基于观测器的不确定时滞系统的鲁棒控制

研究不确定线性时滞系统的状态观测器和基于观测器的鲁棒控制器设计问题,其中不确定性是时变的、不要求满足匹配条件。通过构造增广系统,利用Ｌｙａｐｕｎｏｖ稳定性理论,获得了该不确定系统存在状态观测器和基于观测器的鲁棒控制器的充分条件,同时给出了相应的状态观测器和基于观测器的鲁棒控制器。所得结论推广并改进了已知的一些结果,并通过实例说明了其有效性。     

不确定变时滞系统的状态观测器与基于观测是器的鲁棒控制器设计

研究了具有变时滞的不确定系统的状态观测器和基于观测器的鲁棒控制器设计问 题,其中不确定性是时变的,不要求满足匹配条件.通过构造增广系统,利用线性矩阵不等式 (LMI)方法,获得了该不确定系统存在状态观测器和基于观测器的鲁捧控制器的充分条件, 同时给出了相应的状态观测器和基于观测器的鲁棒控制器.     

不确定时滞系统基于观测器的鲁棒控制器设计

研究了不确定线性时滞系统的状态观测器和基于观测器的鲁棒控制器设计问题，其中不确定性是时变的，通过构造增广系统，利用线性矩阵不等式方法，获得了该不确定系统存在状态观测器和基于观测器的鲁棒控制器的充分条件，同时给出了相应的状态观测器和基于观测器的鲁棒控制器，所给示例说明了本文方法的设计步骤和有效性。     

具有状态观测器的鲁棒重复控制系统设计

针对一类时变不确定系统,研究基于状态观测器的鲁棒重复控制系统设计问题.通过状态观测器重构系统状态,利用重构状态进行状态反馈.基丁2维系统稳定性理论,应川线性矩阵不等式(LMI)方法,推导出了重复控制系统存在状态观测器和重复控制器的一个LMI条件,并用LMI的町行解给出了状态观测器和重复控制器参数的具体形式.最后用数值仿真验证了本文所提方法的有效性.     

基于观测器的时滞系统鲁棒控制器的设计

研究了一类不确定时滞系统基于观测器的鲁棒镇定问题,系统的不确定性时变未知且范数有界,目的是设计状态观测器和线性无记忆观测状态反馈控制器,使其能够镇定一类状态和控制输入不确定性时滞系统。基于Lyapunov稳定性理论,采用线形矩阵不等式这一有效工具,给出了系统基于观测状态反馈鲁棒镇定的充分条件,并且利用线形矩阵不等式的解构造了使得系统鲁棒稳定的基于观测状态反馈控制器,所得结果与时滞相关,从而相对减弱了控制器设计的保守性。数值算例表明了所提出的设计方法的有效性。     

带有状态观测器的网络控制系统非脆弱H_∞控制

研究了存在时变时延的非理想网络环境下基于状态观测器的网络化控制系统非脆弱H_∞鲁棒控制。考虑状态观测器和控制器均存在不确定性,采用Lyapunov稳定性理论和线性矩阵不等式(Linear Matrix Inequality,LMI)方法,得到闭环控制系统H_∞渐近稳定的充分条件,给出非脆弱状态观测器和非脆弱鲁棒控制器的存在条件,通过给出的锥补线性化算法求解控制器和观测器增益矩阵。仿真实例表明了所提方法的有效性和可行性。     

一类基于观测器的网络控制系统鲁棒控制器设计

研究一类基于状态观测器的网络控制系统鲁棒稳定性和鲁棒控制器设计问题.考虑传感器时钟驱动、控制器和执行器事件驱动以及小于等于一个采样周期的不确定时延,建立了基于状态观测器的网络控制系统增广模型.利用线性矩阵不等式方法推导出该系统鲁棒稳定的条件,进一步给出了鲁棒控制律和状态观测器设计方法.数值仿真算例证明了分析方法和结果的有效性.     

状态和控制输入不确定时滞系统基于观测器的鲁棒H_∞控制

研究一类同时存在状态和控制输入不确定性的时滞系统基于观测器的鲁棒Ｈ∞控制问题。系统的不确定性参数是时变的,但其结构已知。通过构造观测器并利用观测器状态进行反馈控制,使系统不仅鲁棒镇定,而且具有一定的Ｈ∞性能。鲁棒Ｈ∞控制器的设计可通过求解两个代数Ｒｉｃｃａｔｉ方程得到     

状态和控制输入不确定时滞系统基于观测器的鲁棒H∞控制

研究一类同时存在状态和控制输入不确定性的时滞系统基于观测器的鲁棒Ｈ∞控制问题。系统的不确定性参数是时变的,但其结构已知。通过构造观测器并利用观测器状态进行反馈控制,使系统不仅鲁棒镇定,而且具有一定的Ｈ∞性能,鲁棒Ｈ∞控制器的设计可通过求解两个代数Ｒｉｃｃａｔｉ方程得到。     

变时滞不确定组合系统基于观测器的鲁棒镇定

研究一类孤立子系统中状态及控制输入均含有时变时滞,且互联项也含有时变时滞的不确定组合系统基于状态观测器的鲁棒控制问题.基于一组线性矩阵不等式（LMIs）解的存在性,并依据Razumikhin-type理论和Lyapunov稳定性理论,给出了保证系统可鲁棒分散镇定的充分条件及相应控制器的设计方法.分散控制器可通过求解一组LMIs得到.最后,利用一个数值例子验证了所给设计方法的有效性.     

Free vibrations of laminated composite plates using second-order shear deformation theory

A complete set of linear equations of the second-order theory of laminated composite plates are obtained. A generalized Levy type solution in conjunction with the state space concept is used to analyze the free vibration behavior of cross-ply and antisymmetric angle-ply laminated plates. Exact fundamental frequencies of cross-ply plate strips are obtained for arbitrary boundary conditions. The exact analytical solutions are obtained for thick and moderately thick plates as well as for thin plates and plate strips. It is shown that the results of the second-order theory are very close to the results of the first-order and third-order theories reported in the literature, and different from those of the classical Kirchhoff’s theory for thick laminates.     

Buckling of initially stressed mindlin plates using a finite strip method

The buckling of initially stressed Mindlin plates is considered using a thick finite strip method. The method is compared with a wide variety of published results and for both thin and moderately thick plates excellent accuracy is obtained. Some further results are obtained for initially stressed rectangular plates with two opposite edges simply supported and various support conditions on the remaining sides. In general, it is found that for moderately thick plates, Mindlin's plate theory gives lower buckling loads than those obtained using classical thin plate theory.     

Identification of processes having direction-dependent responses,with gas-turbine engine applications

Many processes have dynamic responses which are dependent on the direction in which the process variable is moving. The effects of such nonlinear behaviour on the weighting function model of a process obtained by cross-correlation and on the difference equation model obtained by a generalised least-squares procedure are determined theoretically for a process with first-order dynamics perturbed with pseudo-random binary signals. The theory is confirmed by results from a hybrid computer simulation, and computer-simulated results for processes with second-order dynamics are also presented. The theory is used to explain discontinuities in weighting-function models of a gas-turbine engine in which the input-transducer had direction-dependent dynamic responses. Experimental work on a pilot-scale process is reported, and further examples from the literature are examined.     

Surface loading of a thin-walled toroidal shell

Series solutions for elastostatic shell problems can provide results for particular loading cases economically, and give a basis of comparison with finite element method (FEM) solutions. For toroidal shells series solutions have been given by several authors, using mainly a stress approach. In the present study a displacement-based solution is given using the linear Sanders shell theory. This theory is considered to be one of the most accurate first-order theories. The governing equations are first developed in toroidal coordinates. The loading case of a pad of normal pressure on the shell surface is then considered in detail, and series expansions are written for the load, displacement and stress terms. Results are computed using the shell theory for a sample problem, and these results are compared with results obtained using the FEM. The results given provide practical information of interest to designers and furthermore give information about the shell theory and FEM solution characteristics.     

A torsion bending element for thin-walled beams with open and closed cross sections

A finite element is formulated for the torsion problems of thin-walled beams. The element is based on Benscoter's beam theory, which is valid for open and also closed cross-sections. The non-polynomial interpolation presented in this paper allows the exact static solution to be obtained with only one element. Numerical results are presented for three thin-walled cantilever beams, one with a channel cross-section and the two others with rectangular cross-sections. The influence of the transverse shear strain is investigated and the different models of torsion are compared. For one example, the results obtained with one-dimensional torsion elements are compared with those obtained using shell elements.     

Jerk analysis of a six-degrees-of-freedom three-legged parallel manipulator

In this work the jerk analysis of a 3-RRPS parallel manipulator to realize six degrees of freedom is approached by means of the theory of screws. The input/output equations of velocity, acceleration and jerk of the moving platform with respect to the fixed platform are obtained systematically by resorting to reciprocal-screw theory. A numerical example is included in order to show the application of the method of kinematic analysis. Furthermore, the numerical results obtained via screw theory are satisfactorily compared with simulations generated with the aid of commercially available software.     

Mean square average-consensus for multi-agent systems with measurement noise and time delay

Mean square average consensus for multi-agent systems with measurement noise and time delay under fixed digraph is studied in this article. The time-varying consensus-gain is introduced to attenuate the measurement noise. By combining the tools of algebraic graph theory, matrix theory and stochastic analysis, consensus protocols for multi-agent systems with measurement noise and time delay are elaborately analysed. The example and simulation results are given to illustrate the effectiveness of the obtained theoretical results. Moreover, the simulations demonstrate that, the proper consensus-gain function in the consensus protocol is the necessary and sufficient condition for the convergence of the multi-agent systems.     

Containment control of switched multi-agent systems

In this paper, we consider the containment control problem for the switched multi-agent system which is composed of continuous-time and discrete-time subsystems. Continuous-time protocol based on the relative state measurements of agents are designed for the switched multi-agent system with multiple stationary and dynamic leaders, respectively. By using graph theory and matrix theory, some necessary and sufficient conditions are obtained for solving the containment control problem under arbitrary switching. When the leaders are dynamic, impulsive protocol are also proposed for the switched multi-agent system. The simulation results are given to verify the effectiveness of the theoretical results.     

Analysis of composite plates by trigonometric shear deformation theory and multiquadrics

In this paper we used for the first time a trigonometric shear deformation theory for modelling symmetric composite plates discretized by a meshless method based on global multiquadric radial basis functions. This trigonometric theory uses trigonometric functions through the thickness direction, allowing for zero transverse shear stresses at the top and bottom surfaces of the plate. The results obtained are compared with solutions derived from other models and numerical techniques. The results show that the use of trigonometric shear deformation theory discretized with multiquadrics provides very good solutions for composite and sandwich plates.     

Distributed leader-following consensus for second-order multi-agent systems with nonlinear inherent dynamics

In this paper, the leader-following consensus problem for second-order multi-agent systems with nonlinear inherent dynamics is investigated. Two distributed control protocols are proposed under fixed undirected communication topology and fixed directed communication topology. Some sufficient conditions are obtained for the states of followers converging to the state of virtual leader globally exponentially. Rigorous proofs are given by using graph theory, matrix theory and Lyapunov theory. Simulations are also given to verify the effectiveness of the theoretical results.