| The current MEMS (Micro-Electro-Mechanical System) gyroscopes which normally use the electro static force to excite the comb drive are faced with the limitations such as low precision, coupling problem, and poor robustness. They need an order of magnitude improvement in their performance, stability, and robustness. Our main idea is that if the comb drive can be driven to much larger vibrating amplitude than the current one so that the signal at the comb drive can be easily measured, then, consequently, the precision of the MEMS gyroscope shall be improved. We propose to use parametric forcing as excitation.;However, since the two proof masses must be driven into motion in opposite directions, this imposes restrictions on the external forcing. A feasibility study of the parametric excitation using a two-pendulum model is presented. Governing equations are derived by Lagrange equation, and the results are simulated using MATLAB program. Two swing patterns, symmetric and anti-symmetric motion, are illustrated and investigated with different initial conditions.;To predict the beam response with the parametric excitation, a novel approach is presented, which allows calculating the coefficients in the governing equation of a cantilever beam using FEM (Finite Element Method). The results are compared with the analytical result obtained by method of averaging.;An experimental study of a tuning fork beam is presented. For non-contact motion analysis, an Eagle 3-D motion analysis digital camera system is employed. We discuss the practical problems such as limited shaker power, which is caused by open-loop excitation method. A governing equation including the damping effect by the lateral vibration of the tines is presented, and its analytical solution is compared with the experimental results. A good qualitative agreement is obtained. Moreover, a sensitivity study of the parameters in the governing equation is also presented. To clarify the softening nonlinearity of the tuning fork beam, the gravity effect is described for both vertical and inverted pendulum cases. |
