非线性约束下非完整系统的平衡稳定性

Kozlov将Liapunov第一方法推广到非线性力学系统,用来解决保守和耗散力场中,运动力学系统平衡位置的不稳定性.文中讨论的系统运动限于理想的非线性非完整约束.将势能和约束函数展开为Maclaurin级数,对其第一非平凡多项式的阶,确定了相互间关系的5种情况,并对生成的非线性非完整约束方程进行了分析.将3种线性齐次约束下的非完整系统平衡位置的不稳定定理(Kozlov,1986),推广到非线性非完整约束.另外两种情况下的新定理,也是将Kozlov(1994)的结果,拓展到非线性约束下的非完整系统.     

食饵带有扩散的生态—流行病模型的分析

研究了食饵发生扩散且捕食者染病的生态-流行病模型,利用比较定理得到了系统永久持续生存的充分性条件,表明了扩散对系统的持续生存有着很大的影响,并通过定义Liapunov泛函进一步研究了正平衡位置的全局稳定性,这意味着疾病会永远持续下去.     

非完整系统有耗散和循环力时的平衡不稳定性

讨论定常非完整系统在耗散、保守、循环力作用下的不稳定平衡问题．应用方法是基于运动微分方程解的存在性,当t→-∞时,系统渐近地趋于平衡状态．假定在平衡位置附近,动能、Reyleigh耗散函数、位置力都是无限可微函数．结果将通过一个实例说明．部分结果参见Kozlov V V. On the asymptotic motions of systems with dissipation. Prikl Math Mekh, 1994, 58(4): 31-36. (in Russian); Merkin D R. Introduction to the Theory of the Stability of Motion. Moscow: Nauka, 1987. (in Russian); Thomson W, Tait P. Treatise on Natural Philosophy, Part Ⅰ. Cambridge: Cambridge University Press, 1879．     

关于非线性系统的非常稳定性及其应用

本文将C.V.Pao研究Liapunov稳定性的内积法改进、推广和发展,研究了非线性系统的非常稳定性、平衡位置的存在唯一性和Liapunov稳定性.将主要结果直接应用到非线性周期系统的稳态振荡的判定.     

具有乘积型Allee效应的Leslie-Gower捕食模型的动力学

在Leslie-Gower捕食模型中引入乘积型Allee效应,并分析模型的性质.首先,模型存在正向不变集,解是一致有界的.其次,讨论了平衡点存在和稳定的条件,并利用Liapunov函数方法得到正平衡点全局渐近稳定的充分条件.最后,根据Hopf分岔定理分析了分岔现象出现的条件和在这个过程中产生的极限环.     

关于某些三阶方程周期解的存在性,唯一性与稳定性

本文提出B-稳定性的概念,并在非耗散性条件下证明了某些三阶微分方程存在唯一的B-稳定周期解,同时,在耗散性条件下得到一类三阶方程存在平稳振荡的结论。为了方便起见,约定本文所涉及到的函数都是连续的,必要时尚假定是连续可微的。定义一个微分方程的某一解如果在有界解集上是稳定的,但在Liapunov意义下不稳定,则称此解是B-稳定的。     

组合BBM-Burgers方程孤波解的稳定性

讨论了组合BBM-Burgers方程的孤立波解在Liapunov意义下的稳定性,证明了孤波解在初始微扰满足一定条件时具有条件稳定性.     

弱耗散Camassa-Holm方程解的Blowup及衰减性质

本文研究弱耗散Camassa-Holm方程的Cauchy问题,由Kato理论得到了局部适定性的结果,证明了解的blowup及整体存在性,并证明了当耗散系数满足适当条件时,整体解具有衰减性质.     

脉冲泛函微分方程的渐近稳定性

讨论了一类脉冲泛函微分方程的渐近稳定性.通过改进 Liapunov泛函的上界,利用Liapunov泛函第二方法和Jensen不等式,得到了一个一致稳定性定理和一个一致渐近稳定性定理,给出的例子说明了所得结果的优越性.     

一致渐近稳定和周期解、概周期解的存在性

本文建立了系统解一致稳定、解一致渐近稳定和某种Liapunov函数存在的充要条件,并且得到:满足Lipschitz条件而且解一致渐近稳定的概周期系统有唯一的概周期解,周期系统有唯一的周期解。     

The exponential stability and stabilization of non-autonomous mechanical systems with non-conservative forces

The exponential stability of the unperturbed motion of a non-autonomous mechanical system with a complete set of forces, that is, dissipative, gyroscopic, potential and non-conservative positional forces, is investigated. The problem of stabilizing a non-autonomous system with specified non-conservative forces is considered with and without the use of potential forces. The problem of stabilizing a non-autonomous system with specified potential forces by the action of the forces of another structure is studied. The domain of stabilizability of the relative equilibrium position of a satellite in a circular orbit is found.     

On the influence of gyroscopic forces on the stability of steady-state motion : PMM vol. 39, n 6, 1975, pp. 963–973

The question of the influence of gyroscopic forces on the stability of steady-state motion of a holonomic mechanical system when the forces depend upon the velocities of only the position coordinates was answered by the Kelvin-Chetaev theorems [1] on the influence of gyroscopic and dissipative forces on the stability of equilibrium. However, if the gyroscopic forces depend as well on the velocities of the ignorable coordinates, then their influence on the stability of steady-state motions can, as the two problems in [2] show, prove to be entirely different from the influence of gyroscopic forces depending only on the velocities of the position coordinates. In this paper we investigate the influence of gyroscopic forces depending linearly on the velocities of the generalized coordinates, including the ignorable ones, on the stability of the steady-state motion of a holonomic conservative system. We prove that when the gyroscopic forces applied with respect to the ignorable coordinates are given as total time derivatives of certain functions of the position coordinates, the gyroscopic forces can both stabilize as well as destabilize the steady-state motion. Under certain conditions, this influence is also preserved for the action of dissipative forces depending on the velocities of only the position coordinates. In the case of action of dissipative forces depending also on the velocities of the ignorable coordinates, we have indicated the stability and instability conditions of the steady-state motion. Examples are considered. In conclusion, we discuss the conditions under which the application of gyroscopic forces to the system is equivalent to adding terms depending linearly on the generalized velocities to the Lagrange function.     

Lyapunov functions of the mechanical energy type

When examining the properties of the stability and asymptotic behaviour of a system a Lyapunov function is often used as the total mechanical energy of the system /1–7/. By analogy with the division of the energy into kinetic and potential energy, it is proposed below to construct a Lyapunov function in the form of the sum of two subsidiary scalar functions, such that its derivative on account of the system is estimated using some kind of function of these subsidiary functions. Generalizing the results /8/, we examine the case when the derivative of the Lyapunov function can also take positive values, and the equation of comparison the emerges from the estimate of the Lyapunov function does not permit a separation of variables. V.V. Rumyantsev's theorem /3/ on the asymptotic stability with respect to the velocities of the equilibrium position of a dissipative mechanical system is generalized on the basis of the results obtained.     

The stability and stabilization of the motion of non-conservative mechanical systems

Two stability problems are solved. In the first, the stability of mechanical systems, on which dissipative, gyroscopic, potential and positional non-conservative forces (systems of general form) act, is investigated. The stability is considered in the case when the potential energy has a maximum at equilibrium. The condition for asymptotic stability is obtained by constructing Lyapunov's function. In the second problem, the possibility of stabilizing a gyroscopic system with two degrees of freedom up to asymptotic stability using non-linear dissipative and positional non-conservative forces is investigated. Stability of the gyroscopic system is achieved by gyroscopic stabilization. The stability conditions are obtained in terms of the system parameters. Cases when the gyroscopic stabilization is disrupted by these non-linear forces are indicated.     

线性离散系统的部分稳定性

In this paper, we study the partial stability of linear discrete systems by means of Liapunov's functions of quadratic form . We obtain a necessary and sufficient condition for the system being stable with respect to part of variables and generalize Liapunov's equation to the partial stability of linear discrete systems . A method of constructing Liapunov's function of quadratic form for the stability of the systems is given.     

On partial asymptotic stability by the method of limiting equation

Summary The extensions of the Barbashin-Krasovskij theorem to the partial asymptotic stability of the zero solution of a differential system require the boundedness of the uncontrolled coordinates along the solutions. In this paper the Barbashin-Krasovskij method is generalized without supposing «a priori» knowledges on the solutions. At the same time, the results extend one of C. Risito's theorem to nonautonomous differential equations. As an application, stability properties of the equilibrium state of nonholonomic dissipative mechanical systems are studied.     

一类四阶非线性系统的全局渐近稳定性

运用类比法,构造了一类四阶非线性系统的李雅普诺夫函数,得到其平凡解全局渐近稳定的充分性准则,推广并改进了有关这类系统的其它结果.     

Attitude stabilization of a rigid body in conditions of decreasing dissipation

The paper presents the problem of triaxial stabilization of the angular position of a rigid body. The possibility of implementing a control system in which dissipative torque tends to zero over time and the restoring torque is the only remaining control torque is considered. The case of vanishing damping considered in this study is known as the most complicated one in the problem of stability analysis of mechanical systems with a nonstationary parameter at the vector of dissipative forces. The lemma of the estimate from below for the norm of the restoring torque in the neighborhood of the stabilized motion of a rigid body and two theorems on asymptotic stability of the stabilized motion of a body are proven. It is shown that the sufficient conditions of asymptotic stability found in the theorems are close to the necessary ones. The results of numerical simulation illustrating the conclusions obtained in this study are presented.