Gradient-based iterative identification method for multivariate equation-error autoregressive moving average systems using the decomposition technique     

Zhengwei Ge  Feng Ding  Ling Xu  Ahmed Alsaedi  Tasawar Hayat 《Journal of The Franklin Institute》2019,356(3):1658-1676

This paper studies the parameter estimation problems of multivariate equation-error autoregressive moving average systems. Firstly, a gradient-based iterative algorithm is presented as a comparison. In order to improve the computational efficiency and the parameter estimation accuracy, a decomposition-based gradient iterative algorithm is presented by using the decomposition technique. The key is to transform an original system into two subsystems and to estimate the parameters of each subsystem, respectively. Compared with the gradient-based iterative algorithm, the decomposition-based algorithm requires less computational efforts, and the simulation results indicate that this algorithm is effective.  相似文献   

H_∞ output-feedback control for discrete-time switched linear systems via asynchronous switching     

Zhiyong Jiang  Peng Yan 《Journal of The Franklin Institute》2018,355(14):6215-6238

In this paper, we consider the H_∞ hybrid dynamical output-feedback control problem for discrete-time switched linear systems under asynchronous switching. A time-varying multiple Lyapunov-like-function (MLF) approach is applied to derive sufficient conditions that guarantee the stability and weighted l₂-gain performance of the closed-loop systems, where the established conditions explicitly depend on the upper and lower bounds of asynchronous switching delays. An alternative approach is proposed to decouple the bilinear problems of the control synthesis conditions. Convex optimization algorithms are also proposed based on the established conditions to determine the minimum l₂-gain performance. Two numerical examples are provided to illustrate the effectiveness of the proposed method, demonstrating significant improvement over the existing results.  相似文献   

Adaptive synchronization of multi-agent systems via variable impulsive control     

Tiedong Ma  Tiantian Yu  Bing Cui 《Journal of The Franklin Institute》2018,355(15):7490-7508

This paper mainly focuses on the adaptive synchronization problem of multi-agent systems via distributed impulsive control method. Different from the existing investigations of impulsive synchronization with fixed time impulsive inputs, the proposed distributed variable impulsive protocol allows that the impulsive inputs are chosen within a time period (namely impulsive time window) which can be described by the distances of the left (right) endpoints or the centers between two adjacent impulsive time windows. Obviously, this kind of flexible control scheme is more effective in practical systems (especially for the complex environment with physical restrictions). Moreover, the proposed adaptive control technique is helpful to solve the problem with uncertain system parameters. By means of Lyapunov stability theory, impulsive differential equations and adaptive control technique, three sufficient impulsive consensus conditions are given to realize the synchronization of a class of multi-agent nonlinear systems. Finally, two numerical simulations are provided to illustrate the validity of the theoretical analysis.  相似文献   

Chaos control of the permanent magnet synchronous motor with time-varying delay by using adaptive sliding mode control based on DSC     

Shaohua Luo  Ruizhen Gao 《Journal of The Franklin Institute》2018,355(10):4147-4163

This paper focuses on the problem of chaos control for the permanent magnet synchronous motor with chaotic oscillation, unknown dynamics and time-varying delay by using adaptive sliding mode control based on dynamic surface control. To reveal the mechanism of motor system and facilitate controller design, the dynamic behavior of the system is investigated. Nonlinear items of system model, upper bounds of time delays and their derivatives are taken as unknown in the overall process. A RBF neural network with an adaptive law, which eliminates restrictions on accurate model and parameters, is employed to cope with unknown dynamics. In order to solve issues such as chaotic oscillation, ‘explosion of complexity’ of backstepping, and chattering associated with sliding mode control, a sliding mode controller is developed within the framework of dynamic surface control by the hybrid of adaptive technology and RBF neural network. In addition, an appropriate Lyapunov function is employed to demonstrate the system stability. Finally, the feasibility of the proposed scheme is testified by simulation.  相似文献   

Recursive parameter estimation algorithm for multivariate output-error systems     

Yanjiao Wang  Feng Ding  Minhu Wu 《Journal of The Franklin Institute》2018,355(12):5163-5181

In this paper, we consider the parameter estimation issues of a class of multivariate output-error systems. A decomposition based recursive least squares identification method is proposed using the hierarchical identification principle and the auxiliary model idea, and its convergence is analyzed through the stochastic process theory. Compared with the existing results on parameter estimation of multivariate output-error systems, a distinct feature for the proposed algorithm is that such a system is decomposed into several sub-systems with smaller dimensions so that parameters to be identified can be estimated interactively. The analysis shows that the estimation errors converge to zero in mean square under certain conditions. Finally, in order to show the effectiveness of the proposed approach, some numerical simulations are provided.  相似文献   

The wider impacts of high-technology employment: Evidence from U.S. cities     

Tom Kemeny  Taner Osman 《Research Policy》2018,47(9):1729-1740

Innovative, high-technology industries are commonly described as drivers of regional development. ‘Tech’ workers earn high wages, but they are also said to generate knock-on effects throughout the local economies that host them, spurring growth in jobs and wages in nontradable activities. At the same time, in iconic high-tech agglomerations like the San Francisco Bay Area, the home of Silicon Valley, the success of the tech industry creates tensions, in part as living costs rise beyond the reach of many non-tech workers. Across a large sample of U.S. cities, this paper explores these issues systematically. Combining annual data on wages, employment and prices from the Quarterly Census of Employment and Wages, the Department of Housing and Urban Development and the Consumer Price Index, it estimates how growth in tradable tech employment affects the real, living-cost deflated wages of local workers in nontradable sectors. Results indicate that high-technology employment has significant, positive, but modest effects on the real wages of workers in nontradable sectors. These effects appear to be spread consistently across different kinds of nontradable activities. In terms of substantive wider impacts, tech appears benign, though fairly ineffectual.  相似文献   

Adaptive fault-tolerant control for a class of nonlinear multi-agent systems with actuator faults     

Chao Deng  Guang-Hong Yang 《Journal of The Franklin Institute》2017,354(12):4784-4800

This paper considers the distributed adaptive fault-tolerant control problem for linear multi-agent systems with matched unknown nonlinear functions and actuator bias faults. By using fuzzy logic systems to approximate the unknown nonlinear function and constructing a local observer to estimate the states, an effective distributed adaptive fault-tolerant controller is developed. Furthermore, different from the traditional method to estimate the weight matrix, only the weight vector needs to be estimated by exchanging the order of weight vectors and fuzzy basis functions in the fuzzy logic systems. In contrast to the existing results, the assumption that the dimensions of input vector and output vector are equal is removed. In addition, it is proved that the proposed control protocol guarantees all signals in the closed-loop systems are bounded and all agents converge to the leader with bounded residual errors. Finally, simulation examples are given to illustrate the effectiveness of the proposed method.  相似文献   

Leader-following consensus of nonlinear discrete-time multi-agent systems with limited communication channel capacity     

Jia Wu  Huaqing Li  Xin Chen 《Journal of The Franklin Institute》2017,354(10):4179-4195

This paper considers the problem of the leader-following consensus of generally nonlinear discrete-time multi-agent systems with limited communication channel capacity over directed fixed communication networks. The leader agent and all follower agents are with multi-dimensional nonlinear dynamics. We propose a novel kind of consensus algorithm for each follower agent based on dynamic encoding and decoding algorithms and conduct a rigorous analysis for consensus convergence. It is proved that under the consensus algorithm designed, the leader-following consensus is achievable and the quantizers equipped for the multi-agent systems can never be saturated. Furthermore, we give the explicit forms of the data transmission rate for the connected communication channel. By properly designing the system parameters according to restriction conditions, we can ensure the consensus and communication efficiency with merely one bit information exchanging between each pair of adjacent agents per step. Finally, simulation example is presented to verify the validity of results obtained.  相似文献   

冲击损伤的增强X射线实时成像检测     

张咏红  张为民 《科技广场》2008,(5)

对复合材料结构承载能力影响最严重、安全威胁最大的是冲击损伤,因此冲击损伤是复合材料损伤的主要研究对象。本文从增强剂四溴乙烷的浓度、施加方式与时间等方面的选定,进行了冲击损伤的增强X射线实时成像检测研究,其结果是对超声波C扫描检测结果的进一步验证与补充。  相似文献   

建设虚拟建筑电气实验室的理论及研究     

王有熙 《科技广场》2008,(7)

建筑电气实验室由于投资大,设备更新换代快,发展迅速,而大多数高校资源紧张,虚拟建筑电气实验室不失一个可行的缓解办法。本文研究了采用虚拟现实技术建立虚拟建筑电气实验室的可能性和相关技术,建立了其结构模块,为进一步开展相关研究打下良好基础。  相似文献