An Analytical Circuit Model of Switched Reluctance Motors

We have developed a dynamic analytical circuit model to simulate the performance of switched reluctance motors (SRMs). Our model expresses flux linkages as multiple decoupled one-argument functions, either current dependent or rotor position dependent, instead of one two-argument function dependent on both current and rotor position. We propose a novel approach for the computation of the air gap permeance at various rotor positions. By using this analytical model, the performance of a SRM can be simulated very efficiently and with improved accuracy. As an application example, we present a simulation of an 8/6 pole SRM in the system domain, and compare the results with transient finite element analysis (FEA) solutions.      

Measurement and Real-Time Modeling of Inductance and Flux Linkage in Switched Reluctance Motors

This paper presents a real-time model to identify the inductance and the flux linkage of switched reluctance motors (SRMs). A dynamic measurement method is used for the real-time modeling. An artificial neural network (ANN), designed in accordance with the inductance and the flux linkage data obtained from the dynamic measurement method, is used to make the real-time model. Experimental studies are realized to prove the applicability of the dynamic measurement method and the ANN-based model. The experiments are performed by using a TMS320F2812 digital signal processor (DSP). The results show that the dynamic measurement method and the ANN-based model ensure real values in all the positions and load conditions of the motor.      

基于逆系统理论的无轴承永磁同步电机解耦控制研究

应用多变量非线性控制逆系统理论，对无轴承永磁同步电机的多变量、非线性、强耦合的控制对象进行了动态解耦控制研究；介绍了逆系统理论，阐述了无轴承永磁同步电机径向力的产生机理，建立了转矩力和径向悬浮力状态方程，分析了基于逆系统理论解耦控制的可行性，推导出基于逆系统理论的无轴承永磁同步电机转矩力与径向力之间的动态解耦控制算法。仿真结果表明，这种控制策略能够实现转矩力与径向力之间的动态解耦，并且系统具有良好的动、静态性能。     

Analytical Prediction of Cogging Torque in Surface-Mounted Permanent-Magnet Motors

We present a new approach to computing cogging torque based on only one analytical field solution in surface-mounted permanent-magnet (PM) motors. We use conformal transformation to compute the magnetic field created by the permanent magnets in the air gap with a single slot. Then, we derive the cogging torque due to the single-slot effect at different rotor positions directly from the 2-D analytical field solution. The total cogging torque is synthesized from the contribution of each slot. We have applied our approach to predicting the cogging torque of two surface-mounted PM motors, one with 4 poles, 24 slots and the other with 42 poles, 36 slots. The predicted cogging torques for both applications agree well with those obtained from 2-D finite-element analysis.      

Design of Electrical Rotating Machines by Associating Deterministic Global Optimization Algorithm With Combinatorial Analytical and Numerical Models

This paper presents a new methodology of design of electrical rotating machines. The methodology is an extension of previous works of the second author. Indeed, associating combinatorial analytical models with exact global optimization algorithms leads to rational solutions of predesign. These solutions need to be validated by a numerical tool (using a finite-element method) before the expansive phase of hand-making a prototype. Such an automatic numerical tool for computing some characteristic values, such as the torque, was previously developed. The idea of this paper is to extend the exact global optimization algorithm by inserting the direct use of this automatic numerical tool. This new methodology makes it possible to solve design problems more rationally. Some numerical examples validate the usefulness of this new approach.     

Performance Analysis of Linear Permanent-Magnet Motors With Finite-Element Analysis

This paper presents models for finite-element analyses and design of linear permanent-magnet motors (LPMMs) with surface-mounted or interior-buried permanent magnets (PMs). Several different models are studied in order to compare and discuss different LPMM structures. Using an analytical model of LPMMs, equations for thrust are derived. Then, we used 2-D finite-element analysis to illustrate the performance variation of LPMMs caused by the variation of structure parameters. Computer simulation results show that the characteristics and dimensions of the PMs, the shapes and dimensions of the armature, and the exciting current all have significant effects on motor performance. Several design examples based on the effects of these parameters demonstrate the design of the LPMMs. The design consideration presented in this paper can be used to determine preliminary LPMM mechanical structures before hardware implementation.     

Analytical Interpretation and Quantification of Rotational Losses in Stator Cores of Induction Motors

We propose an approach to allocate and delimit a region in which the rotational losses are of most importance in the stator core of induction motors. The delimitation is based on the analysis of points at which the minimum flux density is not null. The analysis of flux paths and values of flux density over a number of motors allows a model of flux density to be proposed for the chosen rotational region. We conducted the process by post-processing finite-element results. A comparison with bench test results shows that the approach can confine the effects of rotational losses within a region allocated in the tooth roots without significant loss of accuracy. We give analytical expressions based on geometrical data. The approach provides a quick method to evaluate the rotational losses by analytical means, bypassing the use of numerical methods at those design stages at which is preferable to reduce the accuracy in favor of computational speed.     

Analytical Models for the Performance of von Neumann Multiplexing

As conventional silicon CMOS technology continues to shrink, logic circuits are increasingly subject to errors induced by electrical noise. In addition, device reliability will become a problem, and circuits will be subject to permanent faults. Rather than requiring the circuit to be defect-free, fault-tolerance techniques can be incorporated to allow the continued operation of these devices in the presence of defects. We present an improved model for the reliability of nand multiplexing, a fault-tolerance technique typically requiring large levels of redundancy. It extends previous models to account for dependence between the inputs and derives the distribution of the outputs of each stage when subject to errors. The Markov chain approach used in earlier models is shown to be correct in modeling the effect of multiple stages. Our new model produces more accurate results for moderate levels of redundancy. An example shows the required hardware redundancy is reduced by 50% versus the previous binomial model. In addition, three new types of errors are modeled: the output stuck-at-one, output stuck-at-zero, and input stuck-at-zero faults     

Analytical Solutions to Models of Local Nonequilibrium Heat Transfer

High Temperature - A series of boundary-value problems of local nonequilibrium heat transfer is considered in terms of the theory of transient heat conduction for hyperbolic-type equations (wave...     

Emulation of Numerical Models With Over-Specified Basis Functions

Mathematical models are frequently used to explore physical systems, but can be computationally expensive to evaluate. In such settings, an emulator is used as a surrogate. In this work, we propose a basis-function approach for computer model emulation. To combine field observations with a collection of runs from the numerical model, we use the proposed emulator within the Kennedy-O’Hagan framework of model calibration. A novel feature of the approach is the use of an over-specified set of basis functions where number of bases used and their inclusion probabilities are treated as unknown quantities. The new approach is found to have smaller predictive uncertainty and computational efficiency than the standard Gaussian process approach to emulation and calibration. Along with several simulation examples focusing on different model characteristics, we also use the method to analyze a dataset on laboratory experiments related to astrophysics.     

Numerical Simulation of Photothermal Lens Spectrometry Models Relevant for Analytical Chemistry

Three numerical models (radial symmetry two-dimensional and three-dimensional with cw and pulsed excitation) that correspond to the samples and schematics of dual-beam thermal lens measurements in solution most commonly used in chemical analysis are implemented by finite element analysis using COMSOL Multiphysics and geometry simulations using MATLAB. The comparison of the results obtained using the implemented models with the existing infinite two-dimensional model by Shen and Snook (J Appl Phys 73(10):5286, 1993.  https://doi.org/10.1063/1.353761) under the same conditions showed their good agreement. The models were used to study the influence of the basic geometric and physical parameters of the sample. Conditions are found under which the boundary conditions for heat transfer and the geometrical parameters of the cell have the strongest and weakest effects on the signal.     

Construction of Differential Material Matrices for the Orthogonal Finite-Integration Technique With Nonlinear Materials

The linearization of an electromagnetic formulation by the Newton method can be expressed similarly as for the linear case, by introducing differential material matrices. For the case of the finite-integration technique applied to an orthogonal grid, the chord material matrix is diagonal whereas the differential material matrices includes off-diagonal bands, representing the cross-directional coupling introduced by the nonlinearity. An approximative Newton method based on a unidirectional differential material matrix yields a diagonal matrix, which has a higher computational efficiency but may lead to a degenerated convergence.     

Programmable Design of Magnet Shape for Permanent-Magnet Synchronous Motors With Sinusoidal Back EMF Waveforms

The characteristics of a permanent-magnet synchronous motor (PMSM) are influenced greatly by the back-electromotive force waveforms in the motor, which are directly related to the magnet shape. We assume that the outer surface of a magnet in a PMSM can be modeled as one part of a cylinder. Using an ANSOFT model, we optimized the radius of the magnet with respect to number of poles, rotor size, and magnet thickness when the total harmonic distortion is below 1%. We then set up a lookup table using the optimization results so that the desired outer radius of a magnet of any new PMSM motor could be derived, subject to the parameter limits. We applied this method to some PMSM prototypes, and confirmed that the calculation results are substantially accurate.      

基于细观层次混凝土骨料模型生成方法研究分析

混凝土细观数值模拟分析成为了一种有前景替代大量宏观试验的方式,但目前数值模拟中缺少成熟的细观力学模型。重点介绍了混凝土的3种细观力学模型,即随机骨料模型、数字图像模型和参数等效化单元模型,详细说明这3种细观骨料模型的生成特点、关键问题和研究成果,对比分析3种细观模型的生成效率、网格化分、计算效率和精确度等,并提出了在这方面有待进一步研究的问题。     

Error Correction of Rainfall-Runoff Models With the ARMAsel Program

Improved predictions can be based on recent observed differences or errors between the best available model predictions and the actual measured data. This is possible in the predicted amount of supplies, services, sewage, transportation, power, water, heat, or gas, as well as in the predicted level of rivers. As an example, physical modeling of the dynamics of a catchment area produces models with a limited forecasting accuracy for the discharge of rivers. The discrepancies between the model and the actually observed past discharges can be used as information for error correction. With a time-series model of the error signal, an improved discharge forecast can be made for the next few days. The best type and order of the forecasting time-series model can be automatically selected. Adaptive modeling in data assimilation calculates updates of the time-series model estimated from the error data of only the last few weeks. The use of variable updated models has advantages in periods with the largest discharges, which are most important in flood forecasting.     

Analytical Solution of Air-Gap Field in Permanent-Magnet Motors Taking Into Account the Effect of Pole Transition Over Slots

We present an analytical method to study magnetic fields in permanent-magnet brushless motors, taking into consideration the effect of stator slotting. Our attention concentrates particularly on the instantaneous field distribution in the slot regions where the magnet pole transition passes over the slot opening. The accuracy in the flux density vector distribution in such regions plays a critical role in the prediction of the magnetic forces, i.e., the cogging torque and unbalanced magnetic pull. However, the currently available analytical solutions for calculating air-gap fields in permanent magnet motors can estimate only the distribution of the flux density component in the radial direction. Magnetic field and forces computed by the new analytical method agree well with those obtained by the finite-element method. The analytical method provides a useful tool for design and optimization of permanent-magnet motors.     

弹塑性强化材料旋转圆盘的渐近解

采用全量理论和幂级数形式的应力一应变曲线,导出了弹塑性强化材料旋转园盘的渐近解。实例表明,本文的方法是可靠的。     

Fast Analytical Determination of Aligned and Unaligned Flux Linkage in Switched Reluctance Motors Based on a Magnetic Circuit Model

The main advantages of the switched reluctance motor are high torque, wide speed range, simple structure and fault tolerance. Because a switched reluctance motor has inherently nonlinear magnetic characteristics and a doubly salient pole structure, a finite-element analysis approach (FEA) is often adopted to obtain accurate magnetic representation. However, the solution time can be large for a FEA simulation if the mesh is detailed and/or many simulations are required. We propose a rapid analytical solution for determining the aligned and unaligned flux linkage using a magnetic circuit model. We present a simple method for obtaining the air-gap permeance for unaligned linkage. The results of our method agree well with FEA solutions.