Vibro-impact responses of capsule system with various friction models

• The dynamics of a capsule system in various friction environments is studied.
• The capsule main body interacts with an externally driven internal mass.
• The system could potentially be applied in medical and engineering applications.
• Our investigations are focussed on the qualitative changes in the capsule dynamics.
• The Coulomb model is fair for relatively large mass ratio of the system.

The dynamics of the vibro-impact system which consists of a capsule main body interacting with a harmonically driven internal mass in various environments is studied in this paper. The environmental resistance is described by four different friction models which take into account Coulomb friction, viscous damping, Stribeck effect, pre-sliding, and frictional memory. Our investigations are mainly focussed on the qualitative changes in the capsule dynamics. The bifurcation analysis is conducted by monitoring the mass velocity and the average progression of the capsule per period of excitation under variation of the mass ratio. By observing the progression of the capsule, we find that directional control of the system can be achieved either by varying its mass ratio or by switching between co-existing attractors.