In this paper, we study the free and controlled motion of an arbitrary two-dimensional body with a moving internal material point through an ideal fluid in presence of constant circulation around the body. We perform bifurcation analysis of free motion (with fixed internal mass). We show that by changing the position of the internal mass the body can be made to move to a specified point. There are a number of control problems associated with the nonzero drift of the body in the case of fixed internal mass.

The phenomenon of a topological monodromy in integrable Hamiltonian and nonholonomic systems is discussed. An efficient method for computing and visualizing the monodromy is developed. The comparative analysis of the topological monodromy is given for the rolling ellipsoid of revolution problem in two cases, namely, on a smooth and on a rough plane. The first of these systems is Hamiltonian, the second is nonholonomic. We show that, from the viewpoint of monodromy, there is no difference between the two systems, and thus disprove the conjecture by Cushman and Duistermaat stating that the topological monodromy gives a topological obstruction for Hamiltonization of the rolling ellipsoid of revolution on a rough plane.

This paper is concerned with the experimental determination of the added masses of bodies completely or partially immersed in a fluid. The paper presents an experimental setup, a technique of the experiment and an underlying mathematical model. The method of determining the added masses is based on the towing of the body with a given propelling force. It is known (from theory) that the concept of an added mass arises under the assumption concerning the potentiality of flow over the body. In this context, the authors have performed PIV visualization of flows generated by the towed body, and defined a part of the trajectory for which the flow can be considered as potential. For verification of the technique, a number of experiments have been performed to determine the added masses of a spheroid. The measurement results are in agreement with the known reference data. The added masses of a screwless freeboard robot have been defined using the developed technique.

This paper is concerned with the problem of the motion of a wheeled vehicle on a plane in the case where one of the wheel pairs is fixed. In addition, the motion of a wheeled vehicle on a plane in the case of two free wheel pairs is considered. A method for obtaining equations of motion for the vehicle with an arbitrary geometry is presented. Possible kinds of motion of the vehicle with a fixed wheel pair are determined.

In this paper, we develop the results obtained by J.Hadamard and G.Hamel concerning the possibility of substituting nonholonomic constraints into the Lagrangian of the system without changing the form of the equations of motion. We formulate the conditions for correctness of such a substitution for a particular case of nonholonomic systems in the simplest and universal form. These conditions are presented in terms of both generalized velocities and quasi-velocities. We also discuss the derivation and reduction of the equations of motion of an arbitrary wheeled vehicle. In particular, we prove the equivalence (up to additional quadratures) of problems of an arbitrary wheeled vehicle and an analogous vehicle whose wheels have been replaced with skates. As examples, we consider the problems of a one-wheeled vehicle and a wheeled vehicle with two rotating wheel pairs.

This paper is concerned with free and controlled motions of a spherical robot of combined type moving by displacing the center of mass and by changing the internal gyrostatic momentum. Equations of motion for the nonholonomic model are obtained and their first integrals are found. Fixed points of the reduced system are found in the absence of control actions. It is shown that they correspond to the motion of the spherical robot in a straight line and in a circle. A control algorithm for the motion of the spherical robot along an arbitrary trajectory is presented. A set of elementary maneuvers (gaits) is obtained which allow one to transfer the spherical robot from any initial point to any end point.

A nonholonomic model of the dynamics of an omniwheel vehicle on a plane and a sphere is considered. A derivation of equations is presented and the dynamics of a free system are investigated. An explicit motion control algorithm for the omniwheel vehicle moving along an arbitrary trajectory is obtained.

This paper deals with the problem of a spherical robot propelled by an internal omniwheel platform and rolling without slipping on a plane. The problem of control of spherical robot motion along an arbitrary trajectory is solved within the framework of a kinematic model and a dynamic model. A number of particular cases of motion are identified, and their stability is investigated. An algorithm for constructing elementary maneuvers (gaits) providing the transition from one steady-state motion to another is presented for the dynamic model. A number of experiments have been carried out confirming the adequacy of the proposed kinematic model.

This paper presents the results of experimental investigations for the rolling of a spherical robot of combined type actuated by an internal wheeled vehicle with rotor on a horizontal plane. The control of spherical robot based on nonholonomic dynamical by means of gaits. We consider the motion of the spherical robot in case of constant control actions, as well as impulse control. A number of experiments have been carried out confirming the importance of rolling friction.

In this paper we consider the problem of motion of a rigid body in an ideal fluid with two material points moving along circular trajectories. The controllability of this system on the zero level set of first integrals is shown. Elementary ?gaits? are presented which allow the realization of the body?s motion from one point to another. The existence of obstacles to a controlled motion of the body along an arbitrary trajectory is pointed out.

The dynamic model for a spherical robot with an internal omniwheel platform is presented. Equations of motion and first integrals according to the non-holonomic model are given. We consider particular solutions and their stability. The algorithm of control of spherical robot for movement along a given trajectory are presented.

The kinematic control model for a spherical robot with an internal omniwheel platform is presented. We consider singularities of control of spherical robot with an unbalanced internal omniwheel platform. The general algorithm of control of spherical robot according to the kinematical quasi-static model and controls for simple trajectories (a straight line and in a circle) are presented. Experimental investigations have been carried out for all introduced control algorithms.

The problem of motion of a vehicle in the form of a platform with an arbitrary number of Mecanum wheels fastened on it is considered. The controllability of this vehicle is discussed within the framework of the nonholonomic rolling model. An explicit algorithm is presented for calculating the control torques of the motors required to follow an arbitrary trajectory. Examples of controls for executing the simplest maneuvers are given.

Inšthis article aškinematic model ofšthe spherical robot isšconsidered, which isšset inšmotion byšthe internal platform with omni-wheels. Itšhas been introduced ašdescription ofšconstruction, algorithm ofštrajectory planning according tošdeveloped kinematic model, itšhas been realized experimental research for typical trajectories: moving along ašstraight line and moving along ašcircle.

We consider the problem of motion of axisymmetric vortex rings in an ideal incompressible and viscous fluid. Using the numerical simulation of the Navier?Stokes equations, we confirm the existence of leapfrogging of three equal vortex rings and suggest the possibility of detecting it experimentally. We also confirm the existence of leapfrogging of two vortex rings with opposite-signed vorticities in a viscous fluid.

We investigate the motion of the point of contact (absolute dynamics) in the integrable problem of the Chaplygin ball rolling on a plane. Although the velocity of the point of contact is a given vector function of variables of the reduced system, it is impossible to apply standard methods of the theory of integrable Hamiltonian systems due to the absence of an appropriate conformally Hamiltonian representation for an unreduced system. For a complete analysis we apply the standard analytical approach, due to Bohl and Weyl, and develop topological methods of investigation. In this way we obtain conditions for boundedness and unboundedness of the trajectories of the contact point.

In our earlier paper [3] we examined the problem of control of a balanced dynamically nonsymmetric sphere with rotors with no-slip condition at the point of contact. In this paper we investigate the controllability of a ball in the presence of friction. We also study the problem of the existence and stability of singular dissipation-free periodic solutions for a free ball in the presence of friction forces. The issues of constructive realization of the proposed algorithms are discussed.

We consider the problem of motion of axisymmetric vortex rings in an ideal incompressible fluid. Using the topological approach, we present a method for complete qualitative analysis of the dynamics of a system of two vortex rings. In particular, we completely solve the problem of describing the conditions for the onset of leapfrogging motion of vortex rings. In addition, for the system of two vortex rings we find new families of motions where the relative distances remain finite (we call them pseudo-leapfrogging). We also find solutions for the problem of three vortex rings, which describe both the regular and chaotic leapfrogging motion of vortex rings.

We investigate the motion of the point of contact (absolute dynamics) in the integrable problem of the Chaplygin ball rolling on a plane. Although the velocity of the point of contact is a given vector function of variables of a reduced system, it is impossible to apply standard methods of the theory of integrable Hamiltonian systems due to the absence of an appropriate conformally Hamiltonian representation for an unreduced system. For a complete analysis we apply the standard analytical approach, due to Bohl and Weyl, and develop topological methods of investigation. In this way we obtain conditions for boundedness and unboundedness of the trajectories of the contact point.

The phenomenon ofšaštopological monodromy inšintegrable Hamiltonian and nonholonomic systems isšdiscussed. Anšefficient method for computing and visualizing the monodromy isšdeveloped. The comparative analysis ofšthe topological monodromy isšgiven for the rolling ellipsoid ofšrevolution problem inštwo cases, namely, onšašsmooth and onšašrough plane. The first ofšthese systems isšHamiltonian, the second isšnonholonomic. Wešshow that, from the viewpoint ofšmonodromy, there isšnošdifference between the two systems, and thus disprove the conjecture byšCushman and Duistermaat stating that the topological monodromy gives aštopological obstruction for Hamiltonization ofšthe rolling ellipsoid ofšrevolution onšašrough plane.

Inšour earlier paper [2] wešexamined the problem ofšcontrol ofšašbalanced dynamically nonsymmetric sphere with rotors with no-slip condition atšthe point ofšcontact. Inšthis paper wešinvestigate the controllability ofšašball inšthe presence ofšfriction. Wešalso study the problem ofšthe existence and stability ofšsingular dissipation-free periodic solutions for ašfree ball inšthe presence ofšfriction forces. The issues ofšconstructive realization ofšthe proposed algorithms are discussed.

In the paper we study the control of a balanced dynamically non-symmetric sphere with rotors. The no-slip condition at the point of contact is assumed. The algebraic controllability is shown and the control inputs that steer the ball along a given trajectory on the plane are found. For some simple trajectories explicit tracking algorithms are proposed.

We discuss explicit integration and bifurcation analysis of two non-holonomic problems. One of them is the Chaplygin?s problem on no-slip rolling of a balanced dynamically non-symmetric ball on a horizontal plane. The other, first posed by Yu.N.Fedorov, deals with the motion of a rigid body in a spherical support. For Chaplygin?s problem we consider in detail the transformation that Chaplygin used to integrate the equations when the constant of areas is zero. We revisit Chaplygin?s approach to clarify the geometry of this very important transformation, because in the original paper the transformation looks a cumbersome collection of highly non-transparent analytic manipulations. Understanding its geometry seriously facilitate the extension of the transformation to the case of a rigid body in a spherical support ? the problem where almost no progress has been made since Yu.N. Fedorov posed it in 1988. In this paper we show that extending the transformation to the case of a spherical support allows us to integrate the equations of motion explicitly in terms of quadratures, detect mostly remarkable critical trajectories and study their stability, and perform an exhaustive qualitative analysis of motion. Some of the results may find their application in various technical devices and robot design. We also show that adding a gyrostat with constant angular momentum to the spherical-support system does not affect its integrability.

Inšthe paper wešstudy control ofšašbalanced dynamically nonsymmetric sphere with rotors. The no-slip condition atšthe point ofšcontact isšassumed. The algebraic contrability isšshown and the control inputs providing motion ofšthe ball along ašgiven trajectory onšthe plane are found. For some simple trajectories explicit tracking algorithms are proposed.

Wešconsider the problem ofšthe motion ofšaxisymmetric vortex rings inšanšideal incompressible fluid. Using the topological approach, wešpresent ašmethod for complete qualitative analysis ofšthe dynamics ofšašsystem ofštwo vortex rings. Inšparticular, wešcompletely solve the problem ofšdescribing the conditions for the onset ofšleapfrogging motion ofšvortex rings. Inšaddition, for the system ofštwo vortex rings wešfind new families ofšmotions inšwhich the mutual distances remain finite (wešcall them pseudo-leapfrogging). Wešalso find solutions for the problem ofšthree vortex rings, which describe both the regular and chaotic leapfrogging motion ofšvortex rings.

In this paper we develop a new model of non-holonomic billiard that accounts for the intrinsic rotation of the billiard ball. This model is a limit case of the problem of rolling without slipping of a ball without slipping over a quadric surface. The billiards between two parallel walls and inside a circle are studied in detail. Using the three-dimensional-point-map technique, the non-integrability of the non-holonomic billiard within an ellipse is shown.

We consider a novel mechanical system consisting of two spherical bodies rolling over each other, which is a natural extension of the famous Chaplygin problem of rolling motion of a ball on a plane. In contrast to the previously explored non-holonomic systems, this one has a higher dimension and is considerably more complicated. One remarkable property of our system is the existence of "clandestine" linear in momenta first integrals. For a more trivial integrable system, their counterparts were discovered by Chaplygin. We have also found a few cases of integrability.

The Hamiltonian representation and integrability of the nonholonomic Suslov problem and its generalization suggested by S. A. Chaplygin are considered. This subject is important for understanding the qualitative features of the dynamics of this system, being in particular related to a nontrivial asymptotic behavior (i. e., to a certain scattering problem). A general approach based on studying a hierarchy in the dynamical behavior of nonholonomic systems is developed.

Wešconsider ašnonholonomic model ofšthe dynamics ofšanšomni-wheel vehicle onšašplane and ašsphere. Anšelementary derivation ofšequations isšpresented, the dynamics ofšašfree system isšinvestigated, ašrelation tošcontrol problems isšshown.

Wešconsider the problem ofšexplicit integration and bifurcation analysis for two systems ofšnonholonomic mechanics. The first one isšthe Chaplygin?s problem onšno-slip rolling ofšašbalanced dynamically non-symmetrical ball onšašhorizontal plane. The second problem isšonšthe motion ofšrigid body inšašspherical support. Wešexplicitly integrate this problem byšgeneralizing the transformation which Chaplygin applied tošthe integration ofšthe problem ofšthe rolling ball atšašnon-zero constant ofšareas. Wešconsider the geometric interpretation ofšthis transformation from the viewpoint ofšaštrajectory isomorphism between two systems atšdifferent levels ofšthe energy integral. Generalization ofšthis transformation for the case ofšdynamics inšašspherical support allowsšus tošintegrate the equations ofšmotion explicitly inšquadratures and, inšaddition, tošindicate periodic solutions and analyze their stability. Wešalso show that adding ašgyrostat does not lead tošthe loss ofšintegrability.

Wešconsider ašnovel mechanical system consisting ofštwo spherical bodies rolling over each other, which isšašnatural extension ofšthe famous Chaplygin problem ofšrolling motion ofšašball onšašplane. Inšcontrast tošthe previously explored non-holonomic systems, this one has ašhigher dimension and isšconsiderably more complicated. One remarkable property ofšour system isšthe existence ofš?clandestine? linear inšmomenta first integrals. For ašmore trivial integrable system, their counterparts were discovered byšChaplygin. Wešhave also found ašfew cases ofšintegrability.

Inšthis paper wešdevelop ašnew model ofšnon-holonomic billiard that accounts for the intrinsic rotation ofšthe billiard ball. This model isšašlimit case ofšthe problem ofšrolling without slipping ofšašball without slipping over ašquadric surface. The billiards between two parallel walls and inside ašcircle are studied inšdetail. Using the three-dimensional-point-map technique, the non-integrability ofšthe non-holonomic billiard within anšellipse isšshown.

Wešconsider the problems ofšHamiltonian representation and integrability ofšthe nonholonomic Suslov system and its generalization suggested byšS.šA.šChaplygin. These aspects are very important for understanding the dynamics and qualitative analysis ofšthe system. Inšparticular, they are related tošthe nontrivial asymptotic behaviour (i.še. tošsome scattering problem). The paper presents ašgeneral approach based onšthe study ofšthe hierarchy ofšdynamical behaviour ofšnonholonomic systems.

We consider the motion of a material point on the surface of a sphere in the field of $2n + 1$ identical Hooke centers (singularities with elastic potential) lying on a great circle. Our main result is that this system is superintegrable. The property of superintegrability for this system has been conjectured by us in [1], where the structure of a superintegral of arbitrarily high odd degree in momemnta was outlined. We also indicate an isomorphism between this system and the one-dimensional $N$-particle system discussed in the recent paper [2] and show that for the latter system an analogous superintegral can be constructed.

The dynamics of self-gravitating liquid and gas ellipsoids is considered. A literary survey and authors? original results obtained using modern techniques of nonlinear dynamics are presented. Strict Lagrangian and Hamiltonian formulations of the equations of motion are given; in particular, a Hamiltonian formalism based on Lie algebras is described. Problems related to nonintegrability and chaos are formulated and analyzed. All the known integrability cases are classified, and the most natural hypotheses on the nonintegrability of the equations of motion in the general case are presented. The results of numerical simulations are described. They, on the one hand, demonstrate a chaotic behavior of the system and, on the other hand, can in many cases serve as a numerical proof of the nonintegrability (the method of transversally intersecting separatrices).

Systems of material points interacting both with one another and with an external field are considered in Euclidean space. For the case of arbitrary binary interaction depending solely on the mutual distance between the bodies, new integrals are found, which form a Galilean momentum vector. A corresponding algebra of integrals constituted by the integrals of momentum, angular momentum, and Galilean momentum is presented. Particle systems with a particle?interaction potential homogeneous of degree $\alpha = ?2$ are considered. The most general form of the additional integral of motion, which we term the Jacobi integral, is presented for such systems. A new nonlinear algebra of integrals including the Jacobi integral is found. A systematic description is given to a new reduction procedure and possibilities of applying it to dynamics with the aim of lowering the order of Hamiltonian systems.
Some new integrable and superintegrable systems generalizing the classical ones are also described. Certain generalizations of the Lagrangian identity for systems with a particle? interaction potential homogeneous of degree $\alpha = ?2$ are presented. In addition, computational experiments are used to prove the nonintegrability of the Jacobi problem on a plane.

Wešconsider the motion ofšašmaterial point onšthe surface ofšašsphere inšthe field ofš2n+1 identical Hooke centers (singularities with elastic potential) lying onšašgreat circle. Our main result isšthat this system isšsuperintegrable. The property ofšsuperintegrability for this system has been conjectured byšus inš[3], where the structure ofšašsuperintegral ofšarbitrarily high odd degree inšmomemnta was outlined. Wešalso indicate anšisomorphism between this system and the one-dimensional N-particle system discussed inšthe recent paper [13] and show that for the latter system anšanalogous superintegral can bešconstructed.

3-particle systems with ašparticle-interaction homogeneous potential ofšdegree $?=-2$šis considered. Ašconstructive procedure ofšreduction ofšthe system byš2šdegrees ofšfreedom isšperformed. The nonintegrability ofšthe systems isšshown using the Poincare mapping.

Systems ofšmaterial points interacting both with one another and with anšexternal field are considered inšEuclidean space. For the case ofšarbitrary binary interaction depending solely onšthe mutual distance between the bodies, new integrals are found, which form ašGalilean momentum vector.

Ašcorresponding algebra ofšintegrals constituted byšthe integrals ofšmomentum, angular momentum, and Galilean momentum isšpresented. Particle systems with ašparticle-interaction potential homogeneous ofšdegree $?=-2$ are considered. The most general form ofšthe additional integral ofšmotion, which wešterm the Jacobi integral, isšpresented for such systems. Ašnew nonlinear algebra ofšintegrals including the Jacobi integral isšfound. Ašsystematic description isšgiven tošašnew reduction procedure and possibilities ofšapplying itštošdynamics with the aim ofšlowering the order ofšHamiltonian systems.

Some new integrable and superintegrable systems generalizing the classical ones are also described. Certain generalizations ofšthe Lagrangian identity for systems with ašparticle-interaction potential homogeneous ofšdegree $?=-2$ are presented. Inšaddition, computational experiments are used tošprove the nonintegrability ofšthe Jacobi problem onšašplane.

We have discovered a new first integral in the problem of motion of a dynamically symmetric ball, subject to gravity, on the surface of a paraboloid. Using this integral, we have obtained conditions for stability (in the Lyapunov sense) of steady rotations of the ball at the upmost, downmost and saddle point.

In this paper, we consider the transition to chaos in the phase portrait of a restricted problem of rotation of a rigid body with a fixed point. Two interrelated mechanisms responsible for chaotization are indicated: (1) the growth of the homoclinic structure and (2) the development of cascades of period doubling bifurcations. On the zero level of the area integral, an adiabatic behavior of the system (as the energy tends to zero) is noted. Meander tori induced by the break of the torsion property of the mapping are found.

For the classical problem of motion of a rigid body about a fixed point with zero area integral, we present a family of solutions that are periodic in the absolute space. Such solutions are known as choreographies. The family includes the well-known Delone solutions (for the Kovalevskaya case), some particular solutions for the Goryachev–Chaplygin case, and the Steklov solution. The "genealogy" of solutions of the family naturally appearing from the energy continuation and their connection with the Staude rotations are considered. It is shown that if the integral of areas is zero, the solutions are periodic with respect to a coordinate frame that rotates uniformly about the vertical (relative choreographies).

The paper contains the review and original results onšthe dynamics ofšliquid and gas self-gravitating ellipsoids. Equations ofšmotion are given inšLagrangian and Hamiltonian form, inšparticular, the Hamiltonian formalism onšLie algebras isšpresented. Problems ofšnonintegrability and chaotical behavior ofšthe system are formulated and studied. Wešalso classify all known integrable cases and give some hypotheses about nonintegrability inšthe general case. Results ofšnumerical modelling are presented, which can bešconsidered asšašcomputer proof ofšnonintegrability.

We discuss system of material points in Euclidean space interacting both with each other and with external field. In particular we consider systems of particles whose interacting is described by homogeneous potential of degree of homogeneity $\alpha=-2$. Such systems were first considered by Newton and—more systematically—by Jacobi). For such systems there is an extra hidden symmetry, and corresponding first integral of motion which we call Jacobi integral. This integral was given in different papers starting with Jacobi, but we present in general. Furthermore, we construct a new algebra of integrals including Jacobi integral. A series of generalizations of Lagrange's identity for systems with homogeneous potential of degree of homogeneity $\alpha=-2$ is given. New integrals of motion for these generalizations are found.

The dynamics of an antipodal vortex on a sphere (a point vortex plus its antipode with opposite circulation) is considered. It is shown that the system of n antipodal vortices can be reduced by four dimensions (two degrees of freedom). The cases $n = 2, 3$ are explored in greater detail both analytically and numerically. We discuss Thomson, collinear and isosceles configurations of antipodal vortices and study their bifurcations.

The dynamics ofšanšantipodal vortex onšašsphere (ašpoint vortex plus its antipode with opposite circulation) isšconsidered. Itšisšshown that the system ofšnšantipodal vortices can bešreduced byšfour dimensions (two degrees ofšfreedom). The cases n=2,3 are explored inšgreater detail both analytically and numerically. Wešdiscuss Thomson, collinear and isosceles configurations ofšantipodal vortices and study their bifurcations.

The paper considers the dynamics of a rattleback as a model of a heavy balanced ellipsoid of revolution rolling without slippage on a fixed horizontal plane. Central ellipsoid of inertia is an ellipsoid of revolution as well. In presence of the angular displacement between two ellipsoids, there occur dynamical effects somewhat similar to the reverse fenomena in earlier models. However, unlike a customary rattleback model (a truncated biaxial paraboloid) our system allows the motions which are superposition of the reverse motion (reverse of the direction of spinning) and the turn over (change of the axis of rotation). With appropriate values of energies and mass distribution, this effect (reverse + turn over) can occur more than once. Such motions as repeated reverse or repeated turn over are also possible.

The paper considers the process of transition to chaos in the problem of four point vortices on a plane. A new method for constructive reduction of the order for a system of vortices on a plane is presented. Existence of the cascade of period doubling bifurcations in the given problem is indicated.

Rolling (without slipping) of a homogeneous ball on an oblique cylinder in different potential fields and the integrability of the equations of motion are considered. We examine also if the equations can be reduced to a Hamiltonian form. We prove the theorem stated that if there is a gravity (and the cylinder is oblique), the ball moves without any vertical shift, on the average.

Wešhave discovered ašnew first integral inšthe problem ofšmotion ofšašdynamically symmetric ball, subject tošgravity, onšthe surface ofšašparaboloid. Using this integral, wešhave obtained conditions for stability (inšthe Lyapunov sense) ofšsteady rotations ofšthe ball inšthe upmost, downmost and saddle point.

Inšthe paper wešpresent ašnew integral ofšmotion inšthe problem ofšrolling motion ofšašheavy symmetric sphere onšthe surface ofšašparaboloid. Wešuse this integral tošstudy the Lyapunov stability ofšsome trivial steady rotations.

Wešoffer ašnew method ofšreduction for ašsystem ofšpoint vortices onšašplane and ašsphere. This method isšsimilar tošthe classical node elimination procedure. However, asšapplied tošthe vortex dynamics, itšrequires substantial modification. Reduction ofšfour vortices onšašsphere isšgiven inšmore detail. Wešalso use the Poincare surface-of-section technique tošperform the reduction ašfour-vortex system onšašsphere.

The paper deals with aštransition tošchaos inšthe phase-plane portrait ofšašrestricted problem ofšrotation ofšašrigid body with ašfixed point. Two interrelated mechanisms responsible for chaotisation have been indicated: 1) growth ofšthe homoclinic structure andš2) development ofšcascades ofšperiod doubling bifurcations. Onšthe zero level ofšthe integral ofšareas, anšadiabatic behavior ofšthe system (asšthe energy tends tošzero) has been noticed. Meander tori induced byšthe breakdown ofšthe torsion property ofšthe mapping have been found.

For the classical problem ofšmotion ofšašrigid body about ašfixed point with zero integral ofšareas, the paper presents ašfamily ofšsolutions which are periodic inšthe absolute space. Such solutions are known asšchoreographies. The family includes the famous Delaunay solution inšthe case ofšKovalevskaya, some particular solutions inšthe Goryachev-Chaplygin case and Steklov?s solution. The ?genealogy? ofšthe solutions ofšthe family, arising naturally from the energy continuation, and their connection with the Staude rotations are considered.

Itšisšshown that ifšthe integral ofšareas isšzero, the solutions are periodic but with respect tošašcoordinate frame that rotates uniformly about the vertical (relative choreographies).

We offer a new method of reduction for a system of point vortices on a plane and a sphere. This method is similar to the classical node elimination procedure. However, as applied to the vortex dynamics, it requires substantial modification. Reduction of four vortices on a sphere is given in more detail. We also use the Poincare surface-of-section technique to perform the reduction a four-vortex system on a sphere.

In this paper we describe new classes of periodic solutions for point vortices on a plane and a sphere. They correspond to similar solutions (so-called choreographies) in celestial mechanics.

We consider the problem of two interacting particles on a sphere. The potential of the interaction depends on the distance between the particles. The case of Newtonian-type potentials is studied in most detail. We reduce this system to a system with two degrees of freedom and give a number of remarkable periodic orbits. We also discuss integrability and stochastization of the motion.

We obtained new periodic solutions in the problems of three and four point vortices moving on a plane. In the case of three vortices, the system is reduced to a Hamiltonian system with one degree of freedom, and it is integrable. In the case of four vortices, the order is reduced to two degrees of freedom, and the system is not integrable. We present relative and absolute choreographies of three and four vortices of the same intensity which are periodic motions of vortices in some rotating and fixed frame of reference, where all the vortices move along the same closed curve. Similar choreographies have been recently obtained by C. Moore, A. Chenciner, and C. Simo for the $n$-body problem in celestial mechanics [6, 7, 17]. Nevertheless, the choreographies that appear in vortex dynamics have a number of distinct features.

In the paper we present the qualitative analysis of rolling motion without slipping of a homogeneous round disk on a horisontal plane. The problem was studied by S.A. Chaplygin, P. Appel and D. Korteweg who showed its integrability. The behavior of the point of contact on a plane is investigated and conditions under which its trajectory is finit are obtained. The bifurcation diagrams are constructed.

The problem of rolling motion without slipping of an unbalanced ball on 1) an arbitrary ellipsoid and 2) an ellipsoid of revolution is considered. In his famous treatise E. Routh showed that the problem of rolling motion of a body on a surface of revolution even in the presence of axisymmetrical potential fields is integrable. In case 1, we present a new integral of motion. New solutions expressed in elementary functions are found in case 2.

The paper is concerned with the problem on rolling of a homogeneous ball on an arbitrary surface. New cases when the problem is solved by quadratures are presented. The paper also indicates a special case when an additional integral and invariant measure exist. Using this case, we obtain a nonholonomic generalization of the Jacobi problem for the inertial motion of a point on an ellipsoid. For a ball rolling, it is also shown that on an arbitrary cylinder in the gravity field the ball's motion is bounded and, on the average, it does not move downwards. All the results of the paper considerably expand the results obtained by E. Routh in XIX century.

The motion of Chaplygin ball with and without gyroscope in the absolute space is analyzed. In particular, the trajectories of the point of contact are studied in detail. We discuss the motions in the absolute space, that correspond to the different types of motion in the moving frame of reference related to the body. The existence of the bounded trajectories of the ball's motion is shown by means of numerical methods in the case when the problem is reduced to a certain Hamiltonian system.

In the paper Motion of a circular cylinder and a vortex in an ideal fluid (Reg. & Chaot. Dyn. V. 6. 2001. No 1. P. 33-38) Ramodanov S.M. showed the integrability of the problem of motion of a circular cylinder and a point vortex in unbounded ideal fluid. In the present paper we find additional first integral and invariant measure of motion equations.

In this work stability of polygonal configurations on a plane and sphere is investigated. The conditions of linear stability are obtained. A nonlinear analysis of the problem is made with the help of Birkhoff normalization. Some problems are also formulated.

We consider two-body problem and restricted three-body problem in spaces $S^2$ and $L^2$. For two-body problem we have showed the absence of exponential instability of partiáular solutions relevant to roundabout motion on the plane. New libration points are found, and the dependence of their positions on parameters of a system is explored. The regions of existence of libration points in space of parameters were constructed. Basing on a examination of the Hill's regions we found the qualitative estimation of stability of libration points was produced.