| In many applications, MEMS structures are subjected to environments that are stochastic in nature. It could be random loading in the case of pressure sensors. On the other hand, due to random vibration of the body in which MEMS devices are attached, they are usually subjected to random base excitation. Therefore, in general MEMS structures are subjected to random environments which may be either random loading or random base excitation. Moreover, as the operating environments of MEMS structures are random, the performance response such as stress, strain, and displacement of the structures are consequently random. In order to explore the dynamic performance of MEMS structures under random environments, the concepts of spectral density function, variance and covariance and the finite element method have to be studied and employed. Random vibration models of multi-degree-of-freedom system and continuous structures have been developed and applied to MEM structures under random loading and base excitation. Experimental results are also conducted on typical MEM structures to verify the analytical model. Moreover, from application point of view the response of a tire pressure due to random pressure fluctuation inside the tire has been studied and a formulation has been proposed to obtain the spectral density function of the tire pressure with respect to the random pavement roughness. The reliability of MEMS structures in random environments has also been addressed briefly. |
