On the stiffness-switching methods for generating self-excited oscillations in simple mechanical systems

The present article proposes stiffness-switching methods for generating artificial self-excited oscillation in simple mechanical and micromechanical systems and theoretically investigates the feasibility of the methods. The basic method proposed involves a stiffness reduction mechanism which operates in an on–off fashion depending on the measured states of the system. The efficacy of the method is first studied in case of a single-degree-of-freedom linear mechanical oscillator and then extended to an essentially nonlinear micromechanical resonator. Analytical and numerical investigations reveal that the stiffness-switching method can be effectively utilized for generating and controlling self-excited oscillations in simple mechanical structures. However, the amplitude of oscillation obtained by the basic method involving only the stiffness reduction mechanism is found to be extremely sensitive to the uncertainties in the inherent damping of the structure. An alternative switching scheme is also proposed to alleviate this shortcoming.