Borislav Gajić
Publications:
Dragović V., Gajić B., Jovanović B.
Spherical and Planar Ball Bearings — a Study of Integrable Cases
2023, vol. 28, no. 1, pp. 6277
Abstract
We consider the nonholonomic systems of $n$ homogeneous balls $\mathbf B_1,\dots,\mathbf B_n$ with the same radius $r$ that are rolling without slipping about a fixed sphere $\mathbf S_0$ with center $O$ and radius $R$.
In addition, it is assumed that a dynamically nonsymmetric sphere $\mathbf S$ with the center that coincides with the center $O$ of the fixed sphere $\mathbf S_0$ rolls without
slipping in contact with the moving balls $\mathbf B_1,\dots,\mathbf B_n$. The problem is considered in four different configurations, three of which are new.
We derive the equations of motion and find an invariant measure for these systems.
As the main result, for $n=1$ we find two cases that are integrable by quadratures according to the Euler – Jacobi theorem.
The obtained integrable nonholonomic models are natural extensions of the wellknown Chaplygin ball integrable problems.
Further, we explicitly integrate
the planar problem consisting of $n$ homogeneous balls of the same radius, but with different
masses, which roll without slipping
over a fixed plane $\Sigma_0$ with a plane $\Sigma$ that moves without slipping over these balls.

Dragović V., Gajić B., Jovanović B.
Spherical and Planar Ball Bearings — Nonholonomic Systems with Invariant Measures
2022, vol. 27, no. 4, pp. 424442
Abstract
We first construct nonholonomic systems of $n$ homogeneous balls $\mathbf B_1,\dots,\mathbf B_n$ with centers $O_1,\ldots,O_n$ and with the same radius $r$ that are rolling without slipping around a fixed sphere $\mathbf S_0$ with center $O$ and radius $R$. In addition, it is assumed that a dynamically nonsymmetric sphere $\mathbf S$ of radius $R+2r$ and the center that coincides with the center $O$ of the fixed sphere $\mathbf S_0$ rolls without slipping over the moving balls $\mathbf B_1,\dots,\mathbf B_n$.
We prove that these systems possess an invariant measure. As the second task, we consider the limit, when the radius $R$ tends to infinity. We obtain a corresponding planar problem consisting of $n$ homogeneous balls $\mathbf B_1,\dots,\mathbf B_n$ with centers $O_1,\ldots,O_n$ and the same radius $r$ that are rolling without slipping
over a fixed plane $\Sigma_0$, and a moving plane $\Sigma$ that moves without slipping over the homogeneous balls. We prove that this system possesses an invariant measure and that it is integrable in quadratures according to the Euler – Jacobi theorem.
