Stability theory of steady motions of nonholonomic systems was created. Routh–Lyapunov–Salvadori theory was spreaded to systems with differential constrains and systems with friction. It was proved that limiting transition from systems with friction to systems with differential constrains is correct by Tikhonov. Steady motions of rigid body on a plane are investigated (under different hypotheses about interaction between a body and a plane).
Main publications:
Karapetyan A. V. Invariant sets of mechanical systems // Modern Methods of Analytical Mechanics and their Applications. Wien–New York: Springer-Verlag, 1998, p. 153–210.
ISTINA