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Instabilities in a vibrating MEMS gyroscope that is subject to periodic fluctuations in input angular rates are investigated. For the purpose of acquiring stability conditions, when the angular rate input is subject to small intensity periodic fluctuations, dynamic behavior of periodically perturbed linear gyroscopic systems is studied in detail. An asymptotic approach based on the method of averaging has been employed for this purpose, and closed-form conditions for the onset of instability due to parametric resonances have been obtained. A numerical approach based on the Floquet-Lyapunov theory is employed for validating the analytical stability predictions. Furthermore, for characterizing the effect due to change in angular rate input, an in-depth natural frequency analysis has been performed. Stability predictions have been illustrated via stability diagrams in the excitation amplitude-frequency space. Based on these results, the dangerous critical frequencies can be avoided during the design process. [ABSTRACT FROM AUTHOR]

Melnikov's method is used to analytically predict the onset of chaotic instability in a rotating body with internal energy dissipation. The model has been found to exhibit chaotic instability when a harmonic disturbance torque is applied to the system for a range of forcing amplitude and frequency. Such a model may be considered to be representative of the dynamical behavior of a number of physical systems such as a spinning spacecraft. In spacecraft, disturbance torques may arise under malfunction of the control system, from an unbalanced rotor, from vibrations in appendages or from orbital variations. Chaotic instabilities arising from such disturbances could introduce uncertainties and irregularities into the motion of the multibody system and consequently could have disastrous effects on its intended operation. A comprehensive stability analysis is performed and regions of nonlinear behavior are identified. Subsequently, the closed form analytical solution for the unperturbed system is obtained in order to identify homoclinic orbits. Melnikov's method is then applied on the system once transformed into Hamiltonian form. The resulting analytical criterion for the onset of chaotic instability is obtained in terms of critical system parameters. The sufficient criterion is shown to be a useful predictor of the phenomenon via comparisons with numerical results. Finally, for the purposes of providing a complete, self-contained investigation of this fundamental system, the control of chaotic instability is demonstated using Lyapunov's method. [ABSTRACT FROM AUTHOR]