A Novel Single-Axis MEMS Tilt Sensor with a High Sensitivity in the Measurement Range from 0∘ to 360∘

Abstract

In this paper, a novel single-axis MEMS tilt sensor is presented. It contains a hexagonal proof mass, six micro-lever force amplifiers and three double-ended-tuning fork (DETF) resonant strain gauges. The proof mass is placed in the center with the micro-levers and the DETFs radially arrayed around. The variation of gravity acceleration applied on the proof mass will result in frequency shifts of the DETFs. Angular tilt can be got by analyzing the frequency outputs. The structural design of the tilt sensor is optimized by finite element simulation and the device is microfabricated using a silicon-on-insulator process, followed by open-loop and closed-loop characterizations. Results show that the scale factor of such sensor is at least 11.53 Hz/degree. Minimum Allan deviation of the DETF oscillator is 220 ppb (parts per billion) of the resonant frequency for an 5 s integration time. Resolution of the tilt sensor is 0.002∘ in the whole measurement range from 0∘ to 360∘.

Electric-Contact Tilt Sensors: A Review

“…However, in the opinion of the authors, such sensors cannot compete with accelerometers—especially manufactured in micro-electro mechanical systems (MEMS) technology or in a conventional technology using, e.g., strain gauges [ 10 ], which are often used for tilt measurements [ 11 ]. Fundamentals of employing MEMS accelerometers for tilt measurements as well as evaluation of their accuracy (being typically in the order of 0.3°) are reported in [ 12 ], whereas some novel measurement methods can be found, e.g., in [ 13 ].…”

Highly sensitive MEMS frequency modulated accelerometer with small footprint

“…However, the constant need for better performance, lower production costs and higher integrability is still driving improvements on the accelerometer state-of-the-art and the seek for alternatives to the well-known open-loop capacitive approaches. The integration of several sensors in the same multi-axis inertial measurement unit (IMU), has been offered by leading semiconductor companies [5], in singlechip format, but with the different sensors fabricated separately (separate dies) and encapsulated at different pressures. A singledie and single-process IMU would require encapsulation of all the sensors (gyroscopes, accelerometers and magnetometers) under the same capsule, at the same pressure [6,7].…”

“…While, gyroscopes are generally encapsulated in vacuum because of the need of high-quality factors, open-loop capacitive accelerometers being sensitive to external vibrations (lack of vibration robustness), require more effort for closed-loop operation at low pressure [7]. Two alternatives can be used to address this limitation: the use of closed-loop approaches to keep the proof-mass at the central position using mechanisms such as sigma-delta [8], or frequency modulated devices [5,[9][10][11]. Resonant MEMS offer as main advantages a high dynamic range (no displacement limitation), immunity to pull-in and a quasi-digital output [9,11].…”

Resonant Accelerometer based on Double-Ended Tuning Fork and a Force Amplification Mechanism

“…Resonant MEMS are a promising solution, since their readout circuit is less power consuming than their capacitive alternative, they can be fabricated on standard MEMS processes and they are immune to pull-in [3]. Lately, frequency modulated MEMS sensors had proven themselves suitable in many applications and several authors have presented gyroscopes [4], accelerometers [2] and inclinometers [5]. Here, a frequency modulated accelerometer composed by DETF resonators on a differential architecture is presented.…”

“…Here, a frequency modulated accelerometer composed by DETF resonators on a differential architecture is presented. Regarding the resonators, single-beam [2] and DETF [5] are commonly used since they are sensitive to stress applied to their extremities. Despite a higher sensitivity reported on single-beam accelerometers (due to their lower cross-sectional area), DETF benefits from zero net force at the anchors and a higher quality factor [6].…”