ESA GNC Conference Papers Repository
Advances in Quartz Coriolis Vibrating Gyroscope for space applications
This paper reports a status on performances of the Quartz MEMS gyroscope developed at ONERA, and introduces future ways of performance improvement. The Vibrating Integrated Gyro (VIG, in the CVG family) is a high-Q quartz tuning fork gyro with two close resonant frequencies: Drive (in plane) and Sense (out of plane). The planar design includes the tuning fork together with its decoupling frame in a single monolithic structure, manufactured by collective etching, thus preserving crystal integrity and allowing quality factors over 150 000. Concerning the associated electronics, innovative design of digital frequency synthesis and synchronous demodulation allowed a significant step in the performance, especially on the thermal bias stability, which is now in the range of 10°/h, and ARW in the range of 0.03°/?h). Signal bandwidth and rate range are configurable by software, respectively up to 100 Hz and 100°/s, depending on the application. It is pointed out that no trimming is performed on the quartz cell and that all compensations are performed by the electronics. Besides, the architecture is still open loop: no force rebalance. So, thanks to this basic configuration, the VIG is a potential low cost tactical gyro, in the state of the art of Coriolis MEMS gyros and is now mature to be transferred to industry for aerospace applications. The sensor electronic architecture ability to be synthesized on programmable devices (micro-controller, FPGA, ASIC) and to be spread over local resources (for example executing control software and signal processing inside the host computer) have been evaluated in the pre-development activities of the NEOSAT program. Latest results concerning qualification and performance of the gyroscope will be presented. Then, beyond the assistance and safe mode gyroscope in the NEOSAT platform, possibilities will be discussed to higher increase performances, and access the 0.001°/?h ARW class, while remaining compatible with common collective micromachining process and flight environments. This opens the way to new fields of applications for this family of sensors, in the domain of precision pointing of payloads, for example new generation of inertial stellar compass (low noise quartz MEMS gyro hybridized star tracker).