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The paper addresses the problem of experimental studies of miniature tilt sensors based on low-range accelerometers belonging to Microelectromechanical Systems (MEMS). A custom computer controlled test rig is proposed, whose kinematics allows an arbitrary tilt angle to be applied (i.e. its two components: pitch and roll over the full angular range). The related geometrical relationships are presented along with the respective uncertainties resulting from their application. Metrological features of the test rig are carefully evaluated and briefly discussed. Accuracy of the test rig is expressed in terms of the respective uncertainties, as recommended by ISO; its scope of application as well as the related limitations are indicated. Even though the test rig is mostly composed of standard devices, like rotation stages and incremental angle encoder, its performance can be compared with specialized certified machines that are very expensive. Exemplary results of experimental studies of MEMS accelerometers realized by means of the test rig are presented and briefly discussed. Few ways of improving performance of the test rig are proposed. [ABSTRACT FROM AUTHOR]

In this paper, an adaptive, autocovariance-based event detection algorithm is proposed, which can be used with micro-electro-mechanical systems (MEMS) accelerometer sensors to build inexpensive and power efficient event detectors. The algorithm works well with low signal-to-noise ratio input signals, and its computational complexity is very low, allowing its utilization on inexpensive low-end embedded sensor devices. The proposed algorithm decreases its energy consumption by lowering its duty cycle, as much as the event to be detected allows it. The performance of the algorithm is tested and compared to the conventional filter-based approach. The comparison was performed in an application where illegal entering of vehicles into restricted areas was detected. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to provide an improved structural design for accelerometers based on cantilever beam-mass structure and offer the descriptions of sensor fabrication, packaging and experiments. Design/methodology/approach – The cantilever beam-membrane (CB-membrane) structure is designed as the sensing element for piezoresistive accelerometers. In the CB-membrane structure, a cantilever beam and two identical membranes as a whole part supports the proof mass. Four piezoresistors are distributed on the surface of the cantilever beam to form a Wheatstone bridge. Finite element method is used to carry out the structural analysis and determine the sensor dimensions. The sensor chip is fabricated by bulk micro-machining technique, packaged in dual-in-line (DIP) way and tested. Findings – Compared with the conventional cantilever beam-mass (CB-mass) structure, the CB-membrane structure can improve the sensor's performances, including response frequency, output linearity and cross-axis sensitivity. The results of simulation and experiments prove that the CB-membrane accelerometer has good performances. Research limitations/implications – The accelerometer is simply packaged and the zero offset voltage has not been compensated. Moreover, the measured response frequency is lower than the simulated value. Further work and study are needed to solve these problems. Originality/value – The accelerometer with CB-membrane structure has good performances as the static and dynamic experiments show and is suitable to detect the spindle vibration of the machine tools. [ABSTRACT FROM AUTHOR]

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]

A bulk micromachined inertial measurement unit (MIMU) is presented in this paper. Three single-axis accelerometers and three single-axis gyroscopes were simultaneously fabricated on a silicon wafer using a bulk micromachining process; the wafer is smaller than one square centimeter. In particular, a global area optimization method based on the relationship between the sensitivity and layout area was proposed to determine the layout configuration of the six sensors. The scale factors of the X/Y-axis accelerometer and Z-axis accelerometer are about 213.3 mV/g and 226.9 mV/g, respectively. The scale factors of the X/Y-axis gyroscope and Z-axis gyroscope are about 2.2 mV/°/s and 10.8 mV/°/s, respectively. The bias stability of the X/Y-axis gyroscope and the Z-axis gyroscope are about 2135 deg/h and 80 deg/h, respectively. Finally, the resolutions of X/Yaxis accelerometers, Z-axis accelerometers, X/Y-axis gyroscopes, and Z-axis gyroscopes are 0.0012 g/ √Hz , 0.0011 g/ √Hz , 0.314 ° /s/ √Hz , and 0.008 ° /s/ √Hz , respectively. [ABSTRACT FROM AUTHOR]

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 introduces an analytical modeling of a convective CMOS accelerometer. The device is a one-axis accelerometer based on a three bridges structure (one heater and two detectors). The modeling relies on the use of heat transfer fundamentals and is validated using experimental data issued from both test-vehicles and FEM analysis. It describes the heat conduction phenomenon that determines the thermal initial condition and then the convection mechanism that provides the sensitivity to the acceleration. Although only the static model is detailed, the dynamic behavior of test samples has been characterized and included into the HDL module. In order to illustrate the use of the model, the sensor is simulated together with its control electronics in an implementation of an A/D modulator. Simulation results are then compared with physical measurement with good agreement. [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]

Analog Devices (ADI) has designed and fabricated a monolithic high-g acceleration sensor (ADXSTC3-HG) fabricated with the ADI silicon-on-insulator micro-electro-mechanical system (SOI-MEMS) process. The SOI-MEMS sensor structure has a thickness of 10 um, allowing for the design of inertial sensors with excellent cross-axis rejection. The high-g accelerometer discussed in this paper was designed to measure in-plane acceleration to 10,000 g while subjected to 100,000 g in the orthogonal axes. These requirements were intended to meet Army munition applications. The monolithic sensor was packaged in an 8-pin leadless chip carrier (LCC-8) and was successfully demonstrated by the US Army Research Laboratory (ARL) as part of an inertial measurement unit during an instrumented flight experiment of artillery projectiles launched at 15,000 g. [ABSTRACT FROM AUTHOR]

The paper deals with performance enhancement of low-cost, consumer-grade inertial sensors realized by means of Micro Electro-Mechanical Systems (MEMS) technology. Focusing their attention on the reduction of bias instability and random walk-driven drift of cost-effective MEMS accelerometers and gyroscopes, the authors hereinafter propose a suitable method, based on a redundant configuration and complemented with a proper measurement procedure, to improve the performance of low-cost, consumer-grade MEMS sensors. The performance of the method is assessed by means of an adequate prototype and compared with that assured by a commercial, expensive, tactical-grade MEMS inertial measurement unit, taken as reference. Obtained results highlight the promising reliability and efficacy of the method in estimating position, velocity, and attitude of vehicles; in particular, bias instability and random walk reduction greater than 25% is, in fact, experienced. Moreover, differences as low as 0.025 rad and 0.89 m are obtained when comparing position and attitude estimates provided by the prototype and those granted by the tactical-grade MEMS IMU. [ABSTRACT FROM AUTHOR]