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A Fiber Bragg Grating low-frequency accelerometer with a single-notched hinge in series is proposed to improve the hinge structure's sensitivity and the cross-sensitivity of the accelerometer of low-frequency seismic waves. The sensitivity and the cross-sensitivity of the accelerometer are improved by connecting the single-notched hinge structure in series and experimentally verified. Based on the theoretical analysis, the resonance frequency and sensitivity formula of the accelerometer are derived. At the same time, the accelerometer is simulated by finite element analysis software to simulate and analyze the characteristics of the accelerometer in terms of resonance frequency, strain distribution, and amplitude-frequency response. The structural parameters of the accelerometer are optimized by numerical analysis software, and the effects of the structural parameters on the sensitivity and resonance frequency of the accelerometer are analyzed. The experimental results show that the resonance frequency of the accelerometer is 110 Hz, the flat region is 0.6–50 Hz, the linearity is as high as 98.9%, the sensitivity is 1040.41 pm/g, and the cross-sensitivity of the accelerometer in the flat interval is 4.94%. This indicates that the accelerometer shows good linearity and cross-sensitivity in the flat interval, which well meets the needs of seismic wave signal monitoring in low-frequency oil and gas exploration. [Display omitted] • Tandem single-notch hinge structure reduces detector cross-sensitivity. • The top of the mass block is provided with a rectangular thin plate to improve sensitivity. • The dual grating packaging method effectively improves the sensitivity of the detector. • Small size, low processing cost, can achieve large area detection. [ABSTRACT FROM AUTHOR]

Aiming at the problem that the deterministic errors caused by non-orthogonal installation, calibration factor, zero bias and other factors in production and in the use of accelerometers need to be calibrated by high-precision instruments, support vector machine regression is used to process the original data output by the accelerometer, and the processed data of each axis are used to establish a parameter calibration model without reference datum through the relationship between the output value of each axis of accelerometer, gravity acceleration and coaxial reversal in the paper. Then, the adaptive mutation rate is used to dynamically adjust the number of reverse learning particles, and the particles of particle swarm optimization algorithm are selected and adjusted according to the reverse learning, which solves the problems that particle swarm optimization algorithm tends to fall into localoptimum and the convergence speed is slow, through which a fast, accurate and simple calibration can be realized, and the performance of particle swarm optimization algorithm is improved. The calibration experiment shows that the improved particle swarm optimization algorithm has higher accuracy and faster convergence speed than the particle swarm optimization algorithm, and the calibration parameter accuracy is higher than that of the least square method, which does not need the datum of each axis. The calibration model proposed in this paper can realize a benchmark-free calibration outside the laboratory. At the same time, the improved particle swarm optimization algorithm can obtain calibration parameters with higher accuracy and faster speed in the rapid calibration, which provides the idea of a new model for accelerometer calibration and expands the application environment of accelerometer. [Display omitted] • The relationship between the gravity acceleration and the output values of each axis of the accelerometer is used. • According to the established model, SVR is used to preprocess the input data of the model. • Reverse learning and mutation rate are proposed to modify the particles of PSO. [ABSTRACT FROM AUTHOR]

• A dynamic characterization method is proposed for accelerometer dynamic calibration. • An iteration estimation procedure of the model coefficients and the order is performed by means of the equivalent matrix of the excitation and response signals, which overcomes the coupling effect of model order on the parameter precision. • The dynamic characteristics of accelerometer could be improved by means of zero-pole offset of the dynamic model. • The requirement of the excitation signal generated by the Hopkinson bar is quantified by the dynamics analysis of stress propagation. • The impact resistance of accelerometer could be improved by vacuum encapsulating technology. The dynamic characterization of accelerometers is the prerequisite and insurance for highly accurate measurement of dynamic acceleration signals. The main problem of dynamic characterization is the lack of effective methods to deal with model coefficients and the order coupling effect, which could severely influence the identification accuracy. This paper presents a novel approach to solve the identification coupling problem through synchronous iteration and compensation. In order to guarantee the precision of the dynamic model, the Hopkinson bar dynamic calibration system with a traceable excitation acceleration signal is proposed. The feasibility of dynamic modelling is proved by the data comparison of experiment result and model regression result in the time domain. Based on the dynamic model, a dynamic compensation model is established, which improves the dynamic performance by frequency coverage extension. Finally, the results of the dynamic modelling and dynamic compensation are demonstrated by means of the calibration experiment in the paper. [ABSTRACT FROM AUTHOR]

Resistivity of the substrate is a key parameter in designing MEMS devices and affects the device performance. Yet, the effects of this parameter on capacitive MEMS accelerometer performance hasn't gotten enough research. In this paper an empirical model for predicting the substrate resistivity impact on MEMS capacitive accelerometer parameters has been developed which include rest capacitance, offset, output noise and scale factor. Also, a stability analysis of MEMS capacitive accelerometer as a function of the substrate's doping concentration was modeled, simulated and then verified by fabricating a z-axis capacitive accelerometer. In the experiment, the rest measured capacitance of accelerometer's top plate was 11.50 pF in positive voltages and 11.97 pF for negative voltages. Also, the rest measured capacitance of the bottom plate was 11.45 pF for a positive bias and 11.92 pF for a negative bias. The measured pull in voltage was −18 V. Overall, a good agreement between the model and experimental data was obtained. Finally, minimum required substrate doping concentration (MDC) was modeled for the best performance of MEMS capacitive accelerometers which is dependent on the accelerometer's application and resolution. [Display omitted] • The impact of substrate resistivity on accelerometer parameters is modeled. • A z-axis capacitive accelerometer is fabricated. • Stability analysis of accelerometer as a function of substrate doping is performed. • Good agreement between the model and experimental data is obtained. • Minimum required doping concentration of capacitive MEMs accelerometer is modeled. [ABSTRACT FROM AUTHOR]

Highlights • Design and model for a low-noise and wideband microfabricated accelerometer. • A new microfabrication process for the fabrication of the device which allows for decoupled tuning of device parameters. • Experimentally verified performance metrics for the accelerometer including noise level of ∼0.5 μg/√Hz. • Experimentally verified bandwidth of 5.2 kHz, and open-loop dynamic range of 145 dB. Abstract We are reporting on the design, fabrication, and experimental results for a micromachiend accelerometer that is intended to be used in the detection of acoustic signals, where the main requirements include low noise, wide bandwidth, and high linearity. The device design requirements are discussed and analytically modelled. Microfabrication details to build prototypes are provided in detail. The final device structure employs membrane as the suspension mechanism and a proof-mass made from the entire thickness of a wafer that is suspended above a fixed electrode. The proposed manufacturing process allows for precise and independent control of the structural components of the device and the capacitive gap. Prototype devices were fabricated and characterized. Measurements on the device performance demonstrate a 0.6 μ g / H z noise floor with resonance frequency of 5.2 kHz, sensitivity of ∼0.9 pF/g, and open-loop dynamic range of higher than 145 dB while operating at atmospheric pressure. The device meets the requirements for measuring sonar signals in the range of 50 Hz to 5 kHz under low environmental noise conditions. [ABSTRACT FROM AUTHOR]

A system has been developed to simulate transport in a medical emergency vehicle with the intent of assisting paramedics improve their skills in en-route cannulation. En-route cannulation makes pre-hospital venous access possible, which in turns helps to minimize the risk of lengthening transfer times. The system is designed to attain full monitoring of transport conditions, not just in the spatial but also in the temporal sense, and to physically recreate these parameters on a fabricated six degree of freedom simulator system. Tests conducted revealed the viability of applying an inertial measurement unit board sensor to collect data from a vehicle during transport and to subsequently reproduce the exact motions encountered on the simulator. It was found that a smartphone could be used to collect transport data that are dominated by perturbations in the O (10 1 ) Hertz scale. With a training arm for venipuncture placed on the simulator, a preliminary study conducted with six participants showed more pronounced performance deterioration amongst those who were untrained in cannulation when the simulator was switched on. The demonstrated system has features that make it amenable for incorporation into a clinical skills laboratory setting. [ABSTRACT FROM AUTHOR]

This paper presents a high-G MEMS accelerometer (HGMA). HGMA employs our-beams and central-island mass silicon structure, which features a robust stability in shock environment. Theoretical analysis is conducted to investigate the influence of structure parameters on the Von Mises stress distribution, mechanical sensitivity and natural frequency. With consideration of smaller stress, higher mechanical sensitivity and natural frequency, the structure parameters are optimized and the theoretical sensitivity of HGMA is calculated as 0.488μV/g. Then, the optimized structure is analyzed with finite element analysis software, which shows a maximum stress of 23.19 MPa and a frequency response of 408.19 kHz when a 100 000 g shock is loaded. Finally, a processing flow is designed and the structure is fabricated. Hopkinson bar is utilized to calibrate HGMA sample, and shows an experimental sensitivity of 0.5611μV/g. Long-term static bias and temperature experiments are arranged to evaluate HGMA. Test results verify the presented theoretical analysis, processing flow, and experiment method, which are of great value for guiding the design, fabrication and calibration of other HGMAs. [ABSTRACT FROM AUTHOR]

A microelectromechanical systems (MEMS) accelerometer estimates the acceleration by detecting a difference in capacitance. This paper presents a small MEMS accelerometer with an asymmetric seesaw design. It was fabricated using a bulk machining process and accurately measures the applied acceleration based on a difference in capacitan ce. The large torque proof mass and chamfered structure of the torsional spring on the small chip were optimized to improve the device sensitivity and robustness of the design structure, respectively, which were the main factors in improving the MEMS sensor performance and maintaining the small chip size. After fabrication, we verified the design optimization by measuring the capacitance–voltage (C–V) curve behavior of the seesaw and making observations using scanning electron microscopy (SEM). The measured capacitance and theoretical calculation results were 249 fF and 239.9 fF, respectively. The SEM observations showed that there was no severe undercutting in the cross section of the structure. According to a finite element method analysis in just the electrical domain, the electrostatic characteristics such as the C–V measurements matched the theoretical values (within 3.6%). Moreover, the sensitivity of the fabricated accelerometer was 11.3 fF/g, and the nonlinearity was 0.62% over the typical range of 1 g. According to the system test results, the accelerometer had cross-sensitivity values of 0.06% (x/z axis) and 2.58% (y/z axis). [ABSTRACT FROM AUTHOR]

Typical hydrophones in line array sensors used to detect covert underwater targets can measure only sound pressure magnitude with the limitation of being unable to identify the direction of an incoming wave. In this paper, a thickness-shear mode vibrator is proposed as the main component of an inertia-type vector hydrophone to measure both the magnitude and direction of acoustic signals from targets. The piezoelectric single crystal lead magnesium niobate-lead titanate with rhombohedral 3 m symmetry constitutes the vibrator. The directional voltage response of the vibrator to an external force is derived, and the validity of the derived response is verified through fabrication of a piezoelectric single crystal vibrator and by comparison of its measured characteristics with the analysis results. [ABSTRACT FROM AUTHOR]

We report on an analytical model for the air damping of laterally oscillating MEMS and MOEMS following up on our recent paper [1] . It can be used to more efficiently design micromechanical devices with tailor-made Q -factors for specific applications. The surface force responsible for the air damping was divided into contributions which were investigated separately. These include squeeze-film damping and the viscous forces responsible for shear wave emission and Couette type flow. Since the squeezing part is mostly underestimated in the current models, we applied more appropriate boundary conditions during the solution of Reynold's lubrication equation. The viscous contributions were investigated with respect to how holes – due to fabrication process or readout – in the moving plate affect the damping. We tested this model against FVM computations (OpenFOAM) and measurements of MOEMS test devices. It was in good agreement with both. [ABSTRACT FROM AUTHOR]

This paper introduces a nano-g level optical accelerometer based on a differential Fabry–Pérot interferometer(DFPI) for low-frequency (less than 1 Hz) noise suppression. The accelerometer has its proof-mass supported by two metal spring beams and has a natural frequency of 40 Hz. The DFPI structure is composed of two fiber end-faces and two reflectors made by gold-coated silicon chips attached on each side of the proof-mass. It is both theoretically analyzed and calculated that the differential structure can suppress noises caused by laser source, optical components and temperature, therefore improves the signal to noise ratio of the accelerometer. Experimental results show that the DFPI accelerometer has a noise floor of 4 ng/ Hz at 3 Hz to 10 Hz, with a displacement noise floor of 0.62 pm/ Hz , a measurement range of 0.88 mg and a sensitivity of 1699.7 V/g. The DFPI mechanism improves the noise performance at 0.1 Hz from 100 ng/ Hz by a single FPI to 24 ng/ Hz by DFPI, and improves the bias instability from 49 ng to 17 ng. The proposed DFPI accelerometer has the potential applications on seismic acceleration measurement for mineral exploration and active vibration isolation. [Display omitted] • Low acceleration noise floor of 4 ng/ Hz @3–10 Hz. • High sensitivity to external acceleration of 1699.7 V/g. • Differential configuration for noise suppression in low frequency. [ABSTRACT FROM AUTHOR]

We consider the deterministic modeling, calibration, and model parameter estimation of two commonly employed inertial measurement units based on real test data acquired from a flight motion simulator. Each unit comprises three tri-axial devices: an accelerometer, a gyroscope, and a magnetometer. We perform the deterministic error modeling and calibration of accelerometers based on an improved measurement model, and the technique we propose for gyroscopes lowers costs by eliminating the need for additional sensors and relaxing the test bed requirement. We present an extended measurement model for magnetometers that reduces calibration errors by modeling orientation-dependent hard-iron errors in a gimbaled angular position-control machine. While we employ the model-based Levenberg-Marquardt optimization algorithm for the parameter estimation of accelerometers and magnetometers, we use a model-free evolutionary optimization algorithm (particle swarm optimization) for estimating the calibration parameters of gyroscopes. Errors are considerably reduced as a result of proper modeling and calibration. [ABSTRACT FROM AUTHOR]

A novel piezoresistive accelerometer was developed with high performance in sensitivity, resonant frequency and cross-axis sensitivity. The accelerometer chip with axially stressed self-supporting sensing beams has been designed, fabricated and tested in our study. We derived the expressions for the location of the sensing beams, stresses and resonant frequency, and then these results were verified by the finite element method (FEM) simulation. The fabricated accelerometer was characterized by the static and dynamic experiments. The results showed that the measuring sensitivity was 0.666 mV/g/3 V and the resonant frequency was 17.1 kHz. Meanwhile, the proposed accelerometer provided an available method for the low cross-axis sensitivity design. Compared with other accelerometers in the literatures, the developed accelerometer exhibited an excellent performance concerning a comprehensive figure of merit (FOM). The results demonstrated the feasibility of the novel structure to improve the accelerometer’s performance. [ABSTRACT FROM AUTHOR]

This paper reports the design, realization and characterization of a novel double differential torsional MEMS accelerometer with improved temperature robustness. Based on the structure of conventional torsional accelerometers, normally composed of two unbalanced proof masses and an identical torsional beam, this work explores a torsional accelerometer with two structural optimizations aiming to improve the temperature robustness: a double differential configuration and an on-chip integrated reference capacitor configuration. The double differential configuration realizes the temperature self-calibration by making the two pairs of unbalanced masses have the same sensitivity to temperature but opposite sensitivity to acceleration. And the on-chip integrated reference capacitor realizes the temperature self-calibration by transferring the temperature dependent reference capacitor from ASIC or PCB into the MEMS structure. Totally ten accelerometer prototypes are fabricated with the pre-buried mask wet-etching method and tested. Comparison tests show that, for most of the accelerometers, by taking the double differential configuration and the on-chip integrated reference capacitor configuration, the temperature sensitivity of the scale factor, the bias stability and the output drift of in the full temperature range are greatly improved. The testing results experimentally demonstrate the effectivity of the optimization for improving temperature robustness. [ABSTRACT FROM AUTHOR]

A miniaturized wireless accelerometer using a piezoelectric micro sensing element is designed, theoretically analyzed, and demonstrated for remote mechanical vibration monitoring. The micro sensing element comprises a micromachined monolithic silicon seismic mass and multiple silicon beams coated with in-plane polarized (Pb, La)(Zr, Ti)O 3 (PLZT) ferroelectric thin film. A low profile compact package is obtained for accommodating all the micro sensing element, charge amplifier and signal processing circuits, radio frequency module, and battery. The electrical output linearly proportional to the vibration acceleration is amplified, digitalized and transmitted to a remote base unit through radio frequency communication. The effects of the device package on the dynamic response of the wireless piezoelectric accelerometer including shielding of ambient interference are investigated. [ABSTRACT FROM AUTHOR]

Blood pressure is an important daily bio-signal but continuous monitoring of blood pressure is not an easy task. Continuous measurement of blood pressure can be provided with pulse arrival time (PAT) which is calculated by electrocardiogram (ECG) and blood pulse wave. In this study, dry conformable and stretchable ECG electrodes and a printed accelerometer are assembled into a wearable device which is aiming for continuous monitoring of blood pressure. Clear ECG signals which are comparable in shape and strength with those from the conventional wet electrode have been obtained. And reliable blood pulse wave with valid peripheral augmentation index is registered by the printed accelerometer. By utilizing paired printed sensors, the PAT is extracted from time difference between R-peak of the ECG signal and starting point of the pulse wave. Finally, a fitting line which is obtained from the graph of PAT vs. reference blood pressure estimates blood pressure reliably with intermittent exercises. [ABSTRACT FROM AUTHOR]

High-temperature-resistant inertial sensors are increasingly requested in a variety of fields such as aerospace, automotive and energy. Capacitive detection is especially suitable for sensing at high temperatures due to its low intrinsic temperature dependence. In this paper, we present high-temperature measurements utilizing a capacitive accelerometer, thereby proving the feasibility of capacitive detection at temperatures of up to 400 °C. We describe the observed characteristics as the temperature is increased and propose an explanation of the physical mechanisms causing the temperature dependence of the sensor, which mainly involve the temperature dependence of the Young's modulus and of the viscosity and the pressure of the gas inside the sensor cavity. Therefore a static electromechanical model and a dynamic model that takes into account squeeze film damping were developed. [ABSTRACT FROM AUTHOR]

A simple empirical equation of rotational stiffness for single-notch circular flexible gemel is proposed. Based on the parameter optimization, we have discussed how to choose the structural parameters to achieve the balance between the sensitivity and the eigenfrequency. By using sequential quadratic programming (SQP) method, two prototypes of FBG accelerometers with eigenfrequency of 650 Hz and 3050 Hz are designed. Furthermore, we also perform the shaking table test for the fabricated prototype sensors. The experimental results show that the measured eigenfrequency and sensitivity are approximately identical to design values. Also, the FBG accelerometers show great anti-interference capacity in flat range which may be applied to the structural–health monitoring. [ABSTRACT FROM AUTHOR]

Fiber Bragg gratings (FBGs) are a type of optical element with several advantages. In this study, we propose a vibration monitoring system consisting of a flexible hinge and a dual FBG. The novel design enables the dual short FBG to be tensile and compressed separately during vibration, while achieving sensitivity enhancement and self-temperature compensation. Through theoretical analysis and experiments, the resonant frequency was 150 Hz. The working frequency bandwidth of the accelerometer ranged from 10 to 100 Hz with a sensitivity of 1711 pm/g. The minimum resolution and detectable acceleration of the proposed system were 0.584 mg and 3 mg, respectively, which are significantly better than similar systems with a single FBG. [Display omitted] • The short FBG is inscribed pointwise using a femtosecond laser. • The dual short FBG of accelerometer simultaneously achieves sensitivity enhancement and self-temperature compensation. • This accelerometer has extremely high sensitivity of 1711 pm/g and excellent thermal stability. [ABSTRACT FROM AUTHOR]

This paper presents acoustic wave detection and analysis with a polymer tunneling sensor fabricated by hot embossing. First, the tunneling sensor is used to detect the acoustic wave generated by a PZT disk. The frequency response of the tunneling sensor is measured by a piezoelectric transducer and laser vibrometer to find the resonance frequency. Next, the performance of the sensor is characterized by measuring the acoustic wave at its resonance frequency. Second, the noise and acceleration amplitude spectral densities of the tunneling sensor are calculated using Fast Fourier Transform (FFT) based on experimental data, proven to be a very effective way to analyze the polymer tunneling sensor. The testing results of the fabricated polymer tunneling vibration sensor are compared with a commercial piezoelectric accelerometer. The results demonstrate that the polymer tunneling vibration sensor exactly follows the response of the commercial accelerometer. [Display omitted] • Acoustic wave detection and analysis with a polymer tunneling sensor fabricated by hot embossing. • Frequency response of the tunneling sensor is measured by a piezoelectric transducer and a laser vibrometer to find the resonance frequency. • Noise and acceleration amplitude spectral densities are calculated using FFT based on experimental data to analyze the tunneling sensor. [ABSTRACT FROM AUTHOR]

For many applications, there is an increasing demand for low cost, high resolution inertial sensors, which are capable of operating in harsh environments. Based on recent developments in optical seismometry, this paper presents a new small interferometric inertial sensor with a resolution of 3 pm/ Hz above 4 Hz. Compared to most state-of-the-art devices, this prototype does not contain any coil, which offers several important advantages: (i) when it is used for active control, it magnifies the control performances around the sensor resonance; (ii) it decreases the thermal noise in the suspension (Brownian motion), (iii) it is compatible with magnetic environments (like particle collider); (iv) as the interference fringes sweep continuously across the detector, it allows a real time calibration of the parameters, and thus the calibration can be continuous monitored and updated. [ABSTRACT FROM AUTHOR]

This paper reports a fabrication process of a capacitive microelectromechanical system (MEMS) accelerometer with a highly symmetrical spring-mass structure for the high device performance, which is composed of eight springs and a central mass. The sandwich accelerometer is constituted by top layer, middle layer and bottom layer. The suspended spring-mass structure in the middle silicon layer is formed simply by double thermally grown oxide layers and the mask-maskless wet anisotropic etching, avoiding the generally adopted deep-groove photolithography when fabricating the thin spring. Moreover, the gap between electrodes can be determined by the thickness of the oxide layer in this process. The surfactant-modified TMAH is selected as the etchant because it not only provides the minimum undercutting at the mass corner, thus saving much space of the compensation parts, but also allows the good control of spring thickness at the low etch rate. The spring shape evolution during etching in surfactant-modified TMAH is simulated and the obtained rhombic cross-section has the advantage of easily identifying the thickness of the spring from its width according to their crystal orientation relation. The three silicon layers are bonded through silicon fusion bonding (SFB) at temperature >1000 °C to relax surface stresses that could be present in the material prior bonding. Preliminary test result shows the sensitivity of 60 mV/g with good linearity of R² = 0.99979 in a closed-loop interface circuit. The advanced accelerometer performance could be expected due to the symmetrical structure, the large proof mass, controllable spring shape, the narrow uniform capacitive gap, and the IC-compatible process. [ABSTRACT FROM AUTHOR]

This paper presents an integrated piezoelectric accelerometer embedded in Low Temperature Co-fired Ceramic (LTCC). The PZT based sensing element, passive layer and seismic mass were integrated through co-firing with multilayer ceramic tapes. Resonance, frequency and sensitivity measurements were made for two different seismic masses. Results show sensitivity up to 6 mV/g without signal amplification, high linearity of output signal and a resonance frequency of 32.7 kHz. Furthermore, the sensor can easily be tailored to specific applications through adjustment of the seismic mass and stiffness of the sensing beams by modification of their dimensions. Compared to other similar structures, the LTCC-PZT accelerometer exhibited a comparable resonance frequency and outstanding sensitivity, even without signal processing. The presented method also enables the manufacture of structures with acceleration sensing on multiple axes and embedded electronics for a compact system-in-package. [ABSTRACT FROM AUTHOR]

Highlights: [•] Optical Fabry–Pérot accelerometer employing mechanical amplification. [•] Eliminates the need for high finesse and difficult fabrication techniques. [•] V beam structure amplifies motion without pivots and angular rotation. [•] Analytical expression are derived explaining the action of amplification. [ABSTRACT FROM AUTHOR]

Highlights: [•] Thermal expansion in micro-scale is used to detect rotation and acceleration. [•] Expansion-based micro sensor is with a good linearity for a large-range rotation. [•] Sensor possesses simple structure, low cost, high shock resistance, and low coupling. [Copyright &y& Elsevier]

Highlights: [•] Arterial movement tracked by implantable accelerometer. [•] Blood pressure determination with high accuracy. [•] Implantable system for long-term monitoring. [ABSTRACT FROM AUTHOR]

Highlights: [•] FBG based accelerometer is designed for suitable and safe placement of FBG sensor. [•] Detailed analysis of modified cantilever beam was performed. [•] Employing Finite Element Method, extensive simulations were performed to get optimised accelerometer parameters, including the material selection, for the selected frequency range. [•] Experimental trials were conducted to calibrate the FBG accelerometer's sensitivity against the conventional electronic (PZT) accelerometer. [•] A novel cantilever beam design based FBG accelerometer was designed, fabricated and tested successfully. [Copyright &y& Elsevier]

Highlights: [•] Interferometric radar sensor with a built-in seismic accelerometer. [•] Differential measurements. [•] Suppression of its own movement. [•] Laboratory tests. [ABSTRACT FROM AUTHOR]

Abstract: We describe the design, modeling, fabrication, and testing of a MEMS inertial switch that can detect accelerations in the x, y, and z axes using a single mass/spring assembly (first reported in Ref. [1]). A spiral spring suspension is used which is compliant in all directions. The inertial switch approach offers zero power draw until an acceleration event occurs. Arrays of individual triaxial sensors are created on a single chip, with each switch designed to close at a different acceleration threshold between 50g and 250g. A resistor ladder connects each switch together in series such that the number of pinouts from the chip is substantially reduced. The response of the switch array to half-sine acceleration pulses of 5–8ms duration is reported, with multiple switches in the array closing and opening in sequence for higher magnitude acceleration pulses. The switch closure time under these conditions is consistently less than 200μs, and bounce is minimal for applied accelerations lower than 200g. [Copyright &y& Elsevier]

Abstract: Sensitivity of a cantilever-mass based fiber Bragg grating (FBG) accelerometer can efficiently be tailored by altering the distance between the axis of the FBG sensor to the neutral axis of the cantilever. To accomplish that in general, a backing patch is used to mount the FBG on the cantilever. A numerical method to quantify the influence of the material constant (Young''s modulus) of the backing patch and its thickness on the sensitivity is presented in this paper. It is explicitly shown that for a specific patch material there is an optimum thickness for which the sensitivity happens to be the maximum. A good agreement between simulation and experimental results is obtained. Finally, it is demonstrated that a sensitivity ∼1062pm/g can be achieved, the enhancement almost by a factor of three as compared to that of the conventional cantilever-mass FBG accelerometer of similar bandwidth. [Copyright &y& Elsevier]

Abstract: In this paper, a novel polymer MOEMS (micro-opto-electro-mechanical systems) accelerometer is reported. Low cost, photopatternable epoxies, EpoClad and EpoCore, are lithographically patterned through a 2 masks process to form this accelerometer in a simple and robust fabrication process. EpoClad is used for the cladding layer and EpoCore for the waveguides, fiber optic clamps and the seismic mass. Fiber optic clamping structures are presented that can be fabricated without extra process steps, and still assure both in-plane and out-of-plane clamping. The acceleration sensing principle is based on light intensity modulation by the seismic mass''s position. A laser diode light source and a photodiode, connected to the sensor core through optical fibers, are used to extract the intensity variation as a function of acceleration. A vibration test was conducted to evaluate the performance of this MOEMS accelerometer. [Copyright &y& Elsevier]

Abstract: Low-cost accelerometers could be used in applications where extremely good characteristics are not a requirement. This paper presents an accelerometer fabricated using printed circuit board (PCB) processing techniques, and laser ablation. Laser is used to remove part of the PCB substrate, releasing a mass suspended by copper beams. The structure is easily bonded to another PCB, creating a variable parallel-plate capacitor with a small gap, which capacitance varies with the movement of the mass, caused by external acceleration. The fabricated accelerometer has been compared to a commercial silicon one, showing good agreement in the measurements. The measured sensitivity was 81fF/g. [Copyright &y& Elsevier]

Abstract: This paper reports a novel capacitive accelerometer with highly symmetrical double-sided beam-mass structure. The highly symmetrical structure is fabricated from single wafer by a novel vertical sidewall protection technique. The good device performance is obtained by highly symmetrical double-sided beam-mass structure and fabrication process that enable formation of a large proof mass, controllable thickness of beam, and a narrow uniform capacitive gap over a large area. The resonance frequency of the accelerometer is measured in open loop system by a network analyzer. The quality factor and the resonant frequency are 34 and 787Hz, respectively. The accelerometer with closed loop interface circuit is calibrated on B&K Vibration Transducer Calibration System (Type 3629). The typical measurement range of the device is 1g, and the maximum range is 2g. The capacitance sensitivity of the fabricated accelerometer is 11.7pF/g. The sensitivity of the device with closed loop interface circuit is 1V/g, and the nonlinearity is 0.39% over the range of 1g. The cross-sensitivity x/z is 0.72% and y/z is 0.50%, respectively. The accelerometer with closed loop circuit has wide bandwidth of DC to 1kHz (3dB). Also the bias stability is 255μg. The device with closed loop circuit has signal to noise ratio (SNR) of 106dB, the average noise floor is (0–100Hz). [Copyright &y& Elsevier]

Abstract: A cantilever based optical accelerometer with enhanced performance characteristics has been proposed. The sensitivity of the accelerometer has efficiently been enhanced by about twice as compared to the conventional design by tailoring the effective distance between the sensor axis to the neutral axis of the cantilever. The sensitivity enhancement has been done without affecting the characteristic resonant frequency of the system. A sensitivity of about 450pm/g is achieved for a specific cantilever-mass arrangement. The architecture requires much simpler design as compared to optical accelerometers based on similar working principle and having sensitivities of this order. [Copyright &y& Elsevier]

Abstract: We present a dual axis accelerometer made with a frontside bulk micromachining on a 0.35μm CMOS. The accelerometer is based on thermal convection where a central suspended hot plate creates a hot gas bubble. In-plane acceleration applied to the body will change the temperature distribution on the device, the latter being measured by four detectors containing six serially connected thermocouples. The paper will present the modelling of the device with a specific spherical model as well as measurements of sensitivity and linearity. [Copyright &y& Elsevier]

Abstract: This paper introduces the operational concept, fabrication and experimental validation of a microelectromechanical systems (MEMS) digital accelerometer (MDA) that consists of a microscale (∼350nL) liquid metal droplet in a microstructured channel etched into photosensitive glass. The MDA exploits not only the liquid metal droplet''s high surface tension, high density and electrical conductivity, but also the photosensitive glass''s mechanical stability and capacity to be photo-etched anisotropically. Photo-etching is used to etch an anisotropic channel into the device. During the etching process, microstructures form uniformly on the glass channel surface; they minimize contact angle hysteresis and allow the liquid metal droplet to move easily on the glass surface. By integrating the liquid metal droplet as a proof-mass to measure an input acceleration inside the microstructured photosensitive glass channel, a simple yet effective digital accelerometer is realized. [Copyright &y& Elsevier]

Abstract: Analysis of various errors of orientation and motion sensors and their influence on resulting compass attitude information are investigated and quantified in this paper. A triple-axis acceleration sensor and a triple-axis magnetic sensor are considered to form a compass module giving full orientation information (attitude). 3D-compass module with PCB-fluxgate sensors and off-shelf acceleration sensor is introduced. Three main sensor error sources are discussed separately and their contribution to final compass heading accuracy is investigated. These are sensor orthogonality error, linearity error and ADC quantization noise. The influence of these errors is simulated on artificial group of test cases which evenly covers various orientations of the compass module. It was found that the errors in the accelerometric system have major influence on the heading accuracy. It was concluded that even low-resolution AD converters may have only a minor influence on the system accuracy, while the dominant error sources are sensor triplet nonorthogonality and sensor non-linearity. [Copyright &y& Elsevier]

Abstract: A continuous-time accelerometer interface is feasible when a high dynamic range together with a wide signal band is required. In this paper the implementation of a continuous-time force-feedback loop for a capacitive sensor element with a full-scale signal of g is presented. The interface is measured to attain a noise equivalent acceleration (NEA) density of 500 at 30Hz for the on-chip digitized output and 300 at 30Hz for the analog output using a capacitive half-bridge sensor element with a single pair of electrodes. The essential circuit structures of the closed-loop sensor will be presented and analyzed in detail. [Copyright &y& Elsevier]

Abstract: This paper presents an innovative optical accelerometer based on an integration of a Fresnel diffractive micro lens with a reflecting membrane. The reflecting membrane mounted on an inertial mass is placed parallel behind the diffractive micro lens. The light intensity at the conjugate position of an applied monochromatic point source is highly sensitive to the displacement of the membrane. The working principle is specifically discussed. In addition, this sensor makes use of a quad beam structure to allow the flat displacement of the inertial mass. Mechanical simulations using finite element method show the designed structure has a wide range of operation. A prototype accelerometer has been successfully developed. Dynamic tests indicate that the accelerometer has promising performance. This accelerometer can be fabricated using microelectromechanical systems (MEMS) technology, with relatively few process steps, so it is suitable for batch production. By optimizing structural designs, it can be a competitive candidate for a number of application fields ranging from vibration monitoring to inertial navigation. [Copyright &y& Elsevier]

Abstract: Large mechanical strain is desirable for many devices such as cantilever-based accelerometers and vibration energy harvesting devices. Air-spaced cantilevers are proposed to significantly increase the mechanical strain experienced by the cantilever beams. In this paper, an analytical model for the bending of symmetric air-spaced cantilevers is established by decomposing the cantilever deformation into pure bending and S-shape bending. This model was further verified by a discrete component model. A criterion to determine the dominant bending mode is presented. Finite element simulations and experiments were also conducted and showed a good agreement with the analytical model. [Copyright &y& Elsevier]

Abstract: A novel mercury-based capacitive accelerometer has been designed and fabricated. The accelerometer features a highly symmetrical cubic structure and capacitive coupling of the high-frequency input voltage, which uses a mercury drop for spring material and flexible interconnection layer between the capacitor plates. The device is mounted on a standard IC package with dimensions of 5mm×5mm×5mm. The structure, working principle, fabrication, and mathematical model of the accelerometer are presented. Since the accelerometer uses a mercury drop as its sensitive electrode instead of a solid, which is commonly used in traditional accelerometers, the conflict between the requirements of high shock and high sensitivity is solved. The measurement results show a sensitivity of 0.2mV(ms−2)−1 with a corresponding resolution of 0.01ms−2, off-axis sensitivity of <5% and good linearity in the output voltage for accelerations up to at least 10ms−2. [Copyright &y& Elsevier]

Abstract: In this paper, we present a novel type of biaxial accelerometer based on a polydimethylsiloxane (PDMS) structure as the mass–spring system and using magnetoresistive (MR) sensors as the detection method. The proof mass of the sensor is a mushroom-shaped polymer magnet made of PDMS filled with permanent magnet powder, whose minute movement under lateral acceleration is precisely sensed by a set of MR sensors. The device aims at consumer electronics applications of low g range and low frequency, such as inclination measurements and motion sensing. An experimental device has been successfully fabricated which showed a linear transfer curve without significant hysteresis. A sensitivity of 0.32mV/(Vg) was obtained. [Copyright &y& Elsevier]

Abstract: This paper reports a novel GaAs micromachined accelerometer based on the meso-piezoresistive effects of resonant tunneling diodes (RTDs). The sensitive unit of the accelerometer is the RTD which is located at the root of the beams. Based on the meso-piezoresistive effects of RTD, the accelerometer transduces acceleration into electrical signal output. This kind of accelerometer has been fabricated by GaAs IC surface processes and control hole etching technology. The output sensitivity and frequency characteristics of the accelerometer have been tested on the vibrating system. The result indicates that when the RTD is biased in the negative differential resistance region, the sensitivity of the suggested accelerometer is up to 90.51mV/g, and when biased in the positive resistance region, the sensitivity is 2.39mV/g. It is obvious that the sensitivity in the negative resistance region is more one order higher than that in the positive resistance region, and the sensitivity of the accelerometer can be adjusted through changing the bias voltage. A frequency range of this structure as high as 1.5KHz has also been achieved. [Copyright &y& Elsevier]

Abstract: This study concerns the integration of convective accelerometers on CMOS. The design approach is based on an HDL modeling of the sensing cell. The development of a monolithic system is then undertaken, using multi-domain simulations, within the microelectronics design environment. For illustration, the sensor equivalent input noise (i.e. the resolution) is computed for various readout circuitry configurations: a simple instrumentation amplifier, a customized low-noise amplifier and a chopper-stabilized amplifier with a track-and-hold signal demodulator. Finally, a noise equivalent acceleration below 1mg/√Hz has been reached, which is interesting for applications in consumer electronics. [Copyright &y& Elsevier]

Abstract: This paper reports on the optimization and robust design of a MEMS accelerometer using the genetic algorithm technique. Performance requirements and MEMS process factors are taken into account. Objective functions are created to optimize each performance aspect and to penalise designs that are not sufficiently robust to manufacturing variations. The variation of performance with robustness is also studied, and increasing the requirement for robustness is shown to have a negative effect on performance. [Copyright &y& Elsevier]

Abstract: In this paper we describe a new accelerometer using ferroelectric material having a large dielectric constant, such as bulk PZT (ɛ r =2600). The measuring principle is detection of the capacitance change caused by the dielectric mass movement in the fringe electrical field. Considering practical fabrication, ferroelectric material is used for the substrate instead of the suspended proof mass. Since capacitance is increased electrically, and not mechanically, it is expected that the sensitivity will be considerably increased while retaining mechanical stiffness. This has the advantage of preventing touch down of the proof mass, and increasing the allowable measuring range of acceleration. The basic principle and the effectiveness of the proposed sensor are confirmed by both the theoretical calculation using an approximate model, and the finite element method (FEM) simulation. A practical sensor device was fabricated with basically only surface micromachining. A preliminary characterization was carried out under atmospheric pressure, confirming linearity between the sensor output and the input acceleration. The sensitivity is increased considerably (∼1000) compared to our previous sensor using polymer Parylene material having a comparatively low dielectric constant (ɛ r =3.15). [Copyright &y& Elsevier]

Abstract: This paper reports a novel miniaturized piezoresistive 6-axis accelerometer designed and fabricated using bulk micromachining technology. Accelerometer consists of highly symmetric single crystalline silicon crossbeam structure with 20 conventional two-terminal p-type piezoresistors diffused on the surface of the beams. This accelerometer measures three components of linear acceleration and three components of angular acceleration on three orthogonal axes simultaneously. The average measured sensitivities of the fabricated sensor for linear accelerations and angular accelerations show a cross-axis sensitivity of <4%. Comparison of the obtained experimental results and finite element simulation shows good agreement. The sensor is ideal for use in biomechanical research applications such as human gesture recognition systems. [Copyright &y& Elsevier]

Abstract: We present a new thin film encapsulation technique for surface micromachined sensors using a polysilicon multilayer process. The main feature of the encapsulation process is that both the sacrificial layer above the silicon sensor structure and the cap layer consist of epitaxial polysilicon. The sacrificial layer is removed by chlorine trifluoride (ClF3) plasmaless gas-phase etching through vents within the cap layer. The perforated cap membrane is sealed by a nonconformal oxide deposition. The method has been applied to a silicon surface micromachined acceleration sensor with high aspect ratio structures, but is broadly applicable. Capacitance–voltage measurements have been performed to show the electrical functionality of the accelerometer. [Copyright &y& Elsevier]

Abstract: In the present work a thermal accelerometer without solid proof mass, based on a silicon sensor was studied. Its principle of operation is based on the acceleration induced thermal exchange variations due to convection between a heater and two series of thermocouples. A specially designed housing was fabricated, which allows the device to be covered with various liquids. The effect of the different liquid viscosities on the sensor characteristics was examined. The dependence of the accelerometer signal on both frequency and acceleration was determined for various configurations. It was found that depending on the packaging configuration the 3db cut-off signal can be adjusted from some Hertz to several hundreds of Hertz. The sensitivity of the device as well as the accuracy of the waveform shapes can also be adjusted by regulating specific packaging parameters. A specially designed electronic interface was implemented for monitoring and controlling the input and output signals of the accelerometer. Different modes of operation were considered in order to improve the long term stability of the device. [Copyright &y& Elsevier]

Abstract: This paper addresses the design of CMOS thermal accelerometers. A test-chip including the sensor and a signal conditioning circuit has been designed, fabricated and characterized. The fabricated prototype exhibits good performance: the measured resolution is better than 30mg (equivalent to 1.7° in inclination) with a sensitivity of 375mV/g. The bandwidth is around 15Hz. This test-chip is used to improve the modelling of heat transfer phenomenon for this family of devices. FEM is successfully used as a first modelling approach. Although thermal convective accelerometers have already been reported and even commercialised, few information regarding behavioural modelling, optimization issues, and their integration on CMOS technology is today available. In particular, no information about response time modelling was reported in the literature. Thanks to experimental results and FEM simulations, we provide in this study information concerning the integration of convection heat transfer accelerometers on CMOS. In addition, the effects of the packaging (i.e. the top and bottom cavities) on both the static sensitivity and the dynamic response of the sensor have been investigated. [Copyright &y& Elsevier]