最优鲁棒EI时滞滤波器的设计原理及性能分析

时滞滤波器能抑制柔性系统的残留振荡，但典型时滞滤波器对系统参数误差的鲁棒性较差，不能有效抑制残留振荡。对于参数大范围变化的柔性系统，将系统参数变化范围作为先验知识，以ZV时滞滤波器的幅频特性作为目标函数，基于优化理论和矢量图法，计算零点频率，设计最优鲁棒EI时滞滤波器。该滤波器的特点是考虑了系统参数的变化范围，系统残留振荡的最大幅值在参数变化区间内相等，从而有更强的鲁棒性，特别是当系统参数大范围变化时，能有效消除柔性系统的残留振荡。     

多模态柔性系统的最优时滞滤波器设计

时滞滤波器是一种消除柔性系统残留振动的有效方法。本文对多模态柔性系统的时滞滤波器设计进行了讨论。在最优随机时滞滤波器的基础上,通过使在某一频率下的残留振动最小,求出最优的时滞时间和频率,来设计最优时滞滤波器,消除系统中所有模态的残留振动。与一般的级联法相比,该方法减少了脉冲个数,大大减小了时滞时间,具有一定的鲁棒性。仿真结果进一步证明了该方法的有效性。     

闭环时滞滤波器消除二阶振荡系统残留振动的仿真研究

将时滞滤波器与位置反馈环节相结合提出闭环时滞滤波控制策略,不仅能阻止操作命令向系统中注入能量,而且能阻尼掉不确定性因素注入系统中的能量,从而有效抑制二阶振荡系统的残留振动。与开环时滞滤波技术相比,有更强的参数鲁棒性和抗外界干扰能力。     

时滞控制下的微梳状驱动器动力学研究

在微梳状驱动器的直、交流两种驱动电压中,加入时滞速度反馈,建立了时滞影响下的微梳状驱动器的单自由度模型。假设驱动器以微小振幅振动,将含速度时滞反馈的静电驱动力进行泰勒近似展开,应用多尺度法得到时滞参数影响下系统的幅频响应方程;驱动频率在共振频率附近时,系统非线性振动随时滞参数改变时发生跳跃现象;不同的直流电压等物理参数状态下的系统振动频率和软硬特性不同,可以通过改变时滞参数控制不同物理参数下的系统的振动的稳定范围和幅值。经过计算并使用数值方法验证了结论,正时滞参数引起系统振动失稳,负时滞参数可使振动幅值跳跃现象消失。     

传动柔性及负载变化弹药传输机械臂位置控制及柔性振动抑制

针对现有坦克自动装弹机无法实现任意角度装填问题,设计出两自由度的弹药传输机械臂。研究考虑链条、转铰柔性且负载变化情况弹药传输机械臂位置控制与柔性振动抑制。将链条与转铰简化为线性无惯量弹簧,采用第二类Lagrange方法建立弹药传输机械臂刚柔耦合动力学模型。基于奇异摄动技术设计系统混合控制策略,柔性振动抑制采用速度反馈控制;刚性部分大范围运动采用基于隐式Lyapunov函数的连续时变增益PD控制,控制器增益为系统状态变量的可微函数,随系统状态变量逐渐趋向于零,增益逐渐趋于无穷大,而控制力始终保持在有界范围内。仿真结果显示,该混合控制器能克服负载变化及柔性振动影响,实现弹药传输机械臂点到点位置控制及柔性振动抑制,具有较强的鲁棒性。     

考虑控制器时滞的建筑结构减振H∞控制方法

在状态空间下直接对结构振动的时滞微分方程离散，并引入适当的增广向量将之转化为不显含时滞项的标准离散形式。在此基础上采用离散的H∞反馈控制理论完成了建筑结构减振控制器的设计，对于地震激励的不确定性有很好的鲁棒性。得到的控制器含有对滞后控制量的线性组合，反映了时滞因素的影响，对大时滞情况也有效。最后通过算例仿真与分析验证了这种控制器的有效性。     

多频激励作用下悬索时滞减振控制研究EI北大核心CSCD

悬索作为一类典型的柔性结构,因其本身质量轻,柔性大,阻尼小等特点,在多频激励的作用下容易产生大幅振动,易造成结构疲劳破坏,从而导致工程灾害的发生。因此,悬索的振动控制是工程实际应用中亟须解决的问题。该研究采用时滞速度反馈控制策略对多频激励下的悬索进行减振控制。基于Hamilton变分原理,建立多频激励下受控悬索的非线性振动控制模型。利用Galerkin法得到离散后的时滞微分方程,通过多尺度法求解受控悬索发生超谐波与亚谐波联合共振时的幅频响应方程,并判断稳态解的稳定性,分析了受控悬索的非线性动力学行为,以及控制系统参数对共振响应的影响。研究结果表明,多频激励时悬索系统同时出现超谐共振和亚谐共振响应的特性,随着时滞值的增大不同分枝之间距离减小,随着控制增益减小分枝的稳定和不稳定解的相位趋于接近。通过调节控制增益和时滞值的大小可以改变共振范围、响应幅值及其相位,达到最优控制效果。     

可消除控制溢出的柔性结构建模新方法

本文利用柔性结构固有振动的不可控及不可观性，建立其低阶集中参数模型，可有效防止柔性结构系统振动控制中的溢出不稳定。     

一类输出时滞系统的振动主动控制方法研究

为实施一类受复杂外扰作用结构系统的低频振动控制,相应的控制系统需引入高阶低通滤波器来消除输出测量中的噪声和高频干扰,以避免观测溢出,从而形成了含输出时滞的受控振动系统.为补偿该类滤波器带来的时滞影响,提出了考虑输出时滞的最优控制方法.首先采用Moore-Penrose广义逆求解方法将含有输出时滞的系统方程转换为对应的输入输出描述形式;然后利用扩维方法将含时滞的系统转换为不显含时滞的系统,并采用传统的LQ方法设计相应的控制律.最后以实际风洞测力试验模型的低频主动减振为研究背景,进行相应的数值仿真和实验验证.结果表明,该方法能有效抑制这类输出时滞系统的低频振动.同时确保输出信号中的高频成分和噪声干扰得到很大程度的衰减,有效避免了控制器的观测溢出问题.     

马尔科夫跳变系统的时滞依赖L2-L∞滤波设计

本文研究带有时滞的Markov跳变系统的L2-L∞滤波问题，其中跳变参数以离散马尔科夫链的形式给出．设计出满阶与降价的滤波器，使得误差系统满足一定的L2-L∞性能指标．本文时滞依赖的方法，以一系列严格的矩阵不等式的形式给出了滤波器存在的充分条件．并以一种统一的形式给出了滤波器的参数．最后，以一个数值实例验证了结论的有效性。     

系统存在建模误差时的鲁棒性故障检测

提出了系统存在建模误差时的一种鲁棒性故障检测方法。假设系统发生故障前有一段正常运行阶段,这个假设在工程中是很容易满足的,该阶段用自适应滤波器对系统进行参数估计,参数估计稳定后用Kalman滤波器进行故障检测。算例表明该方法的参数估计和故障检测效果都很好。     

Vibration isolation of a symmetric rigid plate using struts under static and dynamic axial excitation

This paper presents vibration isolators in the form of post-buckled elastic clamped–clamped struts to relief the vibrating machines from the harmful effects of vibration. These vibrations are in most cases uncontrollable and lead to sudden failure. Therefore, mechanical engineers should control, isolate, and minimize such unwanted vibrations. A mathematical model is introduced consisting of pre-bent post-buckled struts acting as vibration isolators supporting a symmetric rigid plate. The model is subject to axial harmonic excitation at the base, and allowed to displace laterally with respect to axial center line of the isolated plate. The displacement transmissibility is the governing parameter of the isolator’s effectiveness at the mitigating vibrations transmitted from the base to the plate. The transmissibility is calculated over a wide range of frequencies and plotted in form of design charts. The transmissibility plots showed the ranges of frequencies, at which isolation can be maintained. The system resonance frequencies can be easily depicted from the design graphs. The present study reveals that at resonance frequencies the most effective transmissibility is well below unity. Vibration characteristics are determined under specific frequencies such that the physical behavior of the system can be thoroughly analyzed. All variables used are normalized, such that the results aren’t dependent on any material or geometric property, such as the modulus of elasticity of the material, section modulus of the used profile, or the length of the strut. In this way, the obtained results can be applied over a wide range of elastic materials, regardless of the material type or section properties.     

Kalman filtering to suppress spurious signals in adaptive optics control

In many scenarios, an adaptive optics (AO) control system operates in the presence of temporally non-white noise. We use a Kalman filter with a state space formulation that allows suppression of this colored noise, hence improving residual error over the case where the noise is assumed to be white. We demonstrate the effectiveness of this new filter in the case of the estimated Gemini Planet Imager tip-tilt environment, where there are both common-path and non-common-path vibrations. We discuss how this same framework can also be used to suppress spatial aliasing during predictive wavefront control assuming frozen flow in a low-order AO system without a spatially filtered wavefront sensor, and present experimental measurements from Altair that clearly reveal these aliased components.     

Dynamical behaviour of a friction oscillator with simultaneous self and external excitation

Friction-induced self-sustained oscillations, also known as stick-slip vibrations, occur in mechanical systems as well as in everyday life. In engineering applications these vibrations are undesirable and should be avoided. In the present paper it is shown how the very robust limit cycles of stick-slip vibrations can be broken up by a harmonic disturbance. Based on a simple model of a friction oscillator with simultaneous self and external excitation the resulting bifurcation behaviour and the routes to chaos are investigated for a wide range of system parameters. The influence of different types of friction characteristics is elaborated and the admissibility of smoothing procedures is examined by comparing results gained for non-smooth and smoothed friction characteristics.     

基于输入指令整形法的X光机残余振动抑制

为实现骨科手术自动化,研制了用于获取断骨位置和姿态信息的全自动C形臂X光机,但其结构形式决定了它是一种典型的大惯量、高柔性机构,易于产生残余振动.残余振动的存在不利于图像的连续拍摄,且影响拍摄质量.采用输入指令整形技术,针对系统的一、二阶模态,设计输入指令整形器,对系统的输入指令进行整形滤波后,有效地消除了残余振动,提高了系统的响应速度.输入指令整形方法本质上是设计一种滤波器,采用该方法抑制残余振动不需要对原有系统的结构和硬件作任何改动.实验证明,这种方法对于抑制大惯量、高柔性系统中存在的残余振动问题是有效的.     

基于Euler Bernoulli理论的压电系统集中参数模型修正

摘要： 针对压电俘能系统悬臂梁结构集中参数模型的局限性,引入Euler Bernoulli梁振动模型。通过分析两模型在振动时相对位移传递率发现,集中参数模型在基础激励情况下,传递率峰值存在较大偏差。理论分析了Euler Bernoulli及集中参数模型在一阶模态附近位移传递率函数,对集中参数模型进行了修正。仿真结果表明修正后的集中参数模型相对位移传递率峰值与Euler Bernoulli模型在低阶模态吻合良好。     

Novel method for minimizing track seeking residual vibrations ofhard disk drives

Track access time is an important parameter for high-performance hard disk drives (HDDs). Presently, the resonances of the head actuator caused by the pivot-bearing stiffness are an even more urgent problem, since these resonances have become the main design factor that limits further reduction of track access time and improvement of the servo control bandwidth in HDDs. Our objective in this paper is to investigate, from a mechanics and dynamics viewpoint, the influence of the driving force waveforms on residual vibrations and to identify the characteristics of the waveform, which will lead to zero or very low residual vibrations. Using a simplified model of a head actuator assembly and finite-element simulation, we show that the residual vibration of the head actuator assembly depends strongly on the waveform and the time duration of the driving impulse force. If suitable waveform and time duration of the seeking impulse force are appropriately chosen, very low track seeking residual vibrations and quick track access can be achieved     

Using the Weibull distribution to characterise road transport vibration levels

This paper reviews the various ways that have been proposed to characterise road transport vehicle vibrations and recommends a new approach to characterise the vibrations levels during a transport journey. Some 47 road vehicle vibration records, obtained from a broad range of conditions, were analysed, and results show that the root-mean-square (rms) distribution of the vibrations can be accurately modelled with a reduced version of the three-parameter Weibull distribution (shape parameter set to 2). This statistical approach to characterising road vehicle vibrations takes into account the random fluctuations in rms levels that occur naturally during a road journey and can be used to classify the severity of RVV. This offers significant improvement on the simplistic mean rms value that has, so far, been the sole parameter to describe vibration levels during transport. The Weibull location parameter represents the low threshold of the rms level in the record (except when xo is less than zero, in which case the low rms threshold is zero), whereas the Weibull range parameter is proportional to the range of rms level. Results also reveal a strong relationship between the rms mean and the sum of the location and scale parameters. In addition, this enables generation of rms distributions from the mean power density spectrum (PDS) alone. The modified (fixed-shape) Weibull distribution can be used to faithfully describe the entire statistical distribution of the rms level of a journey or transport mode with just two parameters. This new approach can be used in a practical way for quantifying and comparing transport vibration rms levels for design and testing purposes.     

基于Volterra自适应滤波器的发动机运转噪声预测

摘 要：发动机运转噪声的预测对于减小发动机运转噪声干扰、提高发动机异响故障诊断正确率具有重要意义。基于相空间重构理论,采用三阶Volterra自适应滤波器,提出了两种分别采用双传感器、单传感器的发动机运转噪声建模与预测方法。所提方法有效利用了Volterra级数强大的非线性映射能力,充分考虑了发动机运转噪声内在的循环相关性、周期及相位信息等先验知识。试验结果表明,所提方法具有较好的鲁棒性,其精度可以满足实际应用要求。