טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentPaz Ronen
SubjectMicromechanical Embodiment of Vibratory Angular Rate Sensor
DepartmentDepartment of Mechanical Engineering
Supervisor Dr. Itzhak Porat


Abstract

Micromachined gyroscopes are generally based on the coriolis acceleration . For a maximum sensitivity of the sensor, it has to operate at resonance (or near resonance) - the forcing frequency has to be equal, or close to the natural mode. The main drawback of such a sensor is the high sensitivity to changes of parameters ,the problem worsens when the damping decreases. Some of the reasons for the deviation from resonance are the techniques associated with micromachining known today, which do not achieve high accuracy, and there are deviations from desired shapes and dimensions, internal stress, temperature, etc. Several solutions have been proposed ,but they are either expensive ,too complicated, or do not entirely satisfactory.

    In this research we address the problem by adding a degree of freedom. It is embodied on the base of an traditional angular rate sensor, the “Gyrotron” or “Tuning fork gyroscope”, developed by “Sperry Gyroscope Company” in the fifties. A single-degree of freedom micromechanical Gyrotron is suspended by torsional bars (one or two), and consisting of two vibrating masses. The degree of freedom is due to the torsional rotation of the masses.  A two degree of freedom Gyrotron consists of two such systems connected to each other, or alternatively by adding to the traditional tuning fork a rigid body and a torsional bar.

   The research suggests two options to embody the two-degree of freedom gyroscope micromechanically. The first one is by using an electrostatic actuation (comb drive) and capacitive sensing ,where attention is paid to the different mechanisms of damping. The second option is based on a piezoelectric sensing and a piezoelectric actuation.