Orthogonal Sensors Research Articles

Can Fish and Cell Phones Teach Us about Our Health?

Biologging is a scientific endeavor that studies the environment and animals within it by outfitting the latter with sensors of their dynamics as they roam freely in their natural habitats. As wearable technologies advance for the monitoring of human health, it may be instructive to reflect on the successes and failures of biologging in field biology over the past few decades. Several lessons may be of value. Physiological sensors can "encode" for a wider number of states than the one explicitly targeted, although the limits of this are debatable. The combination of orthogonal sensors turns out to be critical to delivering a high value data set. Sensor fusion and engineering for longevity are also important for success. This Perspective highlights successful strategies for biologging that hold promise for human health monitoring.

Orthogonal Sensors for the Trace Detection of Explosives

There is a growing need for an electronic trace detection system that can continuously monitor explosives at trace levels in the vapor phase. Triacetone triperoxide (TATP) is a common explosive used by terrorists as the initiator or the energetic material in improvised explosive devices. TATP still goes largely undetected in many densely populated public venues. Currently, no detection system exists that is capable of continuously monitoring TATP, as well as nitrogen-based explosives such as 2,4-dinitrotoluene. We have demonstrated a thermodynamic sensor platform employing thin film microheaters and metal oxide catalysts that can detect TATP and 2,4-DNT at the parts per billion (ppb) level. The microheaters and catalysts were deposited onto ultrathin alumina ceramic substrates, which are responsible for extraordinary sensitivity. Recently, we have added a conductometric sensor platform to this thermodynamic platform to form an orthogonal sensor capable of interrogating the same catalyst using two different modalities. The orthogonal sensor probes the same catalyst using a thermodynamic protocol, as well as a conductometric protocol where electrical resistivity changes in the catalyst are measured as a function of analyte exposure. The advantages of this added orthogonality in terms of mitigating false-positives and negatives are described within.

Design of a Portable Orthogonal Surface Acoustic Wave Sensor System for Simultaneous Sensing and Removal of Nonspecifically Bound Proteins.

One challenge for current surface acoustic wave (SAW) biosensors is reducing nonspecific adsorption. A device propagating Rayleigh and shear horizontal surface acoustic waves in orthogonal directions fabricated in ST quartz has the capability of achieving simultaneous detection and nonspecific binding (NSB) protein removal. Current measurement methods for a SAW sensor system based on this device require large-size and expensive equipment such as a vector network analyzer (VNA), signal generator, and frequency counter, which are not suitable for portable, especially point-of-care, applications. In this work, a portable platform based on a direct digital synthesizer (DDS) is investigated for the orthogonal SAW sensor, integrating signal synthesis, gain control, phase/amplitude measurement, and data processing in a small, portable electronic system. This prototype was verified for both stability and repeatability, and the results matched very well with VNA measurements. Finally, system performance in real-time sensing and NSB removal was evaluated.

Method of designing a six-axis force sensor for stiffness decoupling based on Stewart platform

This paper presents a design method that yields forces/torques stiffness decoupling for six-axis force sensors based on Stewart platform. The conditions of forces/torques stiffness decoupling are analyzed and then a relationship between the stiffness decoupling and the postures of the elastic limbs is built. Through the relationship, a method of designing stiffness decoupled force sensors is proposed. In order to verify the performance of stiffness decoupling, a tri-three orthogonal sensor which can withstand large axial force/torque is designed, manufactured, and analyzed. Results show that the six-axis force sensor has lower error, so the method of designing decoupled six-axis force sensors can provide reliable guidance for sensor structure design.

Wearable Electrochemical Microneedle Sensor for Continuous Monitoring of Levodopa: Toward Parkinson Management.

Levodopa is the most effective medication for treating Parkinson's disease (PD). However, because dose optimization is currently based on patients' report of symptoms, which are difficult for patients to describe, the management of PD is challenging. We report on a microneedle sensing platform for continuous minimally invasive orthogonal electrochemical monitoring of levodopa (L-Dopa). The new multimodal microneedle sensing platform relies on parallel simultaneous independent enzymatic-amperometric and nonenzymatic voltammetric detection of L-Dopa using different microneedles on the same sensor array patch. Such real-time orthogonal L-Dopa sensing offers a built-in redundancy and enhances the information content of the microneedle sensor arrays. This is accomplished by rapid detection of L-Dopa using square-wave voltammetry and chronoamperometry at unmodified and tyrosinase-modified carbon-paste microneedle electrodes, respectively. The new wearable microneedle sensor device displays an attractive analytical performance with the enzymatic and nonenzymatic L-Dopa microneedle sensors offering different dimensions of information while displaying high sensitivity (with a low detection limit), high selectivity in the presence of potential interferences, and good stability in artificial interstitial fluid (ISF). The attractive analytical performance and potential wearable applications of the microneedle sensor array have been demonstrated in a skin-mimicking phantom gel as well as upon penetration through mice skin. The design and attractive analytical performance of the new orthogonal wearable microneedle sensor array hold considerable promise for reliable, continuous, minimally invasive monitoring of L-Dopa in the ISF toward optimizing the dosing regimen of the drug and effective management of Parkinson disease.

Calibration of Skew Redundant Sensor Configurations in the Presence of Field Alignment Errors

This paper is a nontrivial extension of prior work on rate and position table leveling and inertial and magnetic sensors calibration techniques. The table leveling is essential for a class of calibration techniques using known stimuli, herein referred to as classical techniques. Such techniques are effective for the calibration of inertial sensors as they usually lead to closed-form solutions and body frame calibrations. However, the classical techniques are negatively affected by table leveling and azimuth orientation errors or by changes in the direction of the reference field. These errors are collectively referred to as field alignment errors in this paper. The impact of field alignment errors is usually avoided by using reference-free calibrations which rely on satisfying the invariance of the field modulus constraint. This constraint works well for orthogonal sensor triads as it leads to unique solutions. There is a great body of work dedicated to studying such calibration techniques for orthogonal sensor triads. However, redundant sensor configurations have too many degrees of freedom to satisfy the invariance of the modulus constraint; therefore, require special techniques. This paper introduces a novel approach that can be used to produce body frame calibrations for skew redundant sensor configurations in the presence of field alignment errors. Unlike prior work, no simplifying assumptions are made on the redundant sensor configuration (e.g., multiple orthogonal triads). The new method is showcased for the dodecahedron configuration, one of the most complex skew redundant configurations.

EC probe with orthogonal excitation coils and TMR sensor for CFRP inspection

EC probe with orthogonal excitation coils and TMR sensor for CFRP inspection

High-Sensitivity Real-Time Tracking System for High-Speed Pipeline Inspection Gauge.

Real-time tracking of pipeline inspection gauges (PIGs) is an important aspect of ensuring the safety of oil and gas pipeline inline inspections (ILIs). Transmitting and receiving extremely low frequency (ELF) magnetic signals is one of the preferred methods of tracking. Due to the increase in physical parameters of the pipeline including transportation speed, wall thickness and burial depth, the ELF magnetic signals received are short transient (1-second duration) and very weak (10 pT), making the existing above-ground-marker (AGM) systems difficult to operate correctly. Based on the short transient very weak characteristics of ELF signals studied with a 2-D finite-element method (FEM) simulation, a data fusion model was derived to fuse the envelope decay rates of ELF signals by a least square (LS) criterion. Then, a fast-decision-tree (FDT) method is proposed to estimate the fused envelope decay rate to output the maximized orthogonal signal power for the signal detection through a determined topology and a fast calculation process, which was demonstrated to have excellent real-time detection performance. We show that simulation and experimental results validated the effectiveness of the proposed FDT method, and describe the high-sensitivity detection and real-time implementation of a high-speed PIG tracking system, including a transmitter, a receiver, and a pair of orthogonal search coil sensors.

Estimating rotor unbalance from a single run-up and using reduced sensors

The earlier model-based rotor mass unbalance estimation methods have used two orthogonal sensors per bearing pedestal. It is generally believed that the vibration measurement at two orthogonal directions provides the bigger picture of machine dynamical behaviour. However, in the present study, the concept of the earlier method is applied again but with using only one sensor at a bearing pedestal, rather than the usual pair of sensors arranged in orthogonal directions. The significant reduction in the number of vibration sensors without necessarily compromising the valuable information required for the diagnosis is of great benefit to industries that have huge rotating machines with numerous bearings. The reason is that the computational effort in the complex signal processing will reduce considerably and hence the machine down time will reduce significantly. The concept is applied to experimental rigs with single as well as multiple balancing planes and supported on either side through a stiff ball bearing on a somewhat flexible foundation. The paper presents the experimental apparatus, unbalance estimation and comparison of several unbalance estimations of various scenarios. The results indicate the potentials of the proposed technique for practical applications.

Orthogonal gas sensor arrays by chemoresistive material design.

Gas sensor arrays often lack discrimination power to different analytes and robustness to interferants, limiting their success outside of research laboratories. This is primarily due to the widely sensitive (thus weakly-selective) nature of the constituent sensors. Here, the effect of orthogonality on array accuracy and precision by selective sensor design is investigated. Therefore, arrays of (2-5) selective and non-selective sensors are formed by systematically altering array size and composition. Their performance is evaluated with 60 random combinations of ammonia, acetone and ethanol at ppb to low ppm concentrations. Best analyte predictions with high coefficients of determination (R2) of 0.96 for ammonia, 0.99 for acetone and 0.88 for ethanol are obtained with an array featuring high degree of orthogonality. This is achieved by using distinctly selective sensors (Si:MoO3 for ammonia and Si:WO3 for acetone together with Si:SnO2) that improve discrimination power and stability of the regression coefficients. On the other hand, arrays with collinear sensors (Pd:SnO2, Pt:SnO2 and Si:SnO2) hardly improve gas predictions having R2 of 0.01, 0.86 and 0.28 for ammonia, acetone and ethanol, respectively. Sometimes they even exhibited lower coefficient of determination than single sensors as a Si:MoO3 sensor alone predicts ammonia better with a R2 of 0.68. Graphical abstract Conventional arrays (red) with weakly-selective sensors span a significantly smaller volume in the analyte space than arrays containing distinctly-selective sensors (orthogonal array, green). Orthogonal arrays feature better accuracy and precision than conventional arrays in mixtures of ammonia, acetone and ethanol.

Multi-year measurements of the underwater noise field directionality in the shallow Beaufort Sea during open-water and drifting ice flow conditions

Between 2007 and 2014, over 35 Directional Autonomous Seafloor Acoustic Recorders (DASARs) were deployed over a 280 km swath of the Beaufort Sea continental shelf (20–55 m depth) during the open-water season, in order to monitor the fall (westward) bowhead whale migration. DASARs have one omnidirectional pressure sensor and two orthogonal particle motion sensors, which permit instantaneous measurements of the azimuths of both transient signals and continuous noise between 20 and 500 Hz. The lack of significant shipping or industrial noise in this region provided a rare opportunity to directly measure the properties of wind-driven noise in expanding ice-free regions. Here, we map the azimuthal directionality of the diffuse Beaufort ambient noise field as a function of frequency and space across seven seasons. The dominant directionality of the diffuse ambient noise field varied strongly with frequency and was highly correlated with the received power spectral density. Certain directional features of the ambient noise field remained stable over seven deployment seasons, suggesting that judicious processing of the ambient noise soundscape could provide underwater navigational information in arctic waters. The influence of local drifting floes and sheets of ice on this directionality is also examined. [Work sponsored by ONR.]

The Plasma Wave Experiment (PWE) on board the Arase (ERG) satellite

The Exploration of energization and Radiation in Geospace (ERG) project aims to study acceleration and loss mechanisms of relativistic electrons around the Earth. The Arase (ERG) satellite was launched on December 20, 2016, to explore in the heart of the Earth’s radiation belt. In the present paper, we introduce the specifications of the Plasma Wave Experiment (PWE) on board the Arase satellite. In the inner magnetosphere, plasma waves, such as the whistler-mode chorus, electromagnetic ion cyclotron wave, and magnetosonic wave, are expected to interact with particles over a wide energy range and contribute to high-energy particle loss and/or acceleration processes. Thermal plasma density is another key parameter because it controls the dispersion relation of plasma waves, which affects wave–particle interaction conditions and wave propagation characteristics. The DC electric field also plays an important role in controlling the global dynamics of the inner magnetosphere. The PWE, which consists of an orthogonal electric field sensor (WPT; wire probe antenna), a triaxial magnetic sensor (MSC; magnetic search coil), and receivers named electric field detector (EFD), waveform capture and onboard frequency analyzer (WFC/OFA), and high-frequency analyzer (HFA), was developed to measure the DC electric field and plasma waves in the inner magnetosphere. Using these sensors and receivers, the PWE covers a wide frequency range from DC to 10 MHz for electric fields and from a few Hz to 100 kHz for magnetic fields. We produce continuous ELF/VLF/HF range wave spectra and ELF range waveforms for 24 h each day. We also produce spectral matrices as continuous data for wave direction finding. In addition, we intermittently produce two types of waveform burst data, “chorus burst” and “EMIC burst.” We also input raw waveform data into the software-type wave–particle interaction analyzer (S-WPIA), which derives direct correlation between waves and particles. Finally, we introduce our PWE observation strategy and provide some initial results.

Sniffing Entrapped Humans with Sensor Arrays.

Earthquakes are lethal natural disasters frequently burying people alive under collapsed buildings. Tracking entrapped humans from their unique volatile chemical signature with hand-held devices would accelerate urban search and rescue (USaR) efforts. Here, a pilot study is presented with compact and orthogonal sensor arrays to detect the breath- and skin-emitted metabolic tracers acetone, ammonia, isoprene, CO2, and relative humidity (RH), all together serving as sign of life. It consists of three nanostructured metal-oxide sensors (Si-doped WO3, Si-doped MoO3, and Ti-doped ZnO), each specifically tailored at the nanoscale for highly sensitive and selective tracer detection along with commercial CO2 and humidity sensors. When tested on humans enclosed in plethysmography chambers to simulate entrapment, this sensor array rapidly detected sub-ppm acetone, ammonia, and isoprene concentrations with high accuracies (19, 21, and 3 ppb, respectively) and precision, unprecedented by portable sensors but required for USaR. These results were in good agreement (Pearson’s correlation coefficients ≥0.9) with benchtop selective reagent ionization time-of-flight mass spectrometry (SRI-TOF-MS). As a result, an inexpensive sensor array is presented that can be integrated readily into hand-held or even drone-carried detectors for first responders to rapidly screen affected terrain.

Vector sensor cross-spectral density for surface noise in a stratified ocean-Formulas for arbitrary sensor geometries.

The cross-spectral density between pressure and particle velocity channels of two vector sensors with arbitrary orientation and separation is developed for a noise field consisting of directional sources distributed on a plane. Equations for arbitrary sensor orientations are necessary because cross-spectral density is an averaged product of two sensors' outputs that cannot be projected onto another direction after it is calculated. This prevents the use of existing methods, which calculate cross-spectral density for orthogonal particle velocity sensors, for sensors with different orientations. Analytic solutions to special cases for azimuthally symmetric environments and orthogonal velocity sensor orientations are developed and compared to previous results. The general equations are stated in a form suitable for use with any propagation model that produces Green's functions for pressure and orthogonal particle velocity components. Simulation examples demonstrate how sensor geometry and propagation conditions affect vector sensor array performance for wind-driven surface noise in deep and shallow water environments. Vector sensor beamforming is shown to provide additional gain in these directional noise fields as compared to isotropic noise.

Алгоритм начальной инициализации кватерниона пространственной ориентации в параметрах Родрига-Гамильтона

Introduction. The correction time reduction for the spatial orientation evaluation of a solid under the orientation system initiation is considered. Solid spatial orientation is measured by the integrated values from three orthogonal angular speed sensors. Difference between the actual spatial orientation and the orientation estimated by sensors is adjusted due to the data obtained from other sensors, such as accelerometers and magnetometers. Major existing algorithms deduct data acquired from accelerometers and magnetometers from the evaluation of angular rate through the correction factor thus correcting the spatial orientation assessment error. The higher the solid inclination angle in relation to horizon when the orientation system is switched on, the greater the spatial orientation error is. The algorithm presented herein corrects the spatial orientation evaluation in quaternion components without angular rate sensors which allows minimizing the spatial orientation assessment error within shorter time in comparison with the existing algorithms. Materials and Methods. To implement the correction algorithm, the MPU6050 sensor is used. It is made with microelectromechanical technology, and its body includes three orthogonally located angular velocity sensors and three orthogonally located accelerometers. The output data from MPU6050 sensor is processed by dsPIC33EP256MU806 microchip. The spatial orientation is calculated by the Rodrigues-Hamilton parameters in the quaternion components. The result is input to the Matlab software package which executes the program of visualizing the dependencies on the time of four quaternion components graphically. Research Results . In existing algorithms that use the Rodrigues-Hamilton parameters, at the initial initialization of the orientation system, it is suggested to increase the correction factor, or to use the trigonometric formulas to find the Euler angles and translate them into the RodriguesHamilton parameters. In the first case, the initial initialization time remains sufficiently long, in the second case, due to the use of Euler angles, a phenomenon of “gimbal lock” can be observed. The proposed algorithm performs the initial initialization in a time equivalent to the initialization time in the Euler angles parameters, but it applies only the RodriguesHamilton parameters. Discussion and Conclusions. Using the proposed algorithm will allow a minimum of 5-fold reduction in the initial initialization time of the spatial orientation quaternion. In consequence, the total time required for activating the system will be also reduced due to the fact that the initial initialization is necessary every time the orientation system is switched on. For the correct determination of the spatial orientation according to the proposed algorithm, the necessary condition is the absence of any acceleration on the body other than the gravitational acceleration because the initialization occurs only upon the accelerometer readings.

A Novel System for Yarn Cross-Section Analysis Based on Dual Orthogonal CCD Sensors

ABSTRACTAs a basis for yarn evenness measurement, a novel method based on two orthogonal charge-coupled device (CCD) sensors has been devised. We present a system for analyzing yarn evenness from the coefficient of variation of yarn perimeter, treating the yarn cross-sectional shape like an ellipse with uneven edges. The system architecture, algorithm flow, mathematical principle, and the experimental validation of the proposed technique are presented. A comparison between the proposed method and the conventional Uster Tester 5 and Lawson-Hemphill was made. Results agree quite well with existing methods hence can be implemented as an alternative technique for yarn evenness quantification.

Complete Calibration of Three-Axis Strapdown Magnetometer in Mounting Frame

Three-axis magnetometers (TAMs) are widely used in connection with vehicle navigation systems and many other engineering applications. Technological limitations in sensor manufacturing and unwanted magnetic fields will corrupt the measurements of TAMs. In this paper, a new method is proposed to calibrate strapdown magnetometer in sensor frame. A complete error model, including instrumentation errors (body frame misalignment, scale factors, non-orthogonality, and offsets) and magnetic deviations (soft and hard iron), is elaborated. The calibration process is divided into two steps. The first step is providing a consistent solution to the ellipsoid fitting problem using a non-linear least squares estimator and genetic algorithm. The experimental system mainly consists of tri-axis HMC5843 AMR sensor and proton magnetometer. The true scalar value of magnetic field was obtained with proton magnetometer. Simulated results show that the error average of nonlinear least square is much lower than the genetic algorithm. The results of the calibration algorithm in the first step provide magnetic readings in the calibration frame. In the next step, the three calibrated axes of the given magnetometer, which are nominally orthogonal, are aligned into a true orthogonal sensor mounting frame by offering a rigorous vector analysis of rotational kinematics named vector product operations. In order to determine the magnetometer misalignment in the mounting frame, a surface plate is used as the main reference plate. Therefore, the calibration and alignment methodology is formulated in the sensor frame, without resorting to external information or models about the magnetic field.

Long-term measurements of the ice-free underwater noise field directionality in the shallow Beaufort Sea

Between 2007 and 2014, over 35 Directional Autonomous Seafloor Acoustic Recorders (DASARs) were deployed over a 280 km swath of the Beaufort Sea continental shelf (20-55 m depth) during the open-water season, in order to monitor the westward bowhead whale migration. DASARs have one omnidirectional pressure sensor and two orthogonal particle velocity sensors that permit instantaneous measurement of the azimuths of both transient signals and continuous noise between 20 and 500 Hz, including diffuse wind-driven ocean noise. The lack of significant shipping or industrial noise in this region provides a rare opportunity to directly measure the properties of wind-driven noise in expanding ice-free regions. Here, we map the azimuthal directionality of the diffuse Beaufort ambient noise field as a function of frequency and location across all seven seasons. The dominant directionality of the diffuse ambient noise field varies strongly with frequency and is highly correlated with the received power spectral density. Certain directional features of the ambient noise field remained stable over seven deployment seasons, suggesting that judicious processing of the ambient noise soundscape could provide underwater navigational information in arctic waters. [Work sponsored by ONR.]

Passive detection of low frequency sources using vector sensor channel cross correlation

Acoustic vector sensors consisting of an omnidirectional hydrophone and three orthogonal velocity sensors offer new opportunities for passive detection of acoustic sources at low frequencies. In the frequency range from 10 to 300 Hz, the predominant noise sources in the ocean are surface wave action and distant shipping. Omnidirectional hydrophones are affected by both noise types whereas vertically-oriented velocity sensors are more affected by surface wave action, and horizontally-oriented velocity sensors are more affected by distant shipping. Under these ambient conditions, when no source is present, the vector sensor channels have low cross-correlation levels. When a source is present, propagation conditions cause an increase in correlation between all vector channels. This increase is measurable in the magnitude and phase of the correlation coefficients between each channel pair, which forms the basis of an algorithm for detecting acoustic sources. This paper presents the response of an acoustic vector sensor to both types of ambient noise and demonstrates the change in correlation when a source is present. These noise and signal responses determine a detection threshold for a single frequency source for desired probabilities of detection and false alarm.

Orthogonal lipid sensors determine differential signaling roles of PtdIns(3,4,5)P3 and PtdIns(3,4)P2

Activation of Class I phosphoinositide 3‐kinase (PI3K) leads to formation of PtdIns(3,4,5)P3 and PtdIns(3,4)P2. Although many pleckstrin homology (PH) domains bind both PtdIns(3,4,5)P3 and PtdIns(3,4)P2, spatiotemporal dynamics of these lipids and their differential signaling roles have not been fully defined. To address these questions, we developed orthogonal ratiometric sensors for PtdIns(3,4,5)P3 and PtdIns(3,4)P2 that allowed the simultaneous, spatiotemporally resolved in situ quantification of these lipids in mammalian cells upon growth factor stimulation. Quantitative correlation of spatiotemporal dynamics of PtdIns(3,4,5)P3 and PtdIns(3,4)P2 with the differential plasma membrane recruitment and activation of Akt isoforms shows how differentially PtdIns(3,4,5)P3 and PtdIns(3,4)P2 activate Akt isoforms. Further structural and biophysical studies provided the mechanistic basis for these roles and led to the development of Akt isoform‐selective inhibitors.