DC-DC变换器的输入系统不稳定性

本文简要介绍了直流分布式供电系统中DC-DC变换器输入系统不稳定性的产生原因,提出了两种解决系统不稳定性问题的方法,并给出了参数计算公式。

面向对象系统进展过程的测度方法研究

软件测度方法用于测量系统开发过程中的软件质量。本文提出了测量面向对象系统进展过程的三种测度方法 :系统设计不稳定性 (SDI)、类实现不稳定性 (CII)和系统实现不稳定性 (SII)。这些测度方法的结果有助于实时调整工程计划。此外 。

新型激光模型实现SPP增益补偿的数学分析

设计了有机染料分子的球形波导结构,采用最内层金属金(Au)、外层Si介质的多层球形结构,在环形介质中植入有机染料分子作为增益耦合介质。理论上分析了模型的的受激辐射磁场能量、辐射谱以及有机染料分子增益效果。特性分析结果表明:光波在有机染料分子增益区能够与内层金属实现耦合,发生了多层电场局域化现象,增益对金属-介质间的表面等离子有一定的补偿效果,从增益的高折射区与低折射率区间发生了全反射,实行了表面等离子传播的增益补偿效果。能够通过调节波导参数实现损耗-补偿控制,高折射区能够实现SPP补偿,有机染料分子距离核区越近补偿效果更好,损耗更小。

STABILITY ANALYSIS AND COOPERATIVE CONTROL OF DISTRIBUTED MULTI-AGENT SYSTEM WITH SAMPLED COMMUNICATION

The cooperative control and stability analysis problems for the multi-agent system with sampled com- munication are investigated. Distributed state feedback controllers are adopted for the cooperation of networked agents. A theorem in the form of linear matrix inequalities（LMI） is derived to analyze the system stability. An- other theorem in the form of optimization problem subject to LMI constraints is proposed to design the controller, and then the algorithm is presented. The simulation results verify the validity and the effectiveness of the pro- posed approach.

Stability analysis of time-varying systems via parameter-dependent homogeneous Lyapunov functions

This paper considers the stability analysis of linear continuous-time systems, and that the dynamic matrices are affected by uncertain time-varying parameters, which are assumed to be bounded, continuously differentiable, with bounded rates of variation. First, sufficient conditions of stability for time-varying systems are given by the commonly used parameter-dependent quadratic Lyapunov function. Moreover, the use of homogeneous polynomial Lyapunov functions for the stability analysis of the linear system subject to the time-varying parametric uncertainty is introduced. Sufficient conditions to determine the sought after Lyapunov function is derived via a suitable paramenterization of polynomial homogeneous forms. A numerical example is given to illustrate that the stability conditions are less conservative than similar tests in the literature.

Design for robust stabilization of nonlinear systems with uncertain parameters

Based on Lyapunov stability theory, a design method for the robust stabilization problem of a class of nonlinear systems with uncertain parameters is presented. The design procedure is divided into two steps: the first is to design controllers for the nominal system and make the system asymptotically stabi1ize at the expected equilibrium point; the second is to construct closed-loop nominal system based on the first step, then design robust controller to make the error of state between the origina1 system and the nominal system converge to zero, thereby a dynamic controller with the constructed closed-loop nominal system served as interior dynamic is obtained. A numerical simulation verifies the correctness of the design method.

State feedback control for Lurie networked control systems

The problem of the stability analysis and controller design which the network-induced delays and data dropout problems network-induced delays are assumed to be time-varying and bounded, for Lurie networked control systems （NCSs） is investigated, in are simultaneously considered. By considering that the and analyzing the relationship between the delay and its upper bound, employing a Lyapunov-Krasovskii function and an integral inequality approach, an improved stability criterion for NCSs is proposed. Furthermore, the resulting condition is extended to design a less conservative state feedback controller by employing an improved cone complementary linearization （ICCL） algorithm. Numerical examples are provided to show the effectiveness of the method.

Comparing dynamical systems concepts and techniques for biomechanical analysis

Traditional biomechanical analyses of human movement are generally derived from linear mathematics.While these methods can be useful in many situations,they do not describe behaviors in human systems that are predominately nonlinear.For this reason,nonlinear analysis methods based on a dynamical systems approach have become more prevalent in recent literature.These analysis techniques have provided new insights into how systems(1) maintain pattern stability,(2) transition into new states,and(3) are governed by short-and long-term(fractal) correlational processes at different spatio-temporal scales.These different aspects of system dynamics are typically investigated using concepts related to variability,stability,complexity,and adaptability.The purpose of this paper is to compare and contrast these different concepts and demonstrate that,although related,these terms represent fundamentally different aspects of system dynamics.In particular,we argue that variability should not uniformly be equated with stability or complexity of movement.In addition,current dynamic stability measures based on nonlinear analysis methods(such as the finite maximal Lyapunov exponent) can reveal local instabilities in movement dynamics,but the degree to which these local instabilities relate to global postural and gait stability and the ability to resist external perturbations remains to be explored.Finally,systematic studies are needed to relate observed reductions in complexity with aging and disease to the adaptive capabilities of the movement system and how complexity changes as a function of different task constraints.

Relationship between autonomic nervous system function and acute mountain sickness

Objective: To elucidate the role of the autonomic nervous system (ANS) in acute mountain sickness (AMS) during the initial phase at acute high-altitude exposure. Methods: Ninety-nine healthy sea-level residents rapidly ascended to Tibet plateau (3 675 m altitude) by airplane from Chengdu plain (560 m altitude). ANS function was tested in plain and day 2–4 in Tibet by heart rate variability (HRV), cold pressor test (CPT). AMS was evaluated by clinic symptomatic scores. All subjects were divided into non-AMS group (57, scores≤4) and AMS group (42, scores>4). Results: Compared with non-AMS group, AMS group had higher standard deviation of normal to normal intervals (SDNN), root mean square of delta RR (rMSSD), low-frequency (LF) power, and normalized low-frequency (LFnu) power in plain (P<0.05). After arrival at 3 675 m altitude, AMS group had greater reduction in percentage of delta RR>50 ms(PNN50), rMSSD (P<0.01) and SDNN, LF, total power (TP) (P<0.05). Although no significant differences in the increase of SP and DP during CPT were found between 2 groups in plain, the SP increase during CPT of AMS group was less than non-AMS group (P<0.05) at 3 675 m altitude. AMS symptomatic scores was not only positively correlated with SDNN, rMSSD, LF/HF in plain (P<0.05), but also negatively correlated with HFnu in plain (P<0.05). Conclusion: During the initial high altitude exposure, ANS modulation is generally blunted, but the relatively predominant sympathetic control is enhanced, and this characteristic change of ANS function is positively correlated with the development of AMS.

Application of the Conditional Nonlinear Optimal Perturbations Method in a Theoretical Grassland Ecosystem

Using a simplified nonlinearly theoretical grassland ecosystem proposed by Zeng et al.,we study the sensitivity and nonlinear instability of the grassland ecosystem to finiteamplitude initial perturbations with the approach of conditional nonlinear optimal perturbation （CNOP）.The results show that the linearly stable grassland （desert or latent desert） states can turn to be nonlinearly unstable with finite amplitude initial perturbations.When the precipitation is between the two bifurcation points,a large enough finite amplitude initial perturbation can induce a transition between the grassland statethe desert state or the latent desert.

Second-Order Consensus of Multiple Agents with Coupling Delay

In this paper, we investigate two kinds of second-order consensus algorithms for multiple agents with coupling delay under general fixed directed information topology. Stability analysis is performed based on Lyapunov- Krasovskii functional method. Delay-dependent asymptotical stability condition in terms of linear matrix inequalities （LMIs） is derived for the second-order consensus algorithm of delayed dynamical networks. Both delay-independent and delay-dependent asymptotical stability conditions in terms of LMIs are derived for the second-order consensus algorithm with information feedback.

Guaranteed cost control of uncertain system with input time-delay

For the uncertain continuous-time systems with input time-delay that widely exist in the production processes, we can get the existent conditions for the guaranteed cost control of these systems by using the Lyapunov stability theory, linear matrix inequalities theory and quadratic cost criterion. We can achieve the guaranteed cost control of this system by solving a matrix inequality. A state feed back guaranteed cost control law can be constructed by solving certain parameter-dependent Riccati matrix equation.

The Robust Stabilizing Feedback for a Class of Nonlinear Uncertain Neutral Systems with Multiple Time Delays

The stabilization of a class of neutral systems with multiple time-delays is considered. To stabilize the neutral system with nonlinear uncertainty, a state feedback control law via compound memory and memoryless feedback is derived, by constructed Lyapunov functional, delay-independent stability criteria are proposed that are sufficient to ensure a uniform asymptotic stability property. Finally, two concise examples are provided to illustrate the feasibility of our results.

Synchronization of hyperchaotic Rossler system with uncertain parameters via nonlinear control

Based on the Lyapunov stability theory,a new method for synchronization of hyperchaotic Rossler system with uncertain parameters is proposed. By this method, choosing appropriate control law and adaptive update law of uncertain parameters, all the errors of system variable synchronization and of uncertain param- eter track are asymptotically stable. The theoretical analysis and the numerical simulations prove the efffectiveness of the oroDosed method.

Error code analysis and selection principle of M-ary modulation in network-based control systems

Error codes induced by M-ary modulation and modulation selection in network-based control systems are studied.It is the first time the issue of error codes induced by M-ary modulation is addressed in control field.In network-based control systems,error codes induced by noisy channel can significantly decrease the quality of control.To solve this problem,the network-based control system with delay and noisy channel is firstly modeled as an asynchronous dynamic system(ADS).Secondly,conditions of packet with error codes(PEC)loss rate by using M-ary modulation are obtained based on dynamic output feedback scheme.Thirdly,more importantly,the selection principle of M-ary modulation is proposed according to the measured signal-to-noise ratio(SNR)and conditions of PEC loss rate.Finally,system stability is analyzed and controller is designed through Lyapunov function and linear matrix inequality(LMI)scheme,and numerical simulations are made to demonstrate the effectiveness of the proposed scheme.

Robust Model Predictive Controller Design： Finite and Infinite Horizon

This paper addresses to the problem of designing, modeling and practical realization of robust model predictive control for finite and infinite prediction horizon which ensures a parameter dependent quadratic stability and guaranteed cost for linear polytopic uncertain systems. The model predictive controller design procedure based on BMI and LMI is reduced to off-line output feedback gain calculation. A numerical examples and an application to a real process is given to illustrate the effectiveness of the proposed method.

THE GLOBAL STABILITY OF CONSTANT EQUILIBRIUM OF REACTION-DIFFUSION SYSTEMS——DIFFERENTIAL INEQUALITIES AND LIAPUNOV FUNCTIONAL

In this paper methods of differential inequalities and Liapunov functionals for proving the global stability of constant equilibria of reaction-diffusion systems are given, and examples for showing how to use these methods are also given.

DIVERGENCE RATE OF STATE OF AR SYSTEMS WITH UNSTABLE UNIT ROOTS

The order of weighted sum of noise sequence for stochastic system is estimated by using limit theory in probability. Then the divergence rates of state of unstable AR system driven by noise of martingale difference sequence are established.

Investigations of an enclosed annular rotor-stator system with LES method

In this study, the flows in an enclosed annular rotor-stator system with the Reynolds number ranging from 0.75×105 to 3.75×105 and an aspect ratio of 36.5 are investigated using the LES method. Few studies have explored such a rotor-stator system with this aspect ratio and the flow structure on the rotor side. The mean flow structure varies from a torsional Couette type to a Batchelor type as the Reynolds number increases. The onset of the instability in the B?dewadt layer adjacent to the stator is delayed,whereas it is promoted in the Ekman layer adjacent to the rotor. Both the layers demonstrate rich spiral structures. Turbulent spirals are observed to occur at the rotor disk side that also generates TS-wave-like(Tollmien-Schlichting) structures between adjacent spiral arms. Further, the turbulence at the stator is complex and interesting. Statistically, the turbulence is highly anisotropic near both the rotating and nonrotating disks, which is depicted by the Reynolds stresses.

A diffusive predator-prey system with additional food and intra-specific competition among predators

In this paper, a diffusive predator-prey system with additional food and intra-specific competition among predators subject to Neumann boundary condition is investigated. For non-delay system, global stability, Turing instability and Hopf bifurcation are studied. For delay system, instability and Hopf bifurcation induced by time delay and global stability of boundary equilibrium are discussed. By the theory of normal form and center manifold method, the conditions for determining the bifurcation direction and the stability of the bifurcating periodic solution are derived.