STATE SPACE METHODS FOR DECENTRALIZED H_∞ CONTROL

This paper presents state space methods for decentralized Hoe control, which contain two respects: a parametrization approach and an iterative algorithm. For large scale systems with N subsystems, decentralized Hoe con trollers can be derived by a parametrization result for centralized Her: controllers and designed by an iterative algorithm with structured constraint to the controllers.

Application of the state space model to the system of wave energy conversion Analytical method for wave forces on singleoscillating rectangular buoy

A new analytical method is proposed to analyze the force acting on a rectangular oscillating buoy due to linear waves.In the method a new analytical expression for the diffraction velocity potential is obtained first by use of theeigenfunction expansion method and then the wave excitation force is calculated by use of the known incident wavepotential and the diffraction potential. Compared with the classical analytical method, it can be seen that the presentmethod is simpler for a two-dimensional problem due to the comparable effort needed for the computation ofdiffraction potential and for that of radiated potential. To verify the correctness of the method, a classical example inthe reference is recomputed and the obtained results are in good accordance with those by use of other methods,which shows that the present method is correct.

State space solution to 3D multilayered elastic soils based on order reduction method

Starting with the governing equations in terms of displacements of 3D elastic media, the solutions to displacement components and their first derivatives are obtained by the application of a double Fourier transform and an order reduction method based on the Cayley-Hamilton theorem. Combining the solutions and the constitutive equations which connect the displacements and stresses, the transfer matrix of a single soil layer is acquired. Then, the state space solution to multilayered elastic soils is further obtained by introducing the boundary conditions and continuity conditions between adjacent soil layers. The numerical analysis based on the present theory is carried out, and the vertical displacements of multilayered foundation with a weak and a hard underlying stratums are compared and discussed.

DYNAMIC RESPONSE OF ELASTIC RECTANGULAR PLATES BY SPLINE STATE VARIABLE METHOD

Application of spline element and state space method for analysis of dynamic response of elastic rectangular plates is presented. The spline element method is used for space domain and the state space method in control theory of system is used for time domain. A state variable recursive scheme is developed, then the dynamic response of structure can he calculated directly. Several numerical examples are given. The results which are presented to demonstrate the accuracy and efficiency of the present method are quite satisfactory.

基于state-space-split法的滞回非线性系统随机动力响应分析

采用SSS(state-space-split)法,建立了引入Bouc-Wen滞回模型的杜芬非线性系统在高斯白噪声激励下的概率密度函数(PDF)的近似求解方法,分析了其随机动力响应变化规律。首先,将Bouc-Wen滞回模型引入杜芬非线性系统,分别考虑非线性系统中的几何非线性和材料非线性对动力响应的影响。随后,对该模型进行了等效线性化(EQL)处理,基于等效线性化法结果,介绍了SSS法的简化方法和计算原理,并通过该方法求解了三维FPK方程的近似联合概率密度函数。最后,将该方法应用于三个案例和一个工程实例,通过求解其概率密度函数分布及动力可靠度验证了提出方法的适用性、可行性和优越性。

MLP training in a self-organizing state space model using unscented Kalman particle filter

Many Bayesian learning approaches to the multi-layer perceptron （MLP） parameter optimization have been proposed such as the extended Kalman filter （EKF）. This paper uses the unscented Kalman particle filter （UPF） to train the MLP in a self- organizing state space （SOSS） model. This involves forming augmented state vectors consisting of all parameters （the weights of the MLP） and outputs. The UPF is used to sequentially update the true system states and high dimensional parameters that are inherent to the SOSS moder for the MLP simultaneously. Simulation results show that the new method performs better than traditional optimization methods.

Solution to the Dirac equation using the finite difference method

In this study,single-particle energy was examined using the finite difference method by taking 208Pb as an example.If the first derivative term in the spherical Dirac equation is discretized using a three-point formula,a one-to-one correspondence occurs between the physical and spurious states.Although these energies are exactly the same,the wave functions of the spurious states exhibit a much faster staggering than those of the physical states.Such spurious states can be eliminated when applying the finite difference method by introducing an extra Wilson term into the Hamiltonian.Furthermore,it was also found that the number of spurious states can be reduced if we improve the accuracy of the numerical differential formula.The Dirac equation is then solved in a momentum space in which there is no differential operator,and we found that the spurious states can be completely avoided in the momentum space,even without an extra Wilson term.

模型信息联合校正型自抗扰控制策略

为解决微电网受到不确定扰动时,会对直-直变换器输出的电能质量产生严重影响的问题,该文提出一种模型信息联合校正型自抗扰控制技术(ADRC-MIR)。在该控制策略中,首先借助串联超前校正的思想,以比例微分校正环节对线性扩张状态观测器的扰动观测传递函数进行修正,使其可实现对总和扰动更精确的跟踪;然后,根据状态空间平均法从被控系统中提取部分模型信息,将其写入修正后的线性扩张状态观测器的系数矩阵并最终构建出ADRC-MIR;随后基于理论推导,给出改进控制器的参数整定公式及其物理意义,并从噪声抑制、扰动抑制及其频域特性等方面指出改进后的控制器可提升控制品质的原因。最后通过对比不同工况下的数值仿真验证所提控制策略的可行性与正确性。

轨道车辆垂向轮轨力时域识别对比及其机器学习修正

为了尽可能减小轨道车辆垂向轮轨力时域识别中存在的误差,以时域法为基础,开展了基于机器学习修正的轨道车辆垂向轮轨力识别研究.首先建立了车辆动力学仿真模型,获取了车辆在随机轨道激励下以250km/h速度行驶时的轴箱加速度响应和垂向轮轨力.其次,建立了Green函数法、状态空间法这2种时域法对应的动载荷识别模型,对状态空间法的初值误差进行了分析,并引入多项式拟合法修正其趋势项误差,进而对比分析了2种方法的计算精度和计算效率.然后,针对时域法存在的识别误差,提出采用NARX(nonlinear autoregressive models with exogenous inputs)模型对识别误差进行训练和预测,用于消减模型中存在的如响应观测不全与观测噪声等因素造成的影响,进而对时域法识别结果进行修正,提高识别精度.最后,通过一个10自由度轨道车辆垂向动力学模型,对方法的正确性进行了验证.研究结果表明:2种方法对轨道车辆垂向轮轨力均具有较高的识别精度,对于各轮对的识别精度各有优劣;在计算效率方面,状态空间法比Green函数法更优;经NARX模型修正的2种时域法对轨道车辆垂向轮轨力均具有很好的识别效果,识别值与正演值的Pearson相关系数大于0.99,为极强相关.基于NARX模型的机器学习误差修正方法可有效提高时域识别精度,可以为后续轨道车辆轮轨力预测提供参考,具有较强的工程运用价值.

Simplified Method of Stability Analysis of Nonlinear Systems without Using of Lyapunov Concept

In this paper a new simplified method of stability study of dynamical nonlinear systems is proposed as an alternative to using Lyapunov’s method. Like the Lyapunov theorem, the new concept describes a sufficient condition for the systems to be globally stable. The proposed method is based on the assumption that, not only the state matrix contains information on the stability of the systems, but also the eigenvectors. So, first we will write the model of nonlinear systems in the state-space representation, then we use the eigenvectors of the state matrix as system stability indicators.

模态测试不确定性影响因素分析及传感器布置应用

模态测试结果的准确性会受测试数据采集、数据处理、建模假设和参数估计等不确定性因素的影响.为研究模态测试中模态参数的不确定性水平及不同影响因素对其的影响规律,本文采用状态空间模型和费希尔信息矩阵的快速模态参数不确定性分析方法,探讨包括振动信号的采样时长、采样频率、采样信噪比和结构的阻尼比等多种因素对模态参数不确定性水平的影响,同时提出利用模态参数不确定性水平来优化传感器布置策略的实用性建议.结果表明:模态参数的不确定性水平随采样时长、采样频率、信噪比和传感器数量的增加而降低,随结构阻尼比的增大而升高;对于均匀分布结构,多数传感器布置在结构顶部和中上部,少数布置在中下部时,模态参数的整体不确定性水平较低,是一种相对较优的传感器布置方案.

海上风电场经柔直送出系统的虚拟导纳中频振荡抑制策略

随着柔性直流输电技术在远海风电的广泛应用,海上换流站接入远海风电场时出现了中频振荡现象,严重危害系统安全稳定运行。为此,提出了一种基于虚拟导纳的中频振荡抑制策略。首先,采用模块化状态空间法建立了海上风电场经柔直送出系统的小信号模型。然后,采用参与因子分析方法揭示了影响中频振荡的关键因素,并分析了各关键因素对中频振荡的影响特性。在此基础上,提出在柔直控制系统中添加虚拟导纳的阻尼控制策略,并基于阻尼控制器对中频、LCL振荡的差异影响划分了控制器参数的稳定域。最后,在Matlab/Simulink中搭建时域仿真模型。结果表明,所提策略在系统不同运行工况下均可有效抑制中频振荡,提高了系统稳定性。

A State Space Boundary Element Method with Analytical Formulas for Nearly Singular Integrals

A new method named the state space boundary element method （SSBEM） is estab- lished, in which the problem domain is divided into two parts. One is the boundary element domain which includes the interested inner point, and the other is the state space domain. The boundary integral equation and the state space equation are combined together based on the interfacial continuity condition to form the system equation of the SSBEM. The SSBEM synthe- sizes both advantages of the boundary element method and the state space method. However, it can give inaccurate results when being used to evaluate the mechanical quantity of a point very close to the boundary element, because the Gaussian quadrature fails to calculate the nearly singular integrals. The analytical formulas were developed by part of the authors before intro- duced to deal with the nearly singular integrals. Thus, the SSBEM can yield accurate physical quantities for the points very close to the boundary element. The SSBEM results agree well with those of the finite element method （FEM）, while the discretized elements are far fewer than those of the FEM. Meanwhile, the SSBEM can analyze very thin coating, while the FEM fails due to the limitation of tolerance for Boolean operations.

高压直流输电系统可靠性分析方法综述

高压直流输电系统因具有输送容量大、能耗低且能实现电力系统非同步互联等优势而得到广泛应用,其可靠性分析可为系统提供重要的运维及决策依据。因此,围绕现阶段国内外高压直流输电系统可靠性分析方法进行了归纳总结。首先阐述了传统直流输电、柔性直流输电系统的组成差异,并对输电系统常用的可靠性指标作了相应归纳。其次,从统计法、手册法、状态空间法及其他方法等层面出发,分别对高压直流输电系统可靠性建模的基本原理及研究现状进行了分析,对各类方法的优缺点进行了对比,并探讨了柔性直流输电系统在可靠性分析方面存在的新挑战。最后,针对当前研究中存在的不足,对高压直流输电系统可靠性分析方法进行讨论与展望。

基于R-L分数阶定义的PCCM Boost变换器建模与分析

研究了基于R-L分数阶定义的电感电流伪连续PCCM(pseudo-continuous conduction mode)Boost变换器模型,并由此导出了变换器的状态平均模型,然后推导出升压比,直流静态工作点,电感电流波纹以及输出电压波纹的表达式。结果表明,与基于Caputo分数阶定义下的变换器模型相应表达式比较,R-L分数阶定义下的直流静态工作点和升压比不仅与占空比相关,而且还与电感和电容的阶数有关,输出电压波纹的表达式不仅与分数阶电感的阶数α有关,与分数阶电容的阶数β也相关。电感和电容的阶数对状态变量的直流分量和分数阶PCCM Boost的稳态特性有很大影响。最后,在MATLAB/SIMULINK中搭建了R-L分数阶PCCM Boost变换器数学模型和电路模型,仿真结果显示R-L分数阶PCCM Boost变换器模型的分析结果比其他PCCM Boost模型的分析结果更加稳定,误差更小。

粮食补贴政策的运行机制与改革逻辑——基于不确定性状态依存方法的解释

从种粮主体视角出发,引入劳动市场收入跨度概念,基于空间向量和不确定性状态依存方法构建了粮食补贴政策运行机制与改革逻辑的理论分析框架。基于该理论框架发现:(1)粮食补贴政策的核心作用之一是为粮食产业吸引较高技能禀赋的种粮者;(2)不同类型粮食补贴都会被当成收入性补贴,其产生的收入效应会起到扩大粮食种植面积和促进粮食科技进步的作用。因此应从政策空间、政策目标和政策弹性3个维度改革完善我国粮食补贴政策:一是进一步聚焦政策目标,提高技能型经营主体种粮意愿;二是充分发挥政策乘数效应,补贴聚焦产业链中后端;三是着力优化政策响应机制,抓住信息技术革命契机。

Sequential Monte Carlo Method Toward Online RUL Assessment with Applications

Online assessment of remaining useful life(RUL) of a system or device has been widely studied for performance reliability, production safety, system conditional maintenance, and decision in remanufacturing engineering. However,there is no consistency framework to solve the RUL recursive estimation for the complex degenerate systems/device.In this paper, state space model(SSM) with Bayesian online estimation expounded from Markov chain Monte Carlo(MCMC) to Sequential Monte Carlo(SMC) algorithm is presented in order to derive the optimal Bayesian estimation.In the context of nonlinear & non-Gaussian dynamic systems, SMC(also named particle filter, PF) is quite capable of performing filtering and RUL assessment recursively. The underlying deterioration of a system/device is seen as a stochastic process with continuous, nonreversible degrading. The state of the deterioration tendency is filtered and predicted with updating observations through the SMC procedure. The corresponding remaining useful life of the system/device is estimated based on the state degradation and a predefined threshold of the failure with two-sided criterion. The paper presents an application on a milling machine for cutter tool RUL assessment by applying the above proposed methodology. The example shows the promising results and the effectiveness of SSM and SMC online assessment of RUL.

混凝土芯水泥土复合桩竖向承载特性分析方法

基于Euler梁理论和状态空间法,建立了综合考虑非线性芯桩-水泥土-桩周土界面作用的双层叠合直梁分析模型及其状态方程,推导了成层土中不同组合形式的复合桩截面内力与变形的统一解析解,有效地考虑了复合桩分析中土与结构相互作用、结构局部参数发生变化等难点。通过与已有文献中现场试验和数值计算结果对比,验证了该方法的有效性,并讨论了桩径比、芯长比和水泥土弹性模量对桩承载特性的影响。研究结果表明:(1)桩径比增大,可提供的桩侧摩阻力和桩端阻力增大,复合桩竖向承载力基本呈线性增长;(2)芯长比增大,复合桩竖向承载力的增长幅度逐渐增大;(3)水泥土弹性模量对于桩竖向承载力影响较小。

一种多层组合梁自由振动分析的混合有限元法

基于截面等效,提出了多层组合梁的二维分析模型。使用混合能变分原理,以包含频率函数的节点位移及其能量对偶的应力分量为单元节点未知量,引入混合元对梁长方向进行离散,建立动力学状态空间控制方程;接着引入微分求积法(Differential Quadrature Method,DQM)对控制方程进行梁高度方向的离散,求得组合梁在不同轴力与边界条件下的动力学方程。以混凝土-木材组合梁、波形钢腹板梁和钢-混组合梁为例进行验证。该方法基于二维理论,可为梁理论提供假设依据和误差分析的基准。

潜在空间中的策略搜索强化学习方法

策略搜索是深度强化学习领域中一种能够解决大规模连续状态空间和动作空间问题的高效学习方法,被广泛应用在现实问题中。然而,此类方法通常需要花费大量的学习样本和训练时间,且泛化能力较差,学到的策略模型难以泛化至环境中看似微小的变化。为了解决上述问题,提出了一种基于潜在空间的策略搜索强化学习方法。将学习状态表示的思想拓展到动作表示上,即在动作表示的潜在空间中学习策略,再将动作表示映射到真实动作空间中。通过表示学习模型的引入,摒弃端到端的训练方式,将整个强化学习任务划分成大规模的表示模型部分和小规模的策略模型部分,使用无监督的学习方法来学习表示模型,使用策略搜索强化学习方法学习小规模的策略模型。大规模的表示模型能保留应有的泛化性和表达能力,小规模的策略模型有助于减轻策略学习的负担,从而在一定程度上缓解深度强化学习领域中样本利用率低、学习效率低和动作选择泛化性弱的问题。最后,在智能控制任务CarRacing和Cheetah中验证了引入潜在空间中的状态表示和动作表示的有效性。