的危害和如何防止。     

基于定子电流小波变换的感应电机速度估计算法的研究

提出一种基于齿槽谐波检测的转速估计算法。首先对感应电机定子电流进行小波变换,得到谱后再利用脊线检测算法提取瞬时频率,然后根据齿槽谐波频率估计转速。将该算法在感应电机无速度传感器直接转矩控制系统中进行了仿真,仿真结果表明,使用小波变换的估计算法不受电机参数的影响,明显提高了电机的转速估计精度,并且在整个转速范围内有效,从而也解决的了在低速范围内,转速估计精度低的问题。     

Partial state feedback control of induction motors with magnetic saturation: elimination of flux measurements

In this paper, we present a singularity-free, rotor position tracking controller for the full order, nonlinear dynamic model of the induction motor that includes the effects of magnetic saturation. Specifically, by utilizing the π-equivalent saturation model, we design an observer/controller strategy that achieves semi-global exponential rotor position tracking and only requires stator current, rotor velocity, and rotor position measurements. Simulation and experimental results are included to demonstrate the efficacy of the proposed algorithm.     

Permanent magnet micromotors on silicon substrates

Different types of sliding, rolling, or rotating micromotors with rare-earth-based permanent magnet rotors are presented. The magnets move synchronously with rotating or traveling magnetic fields generated by 25-μm-thick gold current lines on silicon substrates. The magnets are guided in channels or openings in the silicon itself or in additional glass layers. For magnets with a typical dimension of 1 mm, forces and torques of 150 μN and 100 nNm could be achieved. Maximum velocities of 24 cm/s and a rotation frequency of 2000 r.p.m. have been measured. Magnetic clamping to the bottom confines the rotor to the system and allows a motor operation at any tilt angle. Noncontact magnetic transmission of forces to drive a ferromagnetic fluid has been demonstrated