Design Of Sensor System Research Articles

Laser Absorption Sensing Systems: Challenges, Modeling, and Design Optimization

Laser absorption spectroscopy (LAS) is a promising diagnostic method capable of providing high-bandwidth, species-specific sensing, and highly quantitative measurements. This review aims at providing general guidelines from the perspective of LAS sensor system design for realizing quantitative species diagnostics in combustion-related environments. A brief overview of representative detection limits and bandwidths achieved in different measurement scenarios is first provided to understand measurement needs and identify design targets. Different measurement schemes including direct absorption spectroscopy (DAS), wavelength modulation spectroscopy (WMS), and their variations are discussed and compared in terms of advantages and limitations. Based on the analysis of the major sources of noise including electronic, optical, and environmental noises, strategies of noise reduction and design optimization are categorized and compared. This addresses various means of laser control parameter optimization and data processing algorithms such as baseline extraction, in situ laser characterization, and wavelet analysis. There is still a large gap between the current sensor capabilities and the demands of combustion and engine diagnostic research. This calls for a profound understanding of the underlying fundamentals of a LAS sensing system in terms of optics, spectroscopy, and signal processing.

Whole System Design of a Wearable Magnetic Induction Sensor for Physical Rehabilitation

Wearable sensor technologies attract increasing attention for continuous monitoring of human health. Much effort is devoted to exploit well‐designed materials to realize superior abilities, such as high sensitivity, stability, and responsiveness. However, it hardly meets huge demands for practically wearable applications simply focusing on the development of sensing materials in isolation. Comprehensive consideration is given from upstream materials to endure market, including materials design, sensor assembly, signal analysis, theoretical foundation, and final system performance, such as sensitivity, stability, responsiveness, cost, comfortability, and durability. Herein, a systematic design is presented that combines a conductive fiber fabrication based on surface nanotechnology, device assembly process optimization, signal acquisition and analysis, and theoretical simulation, through a new multidisciplinary strategy integrating material science, textile technology, electromagnetics, and electronic engineering. The as‐constructed magnetic inductance sensing system shows approximately six‐times inductance change with regard to joint bending motions during rehabilitation exercises. This integrated design strategy offers a new concept, namely, a whole sensing system design, for wearable technologies in real‐time health monitoring applications.

Simple Self-Referenced Luminescent pH Sensors Based on Upconversion Nanocrystals and pH-Sensitive Fluorescent BODIPY Dyes

We present the design and fabrication of pH responsive ratiometric dual component sensor systems based on multicolor emissive upconversion nanoparticles (UCNP) and pH sensitive BODIPY dyes with tunable p Ka values embedded into a polymeric hydrogel matrix. The use of NIR excitable NaYF4:Yb3+,Tm3+ UCNPs enables background free read-out. Furthermore, the spectrally matching optical properties of the UCNPs and the dyes allow the UCNPs to serve as excitation light source for the analyte-responsive BODIPY as well as intrinsic reference. The blue upconversion luminescence (UCL) of NaYF4:Yb3+,Tm3+ UCNPs excited at 980 nm, that overlaps with the absorption of the pH-sensitive fluorophore, provides reabsorption based excitation of the dye, the spectrally distinguishable green fluorescence of which is switched ON upon protonation, preventing photoinduced electron transfer (PET) within the dye moiety, and the pH-inert red UCL act as reference. The intensities ratios of the dye's fluorescence and the analyte-inert red Tm3+ UCL correlate directly with pH, which was successfully utilized for monitoring time-dependent pH changes of a suspension of quiescent E. coli metabolizing d-glucose.

On the time evolution at a fluctuating exceptional point

Abstract We theoretically evaluate the impact of drift-free noise on the dynamics of P T ${\cal P}{\cal T}$ -symmetric non-Hermitian systems with an exceptional point, which have recently been proposed for sensors. Such systems are currently considered as promising templates for sensing applications, because of their intrinsically extremely sensitive response to external perturbations. However, this applies equally to the impact of fabrication imperfections and fluctuations in the system parameters. Here we focus on the influence of such fluctuations caused by inevitable (thermal) noise and show that the exceptional-point eigenstate is not stable in its presence. To this end, we derive an effective differential equation for the mean time evolution operator averaged over all realizations of the noise field, and via numerical analysis we find that the presence of noise leads to exponential divergence of any initial state after some characteristic period of time. We therefore show that it is rather demanding to design sensor systems based on continuous operation at an exceptional point.

A bipolar electret-based micro-vibration-driven energy harvester with multi-air-gap structure

Micro mechanical energy harvester as a kind of micro power source for micro electro mechanical systems (MEMS) has been paid considerable attention. Electret-based vibration energy harvester (E-MVEH) has been a research highlight due to its high sensitivity, simplicity and compatibility to the fabrication process of MEMS. In this manuscript, a novel E-MVEH with multiple-air-gap structure based on bipolar electrets is comparatively investigated. The E-MVEH with single-air-gap structure consists of an electret membrane (EM) with an electrode on one surface and a counter-electrode supported by means of micro-springs. The E-MVEH with double air gaps is made of a bipolar electret membrane put in the middle of two counter-electrodes that are supported by means of micro-springs. It is essentially equivalent to two variable capacitors in series. The E-MVEH with four air gaps consists of two double-air-gaps E-MVEH in parallel connection. When an external vibration causes a relative displacement between the electret membrane (EM) and the counter-electrode, the capacitance varies, leading to re-organization of the charges on the counter-electrode. Thus, an alternating current is generated and the vibration energy is converted into electric energy. This alternating current can be changed into direct current through a full bridge rectifier. The bipolar EM used in this study is a sandwich FEP/THV/FEP perfluoropolymer EM reported previously by our group. It can display persistent and strong electrostatic field with both polarities on the top and bottom surface, respectively. The experimental results of the output characteristic for the proposed E-MVEH show that there exists a resonant frequency in the vibration frequency range of 30−180 Hz, at which the open-circuit voltage and short-circuit current and hence the output power reach their respective maximum. The resonant frequency moves towards the low frequency with increasing vibration intensity, whereas the effect of air-gap number on the resonant frequency is rather small. On the basis of experimental results and theoretical analysis, the maximum output power is positively correlated to the vibration driving force, the surface potential and the area of the electret membrane, and the air-gap number. When the surface potential of the electret membrane is 1200±50 V, the maximum output power is only 0.19 μW for single-air-gap structure and reaches 27.02 μW for the four-air-gap structures under a vibration driving force of 0.5 N and a load resistance of 55 MΩ. For the four-air-gap structures, the maximum output power increases to 59.12 μW when the surface potential of the electret membrane increases to 2150 V. The multi-air-gap energy harvester fabricated with bipolar electret membrane can produce larger variable capacitance; therefore, the output power is significantly enhanced. This novel E-MVEH provides an up-to-date strategy for the design of self-powered sensor systems.

A Multiprobe Heat Pulse Sensor for Soil Moisture Measurement Based on PCB Technology

Heat dissipation sensors operate based on the temperature dependence of the transient heat conduction within the soil, which is a function of the soil characteristics and its water content. After a heat pulse with controlled energy is applied to a heater, it is possible to show that the maximum temperature rise $\Delta T_{M}$ measured in the temperature sensing element can be related to the volumetric water content of the soil $\theta _{v}$ [m3 m−3]. The design and fabrication of a low-cost soil moisture multiprobe heat pulse sensor system using conventional printed circuit boards and surface-mount devices is presented. The proposed sensor is free of the needles’ deflection problem present in conventional multiprobe sensors and is manufactured using conventional off-the-shelf electronic components. A precision low-power electronic signal conditioning circuit, using an instrumentation switched-capacitor building block, was developed and successfully used in the prototype. Due to an energy-efficient topology for the sensor and a low-power signal conditioning circuit, the average current consumption of the system (with one measurement per day) is only 3 $\mu \text{A}$ . To demonstrate the feasibility of the concept, a prototype of the sensor was tested in soils with volumetric humidity in the range from $\theta _{v} = 0.05 \,\,\rm {m^{3} \, m^{-3}}$ to $\theta _{v} = 0.41 \,\,\rm {m^{3} \, m^{-3}}$ and, with a very low heating energy pulse (3 J), showed a sensitivity, normalized by the total energy applied, $\Gamma = 211 \times \rm {10^{-3}}\,\, {^{\circ }}\rm {C} \, \rm {m^{3} \, m^{-3} \, J^{-1}}$ . Compared with a button heat pulse probe sensor which has $\Gamma = 192 \times \rm {10^{-3}}\,\, {^{\circ }}\rm {C} \, \rm {m^{3} \, m^{-3} \, J^{-1}}$ , the developed sensor shows a higher normalized sensitivity.

Design of composite microneedle sensor systems for the measurement of transdermal pH

Abstract Carbon loaded polystyrene microneedle patches have been prepared using silicone micro-moulding techniques and the ability of the needles to serve as viable transdermal sensors has been evaluated. The population of quinone groups at the interface of the embedded carbon nanoparticles was increased through anodisation and their pH dependent redox transitions exploited as the basis of a reagentless pH sensor. The peak position of the quinone oxidation process was found to shift in accordance with Nernstian behaviour and the influence of penetration depth on response has been investigated. The analytical applicability of the microneedle electrode patch was critically evaluated through using tomato skin as model transdermal skin mimic. Despite the increased complexity of the matrix, the microneedle sensor response was found to compare favourably with conventional/commercial pH probes.

Topography and topology optimization of diesel engine components for light-weight design in the automotive industry

Abstract This paper focuses on the optimal design of connecting rods and optimal design of a particle sensor system in diesel engines in order to save material, reduce costs and enhance quality. Optimization is very significant for developing better designs and means less material, lower costs and better conditions. Topology and topography optimization are new but likewise very important optimization approaches for the automotive industry. One of the aims of this study is to create an optimal design for connecting rod components and to use these components in diesel engines to comply with new emission regulations. An analysis of the connecting rods of an existing model was conducted using mathematical data obtained from numerical formulas in order to determine if the part was suitable for topology optimization. According to the results obtained from the topology optimization of the existing model, a new design was created. A comparison of the new design with the existing one showed that the mass of the model was reduced by 18 %, while all product expectations were me. Another purpose of the study is to provide an optimal design for a particle sensor system and utilize this system in automobiles to achieve the new emission values required by Euro-Norm 6c regulations. Within the scope of this optimization study, a specific particle measurement system foreseen for Renault 1.5 dCi engines was considered and designed optimally. According to the output of the topology and topography optimization methods, the particle sensor system was designed optimally, and the mass of the system was reduced by 26.7 %.

Development and Hybrid Control of an Electrically Actuated Lower Limb Exoskeleton for Motion Assistance

This paper describes a system design and hybrid control algorithm of an electrically actuated lower limb exoskeleton (LLE). The system design mainly includes three parts: mechanical structure design, actuation system design and sensor system design. According to the initial state of the joint angle, LLE can be divided into Non-anthropomorphic state (NAS) and anthropomorphic state (AS). The human motion intention (HMI) estimation can be divided into gait phase classification and reference trajectory estimation. The fuzzy logic is used to detect different phases in the gait phase classification. In the reference trajectory estimation, the kinematic model of the LLE is utilized to obtain a continuous joint trajectory, which is used as input of the control law. To make the LLE accurately follow the movement of people and remain stable, a hybrid dual-mode control strategy is proposed in this paper, i.e., the adaptive impedance control (AIC) method is used to improve the stability and resistance to shock in stance phase, and the active disturbance rejection control with the fast terminal sliding mode control (ADRC-FTSMC) method is employed to improve the response speed and the tracking precision in swing phase. Furthermore, in order to solve the torque discontinuity in the switching process, a smoothing method is proposed during the transition. Finally, the prototype experiments were set up to verify the tracking performance and power-assisted effect of the proposed exoskeleton. The experiments results show the LLE can achieve excellent tracking performance and power-assisted effect based on the proposed HMI methodology and hybrid dual-mode control strategy.

Design of sensor and actuator fault tolerant control system on wind turbine benchmark for Region II

The control system performance of the wind turbine can be unexpected due to the minor fault of its components, such as bias fault in its speed sensor and its converter system. Indeed, the lack of treatment to these faults lead to major problem. This paper discusses the control system design of generator rotor speed that is tolerant of faulty sensors and actuators. The studied wind turbine benchmark is operated in Region II. The controller is developed based on a torque control scheme which generates control signal based on the generator speed measurement using proportional–integral (PI) algorithm. The sensor and actuator faults estimates are obtained by an extended state observer which realizes a new state from a filtered signal of the measurement. Then the sensor fault estimate is submitted to a compensation mechanism in order to correct measurement value while the actuator fault estimate is used to reconfigure control signal value in order to correct control signal.

An Estimate Method of EPFM Constraint Parameter in 3D Cracked Structures for Sensor Structure Design

An estimating method, which conveniently and quickly predicts solutions of constraint parameter $A$ in J-A two-parameter approach of elastic-plastic fracture mechanics (EPFM), was developed and successfully applied on three-dimensional (3D) cracked structures under both uniaxial and biaxial loading condition. The method (estimate formula) for $A$ value estimate was developed theoretically first. Then, based on the obtained numerical solutions of parameter $A $ from finite element analysis (FEA), the coefficient values of the proposed estimate formula were determined for 3D single edge cracked plate (SECP) structures under both uniaxial and biaxial loading, to estimate solutions of parameter $A$ for 3D SECP. Through comparing predicted parameter $A$ values with their FEA numerical solutions from authors and other researchers, it is validated that the proposed estimating method can be used well to predict $A$ values for thin 3D cracked structures. It enables the application of the EPFM J-A two-parameter approach on practical engineering structure analysis and design of sensor and other mechanical systems.

The Growing Role of Complex Sensor Systems and Algorithmic Pattern Recognition for Vascular Dementia Onset

Vascular Dementia is often Clinically diagnosed once the effects of the disease are prevalent in a person’s daily living routines. However previous research has shown various behavioral and physiological changes linked to the development of Vascular Dementia, with these changes beginning to present earlier than clinical diagnosis is currently possible. In this review, works focused on these early signs of Vascular Dementia are highlighted. However, recognizing these changes is difficult. Many computational systems have been proposed for the evaluation these early signs of Vascular Dementia. The chosen works have largely focused on utilizing sensors systems or algorithmic evaluation can be incorporated into a person’s environment to measure behavioral, and phycological metrics. This raw data can then be computationally analyzed to draw conclusions about the patterns of change surrounding the onset of Vascular Dementia. This compilation of works presents current a framework for investigating the various behavioral and physiological metrics as well as potential avenues for further investigating of sensor system and algorithmic design with the goal of enabling earlier Vascular Dementia detection.

Design of a Split-Ring Resonator Sensor for Near-Field Microwave Imaging

Metamaterials have been increasingly used in the past few decades in the design of novel microwave circuits and sensor systems. This paper deals with the design of a split-ring resonator (SRR) sensor for microwave nondestructive evaluation (NDE) applications. Building on prior work in this field, a modified design of the sensor is used for imaging composites. The tip of the sensing ring is extended, and a reference ring is introduced to tailor fit the sensor for imaging and NDE applications. A built-in calibration system, integration of multiple sensors (high and low frequencies), super resolution capability, and high-Q factor are some of the benefits of the sensor. This paper presents the design and development of the sensor system along with experimental results demonstrating the feasibility of the approach for detection of sub-wavelength defects in composites and additive manufactured metals.

All-fiber, thermo-optic liquid level sensor.

This paper proposes an all-optical-fiber sensor for continuous measurements of liquid levels. The proposed sensor utilizes an optically absorbing vanadium doped optical fiber, which is configured as a long-gauge, optically-heated, fiber-optic, Fabry-Perot interferometer that is immersed into the measured liquid. The sensor is excited cyclically by a medium-power 980 nm optical source, which induces periodic temperature variation and, consequently, optical path length modulation within the vanadium doped fiber. The amplitude of this path length variation depends on the liquid level and is measured by an interferometric approach. The relation between the liquid level and the amplitude of optical path length modulation caused by the fiber's temperature variation were investigated analytically, and the theoretical model proved to be in good agreement with the experimental results. Two versions of level sensors are demonstrated experimentally, the first with single-side optical heating power delivery and 0.45 m measurement range, and the second with dual-side power delivery and 1 m of operational measurement span. Experimental measurement level resolutions achieved for 0.45 m and 1m operational measurement span were approximately 2 and 3 mm, respectively. The simple and efficient design of sensor and signal interrogation system, the latter is based solely on a few widely available telecom components, provides straightforward opportunities for use of the proposed system in a variety of industrial applications.

Design and Simulation of an Integrated Wireless Capacitive Sensors Array for Measuring Ventricular Pressure.

This paper reports the novel design of a touch mode capacitive pressure sensor (TMCPS) system with a wireless approach for a full-range continuous monitoring of ventricular pressure. The system consists of two modules: an implantable set and an external reading device. The implantable set, restricted to a 2 × 2 cm2 area, consists of a TMCPS array connected with a dual-layer coil, for making a reliable resonant circuit for communication with the external device. The capacitive array is modelled considering the small deflection regime for achieving a dynamic and full 5–300 mmHg pressure range. In this design, the two inductive-coupled modules are calculated considering proper electromagnetic alignment, based on two planar coils and considering the following: 13.56 MHz frequency to avoid tissue damage and three types of biological tissue as core (skin, fat and muscle). The system was validated with the Comsol Multiphysics and CoventorWare softwares; showing a 90% power transmission efficiency at a 3.5 cm distance between coils. The implantable module includes aluminum- and polyimide-based devices, which allows ergonomic, robust, reproducible, and technologically feasible integrated sensors. In addition, the module shows a simplified and low cost design approach based on PolyMEMS INAOE® technology, featured by low-temperature processing.

Design and Implementation of Acoustic Sensing System for Online Early Fault Detection in Industrial Fans

Industrial fans play a critical role in manufacturing facilities, and a sudden shutdown of critical fans can cause significant disruptions. Ensuring early, effective, and accurate detection of fan malfunctions first requires confirming the characteristics of anomalies resulting from initial damage to rotating machinery. In addition, sensing and detection must rely on the use of sensors and sensing characteristics appropriate to various operational abnormalities. This research proposes an online industrial fan monitoring and fault detection technique based on acoustic signals as a physical sensing index. The proposed system detects and assesses anomalies resulting from preliminary damage to rotating machinery, along with improved sensing resolution bandwidth features for microphone sensors as compared to accelerometer sensors. The resulting Intelligent Prediction Integration System with Internet (IPII) is built to analyze rotation performance and predict malfunctions in industrial fans. The system uses an NI cRIO-9065 embedded controller and a real-time signal sensing module. The kernel algorithm is based on an acoustic signal enhancement filter (ASEF) as well as an adaptive Kalman filter (AKF). The proposed scheme uses acoustic signals with adaptive order-tracking technology to perform algorithm analysis and anomaly detection. Experimental results showed that the acoustic signal and adaptive order analysis method could effectively perform real-time early fault detection and prediction in industrial fans.

Design, Fabrication, and Implementation of an Array-Type MEMS Piezoresistive Intelligent Pressure Sensor System.

To meet the radiosonde requirement of high sensitivity and linearity, this study designs and implements a monolithically integrated array-type piezoresistive intelligent pressure sensor system which is made up of two groups of four pressure sensors with the pressure range of 0–50 kPa and 0–100 kPa respectively. First, theoretical models and ANSYS (version 14.5, Canonsburg, PA, USA) finite element method (FEM) are adopted to optimize the parameters of array sensor structure. Combing with FEM stress distribution results, the size and material characteristics of the array-type sensor are determined according to the analysis of the sensitivity and the ratio of signal to noise (SNR). Based on the optimized parameters, the manufacture and packaging of array-type sensor chips are then realized by using the standard complementary metal-oxide-semiconductor (CMOS) and microelectromechanical system (MEMS) process. Furthermore, an intelligent acquisition and processing system for pressure and temperature signals is achieved. The S3C2440A microprocessor (Samsung, Seoul, Korea) is regarded as the core part which can be applied to collect and process data. In particular, digital signal storage, display and transmission are realized by the application of a graphical user interface (GUI) written in QT/E. Besides, for the sake of compensating the temperature drift and nonlinear error, the data fusion technique is proposed based on a wavelet neural network improved by genetic algorithm (GA-WNN) for average measuring signal. The GA-WNN model is implemented in hardware by using a S3C2440A microprocessor. Finally, the results of calibration and test experiments achieved with the temperature ranges from −20 to 20 °C show that: (1) the nonlinear error and the sensitivity of the array-type pressure sensor are 8330 × 10−4 and 0.052 mV/V/kPa in the range of 0–50 kPa, respectively; (2) the nonlinear error and the sensitivity are 8129 × 10−4 and 0.020 mV/V/kPa in the range of 50–100 kPa, respectively; (3) the overall error of the intelligent pressure sensor system is maintained at ±0.252% within the hybrid composite range (0–100 kPa). The involved results indicate that the developed array-type composite pressure sensor has good performance, which can provide a useful reference for the development of multi-range MEMS piezoresistive pressure sensor.

Towards a Digital Earth: using archetypes to enable knowledge interoperability within geo-observational sensor systems design

Earth System Science (ESS) observational data are often inadequately semantically enriched by geo-observational information systems to capture the true meaning of the associated data sets. Data models underpinning these information systems are often too rigid in their data representation to allow for the ever-changing and evolving nature of ESS domain concepts. This impoverished approach to observational data representation reduces the ability of multi-disciplinary practitioners to share information in a computable way. Object oriented techniques that are typically employed to model data in a complex domain (with evolving domain concepts) can unnecessarily exclude domain specialists from the design process, invariably leading to a mismatch between the needs of the domain specialists, and how the concepts are modelled. In many cases, an over simplification of the domain concept is captured by the computer scientist. This paper proposes that two-level modelling methodologies developed by health informaticians to tackle problems of domain specific use-case knowledge modelling can be re-used within ESS informatics. A translational approach to enable a two-level modelling process within geo-observational sensor systems design is described. We show how the Open Geospatial Consortium’s (OGC) Observations & Measurements (O&M) standard can act as a pragmatic solution for a stable reference-model (necessary for two-level modelling), and upon which more volatile domain specific concepts can be defined and managed using archetypes. A rudimentary use-case is presented, followed by a worked example showing the implementation methodology and considerations leading to an O&M based, two-level modelling design approach, to realise semantically rich and interoperable Earth System Science based geo-observational sensor systems.

Ambulatory sensor for the monitoring of the edema circumference in lower limbs

The monitoring of geometrical variations in segments of the human body is currently not widely used due to the lack of suitable devices. For lower limbs, for example, a simple measuring tape is generally used to periodically measure key dimensions. This measurement approach, and the associated lack of reproducibility, is not compatible with ambulatory monitoring and it is further recognized that precise, standardized reference points are required for the more meaningful monitoring of the lower leg. The paper presents the design and realization of a new sensor system dedicated to the measurement of geometrical variations in the lower limbs, enabling the ambulatory monitoring of leg edemic swelling during daily activity. The sensor is based on an inductive loop directly integrated into a textile band and connected to a miniaturized electronic system which sends, via wireless transmission, the perimeter value of the leg (assuming that its shape is circular) to a laptop and in the near future, to a mobile phone. The inductive loop has been modeled using Matlab to predict the inductance value and determine the necessary parameters of the electronic circuit. The portable, ambulatory device enables the measurement of perimeters ranging from 25 cm to 33 cm, with an accuracy of 0.3 cm. Stability of the sensor over the time is very good (3.4% of the full scale). Hysteresis occurs when the textile is stretched between two extreme values which can be minimized by regular calibration of the system. The presented results are significantly better than those currently obtained using the traditional measuring tape.

Design of an Optical Pressure Measurement System for Intraocular Pressure Monitoring

This paper studies the design and application of an interferometric sensor system intended for measuring intraocular pressure. The system consists of a hermetically sealed, biocompatible, wireless, and powerless interferometric pressure sensor and a portable handheld reader. The interferometric pressure sensor consists of a 200 nm silicon nitride diaphragm, a $10~\mu \text{m}$ SU-8 spacer, and a $200~\mu \text{m}$ glass substrate. As monochromatic light is directed towards the sensor cavity, interference fringes between the silicon nitride diaphragm and the glass substrate form as a function of the applied pressure. In-vitro measurements show pressure in the range of 0–60 mmHg can be determined reliably with an accuracy of ±0.3 mmHg, while ex-vivo experiments using rabbit cornea showed an accuracy of ±0.6 mmHg. The resolution of the sensor is 0.2 mmHg. These results demonstrate the ability of the system to measure small changes in pressure, including intraocular pressure of glaucoma patients.