关于弹性振动的镇定(Ⅱ)

<正> 1.细长的飞行器在推力与垂直于纵轴的空气动力作用下的俯仰与偏航运动可以近似地描述成两端自由弹性梁的运动.本文是工作[1]的继续,讨论弹性振动的镇定问题.在工作[1]中讨论了以细长的飞行器为模型的弹性自由梁振动的镇定问题.在[1]中为了使问题集中到主要方面,讨论的弹性自由梁振动的镇定问题是最简化的数学模型,即在弹性自由梁的运动方程中只考虑了惯性力、弹性力和以弹性梁的角速度作为反馈输入时的     

弹性振动系统的镇定和极点配置问题

本文研究了忽略气动项的情况下细长飞行器弹性振动的镇定问题,指出了可以把它化为两端固定梁的弹性振动的镇定问题,并给出了渐近姿态的表达式。最后我们还讨论了这个弹性系统的极点配置问题,得到了极点配置的公式。     

弹性振动的镇定问题(Ⅲ)

细长体空间飞行器的弹性振动,会引起飞行器的损坏以及其它问题,因此有必要通过飞行器上面安装的仪表所测得的角速度、角度或线加速度作反馈来研究控制的问题.这就需要设计一控制迴路,使得飞行器所表现的弹性振动系统与控制器所形成的闭环系统通过飞行器上加舵力来镇定,我们采用两端自由的弹性梁描述飞行器的弹性振动,仍用线性算子的扰动理论,得出用角速度、角度或线加速度作反馈时带控制器的弹性振动系统的镇定条件。     

弹性振动的镇定问题

细长的空间飞行器在推力空气动力作用下会有弹性振动。这些振动,如果不加控制,会引起飞行器的损坏以及其它问题,于是产生了能否通过飞行器上面的仪表所测得几个部位的弯曲所引起的角速度作反馈,并通过在飞行器上加舵力而使弹性振动镇定下来的问题,我们采用了自由端弹性梁的描述,在观测仪表与加力点不必在同一地方的情形下,找出了能使弹性振动镇定的条件。并且从分布参数系统的能控性与能观测性,讨论了这些条件中的主要部分的物理意义。     

基于Lévy过程混杂微分方程的随机部分镇定

本文基于L′evy噪声镇定混杂微分系统,推广Brown运动镇定的情形.同时,利用Markov链状态空间分为两集合方法,将混杂系统分为两部分:可观测部分和不可观测部分,基于可观测部分镇定整个混杂系统,给出该混杂系统镇定和失稳的充分条件.最后,讨论系统保守性问题.     

带控制器的弹性振动系统的能观性、能控性

<正> 在工作[1]中提出了带有控制迴路的分布参数反馈系统的模型.在工作[2]中讨论了以弹性樑的角速度、角度和线加速度作反馈信号输入到控制器,由控制器的输出端输出信号到舵的执行机构以实现反馈控制弹性振型的镇定问题.那里用的是线性算子的谱扰动方法.在[3]中讨论了不带控制器的弹性振动系统的能观测性和能控性问题,得到了能观测、能控的必要充分条件.在现代控制理论中,一个系统是否能控、能观测,无论在实际工     

具有动态边界的非均匀Euler-Bernoulli梁的边界反馈镇定

本讨论一端带有重物的Euler-Bernoulli梁的边界反馈镇定问题。在生物的质量忽略不计而只考虑重物的转动惯量的情况下，证明了同时在梁的自由端施加力和力矩反馈，闭环系统的能量可被指数镇定。进而对于系统只有力反馈或只有力矩反馈的情况，得到了闭环系统（指数）稳定的充分必要条件。     

非线性系统用状态检测器的有界镇定

近十年来,非线性系统的反馈镇定问题引起了控制界广泛的兴趣.人们发现,系统的非线性使得反馈镇定问题变得相当复杂.首先,如 H.J.Sussmann 指出的,非线性系统的能控性不能保证系统是反馈可镇定的.于是线性系统的经验无法借鉴,从而寻找可镇定条件成为一个新的课题.其次,对于一般非线性系统的反馈镇定研究还缺乏得     

非均质Euler-Bernoulli梁的非线性耗散边界反馈镇定

讨论具有非线性耗散边界反馈的非均质Euler-Bernoulli梁的镇定问题．首先利用非线性半群理论和能量摄动方法，证明了文中所给出的非线性耗散边界反馈控制可以镇定闭环系统的能量，并导出了闭环系统的能量的衰减速度．     

具有分布反馈和边界反馈的非均质Timoshenko梁的指数镇定性

讨论具有分布反馈控制和边界反馈控制的非均质Timoshenko梁的指数镇定问题.首先利用已有的关于线性分布参数系统的渐进稳定性判据,证明所论梁系统的能量可仅由一个分布反馈控制指数镇定.进而利用频域分片乘子方法,在所论梁系统同时具有分布反馈控制和边界反馈控制的条件下,证明其相应的闭环系统能量指数稳定.     

Controllability and observability of coordinated linear systems

This paper develops concepts of controllability and observability for the class of coordinated linear systems, a special class of linear hierarchical systems with a top-to-bottom information structure. The usual concepts of reachability and indistinguishability for linear systems are refined, taking into account the decentralized nature of coordinated linear systems. The corresponding controllability and observability decompositions are derived, and several concepts of controllability and observability for coordinated linear systems are introduced and discussed. These results are then combined to a definition and characterization of stabilizability via dynamic measurement feedback for this class of systems.     

Some new results in differential algebraic control theory

In the differential algebra framework, static state and dynamicstate feedback linearization are considered. The relationshipbetween dynamic feedback and flatness defined by Fliess is discussed.The existence of an equivalent proper differential I–Osystem of a given differential I–O system is discussed,which is closely related to the choice of a proper fictitiousoutput in control design. The concept flatness and its relationwith dynamic feedback linearizability, controllability, observability,invertibility and minimal realization are discussed. Finally,it is demonstrated that many fundamental control concepts andtheir interrelationships can be incorporated into an extendedcontrol diagram.     

Pathological asymptotic behavior of control systems in Banach space

New phenomena arising when a linear dynamical system is defined on an infinite dimensional Banach space, although negligible from an engineering standpoint when only a finite time-interval is considered, become crucial when the asymptotic (feedback) behavior of the system is of interest. Pathologies with respect to the correspondent finite dimensional case are displayed even when the operator acting on the state is bounded.In particular, although in such case, the classical controllability and observability theory admits a natural generalization to infinite dimensions, the finite dimensional relationships between controllability and stabilizability fails. A few examples are given of systems that are approximately controllable and yet are not stabilizable: Moreover, such examples are drawn from a class of systems that can never be exactly controllable. The analysis is carried out using the perturbation theory of the spectrum. Another new feature of the infinite dimensionality of the state space is that even if the spectrum of an operator has the max of its real part equal to 0, yet the associated homogeneous differential equation may be globally asymptotically stable: Its consequence on stabilizability is also examined.     

A locking-free scheme for the LQR control of a Timoshenko beam

In this paper we analyze a locking-free numerical scheme for the LQR control of a Timoshenko beam. We consider a non-conforming finite element discretization of the system dynamics and a control law constant in the spatial dimension. To solve the LQR problem we seek a feedback control which depends on the solution of an algebraic Riccati equation. An optimal error estimate for the feedback operator is proved in the framework of the approximation theory for control of infinite dimensional systems. This estimate is valid with constants that do not depend on the thickness of the beam, which leads to the conclusion that the method is locking-free. In order to assess the performance of the method, numerical tests are reported and discussed.     

Observability of hybrid discrete-continuous systems

We study the statement and solvability of observability problems in linear stationary hybrid discrete-continuous dynamical systems. Necessary and sufficient observability conditions expressed directly via the system parameters are derived. We consider linear observability problems and the dual controllability and reachability problems. The problem of computing the minimum number of inputs for which the system has a given observability is discussed. An example illustrating the results is presented.     

Controllability and observability of a heat equation with hyperbolic memory kernel

The exact controllability and observability for a heat equation with hyperbolic memory kernel in anisotropic and nonhomogeneous media are considered. Due to the appearance of such a kind of memory, the speed of propagation for solutions to the heat equation is finite and the corresponding controllability property has a certain nature similar to hyperbolic equations, and is significantly different from that of the usual parabolic equations. By means of Carleman estimate, we establish a positive controllability and observability result under some geometric condition. On the other hand, by a careful construction of highly concentrated approximate solutions to hyperbolic equations with memory, we present a negative controllability and observability result when the geometric condition is not satisfied.     

Controllability and synchronizability: Are they related?

In the two last decades the concept of observability has been formally linked to that of embedding in the context of nonlinear dynamics. Such a concept has been shown to play an important role in global modeling, data analysis and filtering, to mention a few examples. Preliminary results suggested that observability, at least in some cases, has some influence in synchronization problems. Could the dual concept of controllability also be important in such problems? In the context of synchronization, in general, the role played by controllability properties may not be as relevant as observability is for data analysis. In this work we compute controllability coefficients analogous to the observability ones, now established in the literature, and evaluate their importance in synchronization problems. Two benchmarks have been used in the simulations: the Rössler and the cord systems. The following schemes were investigated: synchronization to external sinusoidal force, complete replacement, uni- and bi-directional coupling of identical oscillators. The results discussed in this work show that controllability and synchronizability are not related in general.     

Timoshenko梁点反馈的稳定性

研究T im oshenko梁点反馈的稳定性.用线性算子半群方法证明了闭环系统的适定性,并应用算子谱特征得到了闭环系统的强渐近稳定性的充分必要条件.同时,给出了保守系统的几个能观性不等式.     

Boundary Controllability and Observability of a One-Dimensional Nonuniform SCOLE System

A hybrid system, composed of an elastic beam governed by an Euler-Bernoulli beam equation with variable coefficients and a linked rigid body governed by an ordinary differential equation, is considered. Various controllability/observability properties of the system under bounday control/observation are studied. It is shown that an open-loop smooth/singular controller of either torque control or force control is sufficient to make the system exactly controllable in arbitrarily short time duration. The work was carried out with the support of the National Natural Science Foundation of China and the Russian Foundation for Fundamental Researches, Grant 02-01-00554.