Abstract
This paper presents a study of the frequency response and the scale-factor of a tuning fork micro-gyroscope operating at atmospheric pressure in the presence of an interference sense mode by utilizing the approximate transfer function. The optimal demodulation phase (ODP), which is always ignored in vacuum packaged micro-gyroscopes but quite important in gyroscopes operating at atmospheric pressure, is obtained through the transfer function of the sense mode, including the primary mode and the interference mode. The approximate transfer function of the micro-gyroscope is deduced in consideration of the interference mode and the ODP. Then, the equation describing the scale-factor of the gyroscope is also obtained. The impacts of the interference mode and Q-factor on the frequency response and the scale-factor of the gyroscope are analyzed through numerical simulations. The relationship between the scale-factor and the demodulation phase is also illustrated and gives an effective way to find out the ODP in practice. The simulation results predicted by the transfer functions are in close agreement with the results of the experiments. The analyses and simulations can provide constructive guidance on bandwidth and sensitivity designs of the micro-gyroscopes operating at atmospheric pressure.
Highlights
In recent years, MEMS inertial devices have been widely adopted for many types of consumer electronic products, including phones, tablets, gaming system, toys and emerging wearable gadgets [1].The micro-gyroscopes used in these consumer electronics are generally classified as rate-grade devices [2]. micro-gyroscopes have many advantages over traditional gyroscopes for their small size, low power consumption, low cost and batch fabrication, high performance micro-gyroscopes are still too expensive for consumer products, even for industrial products.Packaging, as one of the key manufacturing processes of MEMS sensors, provides protection from the environment, such as mechanical protection, optical and thermal protection and electrical interface and isolation
The work reported in this paper focuses on the frequency response and scale-factor of the gyroscope with low Q-factor
Developing high-performance micro-gyroscopes operating at atmospheric pressure is one of the effective ways to further lower the cost
Summary
MEMS inertial devices have been widely adopted for many types of consumer electronic products, including phones, tablets, gaming system, toys and emerging wearable gadgets [1]. A micro-gyroscope working at atmospheric pressure, different from a vacuum packaged one, has a low Q-factor and possibly large coupling damping due to the viscous air surrounding the movable structures. In [9,10,11,12,13], the authors reported several lateral-axis micro-gyroscopes which could work at atmospheric pressure They developed novel torsional sensing comb capacitors to lower the air damping and electrostatic force balanced combs to suppress the mechanical coupling. Slide film damping effects in drive and sense modes were used to achieve large quality factors of gyroscopes even operating at atmospheric pressure [14]. The tuning fork micro-gyroscope operating at atmospheric pressure has large proof masses to increase the signal noise ratio of the Coriolis response and has a large drive force to increase the vibration amplitude in the viscous air. The ZRO caused by quadrature error can be eliminated by phase demodulation while the ZRO caused by coupling damping cannot be canceled out
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