In this paper, we report the design and fabrication of a novel micromachined electro-magnetically driven tuning fork type gyroscope with bar structure proof masses working at atmospheric pressure. The applied angular rate is sensed by detecting the differential change of capacitance between the bar structure electrodes and the fixed electrodes on the glass substrate. Instead of common squeeze-film damping, slide-film damping in the gap between proof masses and glass substrate plays a dominant role, which enables it to achieve high Q-factors and thus eliminate vacuum packaging. The measured Q-factors for driving and sensing modes are 965 and 716, respectively. The sensor obtained a sensitivity of 6 mV/°/s and a non-linearity of less than 0.5%. IntroductionIn automotive industry, the growing needs for micromachined gyroscopes push the researchers to produce even smaller, cheaper and better performing devices. A variety of prototypes have been developed in past years, most of which are of tuning fork vibratory type employing different excitation and detection mechanisms [1]. Electrostatic excitation and capacitive detection mechanism [2, 3, 4] is the most preferred, while others, such as electromagnetic excitation mechanism [5] and piezoelectric drive and piezoresistive read-out [6], have also been reported.Air damping effect is one critical issue that is worth taking into account when designing a gyroscope, which determines the Q-factors for both driving and sensing modes and thus the sensors' performance. For example, in a typical capacitive detection gyroscope where comb-type detection structure is commonly used [7], the squeeze-film damping between comb fingers plays an important role, which usually results in a low Q-factor and requires costly vacuum packaging solution in some cases to achieve better sensitivity. In our previous work [8], slide-film damping effect was introduced to a vibratory gyroscope for achieve good Q-factor, but the electrostatic driving mode had a limited oscillating amplitude.In this paper, we report the design and fabrication of a novel micromachined electro-magnetically driven tuning fork type gyroscope with bar structure proof masses for capacitive detection. The great enough driving amplitude under electro-magnetical excitation, along with high Qfactor for detection mode due to the slide-film damping effect, enable it a good performance at atmospheric pressure. Working principleAs shown schematically in Fig. 1, the gyroscope consists of two silicon oscillating frames, each of which is anchored on glass substrate by four spring beams and is connected each other through a connection ring. Each proof mass with bar structure detection electrodes is connected to the surrounding oscillating frame by two suspension beams. The oscillating frames as well as the proof masses with bar structure can move above the glass substrate along X or Ydirection. The bar structure electrodes and fixed interdigitated electrodes on glass substrate form the detection capacitors. The silicon surface is covered...
Background and objectives 11 Operations 15 Lithostratigraphy 25 Igneous and metamorphic petrology 32 Structural geology 37 Biostratigraphy 39 Paleomagnetism 44 Geochemistry 46 Physical properties 50 Downhole measurements 53 Correlation to seismic data 55 References J.M. Stock et al. Site U1500 IODP Proceedings 2 Volume 367/368 Table T1. Site U1500 core summary. * = base of 10.75 inch casing at 842 m; drilled in with pilot bit and underreamer that extended below the end of the casing. † = excludes core recovered during hole cleaning (ghost core). DRF = drilling depth below rig floor, DSF = drilling depth below seafloor. Core type: numeric core type = drilled interval, R = rotary core barrel, G = ghost core. WOB = weight on bit. Drilling break = fast penetration, unable to maintain any WOB. (Continued on next two pages.) Download table in CSV format.
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