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.     

CADSTEP: Computer-aided design of variable reluctance stepping motors

This paper describes a computer program package, called CADSTEP, for designing variable reluctance stepping motors. The performance specifications like stepping angle, stepping rate, output torque, number of phases, switching sequence, and saturation flux density, etc. form the inputs to the program. The program computes and prints out the dimensions of the motor from which manufacturing drawings may be prepared and the motor manufactured. The program is based on the step-by-step design procedure which in turn, has evolved from the general theory of variable reluctance stepping motors. This is the first time that such computer aided design program for VR stepping motors is being reported. The flow-chart for the program is given.     

Design and simulation of an asymmetric variable reluctance stepping millimotor

A pancake-shaped step motor, which has a geometry with an axial dimension that is much smaller than the radius, was designed and built using a combination of conventional and LIGA-based fabrication methods. Preliminary open loop dynamic testing indicated that the motor rotated normally as designed, but some abnormal phenomena were also observed at certain input frequencies. A simple model was developed to simulate the dynamic behavior of the rotor. The simulation results match the trend of abnormal behavior observed in the test. They indicate that a reliable open-loop operation is feasible for a wide range of operating frequencies.We would like to acknowledge the fabrication, testing, and other assistance of A. A. Jojola, V. E. Lucero, B. G. Carlen, T. R. Christenson, W. D. Bonivert, M. A. Bankert, J. T. Hachman, D. R. Boehme, A. M. Morales and J. M. Hruby. Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Dept. of Energy under Contract DE-AC04-94AL85000.     

A planar variable reluctance magnetic micromotor with fullyintegrated stator and coils

A fully functional electrically excited planar variable reluctance magnetic micromotor has been demonstrated on a silicon wafer. The motor uses a micromachined nickel-iron rotor and a fully integrated stator, in which a toroidal-meander type integrated inductive component is used for flux generations. To reduce the magnetic reluctance in the stator, a modified stator geometry was adopted which removes the yoke used in a conventional magnetic variable reluctance motor. Using polyimide as both an integral structural material as well as an electroplating mold, a 40-μm-thick nickel-iron rotor 500 μm in diameter was microassembled onto a fully integrated nickel-iron stator 120 μm in thickness. When 500 mA of current was applied to each stator, 12° of rotation (1 stroke in this motor) was observed. By applying three phase 200-mA current pulses to the stators, rotation of the rotor was observed. The speed and direction of the rotation could be adjusted by changing the frequency and phase firing order of the power supply, respectively. Continuous rotor rotation was observed at speeds up to 500 rpm; this speed limitation was solely due to the limitation of the maximum frequency of the controller used. The micromotor could be reproducibly started, stopped, reversed, and continuously rotated. The predicted torque for the fabricated micromotor at 500-mA driving current was calculated to be 3.3 nN-m     

Static and dynamic sliding mode control of variable reluctance motors

In this paper, static and a dynamic sliding mode control schemes are proposed for the speed control of a variable reluctance motor (VRM). The proposed controllers guarantee the asymptotic regulation of the speed of the motor to its desired value. Simulation results of the proposed controllers are given to illustrate the developed theory. In addition, the robustness of the proposed sliding mode controllers to changes in the parameters of the motor and to load disturbances is validated through simulation studies.     

Feedback linearizing and sliding mode control of a variable reluctance motor

Direct-drive connection of electric motors represents a suitable solution to friction and backlash problems introduced by mechanical reduction gears. Variable reluctance (VR) are a special type of switched reluctance motors whose construction is well suited for direct-drive connection. Although these motors are traditionally conceived as stepper motors, continuous motion can be obtained by implementing suitable closed-loop control in the drive. The authors' main aim is to design a high-performance robust controller for a VR motor intended for velocity trajectory tracking in robotics applications where continuous motion is required. A cascade controller structure (velocity-torque) is considered. In the design of the torque controller, both feedback linearizing and sliding mode techniques are considered. Feedback linearization performs slightly better in the ideal case, but under more realistic operating conditions the sliding mode controller demonstrates comparable or even better performance. A very simple but extremely robust velocity controller is designed using a dynamic sliding mode approach, ensuring robustness to large variations of load torque and inertia, typical of direct-drive robotics applications. A simulation experiment of the overall controller with the motor connected to a single link robotic arm shows very good tracking properties as well as insensitivity to large variations of load torque and inertia.     

A novel reluctance actuator employing an embedded ferromagnetic foil

In this paper we present a reluctance actuator which contains laser cut ferromagnetic structures for flux guidance made of Mumetal foil. By means of analytic calculations and numeric simulations it is shown that much higher magnetic forces are achievable by using the Mumetal foil compared to electroplated ferromagnetic alloys like nickel–iron. Furthermore, the processing of such foils and the integration of foil structures into the actuator are described.     

步进式加热炉步进装置的电气控制

加热炉在轧钢生产线中广泛应用,它是轧钢工艺的前部工序。步进装置的控制是加热炉电气控制中最为重要的一环。文章以北方某钢厂的2300mm热连轧生产线的节能型组合蓄热步进梁式板坯加热炉改造工程为例,阐述如何更为有效的对步进装置进行控制以满足高产、优质、低耗、节能和无公害及生产操作自动化程度高的工艺要求。     

A note on a norm-preserving continuous Galerkin time stepping scheme

In this note we shall devise a variable-order continuous Galerkin time stepping method which is especially geared towards norm-preserving dynamical systems. In addition, we will provide an a posteriori estimate for the \(L^\infty \)-error.     

一种基于直线开关磁阻电机的太阳跟踪系统设计

本文提出了一个采用直线开关磁阻电机作为伺服机构的新颖的太阳跟踪系统. 同时也提出了三种控制器配置方案以满足不同需要. 按照电磁和机械特性, 该太阳跟踪系统可分解为一个电磁子系统和一个机械子系统. 整个系统的控制器采用级联控制结构, 分别对这两个子系统设计控制器. 仿真结果表明了其建模方法和控制器设计的有效性.     

一种开关磁阻电动机功率变换器故障诊断方法

针对现有开关磁阻电动机功率变换器故障诊断方法存在可靠性不高等问题,提出了一种新型的功率管故障诊断方法。该方法以不对称半桥型功率变换器主电路为研究对象,以常见的功率管开路和短路2种故障情况为诊断对象,通过比较母线电流估算值和实测值来判断故障,结合故障相绕组电流实现故障相的识别,必要时通过中断测试来确定故障点。选取电动机空载、低速度和高速度运行等较难实现故障诊断的工况进行了试验分析,结果表明,该方法均能完成故障类型的定性及故障点的准确定位。     

A new stepping design method and its application in chaotic systems

This paper proposes a new stepping design method for a class of nonlinear systems. Based on this technique, system design is simplified greatly because many coupled nonlinear items can be considered as zero items. This method can be applied to a general class of nonlinear systems. Significantly, we have demonstrated this technique in some chaotic systems and have achieved good results. Simulation results for the Genesio chaotic system are provided to illustrate the effectiveness of the proposed scheme. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Extra stepping stone for testing

As the relatively young profession of software testing graduallymatures, certification is changing to keep up. ISEB has justupdated the content and structure of its practitioner leveland added a stepping stone to reach that standard, as HelenBoddy reports.     

Applications of the closed-loop stepping motor

This paper describes a bang-bang controller which, with a particular novel scheme of discrete-state variable instrumentation, operates the stepping motor as a digital servo. The near time-optimal servomechanism is designed on a second-order basis, and the rather coarse staircase approximation of the switching curve yields good results. All control circuits have been implemented with integrated circuit components. The entire package has been product tested in the field.     

A multiple electrostatic electrodes torsion micromirror device with linear stepping angle effect

Torsion micromirror devices that can achieve linear stepping angle effects play an important role in optical MEMS applications. However, traditional torsion micromirror devices driven by a single electrostatic electrode have difficulty meeting this requirement due to their nonlinear angle-voltage transfer characteristics. In this regard, the concept of a multiple-electrodecontrolled micromirror is proposed to eliminate this drawback. Through this novel design, linear stepping angles can be easily achieved by a set of linearly varied or constantly applied voltages. A simple mathematical model has been developed to predict the angle-voltage transfer characteristics of the proposed device and has been simulated with finite element simulations. The corresponding control strategies of this device, named the linear control strategy and the digital control strategy, are also proposed in this paper. The Cronos/MEMSCAP Multi-User MEMS Process (MUMPs) was used in conjunction with flip-chip bonding technology to fabricate the proposed torsion micromirror device. Experimental data indicates that the relative stepping angle error, between the fabricated device and the mathematical model, are within 5%.     

Some stepping stones in computer forensics

“Well what are we going to do with this lot?” The “lot” that my team at the Computer Crime Unit (CCU) at New Scotland Yard were looking at comprised of bits of computer parts just shipped from Nairobi by the Kenyan Police. Bundles of metal covered in bubble-wrap; this was the evidence of a serious attack on computer systems around the world, and to be honest we were not sure what to do next. It was the box and component parts from a PC that could have been used by a suspect. We put all the component parts back together, turned on the power supply, and, surprise, surprise — nothing happened. This will look good in Court, we could more or less write the brief for any future defence counsel ourselves. “Officer, are you trying to tell the Court that you obtained this evidence from a computer that was operating normally?” Worse, this was not the only evidence due to arrive from other countries. Even worse, reports of system failure were arriving by the hour from medical establishments in the UK and other sites around the world; the press and media were bombarding us for information; the senior bods at the Yard wanted answers and we still did not have a clue who the perpetrator was or how to analyse his program.     

Feedback linearizing control of switched reluctance motors

Motivated by technological advances in power electronics and signal processing, and by the interest in using direct drives for robot manipulators, we investigate the control problem of high-performance drives for switched reluctance motors (SRM's). SRM's are quite simple, low cost, and reliable motors as compared to the widely used dc motors. However, the SRM presents a coupled nonlinear multivariable control structure which calls for complex nonlinear control design in order to achieve high dynamic performances. We first develop a detailed nonlinear model which matches experimental data and establish an electronic commutation strategy. Then, on the basis of recent nonlinear control techniques, we design a state feedback control algorithm which compensates for all the nonlinearities and decouples the effect of stator phase currents in the torque production. The position dependent logic of the electronic commutator assigns control authority to one phase, which controls the motion, while the remaining phase currents are forced to decay to zero. Simulations for a direct drive, single link manipulator with the SRM are reported, which show the control performance of the algorithm we propose in nominal conditions and test its robustness versus the most critical parameter uncertainties of payload mass and stator resistance.     

开关磁阻电机设计程序与实现

在对SR电机的设计技术进行分析研究的基础上,利用VC++6.0语言编制了SR电机的设计与仿真程序,对该程序的系统结构,设计思路,功能模块进行了阐述,并给出了实例样机的算例,其结果与实际基本吻合。     

步进电机控制系统

步进电机是一种将脉冲信号转换为相应角位移的执行元件。它广泛应用于单片机控制系统。本文主要介绍了采用单片机80C196KC根据1－5V的控制信号来控制步进电机转角的一种方法，包括其硬件设计和软件设计。