On local ISS of nonlinear second-order time-delay systems without damping

For a second-order system with vector position, either constant or time-varying delays, and a power nonlinearity of the degree higher than one, which does not contain a velocity-proportional damping term, the conditions of local input-to-state stability are proposed. The result is based on application of Lyapunov-Razumikhin approach, for which new time estimates on decay of solutions are obtained. The approach is extended to attitude stabilization of a rigid body, and it is illustrated by simulations.