共振式混凝土路面破碎车的自适应反推滑模控制

基于共振式混凝土路面破碎车共振机构的结构,给出了其共振频率和振幅的模型.建立了基于比例泵控马达的频率调节的非线性不确定性控制模型,设计了自适应反推滑模的控制算法,针对系统模型中的不确定性项,给出了各参数项的自适应律,基于Lyapunov函数,证明了频率输出跟踪的渐近收敛.仿真和车载测试结果表明,该方法具有较好的频率跟踪性能,能满足共振式路面破碎车的施工控制要求.     

水泥混凝土路面脱空振动映象测试技术

脱空是水泥混凝土路面常见病害,是造成路面板断裂的主要原因。当混凝土面板在受到瞬态激振后,其振动频率主要与其脱空与否、脱空程度等因素有关,因此提出了基于振动频率的混凝土路面脱空振动映象检测技术。简述了振动映象测试原理。对混凝土路面板进行了模态分析和模型试验,获得了面板在不种脱空情况下的振动特性。在对路面板振动频率因子分析和路面瞬态振动信号频谱分析的基础上,发现路面板的振动频率对于脱空是很敏感的,从而建立了基于振动频率的混凝土路面脱空判别标准。研究表明：当路面板下严重脱空时,其振动基频值通常小于50 ;当路面板良好支承时,其振动基频值一般在200 以上;当有低于50 与高于200 的两个振动基频同时存在时,表明路面板下存在轻微脱空。     

电梯系统共振失效的灵敏度研究

以曳引式电梯为研究对象,考虑电梯曳引绳刚度具有时变特性,对电梯系统建立了8自由度耦合振动的动力学模型。在对系统进行模态分析的基础之上,以影响系统模态频率的动力参数作为随机变量,结合DOE试验方法与神经网络技术,得出系统随机变量与系统模态响应之间的显性函数关系式。依据动态结构系统的固有频率与激振频率差的的关系准则,定义了系统共振的失效模式,并对系统的随机变量进行了可靠性灵敏度分析。研究表明,绳头侧刚度和曳引机支撑刚度对频率共振影响最为明显,因此,在电梯系统设计中可以通过修改该动力参数达到有效降低共振的风险。同时,在实际工作中应该严格关注和监视该动力参数的变化,避免发生共振。     

基于跟踪滤波的自适应振动控制

针对频率周期振荡的振动系统讨论自适应控制问题,在频率跟踪的基础上对频率变化的振动响应进行控制,给出相应的估计、滤波与控制方法。首先在子空间辨识原理的基础上,通过测量信号自相关序列的递推运算获得信号频率;然后根据估计频率实时调整带通滤波器的中心频率,使其跟踪信号频率,实现信号分量的跟踪滤波;最后在LMS 方法的基础上构造     

基于谱峭度的滚动轴承故障包络阶比跟踪分析

通过对旋转机械变速运行工况的齿轮箱振动分析研究,提出一种基于谱峭度的滚动轴承故障包络阶比跟踪分析方法。该方法利用旋转机械运行过程中滚动轴承故障引起的冲击性振动会激起其周围结构共振的原理,应用谱峭度方法自适应地确定优化的共振解调带通滤波中心频率和滤波带宽,进而通过共振解调算法获得包含轴承故障初始阶段振动特征的包络信号,再将变速工况下的非平稳包络信号通过等角度重采样转化为角度域的准平稳信号,进而获得消除了频率模糊的阶比谱,实现对旋转机械变速运行工况下的滚动轴承故障诊断。仿真和测试试验结果验证了本方法的有效性。     

一种局域共振型角式声子晶体梁

局域共振型声子晶体梁具有纵向振动带隙和横向振动带隙,一般而言,前者频率范围很窄而且衰减量极小,后者频率范围很宽并且衰减很强,二者往往不在同一频带,因此很难满足同一频带内的多维减振要求。针对这一问题,为充分利用横向振动带隙的宽频带强衰减特性,提出了一种局域共振型角式声子晶体梁,采用传递矩阵法进行了理论分析和数值求解,并进一步在有限元软件中做了仿真验证,结果表明该角梁能够通过纵波与横波的转换,使得三个自由度上的振动均能在同一频带内得到有效的衰减,从而一方面满足了工程上的多维减振需求,另一方面也拓展了声子晶体减振应用场合。     

四边固支功能梯度矩形板的主共振分析

针对四边固支约束的陶瓷-金属材料功能梯度矩形板,在给出非均匀材料的应力应变关系及非线性几何方程基础上,应用虚功原理导出了横向简谐激励力作用下功能梯度板的非线性振动偏微分方程。通过位移函数的设定,利用伽辽金积分法推得了相应的达芬型非线性振动方程。应用多尺度法对非线性系统的主共振问题进行解析求解,得到了稳态运动下的幅频响应方程。基于李雅普诺夫稳定性理论,得到了共振下解的稳定性判别条件。作为算例,给出了不同参数下功能梯度矩形板共振的幅频曲线图和动相平面相轨迹图,讨论了不同参数对系统非线性振动特性的影响     

弯曲共振法共振峰“劈叉”现象研究

使用弯曲共振法测量复合试件阻尼参数时,发现频响曲线有时会在共振频率附近产生"劈叉"现象,表现出两个峰值,与一般经验不符。建立了悬臂梁试件受到不同方向激励的耦合振动模型,通过信号合成复原了"劈叉"曲线,表明频响曲线在共振频率附近产生"劈叉"的原因是正交方向弯曲振动模态的干扰;提出了针对"劈叉"曲线的实验数据处理方法;利用阻尼层模量识别过程判断出"劈叉"曲线上两峰对应的振动方向,辨别主共振峰和干扰峰;进而分析了"劈叉"曲线干扰频率与幅度等对试件损耗因子识别精度的影响。结果表明,在主共振峰可辨条件下,使用弯曲共振法常规计算公式,即可得到相当准确的结果,并解决了"劈叉"曲线数据处理的难题。     

基于桥梁断面压力分布统计特性的抑流板抑制涡振机理研究

通过测量大比例流线形扁平钢箱梁模型（１：２０）涡激共振时表面压力,研究典型钢箱梁常用设计断面涡激振动、静止、以及安装抑流板后涡激共振性能。综合对比分析三种工况模型表面压力系数均值、根方差、局部气动力与涡激气动力相关系数等时域统计特性;表面压力脉动的功率谱、局部测点气动力与总体断面气动力间的在模型竖弯频率处的相位谱和相干函数等频域统计特性。研究发现：竖弯涡激共振产生原因是流线模型上表面下游的气流再附区域强烈压力脉动以及箱梁下表面与总气动力具有较强相关性的压力脉动,整体断面各测点脉动压力具有相同的卓越频率。针对本项研究试验实例,抑流板措施减弱了箱梁中下游位置压力脉动的分布强度和作用时序的相关性,可以有效地抑制涡振。     

转子系统振动的频率可靠性灵敏度分析

摘要：根据转子系统的固有频率与激振频率差的绝对值不超过规定值的关系准则,定义转子系统共振问题的可靠性模式和系统的可靠度,提出避免转子共振的频率可靠性分析方法,应用随机摄动技术、可靠性理论和灵敏度技术,对转子系统共振问题的可靠性灵敏度分析方法进行了研究,并通过数值算例验证了本文方法的有效性。     

弹光调制器谐振特性研究及其谐振频率自跟踪

弹光调制器是一种由各向同性的弹光晶体和压电晶体组成的高品质因数热机电耦合器件,广泛用于偏振测量、光谱测量等诸多领域。但是在高压谐振状态下,其谐振频率会随着温度变化出现漂移,导致弹光调制器的相位调制幅值不稳定以及驱动效率降低。针对该问题,首先对弹光调制器谐振频率特性进行分析,建立了弹光调制器及其高压谐振驱动电路的复合谐振网络模型,提出了利用谐振网络的幅频特性进行频率跟踪的实现方法,并设计了基于现场可编程门阵列(field programmable gate array,FPGA)的控制测试系统,实现了谐振频率跟踪以及调制幅度的测量。通过测试验证了该方案可有效进行谐振频率跟踪,提高了弹光调制器的稳定性以及驱动效率,测试时长大于90 min,相位调制幅度的标准偏差为0.83% rad。

     

Robust control of linear ceramic motor drive with LLCC resonant technique

This study presents a robust control system for a linear ceramic motor (LCM) that is driven by a high-frequency voltage source inverter using two-inductance two-capacitance (LLCC) resonant technique. The structure and driving principle of the LCM are introduced. Because the dynamic characteristics and motor parameters of the LCM are nonlinear and time varying, a robust control system is designed based on the hypothetical dynamic model to achieve high-precision position control. The presentation of robust control for the LCM drive system is divided into three parts, which comprise state feedback controller, feed-forward controller, and uncertainty controller. The adaptation laws of control gains in the robust control system are derived in the sense of Lyapunov stability theorem such that the stability of the control system can be guaranteed. It not only has the learning ability similar to intelligent control, but also its control framework is more simple than intelligent control. With the proposed robust control system, the controlled LCM drive possesses the advantages of good tracking control performance and robustness to uncertainties. The effectiveness of the proposed robust control system is verified by experimental results in the presence of uncertainties. In addition, the advantages of the proposed control system are indicated in comparison with the traditional integral-proportional (IP) position control system.     

锁相环跟踪超声振动系统谐振频率的改进

锁相式频率跟踪超声发生器的频率跟踪范围较小且易出现死锁现象,通常要人为重新启动,系统才能恢复跟踪状态,在应用时会带来麻烦。根据超声振动系统的等效电路研究其阻抗特性,并通过实验绘制换能器特性曲线,分析应用CD4046跟踪串联谐振频率容易造成死锁的具体原因,提出带解锁的频率跟踪系统的方案。实验结果表明此方案有较大的跟踪调节范围与较强的适应负载变化的能力,对超声发生器的具体应用有一定的参考意义。     

Design,real-time modelling,simulation and digital implementation of phase-locked loop-based auto-synchronising current-sourced converter for an induction heating prototype

Induction heating (IH) converters operate just above resonant frequency, at near unity power factor (UPF), to supply power to the targeted work-piece. Some power electronic converter-fed IH systems use power control strategies based on dynamic tracking of the changing resonant frequency as the work-piece gets heated up (since inductance changes). Therefore, the correct in-process determination of the resonant frequency is essential. A method of dynamically detecting the resonant frequency is by calculating the phase-shift between current and voltage continuously during the process. In case of CSI- (and VSI-) fed IH, the phase-shift between voltage and current is zero at resonant frequency. Hence one way of identifying the resonant frequency is by varying the frequency until the phase-shift is zero. For controlling this phase-shift between current and voltage waveforms, most of the controllers use a phase-locked loop (PLL) IC. In this paper, a novel method for the dynamic tracking of resonant frequency is proposed and the practical implementation of the same, using a field-programmable gate array (FPGA) based digital-PLL, is presented. The scheme is first simulated with generated off-line signal samples and then implemented on a real-time model of a CSI-fed IH application. Finally, the digital-PLL logic is implemented on controller hardware and practically tested in a laboratory-made experimental set-up of 2 kW at a nominal frequency of 10 kHz. The switching frequency is auto-synchronising. This fact is practically verified both by varying (i) the geometric dimensions as also (ii) the initial temperature of the work-piece. It is practically observed in the oscillograms that the phase gets locked in few cycles (and hence ensures quick tracking of the dynamically changing resonant frequency for this set-up).     

The Dynamic Response of a Resonant Frequency Tracking System

A study of a resonant frequency tracking system, to be used in measurement systems where the sensing element is a resonant structure is presented. The tracking system was used to lock an oscillator to the resonant frequency of a cavity operating in the X-band. The resonant frequency of the sensor was assumed to be a function of the quantity being measured. A theoretical analysis of the resonant frequency tracking system was done for both linear and nonlinear operations resulting from the properties of the sensor. A model of the tracking system was designed and an analysis of the system response was performed using computer techniques.     

基于Helmholtz共振腔阵列的声学超材料研究

为有效控制特定频段的噪声,基于Helmholtz共振腔阵列,通过Helmholtz共振腔短管位置的控制,设计了一种新型的局域共振型声学超材料。利用COMSOL Multiphysics软件求得新型声学超材料的能带图和传递损失曲线,并与具有单一方向开口的Helmholtz共振腔阵列的传递损失曲线进行对比;同时,为分析新型声学超材料的带隙形成机理,求得了其在带隙频率范围内的声压分布云图。通过试验测试了新型声学超材料的吸声性能。结果表明：新型声学超材料的能带图中产生了2段较窄带隙和1段较宽带隙,在带隙频率范围内,声学超材料传递损失出现峰值;第1带隙和第2带隙较窄,原因是单个Helmholtz共振腔局域共振,声波能量消耗少;第3带隙较宽,原因是Helmholtz共振腔与其周期排列形成的外部波导联合共振吸声,消耗大量声波能量。试验测试结果与仿真计算结果较为吻合,新型声学超材料可有效控制1 300~1 500 Hz和1 500~2 000 Hz频率范围内的噪声。研究结果表明,所设计的新型局域共振型声学超材料可有效实现中低频减振降噪,为声学超材料在中低频的降噪控制研究提供了新的思路。     

An adaptive fuzzy-neural-network controller for ultrasonic motor drive using the LLCC resonant technique

In this study an adaptive fuzzy-neural-network controller (AFNNC) is proposed to control a rotary traveling wave-type ultrasonic motor (USM) drive system. The USM is derived by a newly designed, high frequency, two-phase voltage source inverter using two inductances and two capacitances (LLCC) resonant technique. Then, because the dynamic characteristics of the USM are complicated and the motor parameters are time varying, an AFNNC is proposed to control the rotor position of the USM. In the proposed controller, the USM drive system is identified by a fuzzy-neural-network identifier (FNNI) to provide the sensitivity information of the drive system to an adaptive controller. The backpropagation algorithm is used to train the FNNI on line. Moreover, to guarantee the convergence of identification and tracking errors, analytical methods based on a discrete-type Lyapunov function are proposed to determine the varied learning rates of the FNNI and the optimal learning rate of the adaptive controller. In addition, the effectiveness of the adaptive fuzzy-neural-network (AFNN) controlled USM drive system is demonstrated by some experimental results.     

三质体声共振混合机的动力学特性及其性能分析

为研究三质体声共振混合机的动力学特性,建立了三质体声共振混合机的动力学模型,进而分析了系统物理参数对动力学特性的影响,阐明了物料质量和阻尼变化对声共振混合机动力学响应的影响规律,提出了系统在共振频率附近工作的振幅控制策略。进一步分析了典型声共振混合机在额定载荷下的对地动载荷和所需激振力,并与额定载荷所需的最大推力进行了比较。结果表明,通过选择合理的系统物理参数,三质体声共振混合机在三阶共振频率附近工作,其振幅变化较平缓、负载质体和激振质体的运动相位相反,系统能够兼具能量转换率高、对地动载荷小且激振力小等优点。所得结论有助于进一步提高声共振混合机的工作性能和设计水平。     

斯特林制冷机直线压缩机共振频率与特性研究

文章主要基于斯特林制冷机直线压缩机及其相应简化物理模型,给出了压缩活塞—弹簧振动系统的动力学控制方程,就直线压缩机的共振频率及特性进行了系统分析,对整机优化设计与性能改进具有重要意义。