The equilibrium stability for a smooth and discontinuous oscillator with dry friction

Abstract

In this paper, we investigate the equilibrium stability of a Filippov-type system having multiple stick regions based upon a smooth and discontinuous (SD) oscillator with dry friction. The sets of equilibrium states of the system are analyzed together with Coulomb friction conditions in both $$(f_{\mathrm{n}}, f_{\mathrm{s}})$$ and $$(x, {\dot{x}})$$ planes. In the stability analysis, Lyapunov functions are constructed to derive the instability for the equilibrium set of the hyperbolic type and LaSalle’s invariance principle is employed to obtain the stability of the non-hyperbolic type. Analysis demonstrates the existence of a thick stable manifold and the interior stability of the hyperbolic equilibrium set due to the attractive sliding mode of the Filippov property, and also shows that the unstable manifolds of the hyperbolic-type are that of the endpoints with their saddle property. Numerical calculations show a good agreement with the theoretical analysis and an excellent efficiency of the approach for equilibrium states in this particular Filippov system. Furthermore, the equilibrium bifurcations are presented to demonstrate the transition between the smooth and the discontinuous regimes.