A self-exciting system for percussive-rotary drilling

A dynamic model for a new principle of self-excited percussive-rotary drilling is presented. The system uses the stick-slip phenomenon to generate an impact action superimposed on the drilling process. This is a strongly nonlinear mechanical system with two-degrees-of-freedom, in which friction-induced vibration is used for excitation of impacts. The model has to take account of the returning effect that the impacts have on the parameters of stick-slip motion. The model incorporates friction force as a function of sliding velocity, where the self-excitation of coupled vibration of the rotating bit and the striker tend to a steady-state periodic cycle. Dynamic coupling of vibro-impact action with the stick-slip process brings innovative adaptive features into the drilling process.