Asymptotic properties of the solutions of the equations of motion of gyroscopic systems

The motion of mechanical systems acted upon by gyroscopic and positional forces characterized by a large parameter in the corresponding equations of motion is considered. Periodic solutions of such equations were investigated earlier in [1, 2]. It is proved below that solutions of these equations exist, defined in an interval the length of which is a monotonically increasing unbounded function of the large parameter, and which transfer into the solutions of the corresponding degenerate systems as the large parameter approaches infinity. This function can be specified in more detail if additional assumptions are made regarding the properties of the system and the nature of the forces acting on it.     

The dynamics of systems with large gyroscopic forces and the realization of constraints

Lagrangian systems with a large multiplier N on the gyroscopic terms are considered. Simplified equations of motion of general form with holonomic constraints are obtained in the first approximation with respect to the small parameter ɛ = 1/N. The structure of the solutions of the precessional equations is examined.     

Lowering the order of gyroscopic systems

A method for introducing a small parameter into the equations of gyroscopic systems is proposed. It is shown that to solve the problem of the admissibility of simplifications into the equations of gyroscopic systems, one can use results from the investigation of differential equations with a small parameter for a higher derivative.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 43, No. 3, pp. 381–389, March, 1991.     

Lowering the order of gyroscopic systems

A method for introducing a small parameter into the equations of gyroscopic systems is proposed. It is shown that to solve the problem of the admissibility of simplifications into the equations of gyroscopic systems, one can use results from the investigation of differential equations with a small parameter for a higher derivative.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 43, No. 3, pp. 381–389, March, 1991.     

Admissibility for discrete Volterra equations

In this paper we develop the theory of admissibility for linear discrete Volterra operators and obtain several necessary and sufficient conditions for admissibility in various sequence spaces. Using the results obtained, we study the existence of solutions (such as bounded, exponential or convergent solutions), of linear or nonlinear discrete Volterra summation equations.     

The dynamics of systems with rolling and gyroscopic systems with small generalized velocities and the realization of constraints

Approaches to the construction of mathematical models of systems with rolling and gyroscopic systems with dynamics characterized by the smallness of some of the generalized velocities are discussed. As a rule, a quasistatic approach is used in the modelling of such systems, within the limits of which the generalized accelerations corresponding to small generalized velocities are assumed to be equal to zero. Cases are indicated when the possibility, established by Kozlov, of obtaining the quasistatic equations of gyroscopic systems by the imposition of holonomic constraints is extended to systems with rolling. Additional conditions are formulated that enable one to estimate the error in the quasistatic equations of systems with rolling and gyroscopic systems. It is shown that they can be refined with respect to a small parameter, that is, the ratio of the characteristic values of the “small” and “finite” generalized velocities, using the Dirac formalism, based on an analysis of the constraints between the generalized coordinates and momenta of the system that arise on account of the degeneracy of its Lagrangian on changing to the quasistatic equations.     

On the gyroscopic stabilization of conservative systems

We consider conservative systems with gyroscopic forces and prove theorems on stability and instability of equilibrium states for such systems. These theorems can be regarded as a generalization of the Kelvin theorem to nonlinear systems.     

Stabilization and destabilization in non-conservative gyroscopic systems

Stability of a linear autonomous non-conservative system in presence of potential, gyroscopic, dissipative, and nonconservative positional forces is studied. The cases when the non-conservative system is close to a gyroscopic system or to a circulatory one, are examined. It is known that the marginal stability of gyroscopic and circulatory systems can be destroyed or improved up to asymptotic stability due to action of small non-conservative positional and velocity-dependent forces. The present contribution shows that in both cases the boundary of the asymptotic stability domain of the perturbed system possesses singularities such as “Dihedral angle” and “Whitney umbrella” that govern stabilization and destabilization. Approximations of the stability boundary near the singularities and estimates of the critical gyroscopic and circulatory parameters are found in an analytic form. In case of two degrees of freedom these estimates are obtained in terms of the invariants of matrices of the system. As an example, the asymptotic stability domain of the modified Maxwell-Bloch equations is investigated with an application to the stability problems of gyroscopic systems with stationary and rotating damping, such as the Crandall gyropendulum, tippe top and Jellet's egg. An instability mechanism in a system with two degrees of freedom, originating after discretization of models of a rotating disc in frictional contact and possessing the spectral mesh in the plane ‘frequency’ versus ‘angular velocity’, is described in detail and its role in the disc brake squeal problem is discussed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the stability of linear conservative gyroscopic systems

A simple criterion concerning the stability of linear gyroscopic conservative systems is developed. First, a sufficient condition for stability is established. The proof is based on a transformation converting the original autonomous system into a nonautonomous system, and applying Liapunov's direct method to the latter. Then a theorem is given which provides a necessary and sufficient condition for a restricted class of systems. Illustrative examples are provided.     

The stability of linear potential gyroscopic systems

The stability of linear potential systems with a degenerate matrix of gyroscopic forces is investigated. Particular attention is devoted to the case of three degrees of freedom. In a development of existing results [Kozlov VV. Gyroscopic stabilization and parametric resonance. Prikl. Mat. Mekh. 2001; 65(5): 739–745], the sufficient conditions for gyroscopic stability are obtained. An algorithm for applying these conditions is proposed using the example of the problem of the motion of two mutually gravitating bodies, each of them being modelled by two equal point masses, connected by weightless inextensible rods.     

Suboptimal feedback control of linear gyroscopic systems

A simplified model of reduced dimensionality is presented for a class of linear gyroscopic systems with quadratic performance indices. This model is based on the concept of weakly coupled subsystems and can be used in the synthesis of suboptimal controllers. Controllers based on this model compare favorably with both optimal and conventional controllers.This research was supported by NSF Grant No. GK-3273 and a grant from the Graduate School of the University of Minnesota.     

Indefinite damping in mechanical systems and gyroscopic stabilization

This paper deals with gyroscopic stabilization of the unstable system Mẍ + Dẋ + Kx = 0, with positive definite mass and stiffness matrices M and K, respectively, and an indefinite damping matrix D. The main question is for which skew-symmetric matrices G the system Mẍ + (D + G)ẋ + Kx = 0 can become stable? After investigating special cases we find an appropriate solution of the Lyapunov matrix equation for the general case. Examples show the deviation of the stability limit found by the Lyapunov method from the exact value.      

Asymptotic solutions of Lagrangian systems with gyroscopic forces

We consider Lagrangian systems in the presence of nondegenerate gyroscopic forces. The problem of stability of a degenerate equilibrium pointO and the existence of asymptotic solutions is studied. In particular we show that nondegenerate gyroscopic forces in general have, at least formally, a stabilizing effect whenO is a strict maximum point of the potential energy. It turns out that when we switch on arbitrary small nondegenerate gyroscopic forces, a bifurcation phenomenon arises: the instability properties ofO are transferred to a compact invariant set which collapses atO when the gyroscopic forces are switched off.Work supported by Russian Fund of Basic Research, the Italian Research Council (CNR) and the Italian Ministery of University (MURST)     

Multiple solutions for nonlinear systems with gyroscopic terms

In this paper, we investigate the existence of multiple solutions to some nonlinear systems with gyroscopic terms via variational methods. Some new results are obtained and some results from the literature are improved.