Structurally decoupled micromachined gyroscopes with post-release capacitance enhancement

This paper reports a novel micromachined gyroscope design that provides enhanced decoupling of the drive and sense modes, and increased actuation and detection capacitances beyond the fabrication process limitations. The decoupling mechanism minimizes the effects of fabrication imperfections and the resulting anisoelasticities, by utilizing independent folded flexures and constrained moving electrodes in the drive and sense modes. The post-release capacitance enhancement concept aims to increase the drive and sense capacitances beyond the minimum gap requirement of the micromachining process. The approach is based on designing the stationary components of the electrodes attached to a moving stage that permanently locks into the desired position before the operation of the device, to minimize the electrode gap with a simple assembly step. Bulk-micromachined prototype gyroscopes have been fabricated, and the experimental results have successfully demonstrated the feasibility of the design. It is experimentally shown that over an order of magnitude of capacitance, increase is achieved in the same foot print of the device, without additional fabrication steps. A noise floor of 0.25 degrees /s/ root Hz was demonstrated at 50 Hz bandwidth in atmospheric pressure.