Abstract
Coriolis Vibratory Gyroscope (CVG) is an inertial angular rate measurement sensor. CVG sensor comprises of metal coated hemispherical quartz vibrating structure as the rotation sensing element. It is forced to vibrate at one of its resonant modes by electrostatic excitation. Because of the limited flexibility of the quartz sensing element, the amplitude is limited to the submicron level. An ultra-high vacuum environment is required for the sensing element to sustain vibration for a long time. The criticality in the sensor development is to maintaining an ultra-high vacuum environment for the sensing element. Sensor suffers a problem of vacuum instability during the operation due to the outgassing from its components. This paper presents a novel approach in the identification of various outgassing sources that exist in the sensor, mitigation plan to minimize outgassing rate by selection of suitable raw material, suitable fabrication process of the components, and the surface characterization etc. The research work also presents the cost-effective experimental methodology to measure the outgassing rate from the sensor components to assess the CVG vacuum life, the requirement of the getter to maintain the ultra-high vacuum level throughout the CVG operation.
Highlights
Inertial navigation system [1] uses gyroscope and accelerometer sensors to extract instantaneous angular and position information with respect to an inertial frame, based on the dead reckoning method
The first iterative process is the low outgassing material selection, if the Residual Gas Analysis shows higher level of outgassing elements, raw material need to be changed as per specifications, the second iterative process is the surface characterization, if the surface quality is not improved by the grinding and polishing the process need to be repeated, and the final iterative process is the degassing from the sensor components, if the outgassing rate from the sensor component is beyond allowed range the degassing process is need to be repeated
With the reference to this chamber outgassing rate, Coriolis Vibratory Gyroscope (CVG) sensor components outgassing rate is again measured by repeating the experiment
Summary
Inertial navigation system [1] uses gyroscope and accelerometer sensors to extract instantaneous angular and position information with respect to an inertial frame, based on the dead reckoning method. Most of the aerospace system’s primary demand is, to realize inertial sensors with good bias stability, small volume, low power consumption, and less weight. To meet these requirements, since the last few decades, different physical laws [3] have been used to develop inertial sensors, which are currently in operation. With time it is observed that various sensor components start outgassing [7], [8] from their surfaces into sensor capsules This leads to vacuum degradation and its instability [9], which further leads to sensor malfunction.
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