|M.Sc Student||Perl Tamir|
|Subject||Modeling and Control of Vibratory MEMS Gyroscope|
with Parametric Resonance
|Department||Department of Electrical Engineering||Supervisors||Professor Nahum Shimkin|
|Full Thesis text|
MEMS technology is very appealing for implementation in gyroscopes for angular rate measurement due to its features of small size and low production cost. Applying parametric resonance to the drive mode of two degrees of freedom MEMS gyroscope can improve sensor performance. The main strategy of MEMS gyroscope with parametric resonance is to exploit large bandwidth of the drive mode to achieve inherent mode matching with respect to the sense mode. This way increased sensitivity of the sensor can be achieved.
In this research a control system for MEMS gyroscope with parametric resonance is investigated. A full systematic approach, including the design of conceptual MEMS structure with full actuators and voltages configuration, is presented. The system level architecture includes four control loops, two for each mode.
For the drive mode the control loops have two objectives. The first is to control the drive mode velocity amplitude due to its coupling to the Coriolis force. This is needed for achieving stable sensor output. The second is to actuate the drive mode at the sense mode natural frequency for increased sensitivity. Full formulation and analysis of the drive mode dynamics with parametric resonance was conducted using perturbation theory and multiple scales method. The obtained simplified model was used for control loop design. The analysis consists of linearization of the non-linear system and proper controller design according to the closed loop requirements.
Two complementary control loops for the sense mode are needed to overcome the problems which arise due to the mode matching property of the gyroscope. The first control loop objective is to control the mechanical coupling induced oscillations of the sense mode to avoid pick-off circuits saturation. The second control loop objective is to eliminate the Coriolis
force induced oscillations of the sense mode for enhancing the sensor performance by means of increased sensor bandwidth and reduced sensor output sensitivity to parameter variations. The sense mode control loops undergo basic controller design based on a proportional-integral controller according to closed loop requirements.
A SIMULINK model of the proposed MEMS structure and control loops was developed. Numerical simulations show that robustness of the drive mode control loops to parameter variations of the device can be achieved and that the linear analysis used for the controllers' designs can be used for the prediction of the non-linear system behavior. Sense mode control loops simulations show that increased sensor bandwidth, reduced sensor output sensitivity to parameter variations and desired mechanical coupling induced oscillations of the drive mode can be achieved.