Deep Neural Network Based Behavioral Model of Nonlinear Circuits

With the rapid growth of complexity and functionality of modern electronic systems, creating precise behavioral models of nonlinear circuits has become an attractive topic. Deep neural networks (DNNs) have been recognized as a powerful tool for nonlinear system modeling. To characterize the behavior of nonlinear circuits, a DNN based modeling approach is proposed in this paper. The procedure is illustrated by modeling a power amplifier (PA), which is a typical nonlinear circuit in electronic systems. The PA model is constructed based on a feedforward neural network with three hidden layers, and then Multisim circuit simulator is applied to generating the raw training data. Training and validation are carried out in Tensorflow deep learning framework. Compared with the commonly used polynomial model, the proposed DNN model exhibits a faster convergence rate and improves the mean squared error by 13 dB. The results demonstrate that the proposed DNN model can accurately depict the input-output characteristics of nonlinear circuits in both training and validation data sets.

AN IMPROVEMENT TO THE HARMONIC-BALANCE TECHNIQUE FOR ANALYZING NONLINEAR CIRCUITS

In this paper,an improved method,which is based on the harmonic-balance tech-nique,for speeding up the convergence iteration procedure is presented.As an example,it isapplied to the nonlinear analysis of microwave mixer,in which a simple time domain to fre-quency domain transformation technique for the mixer diode is firstly introduced.The use of thistechnique saves computing time dramatically.And the analyzed results are in good agreementwith the results published.The improved method can also be extended to the CAA of nonlinearcircuits with multi-devices.

SENSITIVITY ANALYSIS OF NONLINEAR CIRCUITS AND SYSTEMS-NONLINEAR TRANSFER FUNCTION APPROACH

Properties of the nonlinear transfer function are studied in this paper and the n-th order stabili-ty, n-th order frequency response and n-th order sensitivity as well as a novel theory and implementationon the sensitivity of nonlinear transfer system are proposed.

Analysis of Nonlinear Electrical Circuits Using Bernstein Polynomials

In electrical circuit analysis, it is often necessary to find the set of all direct current （d.c.） operating points （either voltages or currents） of nonlinear circuits. In general, these nonlinear equations are often represented as polynomial systems. In this paper, we address the problem of finding the solutions of nonlinear electrical circuits, which are modeled as systems of n polynomial equations contained in an n-dimensional box. Branch and Bound algorithms based on interval methods can give guaranteed enclosures for the solution. However, because of repeated evaluations of the function values, these methods tend to become slower. Branch and Bound algorithm based on Bernstein coefficients can be used to solve the systems of polynomial equations. This avoids the repeated evaluation of function values, but maintains more or less the same number of iterations as that of interval branch and bound methods. We propose an algorithm for obtaining the solution of polynomial systems, which includes a pruning step using Bernstein Krawczyk operator and a Bernstein Coefficient Contraction algorithm to obtain Bernstein coefficients of the new domain. We solved three circuit analysis problems using our proposed algorithm. We compared the performance of our proposed algorithm with INTLAB based solver and found that our proposed algorithm is more efficient and fast.

Piezotronic transistors in nonlinear circuit:Model and simulation

For the materials that simultaneously exhibit piezoelectric and semiconductor properties,such as wurtzite Zn O,Ga N and In N,as well as two-dimensional single Mo S2,piezoelectric charges induced by externally applied strain can tune/control carrier transport at a metal-semiconductor contact or semiconductor junction,which is named piezotronic effect.Metal-semiconductor-metal piezotronic transistors are key piezotronic nanodevices for electromechanical applications,and they are typical nonlinear elements.In this paper,a simplified current-voltage analysis solution of piezotronic transistors is developed,which can be used for circuit design and simulation.Furthermore,the typical nonlinear circuit:Chua's circuit based on piezotronic transistors is simulated.We find that the output signal of the piezotronic transistor circuit can be switched and changed asymmetrically by externally applied strain.This study provides insight into the nonlinear properties of the piezotronic transistor,as well as guidance for piezotronic transistor nonlinear circuit application.

Subspace Trajectory Piecewise-Linear Model Order Reduction for Nonlinear Circuits

Despite the efficiency of trajectory piecewise-linear(TPWL)model order re-duction(MOR)for nonlinear circuits,it needs large amount of expansion points forlarge-scale nonlinear circuits.This will inevitably increase the model size as well as the simulation time of the resulting reduced macromodels.In this paper,subspaceTPWL-MOR approach is developed for the model order reduction of nonlinear cir-cuits.By breaking the high-dimensional state space into several subspaces with much lower dimensions,the subspace TPWL-MOR has very promising advantages of re-ducing the number of expansion points as well as increasing the effective region of thereduced-order model in the state space.As a result,the model size and the accuracy of the TWPL model can be greatly improved.The numerical results have shown dra-matic reduction in the model size as well as the improvement in accuracy by using the subspace TPWL-MOR compared with the conventional TPWL-MOR approach.

Wavelet neural network based fault diagnosis in nonlinear analog circuits

The theories of diagnosing nonlinear analog circuits by means of the transient response testing are studled. Wavelet analysis is made to extract the transient response signature of nonlinear circuits and compress the signature dada. The best wavelet function is selected based on the between-category total scatter of signature. The fault dictionary of nonlinear circuits is constructed based on improved back-propagation（BP） neural network. Experimental results demonstrate that the method proposed has high diagnostic sensitivity and fast fault identification and deducibility.

A Neural-based L1-Norm Optimization Approach for Fault Diagnosis of Nonlinear Resistive Circuits

This paper deals with fault isolation in nonlinear analog circuits with tolerance under an insufficient number of independent voltage measurements.A neural network-based L1-norm optimization approach is proposed and utilized in locating the most likely faulty elements in nonlinear circuits.The validity of the proposed method is verified by both extensive computer simulations and practical examples.One simulation example is presented in the paper.

Nonlinear feedback control of a novel hyperchaotic system and its circuit implementation

This paper reports a new hyperchaotic system by adding an additional state variable into a three-dimensional chaotic dynamical system. Some of its basic dynamical properties, such as the hyperchaotic attractor, Lyapunov expo- nents, bifurcation diagram and the hyperchaotic attractor evolving into periodic, quasi-periodic dynamical behaviours by varying parameter k are studied. An effective nonlinear feedback control method is used to suppress hyperchaos to unstable equilibrium. Furthermore, a circuit is designed to realize this new hyperchaotic system by electronic workbench （EWB）. Numerical simulations are presented to show these results.

NEW EFFICIENT ALGORITHM FOR NONLINEAR CIRCUIT SYSTEM

A new efficient algorithm is given for calculation of the steady-state response of non-linear circuit driven by multifrequency signals, which are possibly made up of incommen-surable frequencies. The algorithm is particularly useful when the steady state responseis not periodic. The algorithm is much more efficient than numerical integration methods for circuitscontaining only a few nonlinear elements, compared with the number of inductors andcapacitors. It is based on a combined application of the "harmonic balancen" and "leastsquare approach", and does not require any transient analysis. The algorithm can be usedin a microcomputer.

EQUIVALENT CIRCUIT OF NONLINEAR EFFECT OF SPECTRAL IP

ＥＱＵＩＶＡＬＥＮＴＣＩＲＣＵＩＴＯＦＮＯＮＬＩＮＥＡＲＥＦＦＥＣＴＯＦＳＰＥＣＴＲＡＬＩＰ￥Ｈｅ，Ｊｉｓｈａｎ；Ｌｉ，Ｄａｑｉｎｇ；Ｔａｎｇ，Ｊｉｎｇｔｉａｎ（ＤｅｐａｒｔｍｅｎｔｏｆＧｅｏｌｏｇｙ，ＣｅｎｔｒａｌＳｏｕｔｈＵｎｉｖｅｒｓｉｔｙｏｆ...

三阶三次幂非线性混沌电路的自适应反馈控制和H_(∞)控制

针对三阶三次幂非线性混沌电路,研究其控制问题.首先,给出系统的Lyapunov指数和混沌吸引子,验证系统存在复杂的混沌现象;其次,用自适应反馈控制方法和H_(∞)状态反馈控制方法,设计参数已知和参数未知的自适应反馈控制器以及H_(∞)状态反馈控制器,将混沌系统状态稳定到平衡点上;最后,通过MATLAB软件进行数值仿真验证控制器的有效性,并对两种控制器的控制效果进行比较.

考虑精确磁通的电磁加载装置等效磁路建模

为提高电磁加载装置在控制应用时的模型预测快速性与精确性,考虑电磁加载装置硅钢片表面涡流磁场生成因素与不同轴偏心下有效气隙长度,采用非线性方程拟合硅钢片磁化曲线,建立包含磁极边缘效应、磁极铁心、转子硅钢片动态磁阻与涡流磁场的电磁加载装置非线性等效磁路模型。研究了硅钢片表面涡流磁场生成因素与气隙磁场分布,并与有限元仿真结果比较分析。应用该模型在水润滑轴承试验台上进行电磁加载力测试试验。研究结果表明:等效磁路法对磁场分布的表征与有限元法一致,且对气隙的计算更为精确;电磁加载力稳态误差小于4%,响应时间低于0.55 s。

面向环境射频能量收集的宽频整流电路

整流电路是射频能量回收系统的核心,能够将射频能量转换为直流。但由于整流电路中使用的二极管具有非线性特性,导致整流效率会随频率变化而降低。为解决这一问题,本文提出一种具有宽频带的整流电路,它通过采用与二极管串联的短路线、与二极管并联的开路线以及多级微带线结构来调整阻抗匹配,实现了在宽频带范围内的高转换效率。设计的整流电路在0 dBm的输入功率下,从1.7~2.7 GHz,均达到50%的整流转换效率,最高整流转换效率为63.3%。该宽带整流电路可以运用在无线能量收集系统中。

非晶合金-取向硅钢组合铁心结构设计及其磁-振动特性分析

非晶合金和取向硅钢是制作配电变压器铁心常用的两种软磁材料,各有优劣。采用非晶合金-取向硅钢组合铁心结构可以综合两者的优势。该文以非晶合金和取向硅钢铁心并排的组合结构为基础,选取组合铁心的取向硅钢占比和尺寸参数为自由变量,提出一种基于自由参数扫描法的组合铁心结构设计方法。首先,根据非晶合金-取向硅钢组合铁心结构特点,建立组合铁心的等效双非线性磁路模型;其次,采用磁路法迭代求解组合铁心的磁通密度分布,并制定组合铁心的结构设计流程;最后,根据结构设计结果制作了组合铁心的实验模型,采用实验和有限元仿真结合的方法分析了其磁-振动特性,验证了所提设计方法的准确性,并与传统纯非晶合金和纯取向硅钢铁心进行对比分析,阐述了组合铁心的优势。

大容量发电机断路器TRV开断特性及抑制措施研究

发电机断路器(GCB)位于发电机组和升压变压器之间,针对负荷电流高达50 kA、故障电流高达200 kA以上的大容量机组,GCB传导和开断电流远高于线路断路器,在开断过程中,GCB两端会产生非常严重的瞬态恢复过电压,威胁GCB的可靠性。文中基于某大型核电站的实际接线,单机容量为1 722.2 MVA,利用EMTP-RV仿真计算研究了GCB在各种故障下开断时的TRV的电磁暂态特性,分析配置不同容量电容器对TRV幅值和陡度的影响效果。提出了采用辅助断口装设非线性阻尼电阻抑制TRV的方法,并给出了非线性阻尼电阻参数选取原则,并通过仿真验证了其可行性,针对失步故障非线性阻尼电阻可使TRV幅值降低29.2%,具有更高的灵活性与经济性。

Mapping equivalent approach to analysis and realization of memristor-based dynamical circuit

A novel mapping equivalent approach is proposed in this paper, which can be used for analyzing and realizing a memristor-based dynamical circuit equivalently by a nonlinear dynamical circuit with the same topologies and circuit parameters. A memristor-based chaotic circuit and the corresponding Chua＇s chaotic circuit with two output differentiators are taken as examples to illustrate this approach. Equivalent dynamical analysis and realization of the memristor-based chaotic circuit are performed by using Chua＇s chaotic circuit. The results indicate that the outputs of memristor-based chaotic circuit and the corresponding outputs of Chua＇s chaotic circuit have identical dynamics. The proposed approach verified by numerical simulations and experimental observations is useful in designing and analyzing memristor-based dynamical circuits.

考虑磁滞效应的非晶合金-取向硅钢组合铁心双非线性励磁特性研究

非晶合金-取向硅钢组合铁心可以综合传统纯非晶合金和纯取向硅钢铁心的优势,在配电变压器领域具有广阔的应用前景。对含有2种非线性软磁材料的组合铁心励磁特性进行分析是实现其结构优化设计的前提。首先,建立组合铁心在开路励磁条件下的等效电路模型,并根据基尔霍夫第二定律列写其回路电压方程;其次,根据组合铁心的结构特点建立其等效双非线性磁路模型,并基于安培环路定律和磁通连续性原理列写其磁路方程;再次,根据导数变换将磁路方程耦合至回路电压方程中的电动势项,并采用Jiles-Atherton磁滞模型表征非晶合金和取向硅钢的非线性磁化特性,从而建立考虑磁滞效应的组合铁心双非线性电路-磁路耦合模型;最后,基于该耦合模型,求解组合铁心的励磁电流、磁通密度分布和空载损耗,通过与实测结果进行对比,验证所提方法的准确性。

双稳态压电超结构的超传输滞回效应与非互易编码特性

利用超结构的非线性效应能够实现新颖的振动能量传输调控现象.双稳态超结构存在非线性超传输特性,即在超结构线性化带隙内,当激励幅值超过某个临界值时,传输的振动能量将突变到很大值.文章针对含双稳态分流电路的压电超结构梁,建立了力电耦合非线性动力学数值模型,并采用伽辽金法对数值模型进行降阶处理以提升计算效率.基于上述模型研究了双稳态压电超结构的振动能量非线性传输特性,发现超结构线性局域共振带隙内的超传输特性存在滞回效应,也即向上扫幅激励和向下扫幅激励两种工况下超传输临界值不同.通过改变双稳态电路两个稳定平衡点的间距或者电路在稳定平衡点的共振强度可以移动超传输滞回区间.进一步通过在双稳态压电超结构一侧布置线性共振电路来引入系统非对称性,可使得正方向和反方向的超传输滞回区间发生偏离,利用这种非互易的超传输滞回效应可以在不同激励幅值区间实现不同模式的非互易编码.增强系统非对称性可使得正方向和反方向的超传输滞回区间偏离更加显著,故非互易编码区间具有可调性.文章极大地拓展了超材料的非互易模式,正方向和反方向能量传输性能不再局限于传统超材料固定的“传输”或“非传输”状态,通过合适的非互易编码设计可以实现弹性信息的单向传输功能.

基于坐标变换辅助势的轴对称电磁场仿真

将轴对称静磁场的坐标变换辅助势法推广应用到包含绞线圈、非线性磁导率铁芯、外电路及运动耦合的轴对称电磁场有限元分析中,并通过国产低频电磁仿真软件INTESIM-Emag编程实现。数值算例表明,基于坐标变换辅助势法的技术方案可获得较高的计算精度。某轴对称电磁阀的动态性能仿真说明该方案对工程问题仿真的适用性和准确性。