基于信号完整性分析的TPM芯片设计

由于可信计算平台自身的设计原理及机制上的缺陷,其在面对物理攻击时很难有效地保护整个平台系统的安全性,而基于信号完整性分析的TPM芯片设计思想已给出了较好的解决方案.在上述研究工作的基础上,进一步提出了逻辑分层的TPM-APM（TPM-analog parameter measurement）子模块改进设计方案.通过对时延模拟参数的度量,给出了TPM芯片中TPM-APM子模块的工程实现方法,并使用眼图比对法,为TPM-APM子模块实现的可行性进行了验证.分析结果表明,引入改进设计的TPM-APM子模块可增强可信计算平台面对物理攻击时的防御能力.     

通信受限网络控制系统的H∞ 控制

针对一类通信受限的网络控制系统,研究其随机稳定性和 ∞控制问题.考虑到系统存在随机丢包、时延、对数量化和概率传感器故障等因素,提出一种新的网络控制系统模型.基于Lyapunov稳定性理论,得到了系统随机稳定性的充分条件,并利用线性矩阵不等式技术,给出了系统 ∞控制器的设计方法.数值仿真算例验证了所得结论的有效性.     

On a geometric characterisation of zeros for non-square linear systems with time-delay in state

The concept of invariant zeros in a linear time-invariant system with point delay in state vector is discussed in the state space framework. These zeros are treated as the triples: complex number, non-zero state-zero direction and input-zero direction. Such treatment is strictly related to the output-zeroing problem and in that spirit the zeros can be easily interpreted. As is shown, for systems with matrix CB of full row-rank, general formulas for output-zeroing inputs can be obtained as well as a characterisation of invariant zeros as the roots of a certain quasi-polynomial can be given. The question of degeneracy/non-degeneracy of the system is also addressed. Moreover, it is shown that diagonal decoupling can be achieved by constant state feedbacks and a pre-compensator. The transfer matrix of the decoupled system is square and does not contain delay. The mathematical tools used in the analysis are the Moore–Penrose pseudo-inverse and singular value decomposition of a matrix.     

Hankel-norm model approximation for LPV systems with parameter-varying time delays

This article is concerned with Hankel-norm model approximation (HNMA) for linear parameter-varying systems with parameter-varying time delays. For a given stable system, our attention is focussed on the construction of reduced-order models, which approximate the original system well in a Hankel-norm sense. By applying the slack matrix approach, a delay-dependent sufficient condition is proposed for the robustly asymptotic stability with a Hankel-norm error performance for the error system. Then, the HNMA problem is solved by using the projection approach, which casts the model approximation into a sequential minimisation problem subject to linear matrix inequality constraints by employing the cone complementary linearisation algorithm. Finally, a numerical example is provided to illustrate the effectiveness of the proposed methods.     

Robust adaptive fault-tolerant control for time delay uncertain nonlinear systems with time-varying performance bounds

In this paper, a robust adaptive fault tolerant controller guaranteeing with time-varying performance bounds is designed for a class of time delay uncertain nonlinear systems subject to actuator failures and external disturbance. The influence of time delay on the system is mitigated and the system performance can be guaranteed by introducing a positive nonlinear control gain function and the generalised restricted potential function. A new method with more design degrees of freedom is developed to ensure the norm of the system state within a-priori, user-defined time varying performance bounds. Using the online estimation information provided by adaptive mechanism, a robust adaptive fault-tolerant control method guaranteeing time varying performance bounds is proposed. It is shown that all the signals of the resulting closed-loop system are bounded and the system state less than a-priori, user-defined performance bounds. Finally, simulation results are given to demonstrate the efficacy of the proposed fault-tolerant control method.     

Inventory model with two rates of production for deteriorating items with permissible delay in payments

Some decentralized smoothing problems are solved by applying a forward-pass fixed-interval smoother formula in discrete-time systems. It is assumed that a simple estimation structure consists of a global processor and of two local processors. Two cases are considered for the problems of decentralized smoothing and smoothing update: when the local backward-pass information filtered estimates are available, and when the local-smoothed estimates are available. Some features of present algorithms are discussed from the point of view of data transmissions and numerical computations, etc.     

Computation of robust stability bounds for time-delay systems with nonlinear time-varying perturbations

This paper is concerned with the computation of robust stability bounds for time-delay systems with nonlinear time-varying perturbations. Firstly, a delay-independent condition on the robust stability is presented and a method to determine the maximum upper bound of robust stability is given. Then, a delay-dependent robust stability condition is provided. All results are given in terms of linear matrix inequalities where efficient solution procedures are available. Numerical examples have shown that the results are less conservative than some previous established bounds.     

H ∞ control of networked control systems with state quantisation

This article addresses the problem of controller design for networked control systems over digital communication. The systems under consideration are stabilised via state feedback, where the effects of sampled signal, state quantisation, network-induced delay and packet dropout are considered. The proposed delay-dependent stability criteria are formulated in the form of a linear matrix inequality, which ensure asymptotic stability and a prescribed H _∞ performance level for networked control systems with admissible uncertainties. Maximum allowable delay bound of networked control systems is obtained by solving a convex optimisation problem. Furthermore, a numerical example is given to illustrate the effectiveness of the main result.     

Stabilisation of controlled positive delayed continuous-time systems

This article solves the stabilisation problem by output feedback control for linear continuous-time systems with delay. This technique can be applied for both positive systems and controlled positive systems (systems becoming positive in closed-loop). The synthesis of feedback controllers is solved in terms of linear programs, extending the solution also to stabilisation with bounded control and stabilisation by controllers with the memory of the delayed state. The proposed conditions do not involve the value of the delay. Some examples illustrate the proposed approach.     

Global exponential stability analysis for neutral delay-differential systems: an LMI approach

For neutral differential systems with time-varying or constant delays, the problems of determining the global exponential stability and estimating the exponential convergence rate are investigated in this paper. By using the Lyapunov method, some useful criteria of global exponential stability for the systems are derived. These stability conditions are formulated as linear matrix inequalities (LMIs) which can easily be solved by various convex optimization algorithms. Numerical examples are given to illustrate the application of the proposed method.