Tubular modular permanent-magnet machines equipped with quasi-Halbach magnetized magnets-part II: armature reaction and design optimization

Using the analytical formulas derived in Part I for predicting the magnetic field distribution, thrust force, and electromotive force of a three-phase tubular modular permanent-magnet machine equipped with quasi-Halbach magnetized magnets, this paper analyzes the armature reaction field, and addresses issues that are pertinent to the design optimization of the machine. It shows that optimal values of the ratio of the axial length of the radially magnetized magnets to the pole pitch exist for both maximum force capability and minimum force ripple. The utility and accuracy of the analytical predictions and design optimization technique are demonstrated on a 9-slot/10-pole machine.     

Tubular modular permanent-magnet machines equipped with quasi-Halbach magnetized magnets-part I: magnetic field distribution, EMF, and thrust force

This paper describes the analysis, design, and experimental characterization of three-phase tubular modular permanent-magnet machines equipped with quasi-Halbach magnetized magnets. It identifies feasible slot/pole number combinations and discusses their relative merits. It establishes an analytical expression for the open-circuit magnetic field distribution, formulated in the cylindrical coordinate system. The expression has been verified by finite-element analysis. The analytical solution allows the prediction of the thrust force and electromotive force in closed forms, and provides an effective tool for design optimization, as will be described in Part II of the paper.     

Fringing in tubular permanent-magnet machines: Part I. Magnetic field distribution, flux linkage, and thrust force

This paper extends an analysis developed for tubular permanent-magnet machines to account for the effect of fringing associated with the finite length of the ferromagnetic armature core. The magnetic field distribution, established by using an analytical technique formulated in the cylindrical coordinate system, provides an accurate means of evaluating the effect of the fringing flux on the thrust force and the back-electromotive force. Finite-element calculations confirm the analytically derived results. In Part II of the paper, the analysis is used to predict the cogging force that results from end effects and to facilitate minimization of the force.     

Mechanical behavior of axially magnetized permanent-magnet gears

We studied permanent-magnet (PM) gears with axially magnetized permanent magnets and a plane air gap in terms of mechanical behavior. We determined the torque and forces exerted between the two rotors of these devices, using a seminumerical method based on the calculation of the forces between the magnets of the rotors. The study deals with the general behavior of such devices and presents some very interesting configurations for their mechanical stability     

Influence of an aperture on the performance of a two-degree-of-freedom iron-cored spherical permanent-magnet actuator

This paper describes a computational and experimental study of a two-degree-of-freedom spherical permanent-magnet actuator equipped with an iron stator. In particular, it considers the effect of introducing an aperture in the stator core to facilitate access to the armature. The resultant magnetic field distribution in the region occupied by the stator windings, the net unbalanced radial force, and the resulting reluctance torque are determined by three-dimensional magnetostatic finite-element analysis. The predicted reluctance torque is validated experimentally, and its implications on actuator performance are described.     

Evaluation of superposition technique for calculating cogging torque in permanent-magnet brushless machines

We evaluate the superposition method for calculating the cogging torque in permanent-magnet brushless machines, the resultant torque being synthesized from cogging torque components associated with a pair of magnets. Although finite-element analyses and measurements show that the resultant cogging torque cannot be synthesized directly from the torque components due to a single magnet, we use the concept of a fictitious single magnet to analytically establish the relationship between the cogging torque and key design parameters. The method is particularly useful in assessing the influence of the slot number and pole number combination.     

大型机电驱动系统的优化--现代电子数据处理方法的能力和限制

 大功率特殊电驱动大多数受到技术可行性的限制,它要求持续采用先进的、柔性的计算方法．这种驱动系统的优化前提是在考虑了所实施的设备系统间的各种相互作用后,对过程作出全面的、专业性的评估．讨论在计划和设计大型定制电气驱动时,合理应用高效的电子数据处理方法所面临的机遇和风险．     

Design and performance of a permanent-magnet rotary refrigerator

In order to demonstrate the potential of magnetic refrigeration to provide useful cooling near room temperature, Astronautics Corporation of America constructed a rotary magnetic refrigerator (RMR) in 2001. The RMR uses the active magnetic regenerator (AMR) cycle with an aqueous heat transfer fluid. The required change in magnetic field is produced by the rotation of a wheel packed with porous beds of magnetocaloric material through a 1.5 T Nd₂Fe₁₄B permanent magnet with steel flux concentration poles. A pump, and valves mounted to the wheel, control heat transfer fluid flow through the magnetocaloric beds and heat exchangers. This rotary design allows quiet, reliable operation over a range of frequencies (0.5–4 Hz), heat transfer fluid flow rates and cooling power. The performance of the device using Gd and Gd alloy spherical particles is reported and analyzed. We also describe the performance effects of introducing layered beds and an La(Fe_1−xSi_x)₁₃H_y alloy with a first order magnetic transition.     

碳纤维复合材料传动轴承扭性能优化设计

利用数值模拟分析的方法研究了铺层角度、厚度、顺序以及对称性对碳纤维复合材料传动轴抗扭性能的影响规律。研究发现结构抗扭截面系数在单向铺层方向为接近0°、45°及接近90°时较高,且随着铺层厚度增加而增大;扭转刚度则在40°～70°较好。在接近0°和接近90°铺层间铺设45°铺层能提高零件抗扭性能;与反对称铺层方案相比对称铺层方案更有利于零件承受扭矩。将优化铺层方案应用在某型号风机传动轴的设计中,试验证明能够满足使用要求并达到节约原材料的目的。     

Design and performance of permanent-magnet DC linear motors

Energy-efficient direct linear electric drives are gaining increased attention as a result of continuous developments in high-energy permanent magnets and advances in power electronics and microcontrollers. This paper presents a step-by-step approach to the design of permanent-magnet dc linear motors (PMDCLMs). The problems of armature reaction and saturation of the permeable members of the motor lead to a nonlinear and asymmetric air-gap magnetic flux density as a function of position and, consequently, the static thrust versus position characteristics of PMDCLMs. The paper describes a prototype PMDCLM that reveals these phenomena and presents design concepts aimed at alleviating these problems.     

Fringing in tubular permanent-magnet Machines: part II. Cogging force and its minimization

In Part I of the paper, analytical field solutions, which account for the fringing flux associated with the finite length of the ferromagnetic armature core in tubular permanent-magnet machines, are established. In Part II, the technique is applied to both slotless and slotted machines, and the results are verified by finite-element calculations. The analytical field solutions enable the resultant cogging force associated with the finite length of the armature to be determined as a function of the armature displacement, for both radially and Halbach magnetized stators. Thus, they not only provide an effective means for evaluating the influence of leading design parameters on the cogging force waveform, but also facilitate its minimization.     

SR电机调速系统控制器设计

利用DSP的速度及硬件资源优势,设计了相应的外围检测、电流限幅、倍频、PWM调理等功能电路以及保护电路,使控制系统结构紧凑,可靠性高.实现了系统的电压PWM斩波控制方式下的稳定运行.     

亚波长径向偏振光栅的设计

针对现有电力光学电流传感中法拉第旋转角的非线性测量、解调模式的光强依赖性等问题,本文设计了一种环型亚波长偏振光栅,其光栅矢量径向分布,可将偏振光的偏振分布转化为光斑强度分布并与偏振面同步旋转。应用琼斯矩阵对其偏振特性进行分析,运用严格耦合波理论对光栅进行仿真分析与优化设计,并制备了辐射状的环型铝金属光栅。测试结果表明,光栅TM光的透过率大于80%、整体消光比大于100,可实现对光偏振态的直接检测,并具有线性测量范围大、测量结果不依赖于光的绝对强度等优点,可用于基于图像分析的偏振检测技术。     

Joint optimization of maintenance,buffers and machines in manufacturing lines

This article considers a series manufacturing line composed of several machines separated by intermediate buffers of finite capacity. The goal is to find the optimal number of preventive maintenance actions performed on each machine, the optimal selection of machines and the optimal buffer allocation plan that minimize the total system cost, while providing the desired system throughput level. The mean times between failures of all machines are assumed to increase when applying periodic preventive maintenance. To estimate the production line throughput, a decomposition method is used. The decision variables in the formulated optimal design problem are buffer levels, types of machines and times between preventive maintenance actions. Three heuristic approaches are developed to solve the formulated combinatorial optimization problem. The first heuristic consists of a genetic algorithm, the second is based on the nonlinear threshold accepting metaheuristic and the third is an ant colony system. The proposed heuristics are compared and their efficiency is shown through several numerical examples. It is found that the nonlinear threshold accepting algorithm outperforms the genetic algorithm and ant colony system, while the genetic algorithm provides better results than the ant colony system for longer manufacturing lines.     

Dynamic performance of a brushless DC tubular drive system

The authors describe the computer-aided analysis of the dynamic performance of a tubular linear machine system with permanent magnetic cogging forces. These forces include not only the conventional tooth cogging force apparent in both linear and rotary machines but also a force unique to permanent magnet linear machines that is due to the finite length of the stator. System equations which describe both the machine and the inverter supply are solved by a step-to-step numerical method to find the dynamic performance of the machine in an oscillator mode. The work is verified by experimental results obtained for a practical model     

Simplified direct optimization of tubular truss structures

The general problem of optimum design of trusses composed of tubular elements requires the determination of cross-sectional dimensions for each element which satisfy a set of side constraints on those dimensions as well as Euler and local buckling constraints. A formulation is presented which eliminates the necessity to use mathematical programming methods for the determination of feasible cross-sectional dimensions. The minimization problem is shown to be expressible in terms of area variables only, with each area subject to bounds which are functions of truss stiffness but which may be obtained by explicit analysis of the element ‘desing space’ for any design. This‘direct’ formulation is completely general and compatible with any minimization algorithm. The formulation also leads to a simple and efficient recursive procedure for producing near-optimal fully-constrained designs. Several examples illustrate results obtained by both the direct and recursive procedures.     

Eddy-current loss in the rotor magnets of permanent-magnet brushless machines having a fractional number of slots per pole

We develop an analytical model for predicting the eddy-current loss in the rotor magnets of permanent-magnet brushless machines that have a fractional number of slots per pole, when either all the teeth or only alternate teeth are wound, and in which the unwound teeth may be narrower than the wound teeth. The model enables the magnetic field distribution in the air gap and magnet regions to be determined, by neglecting the eddy-current redistribution effect and assuming that the eddy currents are resistance limited. It can account for space-harmonic magnetomotive forces (MMFs) resulting from the winding distribution and time-harmonic MMFs due to nonsinusoidal phase currents, as well as for the effect of curvature and circumferential segmentation of the magnets. We have validated the model by finite-element analysis, and used it to investigate the eddy-current loss in the magnets of three surface-mounted magnet brushless motors that have similar slot and pole numbers, and employ identical rotors but different stators, when they are operated in brushless ac (BLAC) and dc (BLDC) modes. We show that the stator winding configuration, as well as the operational mode, significantly influence the resultant eddy-current loss.     

Multiobjective design optimization of air-core linear permanent-magnet synchronous motors for improved thrust and low magnet consumption

Although air-core linear permanent-magnet (PM) synchronous motors are widely used in precision applications because of their advantages such as fast dynamics, lack of detent force, and negligible iron loss, they basically suffer from low developed thrust, thrust ripple, and excessive use of permanent-magnet materials, all of which lead to undesirable performance and high production cost. In this paper, we analyze performance characteristics of an air-core linear PM synchronous motor by varying motor design parameters in a layer model and a d-q model of the machine. We propose a multiobjective design optimization to improve thrust, thrust ripple, and consumed magnet volume independently and simultaneously by defining a flexible objective function. A genetic algorithm is employed to search for optimal designs. The results confirm that desirable thrust mean and substantial reduction in magnet volume and thrust ripple can be achieved. We draw several design conclusions from the motor analysis and design optimization. Finally, we carry out a time-stepping finite-element analysis to evaluate the effectiveness of the machine models and the optimization method.