A grid of dielectric sensors to monitor mold filling and resin cure in resin transfer molding

A grid of 50 dielectric sensors has been embedded in the walls of a mold to monitor resin transfer molding (RTM). The capacitance of each sensor increased as resin occupied the space between sensor plates, and it decreased with curing. Monitoring data can be used for process control to prevent dry spots and to determine when to de-mold the part. In previous studies, Skordos et al. [Skordos AA, Karkanas PI, Partridge IK. A dielectric sensor for measuring flow in resin transfer molding. Meas Sci Technol 2000;11:25–31] used a lineal sensor, Hegg et al. [Hegg MC, Ogale A, Mescher A, Mamishev AV, Minaie B. Remote monitoring of resin transfer molding processes by distributed dielectric sensors. J Compos Mater 2005;39(17)] used three large sensors. As experimentally shown in this study, these lineal or large-plate dielectric sensors may mislead since a sensor measures total fraction of the sensor’s plate area occupied by resin but not the resin’s whereabouts. To avoid ambiguity and yet maintain detailed monitoring, a sensor grid was made at the projections of embedded orthogonal electrodes. The developed sensor operation system eliminated tedious and costly manufacturing of conventionally shielded separate sensors. The success of the developed sensor system was demonstrated in RTM experiments.     

The influence of electric-field bending on the nonlinearity ofcapacitive sensors

Three-layered electrode structures are often employed in multiple-electrode capacitive position sensors. Even when advanced algorithms and well-designed guarding electrodes are used, the electric-field-bending effect is still one of the major contributors to the nonlinearity of capacitive position sensors. In this paper, the effects of electric-field bending on linearities of five capacitive linear-position sensors have been studied based on a physical model of the capacitive sensor. It is shown that the effect of electric-field bending on linearities strongly depends on the sensor structures, and that it is significantly reduced when advanced sensor structures and algorithms are used. The results are very useful for optimizing the sensor structure according to its application     

基于F-P滤波器的光纤光栅振动传感解调系统的研究

光纤光栅传感技术较其它传感技术有其独特的优点,在振动传感中有很大的发展前景。文章提出了一种利用法布里-玻罗腔作为滤波器,将FBG传感振动信号产生的Bragg波长的漂移转化为F-P滤波器透过光强度的变化来传感解调的方法,通过实验验证,可知该方法能克服相位型光纤振动传感器和匹配光纤光栅振动传感器的一些缺点,性能稳定,价格低廉,精确度高,具有较高的实用价值,有望在实际应用中推广。     

Chemiresistive Sensor Arrays for Gas/Volatile Organic Compounds Monitoring: A Review

Gas detection and monitoring are essential due to their direct impact on human health, environment, and ecosystem. Chemiresistive sensors are one of the most used classes of sensors for monitoring and measurement of gases thanks to their ease of fabrication, customizability, mechanical flexibility, and fast response time. While chemiresistive sensors can offer good sensitivity and selectivity to a particular gas in a controlled environment with known interferences, they may not be able to differentiate between various gases having similar physiochemical properties under uncontrolled conditions. To address this shortcoming of chemiresistive gas sensors, sensor arrays have been the subject of recent studies. Gas sensor arrays are a group of individual gas sensors that are arranged to simultaneously detect and differentiate multiple cross-reactive gases. In this regard, various sensor array technologies have been developed to differentiate a given set of gases using multivariate algorithms. This review provides an insight into the different algorithms that are used to extract the data from the sensor arrays, highlighting the fabrication techniques used for developing the sensor array prototypes, and different applications in which these arrays are used.     

网格式柔性应变传感器的制备及应用

鉴于柔性应变传感器在人体运动监测、健康监测等领域的广泛应用,设计出兼具高灵敏度和大应变范围的柔性应变传感器具有重要的意义。本文基于Ecoflex-石墨烯复合材料,通过模板法制备了四边形和六边形网格式柔性应变传感器。通过对比两种不同网格结构传感器的应变范围与拉伸断裂极限,发现六边形网格柔性应变传感器的综合性能更优异,并在80%应变条件下进行拉伸/释放疲劳寿命检测,此传感器表现出良好的可靠性,同时该传感器在手肘关节运动和人体不同呼吸状况监测方面表现良好。将六边形网格柔性应变传感器组合构建多通道检测系统,实现了多种手势识别,这在人工智能和运动识别领域具有广阔的市场应用前景。     

Superstructured fiber-optic contact force sensor with minimal cosensitivity to temperature and axial strain

In this work a new superstructured, in-fiber Bragg grating (FBG)-based, contact force sensor is presented that is based on birefringent D-shape optical fiber. The sensor superstructure comprises a polyimide sheath, a stress-concentrating feature, and an alignment feature that repeatably orients the sensor with respect to contact forces. A combination of plane elasticity and strain-optic models is used to predict sensor performance in terms of sensitivity to contact force and axial strain. Model predictions are validated through experimental calibration and indicate contact force, axial strain, and temperature sensitivities of 169.6 pm/(N/mm), 0.01 pm/με, and -1.12 pm/°C in terms of spectral separation. The sensor addresses challenges associated with contact force sensors that are based on FBGs in birefringent fiber, FBGs in conventional optical fiber, and tilted FBGs. Relative to other birefringent fiber sensors, the sensor has contact force sensitivity comparable to the highest sensitivity of commercially available birefringent fibers and, unlike other birefringent fiber sensors, is self-aligning with respect to contact forces. Unlike sensors based on Bragg gratings in conventional fiber and tilted Bragg gratings, the sensor has minimal cosensitivity to both axial strain and changes in temperature.     

Mass transfer and gas-phase calibration of implanted oxygen sensors

A protocol is described for validation of implanted oxygen sensors, in which sensors are calibrated in the gas phase where concentration boundary layers are absent. Calibration prior to sensor implantation and confirmation after sensor explantation allows separation of tissue mass transfer effects from sensor variance and drift. A model is given here that describes the oxygen-dependent signal current in terms of oxygen mass transfer to the sensor, permeability of the sensor membrane, and electrode area. The parameter used in the model to describe mass transfer to implanted sensors is consistent with experimental observations and allows comparisons with nonimplanted sensors. This method provides a bridge between the complementary approaches of empirical calibration and model-based calculation for determining oxygen concentration from the sensor response.     

自适应空间有源消声最佳消声效果的实现

本文针对一个自适应有源消声控制系统以及一个以点声源为次级源的声系统，就如何实现空间最佳消声效果问题进行了讨论，给出了误差传声器的个数及空间位置与空间消声效果之间的关系，提出误差传声器应放置在实现消声后声压的极小方向上。所得结论在实验中得到了证实。     

半导体陶瓷型薄膜气敏传感器的研究进展

半导体陶瓷型薄膜气敏传感器,具有灵敏度高、与气体反应快、制备成本较低等优点,已经成为近年传感器研究和开发的重点．是未来气敏传感器的发展方向之一。本文介绍了陶瓷型半导体薄膜气敏传感器常见的器件结构、薄膜材料的主要制备方法．部分主要的半导体金属氧化物薄膜气敏材料．以及近期相关的研究进展,并扼要分析了今后的发展方向。     

Fundamental performance comparison of a Hartmann and a shearing interferometer wave-front sensor

The performance of ground-based optical imaging systems is severely degraded from the diffraction limit by the random effects of the atmosphere. Adaptive-optics techniques have been used to compensate for atmospheric-turbulence effects. A critical component in the adaptive-optics system is the wave-front sensor. At present, two types of sensors are common: the Hartmann-Shack wave-front sensor and the shearing interferometer wave-front sensor. In this paper we make a direct performance comparison of these two sensors. The performance calculations are restricted to common configurations of these two sensors and the fundamental limits imposed by shot noise and atmospheric effects. These two effects encompass the effects of extended reference beacons and sensor subaperture spacings larger than the Fried parameter r(0). Our results indicate comparable performance for good seeing conditions and small beacons. However, for poor seeing conditions and extended beacons, the Hartmann sensor has lower error levels than the shearing interferometer.     

An Information Fusion-Based Multiobjective Security System With a Multiple-Input/ Single-Output Sensor

In the framework of sensor fusion, multiple sensors corresponding to the number of physical variables that must be measured are used. In this paper, we propose a novel sensing approach that simultaneously deals with heterogeneous physical variables with a sensor. It is fundamentally different from sensor fusion. The proposed approach takes into consideration the fact that any sensor that detects a certain physical variable is influenced to a degree by other physical variables, which are designated as noise. The objective in conventional sensor design has been the minimization of noise. In contrast, the proposed approach takes advantage of sensors that are easily influenced by many physical variables and makes full use of the multisensing characteristics of these sensors. The system designed using this concept has advantages in terms of cost performance and system simplification compared to existing approaches. This concept can be realized by developing a novel multiple-input/single-output sensor that can detect various variables, including pressure, acceleration, temperature and incandescent light emission, by a single device. We apply the sensor to monitor the symptoms of fire, earthquakes, and break-ins for the purpose of home security. The proposed security system is realized through statistical signal processing and machine learning techniques     

Study on the method of precision adjustment of star sensor

Star sensors are indispensable spatial measurement sensors for high-resolution earth observation and astronomical observations, and the demand for high measurement accuracy of satellite sensors continues to increase; thus, the star sensor optical machine adjustment error cannot be ignored. The commonly used installation error correction method cannot solely meet the precision analysis requirements. In this paper, the relationship between the optical machine installation and the star sensor measurement error is analyzed, and several common adjustment error correction methods are compared. An adjustment method for optical machines is proposed to meet the requirements of very high precision star sensors. The assembly precision requirements of the investigated very high precision star sensor are analyzed considering the whole machine, and then the optical components are controlled through optical precision adjustments to satisfy the precision requirements. Finally, through the complete machine calibration, the star sensor precision adjustment for an optical machine structure is verified. This method meets the requirements of very high precision sensors and is suitable for the precision adjustment of optical machine structures, which is of practical significance to improve the precision of star sensors.     

特种传感器发展及趋势

特种传感器在国家重大工程中不可或缺,本文介绍了国际上主要国家在特种传感器方面的发展计划和策略,总体描述了我国在该领域的发展水平及与国外的差距,分别从高温压力传感器、微位移传感器、量子磁传感器、振动传感器、湿度传感器等几个方向,对比了国内外主要研究单位、主要产品的水平,并对我国特种传感器的发展趋势提出了预判与建议。     

Development of Low-cost Chemical and Micromechanical Sensors Based on Thick-film,Thin-film and Electroplated Films

Various films could be used as sensing materials or as constructional materials for the fabrication of chemical and micromechanical sensors. To illustrate this potential, three sensors fabricated by very different film deposition technologies are given as examples. The sensors are a humidity sensor in thickfilm technology, a multi-functional gas sensor in thin-film technology and a three-dimensional acceleration sensor chip manufactured by electroplating techniques. Design, fabrication and characterisation of these sensors are described in this paper.     

基于信息融合的矿井一氧化碳检测方法的研究

电化学传感器在检测矿井一氧化碳含量时,容易受到矿井中甲烷气体的影响。为了解决这个问题,将催化传感器与电化学传感器构成一体,利用两个传感器的输出信号,经过BP神经网络的训练,得到了一个分析一氧化碳的信息融合数学模型。实验表明,利用研究的信息融合信号处理方法,可以提高一氧化碳含量检测的可靠性。     

Location information-aided task-oriented self-organization of ad-hoc sensor systems

A novel task-oriented self-organization algorithm that accounts for mostly location-dependent tasks and heterogeneous sensors inherent in dense ad-hoc sensor systems is proposed. It forms a sensor group for an announced task by sequentially selecting the best matched sensors using a leader election algorithm and a residual task calculation algorithm. To improve the associated communication overhead, the sensor node location information is used in task broadcasting, thus confining the algorithm implementation to a dynamically maintained contributor group which comprises of those sensors which may contribute to the task. Sensor localization is based on a refinement of an algorithm in which utilizes only the neighborhood information of each sensor node corresponding to its each preset radio transmission power level. The proposed self-organization algorithm and how various system parameters affect its performance are examined via extensive simulations. In a densely deployed sensor system, when the refined localization scheme is demonstrated to achieve very good localization, the proposed self-organization algorithm consistently yields a sensor group that covers the announced task.     

Sensor Fusion Methodology to Overcome Cross-Axis Problem for Micromachined Thermal Gas Inertial Sensor

Micromachined thermal gas inertial sensors are novel devices that take advantages of simple configuration, large working range, high shock resistance, and good reliability in virtue of using gaseous medium instead of mechanical proof mass as key moving and sensing elements. Basing on multidimentional movements of gas flow in a small chamber, the sensor generally undergoes a cross-axis problem. In this paper, a study on the cross-axis sensitivity of the thermal gas rotation sensor is reported. The cross-axis problem of the sensor is resulted from the multidimensional coupling movement of the convection flow in the sensor chamber and possibly be diminished by a tailored structural design. Unlike using a complex scheme on the mechanical structure, combining more than two sensors to form an integrated compensation system and using a fusion methodology to decouple cross rotations are proposed in this paper. The method helps to enhance practical applications for thermal rotation sensors.      

Overview of automotive sensors

An up-to-date review paper on automotive sensors is presented. Attention is focused on sensors used in production automotive systems. The primary sensor technologies in use today are reviewed and are classified according to their three major areas of automotive systems application-powertrain, chassis, and body. This subject is extensive. As described in this paper, for use in automotive systems, there are six types of rotational motion sensors, four types of pressure sensors, five types of position sensors, and three types of temperature sensors. Additionally, two types of mass air flow sensors, five types of exhaust gas oxygen sensors, one type of engine knock sensor, four types of linear acceleration sensors, four types of angular-rate sensors, four types of occupant comfort/convenience sensors, two types of near-distance obstacle detection sensors, four types of far-distance obstacle detection sensors, and and ten types of emerging, state-of the-art, sensor technologies are identified     

Integrated Heat-Flux Sensors for Harsh Environments Using Thermal-Spray Technology

Heat-flux sensors are widely used in thermal and heat-transfer engineering applications. Commercial heat-flux sensors currently available for harsh environments, however, remain limited due to complications in positioning/attaching the sensor onto the component, the inability to operate at high temperatures, and potentially altering or degrading the engineering device by the physical presence of the sensor. In this paper, heat-flux sensors have been fabricated for the first time entirely by using a thermal-spray technology. The sensors are fabricated directly onto engineering surfaces and consist of five to seven thermocouples arranged electrically in series and thermally in parallel, such that the heat flux is measured normal to the surface, on which the sensor resides. Devices are tested under both steady-state and transient conditions at temperatures up to 100$^circhboxC$. They exhibit a very good linearity between the heat flux and voltage output. Analytical modeling of the steady-state and transient responses is also presented and compared to experimental results. If successful, thermal-spray heat-flux sensors could represent a significant enabling technology for heat-flux sensing at high temperatures, in harsh environments, and in embedded sensor applications.     

冲击加速度传感器频域校准技术研究

为获得更为真实的传感器频响特性,利用激光干涉仪对传感器进行动态校准,在传感器输入和输出数据的基础上,确定系统模型结构、阶次,基于输出误差模型,采用系统辨识实验法,辨识传感器模型的各项参数,从而建立被校冲击加速度传感器的数学等价模型,进而将模型方程转换为传递函数,并绘制出传感器的幅频、相频特性曲线,最终实现被校传感器的冲...