This paper describes a technique for detection of anisoelasticities in rate integrating gyroscopes as part of a self-calibrative control architecture. In contrast to laser trimming typically done in post processing to compensate for structural imperfections, the on-chip control architecture uses feedforward voltage control to tune the non-linear negative spring effects inherent in parallel plate electrodes in order to electrostatically 'trim' the structural non-idealities. As the first steps toward the feedforward control realization, we present three different algorithms that can be implemented on-chip for identification of structural anisoelasticities. The first technique utilizes the results of measured static displacements, requiring precise knowledge of displacements and applied forces. The second technique involves solving for the non-ideal stiffness parameters using Principal Component Analysis and Fourier transforms of the dynamic system response. The last technique embellishes on the second by the addition of an energy compensation control to overcome damping effects in low Q systems. Finally, the implementation of this algorithm in the electrostatic trimming' of structural imperfections is discussed.
Proc. SPIE. 4334, Smart Structures and Materials 2001: Smart Electronics and MEMS
KEYWORDS: Microelectromechanical systems, 3D modeling, Thermal effects, Finite element methods, Thermal analysis, Gyroscopes, Chemical elements, Thermal modeling, Systems modeling, Temperature metrology
This paper describes the structural and thermal modeling of a Micro Electro Mechanical System (MEMS) z-axis angular gyroscope. The gyroscope consists of a oscillating proof mass supported by a suspension made up of six concentric interconnected rings rigidly attached to an anchored frame. The device is capable of measuring angular displacement through precession of the proof mass line of oscillation in the presence of rotation induced Coriolis force. Using a strain energy method, a closed form solution for the effective stiffness of the suspension system is developed, which is confirmed using finite element modeling. A comparative study of the suspension with a commonly used serpentine spring suspension demonstrates that the studied device is robust to thermal fluctuations and residual stresses. A parametric analysis is used to identify an appropriate micromachining technology suitable for the fabrication of the angular gyroscope.