Alexandra Zobova

• PhD
• Senior Researcher at Tel Aviv University

We report on a new architecture and theoretical and experimental feasibility study of a resonant accelerometer, combining a robust single proof mass design with a compliant parallel motion linkage -type force amplifier. The device, incorporating four effectively oblique force-transmitting links and a resonant sensing beam attached at its ends to tw...

This research provides the theoretical feasibility study of a novel architecture of a MEMS differential resonant accelerometer, with switchable and tunable electrostatic transmission between the proof mass and the vibrating sensing beams. The same beams are used for sensing of the inertial force, while the transmission is switched ON, and for the d...

For the nonsymmetrical vehicle configuration, we propose a numerical procedure of solving boundary-value problems that uses parametric continuation of the solution obtained for the symmetric vehicle. It shows that the proposed type of control can be used for an arbitrary vehicle configuration.

This review presents a collection of the solved dynamic problems taking into account the normal and shear stress distributions in the contact region due to the deformation of contacting bodies. The considered dynamic problems differ in the number of degrees of freedom and the type of relative displacements of contacting bodies (2-D models with roll...

In this paper, we consider the dynamics of a mobile vehicle moving under control on a perfectly rough horizontal plane. The vehicle consists of a horizontal platform and three omni-wheels that can rotate independently. An omni-wheel has freely rotating rollers on its rim [1]. We use its simplest model: an omni-wheel on a perfectly rough plane is mo...

This paper investigates the influence of the material properties on the deceleration dynamics of a deformable cylinder rolling with slipping on a half-space of the same material. The interaction of the cylinder and the half-space is described by the 2D quasistatic contact problem of viscoelasticity (Goryacheva: J Appl Math Mech 37(5):877–885, 1973;...

The deceleration of a viscoelastic cylinder rolling with slipping on a viscoelastic half-space of the same material without driving forces and torques is studied. The interaction of the cylinder and the half-space is described from the solution of the 2D quasistatic contact problem of viscoelasticity (Goryacheva in J Appl Math Mech 37(5):877–885, 1...

Our goal is to build up an efficient computer model of the omni-vehicle comprising several omni-wheels (each one carries several freely rotating rollers on its periphery); the vehicle rolls without control on a horizontal plane. For simulating contact interaction we use the holonomic non-ideal constraints instead of ideal non-holonomic ones. Althou...

We consider the motion of a vehicle with omni-wheels that moves along a horizontal plane without slipping. The mass of the rollers is non-zero and influences the dynamics of the system. The system is a multibody system of rigid bodies with non-holonomic constraints. The angular speed of the roller that enters in contact with the plane does not obli...

The deceleration of an infinite rigid cylinder sliding along a surface of a viscoelastic halfspace is studied (the axis of the cylinder at plane-parallel motion is horizontal). It is assumed that there are no tangential stresses in the contact area. The distribution of contact pressures, the size of contact area, and the dependence of resistance fo...

The quasi-static plane-parallel motion of an infinite elastic cylinder along a horizontal foundation made of the same material is studied (the cylinder axis is horizontal). The distribution of normal and tangential stresses in the region of contact interaction between the cylinder and plane is derived from the solution to the problem of the theory...

We consider the dynamics of an absolutely rigid body moving along a rough horizontal plane. We assume that the plane deforms during the motion so that the contact patch is non-planar and has non-zero, but comparatively small area. In the contact patch, the vertical reactions are proportional to the vertical deformations and their rates, that is, we...

The dynamics of a symmetrical vehicle with omniwheels, moving along a fixed, absolutely rough horizontal plane, is considered, making the following assumptions: the mass of each roller is nonzero, there is a point contact between the rollers and the plane, and there is no slip. The equations of motion composed with the use of the Maxima symbolic co...

The dynamics of a mobile vehicle with three omni wheels is considered for the case when the vehicle moves on a fixed perfectly rough plane by inertia. In order to study the effect of wheel roller inertia on the stability of the rectilinear motion of the vehicle, the fore wheel is modeled by the following rigid bodies: a wheel disk and a supporting...

For the first time, the dynamic problem of plane-parallel rolling with the slip of an elastic cylinder along an elastic base of the same material is analyzed. The distribution of the normal and tangential stresses in the contact-interaction region consisting of relative slip and stick subregions corresponds to the solution of the quasi-static probl...

We consider the dynamics of a tippe-top on a visco-elastic plane with dry friction. Tippetop is a rigid dynamically symmetric sphere with the center of mass that lies on the dynamical axis of symmetry but does not coincide with the center of the sphere. It was shown earlier [1] that the full mechanical energy conserves only on the steady-state moti...

We consider the dynamics of an absolutely rigid body moving on a rough horizontal plane. We assume that the plane deforms during the motion and the normal reaction in each infinitesimal area is proportional to the deformation and its rate (Kelvin-Voigt model). On the rigid body, moving along the plane, the dry friction distributed over the contact...

We present a multibody simulator being used for compliant humanoid robot modelling and report our reasoning for choosing the settings of the simulator’s key features. First, we provide a study on how the numerical integration speed and accuracy depend on the coordinate representation of the multibody system. This choice is particularly critical for...

Models of distributed dry friction are analysed. In constructing the models, it is assumed that contact exists between the two bodies over a certain area, with Amonton–Coulomb dry friction in each infinitesimal region of this area. Static models (Contensou–Erismann friction and its modifications) and dynamic models (phenomenological models, a dynam...

In this paper, we discuss some very important features for getting exploitable simulation results for multibody systems, relying on the example of a humanoid robot. First, we provide a comparison of simulation speed and accuracy for kinematics modeling relying on relative vs. absolute coordinates. This choice is particularly critical for mechanisms...

We consider dynamical problems arising in connection with the interaction of an absolutely rigid ball and a viscoelastic support plane. The support is a relatively stiff viscoelastic Kelvin-Voigt medium that coincides with the horizontal plane in the undeformed state. We also assume that under the deformation the support induces dry friction forces...

The dynamics of a two-sphere tippe top on a rough horizontal plane is considered. The top is bounded by a nonconvex surface consisting of two spherical segments of distinct radii and a cylinder; the cylinder axis coincides with the common symmetry axis of the segments. If the top is initially placed so that its center of mass is almost in the lowes...

Dynamics of a two-spherical tippe-top on a rough horizontal plane is considered. The tippe-top is bounded by a non-convex surface that consists of two-spheres and a cylinder; the axis of cylinder coincides with the common spheres’ axes of symmetry. Being fast spun around its axis of symmetry the tippe-top overturns from the bottom (the big sphere)...

The motion of the tippe top on a horizontal plane is considered taking into account sliding friction within the Contensou model. The tippe top is modelled by two spherical segments rigidly joined by a rod directed along the common axis of symmetry of the segments. The dimensions of the spherical segments and the rod are chosen so that, as the axis...

The motion of an omni-mobile vehicle on a horizontal plane is considered. The wheels are modelled by absolutely rigid discs. Slippage in a certain direction, which makes a constant non- zero angle with the plane of a disc, is possible at the contact point of a wheel and the plane, and the planes of the discs are fixed with respect to the platform o...

The dynamics of a vehicle whose three omniwheels are symmetrically arranged is considered in the case when the vehicle moves on a horizontal plane. Two wheels are parallel to each other, whereas the third one is perpendicular to them; the centers of the wheels are located at the vertices of an isosceles triangle. A phase portrait is constructed und...

In this paper, the problem of motion of heavy rigid body in the rough plane is studied. The surface of body is such that the axis of rotation has two “points,” where the plane tangent to the surface is not specified. The motion is described by two systems of equations; each of them is true for its side of the phase space. One of them is a system of...

The problem of the existence of first integrals which are linear functions of the generalized velocities (momenta and quasi-velocities) is discussed for conservative non-holonomic Chaplygin systems with symmetry, as well as methods for investigating the existence, stability, and bifurcation of the steady motions of such systems. These methods are b...