Delay-dependent robust ℋ ∞ control for uncertain stochastic time-delay system

This article deals with the problem of robust stabilisation and ?_∞ control for a class of uncertain stochastic time-delay system. The parametric uncertainties are real time-varying and norm bounded. The aim is to design a memoryless state-feedback control law such that the closed-loop system are robustly stochastically asymptotically stable in the mean square and the effect of the disturbance input on the controlled output is less than a prescribed level for all admissible parameter uncertainties. New sufficient conditions for the existence of such control law are presented based on the linear matrix inequalities approach. Numerical examples are given to illustrate the effectiveness of the developed techniques.     

Quadratic Stabilization of Switched Uncertain Linear Systems: A Convex Combination Approach

We consider quadratic stabilization for a class of switched systems which are composed of a finite set of continuoustime linear subsystems with norm bounded uncertainties. Under the assumption that there is no single quadratically stable subsystem, if a convex combination of subsystems is quadratically stable, then we propose a state-dependent switching law, based on the convex combination of subsystems, such that the entire switched linear system is quadratically stable. When the state information is not available, we extend the discussion to designing an output-dependent switching law by constructing a robust Luenberger observer for each subsystem.      

带有非线性不确定奇异系统的积分滑模控制

针对一类含有非线性不确定的奇异系统, 提出了一种面向性能的鲁棒控制器. 控制器由3部分组成: 积分滑模控制、附加的非线性控制及复合非线性反馈控制. 积分滑模控制可将匹配不确定完全抵消并使系统轨迹进入理想滑模; 附加的非线性控制用来抑制理想滑动模态上非匹配不确定对系统稳定性和性能的影响; 复合非线性反馈控制则保证闭环系统输出按性能要求渐近地跟踪参考输入信号. 最后通过算例说明所提算法的有效性.     

基于事件触发脉冲控制的具有ROUs和RONs的非线性多智能体系统的领导跟随一致性研究

设计了一个基于Lyapunov函数的事件触发函数,并在此基础上研究了一类具有随机发生不确定性和随机发生非线性的多智能体系统在事件触发脉冲控制策略下的领导跟随一致性。与人为设置脉冲时刻序列的控制方式不同,事件触发脉冲控制策略中脉冲控制时刻的产生依赖于事件触发函数,且当触发条件被满足时才激发脉冲控制,从而减少不必要的控制次数以及系统的资源消耗。基于脉冲微分方程理论、代数图论和Lyapunov稳定性理论,给出了受控多智能体系统实现领导跟随一致性所需要满足的充分性条件,同时证明了Zeno行为可以被排除。最后,通过Matlab实例仿真验证了本文理论结果的有效性。     

钻柱在钻井液反馈影响下的横向振动

在假设钻柱为无扶正器的均质等截面弹性管，且两端为铰支的情况下，既考虑钻柱内钻井液流速和轴向力对钻柱振动的影响，又考虑振动的钻柱对钻井液的反馈影响，建立了钻井液在钻柱内流动时钻柱横向振动微分方程，推导出钻井液波动压力计算式，并给出了钻柱横向振动固有频率方程。定性分析时取频率方程前两阶进行近似计算，讨论了钻井液滚动压力对钻柱固有频率的影响。     

“制器尚象”造物思想对当代陶艺的价值研究

目的研究"制器尚象"造物思想对当代陶瓷艺术设计的价值和意义。方法分析当今中国陶艺创作的思想与工艺技术的现状与问题,将"象"之要义从象形、象理、象德进行解析,在外形、材质、巧工、情感传递4个方面解读"制器尚象"的美学特征、造物哲理和蕴涵在古人造物过程中的哲匠精神。结论当代陶瓷艺术创作应注重"制器尚象"造物思想的传承创新和工艺技术的精湛用心,以执着追求的匠心精神创造出具有时代审美需求和民族特色的陶艺精品。     

A suitable computational strategy for the parametric analysis of problems with multiple contact

The aim of the present work is to develop an application of the LArge Time INcrement (LATIN) approach for the parametric analysis of static problems with multiple contacts. The methodology adopted was originally introduced to solve viscoplastic and large‐transformation problems. Here, the applications concern elastic, quasi‐static structural assemblies with local non‐linearities such as unilateral contact with friction. Our approach is based on a decomposition of the assembly into substructures and interfaces. The interfaces play the vital role of enabling the local non‐linearities, such as contact and friction, to be modelled easily and accurately. The problem on each substructure is solved by the finite element method and an iterative scheme based on the LATIN method is used for the global resolution. More specifically, the objective is to calculate a large number of design configurations. Each design configuration corresponds to a set of values of all the variable parameters (friction coefficients, prestress) which are introduced into the mechanical analysis. A full computation is needed for each set of parameters. Here we propose, as an alternative to carrying out these full computations, to use the capability of the LATIN method to re‐use the solution to a given problem (for one set of parameters) in order to solve similar problems (for the other sets of parameters). Copyright © 2003 John Wiley & Sons, Ltd.     

PID Control of Planar Nonlinear Uncertain Systems in the Presence of Actuator Saturation

This paper investigates PID control design for a class of planar nonlinear uncertain systems in the presence of actuator saturation.Based on the bounds on the growth rates of the nonlinear uncertain function in the system model,the system is placed in a linear differential inclusion.Each vertex system of the linear differential inclusion is a linear system subject to actuator saturation.By placing the saturated PID control into a convex hull formed by the PID controller and an auxiliary linear feedback law,we establish conditions under which an ellipsoid is contractively invariant and hence is an estimate of the domain of attraction of the equilibrium point of the closed-loop system.The equilibrium point corresponds to the desired set point for the system output.Thus,the location of the equilibrium point and the size of the domain of attraction determine,respectively,the set point that the output can achieve and the range of initial conditions from which this set point can be reached.Based on these conditions,the feasible set points can be determined and the design of the PID control law that stabilizes the nonlinear uncertain system at a feasible set point with a large domain of attraction can then be formulated and solved as a constrained optimization problem with constraints in the form of linear matrix inequalities(LMIs).Application of the proposed design to a magnetic suspension system illustrates the design process and the performance of the resulting PID control law.     

Delay-dependent robust stability for neutral systems with mixed discrete-and-neutral delays

This paper focuses on the problem of delay-dependent robust stability of neutral systems with different discrete-and neutral delays and time-varying structured uncertainties. Some new criteria are presented, in which some flee weighting matrices are used to express the relatiomhips between the terms in the Leibniz-Newton formula. The criteria include the information on the size of both neutral-and-discrete delays. It is shown that the present results also include the results for identical discrete-and-neutral delays as special cases.A numerical example illustrates the improvement of the proposed methods over the previous methods and the influences between the discrete and neutral delays.     

弹道坐标中三维鲁棒非线性导引律

本文针对机动目标拦截问题,考虑导弹控制系统动态特性及其不确定性,利用分块反步设计思想,结合输入-状态稳定性理论,在弹道坐标系中设计了一种三维非线性鲁棒导引律.与大多数已有的导引律相比,本文直接地在弹道坐标系中设计导引律,并且所设计的导引律可有效克服控制系统动态特性和不确定性对制导效果的影响,理论分析和数值仿真表明,本文设计的导引律对目标机动和控制系统所受的外来有界扰动均具有较强的鲁棒性.