基于准Z源的本质安全开关变换器的设计

针对一种输出本质安全型准z源Buck变换器拓扑结构进行了分析,准Z源Buck变换器可以有效地延缓输出端短路或开路时变换器向短路／开路故障点的释能速度,与截止型输出保护电路相配合,可以有效地减小火花放电能量,提高电源的本安特性。由于当准zNN络参数L1、C1远小于常规变换器滤波网络参数LC,因此本文按常规Buck变换器完成了准Z源Buck变换器的设计,利用LM2576-ADJ芯片对BUCK变换器进行了设计,论文最后采用常用的截止型输出保护电路验证了理论分析的正确性。     

软开关变换器的设计与仿真研究

针对开关电源开关损耗和电磁辐射的问题，建立了一种采用软开关技术的零电压开关（ZVS）PWM变换器的电路，利用PSpice软件对这种变换器进行仿真研究，分析其暂态和稳态时的性能。仿真表明，合理选择器件参数，当软开关变换器电路中L1=0.3mH，L2=3μH，C1=500p时，开关损耗小，造成的电磁干扰小。仿真发现暂态时开关器件承受了较高的电压应力，实际应用时应考虑开关器件安全性。     

达芬振子激励分叉在多普勒频移检测中的应用

以达芬(Duffing)振子模型在单频外激励下的分叉原理为基础,提出一种可在强噪声背景下检测微弱水声探测信号多普勒频移的新方法。当达芬振子的激励振幅超过某一临界参数时系统由混沌状态突变为周期状态。根据这一原理,首先在无噪声条件下确定达芬振子由混沌状态向周期振荡转变的分叉参数阈值,然后根据噪声强度适当调节分叉参数,使得系统输出稳定在单一周期状态。当噪声中含有微弱的多普勒回波时,通过理论分析可知系统输出为阵发混沌状态,且可根据混沌状态的间隔周期较准确地求出回波信号的多普勒频移。     

降压型DC/DC变换器的仿真研究

本文建立了一种降压型DC/DC变换器(Buck电路)的数学模型,并利用PSpice软件对这种DC/DC变换器进行仿真研究,分析其暂态和稳态的过程及形成机理。仿真表明,当电路元件取不同参数时,输出电压就会明显不同。仿真结果为实际电路的设计提供有益的参考。     

某发动机转子-机匣系统局部碰摩的混沌运动研究

以某发动机实验器为基础，研究了转子-机匣系统发生碰摩时的分叉与混沌行为。分析了转子径向碰摩刚度比、偏心质量等参数对转子分叉与混沌特性的影响并与试验结果进行了比较。当转子机匣系统发生碰摩时呈现出非常丰富的动力学行为，除了通过倍周期、阵发性和拟周期分叉进入混沌外，还发现了孪生叉形分叉现象。     

考虑非线性涡动时裂纹转子的分叉与混沌特性

分析了裂纹转子在非线性涡动影响下的动力学行为，特别是系统响应的分叉与混沌特性。通过大量数值计算表明：当刚度变化比ΔＫ较大时，系统在亚临界转速区的１２Ωｃ、２３Ωｃ附近具有丰富的非线性力学行为，有可能出现倍周期分叉、拟周期响应及混沌现象。随着ΔＫ的增大，在１２Ωｃ、２３Ωｃ附近周期解分别由低频进动分量分叉和谐波分量分叉两种不同的方式变到拟周期。随继续增大，首先在２３Ωｃ附近出现混沌，通向混沌的道路一方面是由拟周期进入，另一方面则与周期３解有关。当ΔＫ非常大时，在１２Ωｃ附近也由拟周期通向混沌。本文还发现许多周期３解随初值的改变而变为其它周期数解的情形。     

物理非线性杆动力分析的有限元分析

本文利用有限元方法对物理非线性粘弹性等直杆受轴向简谐外力激励的动态响应进行了数值计算。分析了其发生分叉和混沌的参数特性,发现当作为参数的外激励振幅小于某一临界值时,系统的响应是规则的周期振动,若大于该值,系统的出现分叉和混沌,文中给出了特定参数下的奇怪吸引子图形以及参数空间上的分叉图。     

周期激励Ueda电路系统的双参数特性分析

数值计算周期激励Ueda电路系统在双参数平面上的最大Lyapunov指数,得到系统在双参数平面上周期运动、拟周期运动和混沌运动的参数区域。结合单参数分岔图和庞加莱截面图讨论多参数耦合对系统运动稳定性的影响以及系统在参数平面上的分岔混沌过程,表明在不同的参数匹配下系统的局部动力学特性非常复杂,参数之间的相互耦合关系对系统分岔与混沌过程的影响非常明显:当外激励幅值小于1.0时,系统在外激励频率小于1.181或大于1.936的区域内均为拟周期运动;当外激励幅值大于1.0时,系统在外激励频率小于0.9和大于2.5的区域内出现混沌运动和周期运动相交替的现象;选取合适的参数,系统由拟周期运动经锁相退化为周期运动,后经倍周期分岔序列进入混沌运动;在给定系统参数下,当外激励频小于0.2时,系统振子发生颤振。     

一类非光滑系统的无模型自适应混沌控制

以一类单自由度非光滑系统为研究对象。分析了系统n-1周期运动经周期倍化分岔通向混沌运动的动力学行为。研究了系统混沌运动的控制问题,提出了一种无模型自适应参数反馈混沌控制方法。该混沌控制方法基于无模型自适应控制方法的思想设计混沌控制器:仅利用被控系统的输入/输出数据在线估计伪偏导数以建立系统的非参数时变动态线性化模型,进而基于该非参数时变动态线性化模型进行混沌控制器设计。当系统进入混沌运动状态后,利用混沌控制器输出微幅调整量施加于系统的可控参数,对混沌系统进行参数反馈控制,将系统的混沌运动控制为期望的周期运动。该混沌控制方法不依赖被控系统的数学模型,可适用于系统模型未知而仅获得系统输入/输出数据的情况,且具有控制器设计简单、计算量小等优点。数学证明了控制系统的稳定性和收敛性,仿真结果验证了该控制方法的可行性和有效性。     

开闭裂纹挠性转子动特性研究

采用裂纹深度修正的非线性开闭裂纹模型 ,研究涡动影响下挠性裂纹转子的动力学行为。数值仿真表明 :裂纹深度与非线性响应之间有比较确定的关系。随着裂纹深度增加 ,裂纹转子会在 m/ n倍临界转速附近出现次谐波分叉现象和拟周期运动 ;在亚临界转速范围内 ,系统在 2 / 3倍临界转速处可通过倍周期分叉途径进入混沌状态 ;在超临界转速范围内 ,1、2倍临界转速的不稳定区不断扩大 ,非线性因素抑制作用使系统产生周期跳变、倍分叉和混沌等非线性力学行为 ;阻尼对系统响应有很大影响。     

Hybrid control approach for the output voltage regulation in buck type DC?DC converter

Buck converter is modelled as a hybrid automaton for the purpose of designing an appropriate control law to regulate its output voltage. The circuit when operated in continuous current mode is pulled into a limit cycle, specified by the regulation specifications, although the switching frequency varies with the load. On the other hand, under light-load conditions, the circuit is pulled into a fixed-frequency limit cycle in discontinuous current mode to satisfy the regulation criteria. Therefore, the controller design is generic in the sense that the required regulation is met throughout the operating range of the buck converter. The control problem is simplified as a guard selection problem and guards, denning the discrete states, are derived using a simple circuit theoretical approach, by imposing certain regulation and control constraints. Satisfactory operation of the buck converter under the proposed scheme is demonstrated using computer simulations and laboratory experiments. The suitability and simplicity of the proposed control scheme over a wide range of disturbances is highlighted.     

Switched-boost action: a phenomenon for achieving time-division-multiplexed multi-port power transfer for nanogrid applications

Multi-port power converter topologies are used to interface multiple terminals (source or load) using a single converter topology. In this paper, the possibility of using switch node of a power converter stage as interface to multiple output stages has been investigated. This interfacing of multiple outputs at the same switch node occurs using time-division multiplexing of the available input power. The multiplexing of input power into different ports occurs using a phenomenon that is denoted as ‘switched-boost action’ in the work and this concept has been illustrated using the boost converter topology. The proposed approach has been used to interface the boost-derived architectures to different types of outputs—ac, dc and isolated dc. The circuit operation has been validated using experimental results. These circuits have been proposed as possible candidates for nanogrid applications.     

一类三自由度含间隙系统的分岔与混沌

通过对工程中一种三自由度弹簧摇床的建模,选择一个碰撞界面作为Poincaré映射的截面,解析法和数值法相结合,证明三自由度含间隙系统通向混沌的道路不仅有典型的倍周期道路、拟周期道路和阵发性混沌,而且还存在包含Neimark-Sacker分岔的倍周期道路、包含叉式分岔的倍周期道路等复杂的混沌演化过程。对该系统分岔与混沌行为的研究,为工程实际中含间隙机械系统和冲击振动系统的优化设计提供了依据。     

Theoretical investigation of a semiconductor ring laser driven by Chua’s oscillator

The modeling and numerical investigation of the dynamical behavior of a semiconductor ring laser (SRL) driven by Chua’s oscillator are reported. By increasing the coupling strength between the SRL and Chua’s oscillator at a fixed bias current, the SRL exhibits an intermittency route to anti-phase chaos. However, for a fixed value of the coupling strength, we report a period-doubling route to out-of-phase and anti-phase chaos when varying one of the parameters of the Chua’s oscillator are reported. We also demonstrate that a SRL driven by the chaotic output of Chua’s oscillator generates a more complex chaos compared to the one found in a SRL subject to a sinusoidally modulated current. This new way of modulation of semiconductor lasers would not only bring a general benefit in the physical equipment and reduce their cost but could have an impact for some relevant engineering applications.     

Novel zero voltage switching dual-switch forward converter with ripple current cancellation

A zero voltage switching (ZVS) dual-switch forward converter with ripple current cancellation is presented. In the proposed converter, active clamp circuit is used to clamp the voltage stresses and to realise ZVS of all switching devices. Active clamp boost converter with power factor correction is used in the front stage of the proposed converter to draw a sinusoidal line current from the AC source and to maintain a constant voltage at the DC bus. The second stage of the proposed converter is a dual-switch forward converter with current doubler rectifier to obtain the isolated low output voltage. Active clamp circuit used in the DC/DC converter can recycle the energy stored in the leakage inductor and magnetising inductor so that the voltage stresses on the switches are limited and the ZVS feature is realised. The current doubler rectifier offers the ripple current cancellation at the output capacitor and reduces the current stress of the transformer secondary winding. The circuit configuration and principle of operation are analysed and discussed in detail. Experimental results with a laboratory prototype based on a 90-260 V_rms input and 12 V/30 A output were provided to verify the effectiveness of the proposed converter.     

振动磨的周期运动稳定性与分岔

由于碰撞的存在,振动磨系统的响应呈现出复杂的周期运动或混沌运动。本文将振动磨的模型进行简化,建立一维、两自由度、受简谐激振力作用的振动磨碰撞振动力学模型。基于Poincare映射原理,根据映射Jacobi矩阵分析振动磨周期运动的稳定性,并通过理论分析和数值仿真,研究振动磨周期运动的稳定性与分岔,以及由倍周期分岔通向混沌的过程。     

新SH-COS混沌弱信号检测系统设计

将混沌理论应用于弱信号检测,设计了一种由三维混沌和余弦函数合成的全新的混沌弱信号检测系统——SH-COS系统,并对其进行了动力学特性的理论分析,用Matlab及Muhisim进行了电路仿真分析.与目前广泛探讨的Duffing混沌弱信号检测系统以及锁相放大器的性能相比,新设计的混沌弱信号检测系统抗噪性能强、检测精度高,而且具有信号检测的广域多样性,弥补了检测系统混沌与大周期状态难以区分、大周期状态不稳定等不足.新系统输出的大周期态具有收敛性,仿真对比结果验证了设计方法的正确性,进一步改善了混沌系统的弱信号检测性能,使定量检测成为可能,因而更适合应用于实际工程领域.     

Use of Digital-to-Analog Converters in Circuit Design

High-quality digital-to-analog converters are now available at relatively low prices and can be used to advantage in many instrumentation applications. The examples that are considered in this paper include a very general transducer output linearizing analog-to-digital converter, an analog multiplier and a more general signal processing circuit that has an output E0 of the form E0 = KEs1f(Es2) where K is a constant, Es1 and Es2 are input voltages and f(Es2) is any prescribed function of Es2.     

A Low-Complexity Circuit for On-Sensor Concurrent A/D Conversion and Compression

A low-complexity circuit for on-sensor compression is presented. The proposed circuit achieves complexity savings by combining a single-slope analog-to-digital converter with a Golomb-Rice entropy encoder and by implementing a low-complexity adaptation rule. The adaptation rule monitors the output codewords and minimizes their length by incrementing or decrementing the value of the Golomb-Rice coding parameter k. Its hardware implementation is one order of magnitude lower than existing adaptive algorithms. The compression circuit has been fabricated using a 0.35 muM CMOS technology and occupies an area of 0.0918 . Test measurements confirm the validity of the design.     

Chaotization of mitron oscillations

The possibility of obtaining chaotic oscillations in a mitron (voltage-tuned magnetron) is considered and illustrated by experimental results. It is shown that a mitron is capable of operating in a chaotic regime characterized by a scenario of transition to chaos via period-doubling (flip) bifurcations.