Stability, bifurcation and chaos of a high-speed rub-impact rotor system in MEMS

A general model of a Jeffcott micro-rotor system with rub-impact is established based on the classic impact theory and is analyzed by the modern nonlinear dynamics and bifurcation theories. An investigation is carried out on the stability of the rub solutions of the rotor system and the results provide a better understanding of the dynamical characteristics, such as the transition among periodic, quasi-periodic and chaotic responses, of the rotor system with rub-impact under different system parameter combinations. Nonlinear behaviors of rub-related vibrations are studied with a large number of numerical simulations. The effects of rotating speed, imbalance, damping coefficient, impact stiffness, and friction coefficient on the micro-rotor responses are investigated in detail. It is demonstrated that the system goes through an extraordinary route to chaos and alternates among the periodic, quasi-periodic and chaotic motions as the system parameters change. These forms of dynamical characteristics can be effectively used to diagnose the rub-impact fault. The results help engineers to optimize the design of micro-rotating machinery in MEMS, as well as to develop sensitive monitoring/diagnosis systems assessing machinery conditions.