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摘 要:在圆形三向网架非线性动力学基本方程的基础上,用拟壳法给出了圆底扁球面三向网壳的大挠度方程和非线性动力学基本方程。在固定边界条件下,引入了异于等厚度壳的无量纲量,对基本方程和边界条件进行无量纲化。并将扁球面网壳的大挠度解当作扁球面网壳的初始缺陷,通过Galerkin作用得到了一个含二次、三次的非线性动力学方程。通过求Melnikov 函数,给出了具有初始缺陷的扁球面网壳系统可能发生混沌运动的临界条件。并通过数字仿真绘出了平面相图,证实了混沌运动的存在并且可以通过改变参数来抑制系统混沌运动的发生。同时也发现了考虑初始缺陷的扁球面系统固有频率增大了,从而发生混沌运动的临界载荷值减小了。 相似文献
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考查地震或水下非接触爆炸冲击下旋转机械的动态响应特性,一般从研究转子系统基础冲击响应出发。由于陀螺效应和转子-轴承的交互效应,转子系统运动方程系数矩阵呈非对称性,不能在模态坐标下解耦,无法利用常规模态叠加法求解,所以以往的研究一般采用数值积分如Newmark法等进行迭代求解,但数值积分法相对模态叠加法要耗费较多的计算资源。提出了一种复数域内转子系统冲击响应计算方法,无需坐标解耦但仍可以利用线性叠加法进行响应求解。首先将激励和响应傅立叶展开成复数形式,包括正向旋转项和反向旋转项,根据方程左右两边相同频率前系数相等的事实得到特征方程,将特征方程写成简单矩阵束的本征方程形式,求得矩阵束的本征值和本征向量,将本征向量正规化,进一步得到矩阵束的逆阵,将逆阵元素取名为“频响因子”,将逆阵与激励相乘即可得到频率响应幅值,将所有频率响应成分叠加即可得到系统响应。通过一个工程实例,比较了所提方法与数值积分方法的结果,比较分析表明,所提方法满足工程要求,可以作为转子系统基础冲击响应和瞬态响应计算的一种普适方法。 相似文献
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针对地震模拟试验常采用的开环迭代控制存在控制精度差的缺点,提出一种用于地震模拟的自适应控制方法。该方法不断识别系统的传递函数,来克服液压系统的时变性,获得较高的地震模拟波形复现精度。在此基础上,通过分析控制方法中预试验步骤存在的不足,实现试验方法改进,使得无需预试验步骤能直接进行正式试验,且首帧试验中的参考时域信号和控制时域信号相关系数较高。在浙江大学构建的振动台上进行若干典型地震波试验表明:改进后的试验方法在不进行预试验的情况下,首帧地震模拟试验获得75%以上的输入输出信号时域相关系数,同时能缩短试验时间;多帧地震模拟试验后,通过更新系统传递函数,地震模拟输入输出信号时域相关系数能稳定在95%以上。 相似文献
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基于二进小波边缘提取算法,提出一种基于后验概率模型的分类器图像融合方法。首先通过二进小波进行图像边缘检测,分别求得水平与垂直方向的边缘点,再使用最优决策函数方法对输入样本进行分析并在所有分类器中寻找一个最优的分类器,从而得到最终分类结果。该方法在图像的边缘点具有很好的分类效果等优点。 相似文献
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采用1/4车模型分别对两种半主动控制策略即SH(Sky-hook, SH)和ADD(Acceleration Driven Damping, ADD)控制进行分析,根据分析结果引入了一种新型SH-ADD混合控制策略。利用随机激励下的功率谱密度曲线代替单频谐波激励下的传递函数曲线,改进了该混合控制策略转换系数的计算方法。在采用ADAMS软件建立高速铁道车辆整车模型的基础上,对改进后的SH-ADD控制策略进行了仿真分析。仿真结果表明,该控制策略可以同时兼顾低频和中高频率范围内的振动控制效果,较SH控制和ADD控制可大幅提高车辆的横向平稳性能。 相似文献
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针对座椅悬架系统的参数不确定性和位移测量难题,基于线性矩阵不等式和H∞最优控制理论,建立了座椅悬架系统的参数不确定性H∞输出反馈控制器。控制器利用估计的状态采用鲁棒控制策略计算期望控制力。磁流变阻尼器的控制电压在满足半主动和极值约束条件下,比较期望控制力与当前阻尼力的大小,应用开关控制算法进行调整,使得磁流变阻尼器产生跟踪期望控制力的阻尼力。数值仿真结果证明,该控制器在仅利用座椅架的加速度作为测量输出进行状态估计,以及在座椅悬架系统具有参数不确定性的情况下,仍能有效地对座椅外部激励进行隔振,改善驾驶员的乘坐舒适性。 相似文献
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磁流变式调谐液柱阻尼器(MR-TLCD)是由调谐液柱阻尼器(TLCD)和磁流变液阻尼器(MRD)组成的新型半主动控制装置。依据Lagrange方程建立了MR-TLCD与单自由度结构耦合动力方程,从耗能受力角度详细阐述了MR阻尼力、TLCD液体恢复力是阻尼力还是负阻尼力。基于MTALAB/Simulink工具箱,仿真分析了单自由度被控结构受风致振动时简单双态控制、离复位控制和两级双态控制三种半主动算法下的减振效果。结果表明提出的两级双态控制算法效果最优,离复位控制次之,简单双态控制也远好于被动控制效果。综合考虑MR-TLCD与被控结构组成的动力系统,两级双态控制最趋于稳定。三种控制算法均显示良好控制效果,且结构位移控制效果略好于结构加速度。 相似文献
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Jianbo Yu 《国际生产研究杂志》2013,51(23):6746-6762
Abnormal patterns exhibited in control charts can be associated with certain assignable causes for process variation. Hence, accurate and fast control chart pattern recognition (CCPR) is essential for significantly narrowing down the scope of possible causes that must be investigated, and speeds up the troubleshooting process. This study proposes a Gaussian mixture models (GMM)-based CCPR model that employs a collection of several GMMs constructed for CCPR. By using statistical features and wavelet energy features as the input features, the proposed CCPR model provides a more simple and effective training procedure and better generalisation performance than using a single CCPR recogniser, and hence is easier to be used by quality engineers and operators. Furthermore, the proposed model is capable of adapting novel control chart patterns (CCPs) by applying a dynamic modelling scheme. The experimental results indicate that the GMM-based CCPR model shows good detection and recognition performance for current CCPs and adapts further novel CCPs effectively. Moreover, the proposed model provides a promising way for the on-line recognition of CCPs because of its efficient computation and good pattern recognition performance. Analysis from this study provides guidelines for developing GMM-based statistical process control (SPC) recognition systems. 相似文献
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通过引入状态变换,将含控制时滞的海洋平台系统转化为无时滞系统.然后,通过引入渐近稳定的期望系统,基于波浪力线性外系统近似模型,给出了海洋平台系统基于二次型性能指标泛函的前馈反馈最优跟踪控制器设计方法及其控制器的存在唯一性条件.控制器的前馈增益矩阵和反馈增益矩阵可分别经由求解代数Riccati方程和Sylvester方程得到.仿真算例表明了方法的有效性,且在减小平台的振动幅值和控制力方面,前馈反馈最优跟踪控制方法优于前馈反馈最优控制方法. 相似文献
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In the experimental demonstration of aseismic control systems, difficulties were encountered in the measurement of the displacement response of the structure. During earthquake ground motions, both the building and the ground are moving so that there is no absolute reference for the determination of the displacement response. An optimal control algorithm is proposed herein, which utilizes the measurements of acceleration and velocity responses rather than the displacement and velocity measurements. Such an optimal algorithm is developed based on the instantaneous optimal control theories, and it is evaluated and compared with other available optimal control laws. Numerical results indicate that the performance of the proposed optimal algorithm is as good as that of other optimal control laws currently available. However, the contribution of such an optimal control law to the practical implementation of active control systems for seismic hazard mitigations may be quite significant. 相似文献
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The correct, prompt recognition and analysis of unnatural and significant patterns in Schewhart’s control charts are very important since they remind out-of-control conditions. In fact, pattern extraction increases the sensitivity of charts when identifying out of control conditions. Artificial neural networks have been used to identify unnatural patterns in many research studies due to their high efficiency in pattern recognition. In most of such studies, there is a significant risk of misclassification of highly sensitive patterns. To put it more clearly, the proposed models offered for the recognition of patterns with low parametric coefficients are mistaken. This study, offers a model for the recognition and analysis of basic patterns in process control charts using LVQ and MLP networks along with a fitted line analysis. In this model, not only does risk of misclassification at different levels of sensitivity decrease remarkably, but there will also be the possibility for recognition and analysis when basic pattern occur simultaneously. The efficiency and effectiveness of the model are shown by conducting tests based on simulation. 相似文献
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A minimax optimal control strategy for uncertain quasi-integrable Hamiltonian systems with time-delayed bounded feedback control is proposed. First, a quasi-integrable Hamiltonian system with time-delayed bounded control forces and uncertain excitation and system parameters is converted into a set of Itô stochastic differential equations without time delay. Then, the partially averaged Itô stochastic differential equations for the energy processes are derived by using the stochastic averaging method for quasi-integrable Hamiltonian systems. For these equations together with an appropriate performance index, a worst-case optimal control strategy is derived via solving a stochastic differential game problem. The worst-case disturbances and the optimal bounded controls are obtained by solving a Hamilton–Jacobi–Isaacs (HJI) equation. Finally, two examples are worked out in detail to illustrate the application and effectiveness of the proposed method. 相似文献
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Robust optimal Robin boundary control for the transient heat equation with random input data 下载免费PDF全文
J. Martínez‐Frutos M. Kessler A. Münch F. Periago 《International journal for numerical methods in engineering》2016,108(2):116-135
The problem of robust optimal Robin boundary control for a parabolic partial differential equation with uncertain input data is considered. As a measure of robustness, the variance of the random system response is included in two different cost functionals. Uncertainties in both the underlying state equation and the control variable are quantified through random fields. The paper is mainly concerned with the numerical resolution of the problem. To this end, a gradient‐based method is proposed considering different functional costs to achieve the robustness of the system. An adaptive anisotropic sparse grid stochastic collocation method is used for the numerical resolution of the associated state and adjoint state equations. The different functional costs are analysed in terms of computational efficiency and its capability to provide robust solutions. Two numerical experiments illustrate the performance of the algorithm. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Fu‐Kwun Wang Berihun Bizuneh Xiao‐Bin Cheng 《Quality and Reliability Engineering International》2019,35(6):1634-1645
The statistical learning classification techniques have been successfully applied to statistical process control problems. In this paper, we proposed a one‐sided control chart based on support vector machines (SVMs) and differential evolution (DE) algorithm to monitor a process with multivariate quality characteristics. The SVM classifier provides a continuous distance from the boundary, and the DE algorithm is used to obtain the optimal parameters of the SVM model by minimizing mean absolute error (MAE). The average run length of the proposed chart is computed using the Monte Carlo simulation approach. Several simulated cases are conducted using a multivariate normal distribution with 10 and 20 dimensions and three different process shift scenarios. In addition, we consider two non‐normal distribution cases. The ARL performance of the proposed chart is better than the distance‐based SVM chart. A real example is used to illustrate the application of the proposed control chart. 相似文献
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介绍进口ITCC控制系统TS3000结合国产DCS控制系统ECS100在灵谷化工KDON-50000/72600型空分设备中的应用,叙述了空压机防喘振控制的工作原理和具体控制过程;分析了液氧泵的自动切换控制。 相似文献