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Title: Exploitation of nonlinear effects in micro-electromechanical resonators
Author: Deng, Chenchen
ISNI:       0000 0004 2723 814X
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2011
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Microelectromechanical Systems (MEMS) are well developed in various fields benefiting from the rapid improvement of fabrication technology. Because of the low cost, small mass and high frequency, micromechanical resonators are of great interest to be used in the sensing technology. The mass change of a linear resonator can be identified by monitoring the resonant frequency. Any resonant frequency changes can be detected by the resulting change in amplitude or phase of the resonator's response at a particular frequency. A popular method to increase the sensitivity of the linear resonator is using force feedback to increase the effective Q value of a MEMS resonator by partially cancelling the effects of viscous damping. Alternative methods to enhance the sensitivity of the resonator have been proposed in this thesis using the non-linear behaviour of the resonator which is known as Duffing nonlinearity. A Duffing resonator has sudden transitions in both amplitude and phase at two jump frequencies which could be exploited to enhance the sensitivity of resonator based sensors. Numerical simulations and tests of a 'Duffing' circuit presented a driving scheme to give rise to fast, reliable, sensitive mass sensors. Two types of feedback methods to create a Duffinglike non-linearity are proposed using micromechanical resonators with low native Q values. One is using the force feedback to enhance the Q value and deliberately driving the system into the nonlinear region with a large excitation force. The other one is to generate a displacement cubed feedback term and add it to the primary drive. Both methods show that changes in resonant frequency of a Duffing resonator can create a dramatically larger change in phase than the equivalent linear resonator. In addition to the sensitivity analysis, the transient behaviour of the Duffing resonator following a parameter change has also been investigated in this thesis.
Supervisor: Collins, Steve Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Electrical engineering ; Sensors ; Electronics