共查询到20条相似文献，搜索用时 593 毫秒
1.
Ivan Bradaric Athina P. Petropulu Konstantinos I. Diamantaras 《Journal of The Franklin Institute》2002,339(2):161-187
Higher-order statistics (HOS) are well known for their robustness to additive Gaussian noise and ability to preserve phase. HOS estimates, on the other hand, have been criticized for high complexity and the need for long data in order to maintain small variance. Since rank reduction offers a general principle for reduction of estimator variance and complexity, we consider the problem of designing low-rank estimators for HOS. We propose three methods for choosing the transformation matrix that reduces the mean-square error (MSE) associated with the low-rank HOS estimates. We also demonstrate the advantages of using low-rank third-order moment estimates for blind system estimation. Results indicate that the full rank MSE corresponding to some data length N can be attained by a low-rank estimator corresponding to a length significantly smaller than N. 相似文献
2.
Mauro Cappelli Bernardino Castillo–Toledo Stefano Di Gennaro 《Journal of The Franklin Institute》2021,358(2):1308-1326
In this work, dynamic controllers are designed for reactor power, pressurizer water level, and pressure control in the primary circuit of a pressurized water reactor. These nonlinear controllers use super-twisting sliding-mode estimators to enhance their robustness versus parameter variations and external disturbances. Hence, the perturbative terms can be canceled by the control, thus improving the dynamic behavior of the controlled system. The designed controllers ensure good performances and better transient behavior, also in the presence of uncertainties and disturbances. A performance study of the proposed controllers is carried out in the presence also of unmodeled dynamics. 相似文献
3.
测量平差模型的抗差解 总被引：1，自引：0，他引：1
杨元喜 《中国科学院研究生院学报》1995,(2)
抗差Ｍ估计是使用最广泛、计算较简明的抗差估计法，基于多维Ｍ估计原理，建立了经典测量平差函数模型的抗差解，并推导出相应的误差影响函数；为了使抗差估计适于不同类型以及不同先验精度的各类观测的混合平差，将采用等价权原理构造抗差解式。 相似文献
4.
This work investigates joint time-frequency synchronization and channel estimation in two-way relay networks (TWRN) that utilize amplify-and-forward (AF) relay strategy. A two-way transmission model for joint time-frequency synchronization and channel estimation in TWRN is provided. Due to the high dimension and complexity of the model, the maximum likelihood (ML) algorithm is over complex and a standard Markov chain Monte Carlo (MCMC) algorithm is ineffective. We instead develop a hybrid Metropolis–Hastings–Gibbs algorithm in order to facilitate joint time-frequency recovery and effective channel estimation. In particular, we present a reparameterized model to facilitate Gibbs sampling with respect to the self-interference channel. Then the second order truncated Taylor series approximation is adopted for carrier frequency offsets (CFOs) estimation. Furthermore, a heuristic way of determining update order of parameters is proposed and initial value of the Markov chain is discussed as well. To test the robustness and objectivity of our proposed algorithm, two MCMC estimators, each with its own prior distribution, are compared against each other. Numerical results are provided to verify the effectiveness and robustness of proposed algorithm in terms of both mean-square errors (MSE) and estimation bias. The bit error rate (BER) performance results are further offered for comparison. 相似文献
5.
本文在加权平方损失下导出了平衡的双向分类随机效应模型中方差分量的Bayes估计,并利用 非参数方法构造了方差分量的经验Bayes (EB)估计。在适当的条件下证明 了EB估计的收敛速度。最后,给出一个满足主要结果的例子。 相似文献
6.
Wieslaw Krajewski Stefano Miani Umberto Viaro 《Journal of The Franklin Institute》2005,342(6):674-687
The paper considers the problem of designing PI controllers for industrial processes approximated by a first-order time-delayed model. The suggested frequency-domain approach is based on a normalized open-loop transfer function and makes use of the loci of constant stability margins and other performance indices in the parameter space. In this way, it is possible to evaluate the effects of uncertainties in the process parameters and, thus, control system robustness. Some examples show how the procedure operates. 相似文献
7.
Koksal Erenturk 《Journal of The Franklin Institute》2010,347(7):1171-1185
This study presents application of a fuzzy controller to a nonlinear two-mass system control. The proposed controller structure is strengthened with a gray estimator. Firstly, a complete state-space mathematical model for a nonlinear two-mass system is developed and numerically simulated. Then, a fuzzy controller is designed to regulate the speed of the system. In order to perform a dynamic and powerful control action, future error values are estimated by gray modeling technique. The gray estimators of the torsional torque and the load machine speed are tested with open-loop and closed-loop control structures to test the robustness of the proposed method for step changes in input parameters. It is observed that the tracking ability of the gray estimators is not influenced for different operation modes. The performances of the control structures, which are supported with gray estimators, are given and no additional feedbacks are required for robust control action. The simulation results are confirmed by experimental results and conclusions are given. 相似文献
8.
Unifying terminology usages which captures more term semantics is useful for event clustering. This paper proposes a metric of normalized chain edit distance to mine, incrementally, controlled vocabulary from cross-document co-reference chains. Controlled vocabulary is employed to unify terms among different co-reference chains. A novel threshold model that incorporates both time decay function and spanning window uses the controlled vocabulary for event clustering on streaming news. Under correct co-reference chains, the proposed system has a 15.97% performance increase compared to the baseline system, and a 5.93% performance increase compared to the system without introducing controlled vocabulary. Furthermore, a Chinese co-reference resolution system with a chain filtering mechanism is used to experiment on the robustness of the proposed event clustering system. The clustering system using noisy co-reference chains still achieves a 10.55% performance increase compared to the baseline system. The above shows that our approach is promising. 相似文献
9.
比例Bootstrap及其方差估计的相合性 总被引：1，自引：0，他引：1
研究了比例Bootstrap,介绍其与通常的Bootstrap方法的差异;对简单随机抽样,在均匀回答的假定下,就缺失数据采取回归插补和比率插补的情形,证明了由比例Bootstrap方法得到的方差估计具有相合性;最后,通过模拟验证了理论结果. 相似文献
10.
泊松回归模型常常用于计数数据的研究中,然而在实际数据中零值的比例可能远远大于泊松分布中取零值的概率,而且这些零值通常都有其特殊含义.此外计数数据可能是分组数据,即观测到的数据不是确切值而只是已知其落在某一个区间范围之内;或者某些特定的数据,例如工资,要先对它进行人为的分组然后再进行分析.考虑一种零膨胀泊松半参数回归模型来处理上述分组计数数据.该模型中泊松分布的期望与协变量之间采用部分线性连接函数,而零值的概率与协变量之间采用线性连接函数.利用Sieve极大似然估计方法来估计该回归模型中参数和非参数函数,并提出了一种得分检验方法来检验是否存在零膨胀.在一定正则条件下,获得了Sieve极大似然估计的渐近性质,证明了参数部分的估计是强相合,渐近正态及渐近有效的;同时非参数函数的估计达到了最优收敛速度.模拟研究表明,估计和检验方法效果都比较好,最后将此模型和推断方法应用于一组公共卫生领域实际数据研究. 相似文献
11.
This paper discusses PID controller tuning for integrating processes with varying time-delays. Most of the existing tuning rules for the first-order lag plus integrator plus delay (FOLIPD) processes that we mainly focus on have the same general structure, and the properties of these rules are discussed in conjunction with varying time-delays. The analysis leads to novel tuning rules, where the maximum amplitude of an arbitrarily varying time-delay can be given as a parameter, which makes the use of the rules attractive in several applications. We will also extend the analysis to integrating processes with second-order lag and apply the design guidelines for a networked control application. In addition, we propose a novel tuning method that optimizes the closed-loop performance with respect to certain robustness constraints while also providing robustness to delay variance via jitter margin maximization. Further, we develop new PID controller tuning rules for a wide range of processes based on the proposed method. The new tuning rules are discussed in detail and compared with some of the recently published results. The work was originally motivated by the need for robust but simultaneously well-performing PID parameters in an agricultural machine case process. We also demonstrate the superiority of the proposed tuning rules in the case process. 相似文献
12.
In this paper, the event-triggered distributed H∞ state estimation problem is investigated for a class of state-saturated systems with randomly occurring mixed delays over sensor networks. The mixed delays, which comprise both discrete and distributed delays, are allowed to occur in a random manner governed by two mutually independent Bernoulli distributed random variables. In order to alleviate the communication burden, an event-triggered mechanism is utilized for each sensor node to decide whether or not its current information should be broadcasted to its neighbors. The aim of this paper is to design event-triggered state estimators such that the error dynamics of state estimation is exponentially mean-square stable with a prescribed H∞ performance index. By resorting to intensive stochastic analysis, sufficient conditions are first derived to guarantee the existence of the desired estimators, and the parameters of the desired distributed estimators are then obtained in light of the feasibility of a certain set of matrix inequalities. A numerical example is employed to illustrate the usefulness of the proposed distributed estimation algorithm. 相似文献
13.
This paper is concerned with the distributed Kalman filtering over the wireless sensor networks (WSNs) in the presence of intermittent observations and different sensing states, where only task nodes are required to estimate the state of a linear time-invariant discrete-time system. A class of flexible binary values is used to develop the adaptability of flexible optimal Kalman filtering (FOKF) for variable sensing states. Based on the minimum error covariance trace principle, two classes of FOKFs have optimal collaborative estimation via their own and community observations, including the original FOKF and the FOKF with uncertain noise variance. The performance analysis of these two types of filters show that they have high estimation accuracy, strong robustness, low energy consumption and user-friendliness. The proposed algorithms are applied to estimate and track the position of a moving target in WSNs. The simulation illustrates that the proposed filters have superior performance, compared with the existing algorithms. 相似文献
14.
This paper studies the distributed Kalman consensus filtering problem based on the event-triggered (ET) protocol for linear discrete time-varying systems with multiple sensors. The ET strategy of the send-on-delta rule is employed to adjust the communication rate during data transmission. Two series of Bernoulli random variables are introduced to represent the ET schedules between a sensor and an estimator, and between an estimator and its neighbor estimators. An optimal distributed filter with a given recursive structure in the linear unbiased minimum variance criterion is derived, where solution of cross-covariance matrix (CCM) between any two estimators increases the complexity of the algorithm. In order to avert CCM, a suboptimal ET Kalman consensus filter is also presented, where the filter gain and the consensus gain are solved by minimizing an upper bound of filtering error covariance. Boundedness of the proposed suboptimal filter is analyzed based on a Lyapunov function. A numerical simulation verifies the effectiveness of the proposed algorithms. 相似文献
15.
《Journal of The Franklin Institute》2023,360(2):1284-1307
This paper considers the trajectory tracking for a cable-suspended rigid body carried by multiple quadrotors while maintaining the desired formation. A three-loop control structure is proposed based on the Super Twisting Sliding Mode (STSM) controller with high robustness to compensate for uncertainties and disturbances. In the proposed structure, a proper formation based on a centralized approach creates advantages such as collision avoidance and non-entanglement of the cables, which leads to uniform load distribution on all quadrotors to optimize energy consumption. The corresponding equations are formulated as a convex constrained optimization problem with an analytical solution for calculating the cables' tension. This approach is a straightforward and computationally efficient method for real-time applications. In addition to proving the system's stability by Lyapunov theory, the simulation results show good performance in the presence of disturbance and uncertainty. 相似文献
16.
Accurate term discrimination in information retrieval is essential for identifying important terms in specific documents. In addition to the widely known inverse document frequency (IDF) method, alternative approaches such as the residual inverse document frequency (RIDF) scheme have been introduced for term discrimination. However, existing methods' performance is not unconditionally convincing. We propose a new collection frequency weighting scheme derived from the negative binomial distribution model of term occurrences. Factorial experiments were performed to examine potential interaction effect between collection frequency weight methods and term frequency weight methods according to the mean average precision and normalized discounted cumulative gain performance assessors. The results indicate that our proposed term discrimination method offers a significant gain in accuracy as compared to the IDF and RIDF scheme. This finding is reinforced by the fact that the results show no interaction effects among factors. 相似文献
17.
Weibull分布基于定数逐次截尾寿命数据的统计分析 总被引：3，自引：0，他引：3
讨论Weibull分布基于定数逐次截尾寿命数据的参数估计，得到了参数的逆矩估计量和区间估计，模拟结果显示在中小样本情况下所给估计量优于参数的最大似然估计． 相似文献
18.
《Information processing & management》2005,41(5):1193-1205
This paper examines a real-time measure of bias in Web search engines. The measure captures the degree to which the distribution of URLs, retrieved in response to a query, deviates from an ideal or fair distribution for that query. This ideal is approximated by the distribution produced by a collection of search engines. Differences between bias and classical retrieval measures are highlighted by examining the possibilities for bias in four extreme cases of recall and precision. The results of experiments examining the influence on bias measurement of subject domains, search engines, and search terms are presented. Three general conclusions are drawn: (1) the performance of search engines can be distinguished with the aid of the bias measure; (2) bias values depend on the subject matter under consideration; (3) choice of search terms does not account for much of the variance in bias values. These conclusions underscore the need to develop “bias profiles” for search engines. 相似文献
19.
本文对基于复杂网络社会动力学进行了全面的研究,讨论了社会网络包含的具体内容,着重介绍了度与度分布,加权网络及社团结构及聚类算法与社会网络动力学的关联,并关注社会网络鲁棒性与社会网络自组织临界性研究等动力学具体表现,为目前的社会网络动力学分析提供一种比较实用的研究方法。 相似文献
20.
This paper is concerned with the event-triggered H∞ state estimation problem for a class of discrete-time complex networks subject to state saturations, quantization effects as well as randomly occurring distributed delays. A series of Bernoulli distributed random variables is utilized to model the random occurrence of distributed delays. For the energy-saving purpose, an event-triggered mechanism is proposed to decide whether the current quantized measurement should be transmitted to the estimator or not. For the state-saturated complex networks, our aim is to design event-triggered state estimators that guarantee both the exponential mean-square stability of and the H∞ performance constraint on the error dynamics of the state estimation. Stochastic analysis is conducted, in combination with the Lyapunov functional approach, to derive sufficient conditions for the existence of the desired estimators whose gain matrices are obtained by solving a set of matrix inequalities. An illustrative example is exploited to show the usefulness of the estimator design algorithm proposed. 相似文献