1,720,982 research outputs found
METODO PER COMPENSARE NON LINEARITÀ MECCANICHE E DELETTRICHE DI OSCILLATORI BASATI SU DISPOSITIVI MEMS E RELATIVO SISTEMA MEMS
No full textUn sistema include un oscillatore microelettromeccanico e un’unità elettronica di elaborazione.
L’oscillatore include: un dispositivo, comprendente una struttura mobile e oscillante a una 5 frequenza di lavoro (fW); un circuito di sostegno, configurato per sostenere oscillazioni del dispositivo; un terminale di compensazione, capacitivamente accoppiato alla struttura mobile e configurato per applicare un segnale di compensazione (VTUNE) alla struttura mobile; e un terminale di modulazione, cooperante con il circuito di sostegno per controllare un’ampiezza delle oscillazioni. L’unità elettronica di elaborazione è configurata per: applicare al terminale di modulazione un segnale di modulazione (VMOD); generare, a partire da 15 un segnale di uscita (VOUT) dell’oscillatore, un segnale di lettura (VM) indicativo di una variazione di frequenza (Δf) rispetto alla frequenza di lavoro (fW); demodulare il segnale di lettura (VM) impiegando il segnale di modulazione (VMOD), ottenendo un segnale di errore (VERR) indicativo di una differenza di fase tra il segnale di modulazione (VMOD) e il segnale di lettura (VM); e generare il segnale di compensazione (VTUNE) da un confronto tra il segnale di errore (VERR) con un segnale di riferimento (VREF)
Exploiting Shaped Combs within FM Accelerometers for Low-Noise and Wide Dynamic Range Applications
Full text linkThe work presents the first frequency-modulated (FM) in-plane accelerometer exploiting shaped combs as frequency-tuning mechanism. Their inherent advantage lies in that, while the overall tuning coefficient is unaltered with respect to former implementations based on parallel-plate tuning, the resonant-mode motion amplitude can be increased, without limitations from parallel-plate gaps. This enables lowering equivalent frequency noise down to ∼ 15μ g/√ Hz while guaranteeing a full-scale range at about 60 g, within 1.8-mm2 overall area. Such performances are demanded by all applications simultaneously requiring low noise and large dynamic range
Ultra Low-Noise Readout for a MEMS Epitaxial Polysilicon Temperature Sensor
No full textThis work discloses the development of an ultralow- noise readout for a polysilicon-MEMS-based temperature sensor. The system relies on a multi-mode resonator realized in a conventional epitaxial polysilicon process, and exploits the slightly different temperature dependence of the resonance frequency of a flexural mode and a torsional mode. Instead of using the consolidated relative counting method, widely discussed in the literature, the system employs a single free-running counter and retrieves the temperature information after a discretetime derivative operation. This enables shaping of quantization and phase noise at high-frequency, then filtered by a secondorder low-pass filter. The residual experimental white noise floor is measured as about 0.001 °C/ √ Hz, representing a 30-fold improvement with respect to previous work
Neural networks based surrogate modeling for efficient uncertainty quantification and calibration of MEMS accelerometers
No full textThis paper addresses the computational challenges inherent in the stochastic characterization and uncertainty quantification of Micro-Electro-Mechanical Systems (MEMS) capacitive accelerometers. Traditional methods, such as Markov Chain Monte Carlo (MCMC) algorithms, are often constrained by the computational intensity required for high-fidelity (e.g., finite element) simulations. To overcome these limitations, we propose to use supervised learning-based surrogate models, specifically artificial neural networks, to effectively approximate the response of MEMS capacitive accelerometers. Our approach involves training the surrogate models with data derived from initial high-fidelity finite element analyses (FEA), providing rich datasets to be generated in an offline phase. The surrogate models replicate the FEA accuracy in predicting the behavior of the accelerometer under a wide range of fabrication parameters, thereby reducing the online computational cost without compromising accuracy. This enables extensive and efficient stochastic analyses of complex MEMS devices, offering a flexible framework for their characterization. A key application of our framework is demonstrated in estimating the sensitivity of an accelerometer, accounting for unknown mechanical offsets, over-etching, and thickness variations. We employ an MCMC approach to estimate the posterior distribution of the device's unknown fabrication parameters, informed by its response to transient voltage signals. The integration of surrogate models for mapping fabrication parameters to device responses, and subsequently to sensitivity measures, greatly enhances both backward and forward uncertainty quantification, yielding accurate results while significantly improving the efficiency and effectiveness of the characterization process. This process allows for the reconstruction of device sensitivity using only voltage signals, without the need for direct mechanical acceleration stimuli
Epitaxial Polysilicon MEMS Temperature Sensor with 0.043 °C Resolution at 4-Hz Data Rate
Full text linkThis work discloses a temperature sensor based on a polysilicon microelectromechanical systems (MEMS) resonator. The system exploits the temperature drift of the resonance frequency of two modes of a single MEMS structure and associated analog and digital electronics. The temperature coefficient of the two modes is found to differ by about 2 ppm/°C, enough to enable the implementation of a relative counting technique to measure the relative temperature. The design uses phase-locked loops to compensate for the challenge posed by the similarity between resonance frequencies and temperature coefficients of the two modes, which, otherwise, would hinder the achievable resolution. The temperature readout is entirely digital, based on counters and a combinational logic that computes temperature in real time. The sensor achieves 0.043 °C resolution with a 4-Hz output data rate (ODR). Fabricated in epitaxial polysilicon, this implementation is compatible with on-chip temperature measurement of large-volume, polysilicon-based inertial sensors, as a substitute for (or additional aid of) onboard or on-application-specific integrated circuit (ASIC) temperature sensors. The latter may be affected by spatial and temporal temperature differences with respect to the MEMS substrate, as extensively proved in this work
Analysis of frequency stability and thermoelastic effects for slotted tuning fork MEMS resonators
Full text linkMicroElectroMechanical Systems (MEMS) resonators are attracting increasing interest because of their smaller size and better integrability as opposed to their quartz counterparts. However, thermal drift of the natural frequency of silicon structures is one of the main issues that has hindered the development of MEMS resonators. Extensive investigations have addressed both the fabrication process (e.g., introducing heavy doping of the silicon) and the mechanical design (e.g., exploiting proper orientation of the device, slots, nonlinearities). In this work, starting from experimental data published in the literature, we show that a careful design can help reduce the thermal drift even when slots are inserted in the devices in order to decrease thermoelastic losses. A custom numerical code able to predict the dynamic behavior of MEMS resonators for different materials, orientations and doping levels is coupled with an evolutionary optimization algorithm and the possibility to find an optimal mechanical design is demonstrated on a tuning-fork resonator
-Biaxial Accelerometers
No full textMicro-electro-mechanical systems (MEMS) accelerometers are entering high-end applications, thanks to their improved performance and low costs. Biaxial sensors able to measure two in-plane components of the external acceleration by exploiting a single proof-mass have been recently proposed and optimized both mechanically and electronically in order to minimize cross-axis sensitivity, while preserving a good symmetry between the two axes and high performance. To the author's best knowledge, only a very few commercial high-performance xz- or yz-biaxial MEMS accelerometers are available so far. In this work, we propose an innovative design strategy for xz-biaxial MEMS capacitive accelerometers immune from electrostatic nonlinearities and pull-in instabilities usually related to out-of-plane readout schemes. In particular, thanks to the proposed motion conversion mechanism realizable through the Thelma-double fabrication process of STMicroelectronics, we predict a sensitivity bigger than 30 fF/g on both axes, a cross-axis sensitivity smaller than 0.04% and a nonlinearity lower than 1% at 50 g
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