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Mild Cognitive Impairment (MCI) is a cognitive state frequently observed in older adults, characterized by significant alterations in memory, thinking, and reasoning abilities that extend beyond typical cognitive decline. It is worth noting that around 10–15% of individuals with MCI are projected to develop Alzheimer's disease, effectively positioning MCI as an early stage of Alzheimer's. In this study, a novel approach is presented involving the utilization of eXtreme Gradient Boosting to predict the onset of Alzheimer's disease during the MCI stage. The methodology entails utilizing data from the Alzheimer's Disease Neuroimaging Initiative (ADNI). Through the analysis of longitudinal data, spanning from the baseline visit to the 12-month follow-up, a predictive model was constructed. The proposed model calculates, over a 36-month period, the likelihood of progression from MCI to Alzheimer's disease, achieving an accuracy rate of 85%. To further enhance the precision of the model, this study implements feature selection using the Recursive Feature Elimination technique. Additionally, the Shapley method is employed to provide insights into the model's decision-making process, thereby augmenting the transparency and interpretability of the predictions. [ABSTRACT FROM AUTHOR]

In this paper, a novel high temperature superconducting (HTS) thin film device as planar levitator and fault current limiter is firstly proposed and tested. Nowadays, planar magnetic levitation (maglev) levitator (PML) employed in planar maglev system is a promising high-precision positioning mechanism for modern high-end industrial fields, due to the attractive features of noncontact, zero friction, high precision, light weigh, simple structure, high reliability, fast response and fewer interfering factors, etc. In contrast to other maglev technologies, HTS maglev technology has the advantages of passive self stabilization levitation, light weight, high vacuum gain, simple structure, energy saving and no electromagnetic pollution, etc. Thus, the PML fabricated by HTS thin film can further simplify the system control strategy and improve operation efficiency. In this paper, we designed and fabricated the double sided YBa2Cu3O7-x thin film based PML and analyzed its levitation force characteristics. Besides, we also tested its fault current limiting performance, which can be employed to limit the fault current in the planar maglev system. It can be found from the experimental results that, the HTS-PML can offer the levitation force more than 400 kN/m3 and 100 N/kg, meanwhile, it can also generate the quench resistance more than 15 Ω to limit the fault current effectively. This work is perspective for the future planar maglev applications, to improve the system compactness, stability, reliability, miniaturization and lightweight with multifunctional integrated design. [ABSTRACT FROM AUTHOR]

Persistent Scatterer InSAR (PS-InSAR) technology enables the monitoring of displacement in millimeters. However, without the use of external parameter correction, radar scatterers exhibit poor geopositioning precision in meters, limiting the correlation between observed deformation and the actual structure. The integration of PS-InSAR datasets and building databases is often overlooked in deformation research. This paper presents a novel strategy for matching between PS points and building contours based on spatial distribution characteristics. A convex hull is employed to simplify the building outline. Considering the influence of building height and incident angle on geometric distortion, an adaptive buffer zone is established. The PS points on a building are further identified through the nearest neighbor method. In this study, both ascending and descending TerraSAR-X orbit datasets acquired between 2016 and 2019 were utilized for PS-InSAR monitoring. The efficacy of the proposed method was evaluated by comparing the PS-InSAR results obtained from different orbits. Through a process of comparison and verification, it was demonstrated that the matching effect between PS points and building contours was significantly enhanced, resulting in an increase of 29.2% in the number of matching PS points. The results indicate that this novel strategy can be employed to associate PS points with building outlines without the need for complex calculations, thereby providing a robust foundation for subsequent building risk assessment. [ABSTRACT FROM AUTHOR]

A novel monolithic compliant Lorentz-force-driven XY nanopositioning system (MCLNS) is designed, analyzed, and experimentally assessed with the aim of high-resolution positioning across a large workspace. A double-symmetric Lorentz-force actuator (DSLA) with the benefits of zero friction, high thrust, and large stroke is proposed to generate the actuation force. Correspondingly, a monolithic four-prismatic parallel compliant mechanism (4P-PCM) is exploited to transmit the actuation motion to the central platform and minimize the parasitic motion. The unique integration of four DSLAs and one 4P-PCM make the proposed MCLNS possess compact structure and stable performance. The characterization of the MCLNS is formulated by a specially established analytical model and validated by finite-element analysis simulation and experimental tests. Experimental studies show that the workspace of the MCLNS prototype is large than 0.87 × 0.87 mm2 and the positioning resolution of the MCLNS prototype is better than 9 nm. By means of a nonlinear forward proportional integral derivative control strategy, the maximum contouring error of the MCLNS is maintained within 2.7% while tracking a 1257 μ m s−1 circular trajectory. [ABSTRACT FROM AUTHOR]

Development of bulk acoustic wave filters with ultra-wide pass bands and operating at high frequencies for 5th and 6th generation telecommunication applications and micro-scale actuators, energy harvesters and sensors requires lead-free piezoelectric thin films with high electromechanical coupling and compatible with Si technology. In this paper, the epitaxial growth of 36°Y-X and 30°X-Y LiNbO3 films by direct liquid injection chemical vapour deposition on Si substrates by using epitaxial SrTiO3 layers, grown by molecular beam epitaxy, has been demonstrated. The stability of the interfaces and chemical interactions between SrTiO3, LiNbO3 and Si were studied experimentally and by thermodynamical calculations. The experimental conditions for pure 36°Y-X orientation growth have been optimized. The piezoelectricity of epitaxial 36°Y-X LiNbO3/SrTiO3/Si films was confirmed by means of piezoelectric force microscopy measurements and the ferroelectric domain inversion was attained at 85 kV.cm−1 as expected for the nearly stoichiometric LiNbO3. According to the theoretical calculations, 36°Y-X LiNbO3 films on Si could offer an electromechanical coupling of 24.4% for thickness extension excitation of bulk acoustic waves and a comparable figure of merit of actuators and vibrational energy harvesters to that of standard PbZr1− x Ti x O3 films. [ABSTRACT FROM AUTHOR]

This study presents a method to enhance data processing by integrating a unidirectional analogue artificial neuromorphic memristor device with a piezoelectric nanogenerator, taking inspiration from biological information processing. A self‐powered unidirectional neuromorphic resistive memory device is proposed, comprising an ITO/ZnO/Yb2O3/Au structure combined with a high‐sensitivity piezoelectric nanogenerator (PENG) ITO/ZnO/Al. The memristor device is operated at a voltage sweep of ±4 V with a low operating current in a range of 1.4 µA. The filament formation is studied using a conductive mode atomic force microscope. The integration enables the creation of a self‐powered artificial sensing system that converts mechanical stimuli from the PENG into electrical signals, which are subsequently processed by analogue unidirectional neuromorphic device to mimic the functionality of a neuron without requiring additional circuitry. This emulation encompasses crucial functions such as potentiation, depression, and synaptic plasticity. Furthermore, this study highlights the potential for hardware implementations of neural networks with a weight change of memristor device with nonlinearity (NL) of potentiation and depression of 1.94 and 0.89, respectively, with an accuracy of 93%. The outcomes of this research contribute to the progress of next‐generation low‐power, self‐powered unidirectional neuromorphic perception networks with correlated learning and trainable memory capabilities. [ABSTRACT FROM AUTHOR]

Electrostatic micro electro mechanical system (MEMS) as an actuator is one of the most widely used actuators in micro dimension systems. Due to the high nonlinear characteristics in the micro actuator's model, nanopositioning has been a challenging problem for researchers. In addition, the system is subject to uncertainties associated with the system's unknown parameters and un‐modelled dynamics. Thus, to overcome these problems and achieve precise positioning a robust non‐linear control method is required. In this research, an optimal voltage control algorithm is initially designed utilizing the nonlinear predictive control approach. The Taylor expansion sequence is used to estimate the final position of the parallel plate actuator. To approximate unknown disturbances, a radial basis function neural network (RBFNN) has been designed. The estimations made were used in updating the control input in the previous step, and the obtained results showed an increase in the robustness of the designed controller. The stability of the closed‐loop system is also analyzed. Finally, a comparison is accomplished between the potential of the proposed controller and that of the feedback linearization and sliding mode controllers. The obtained results indicate better performance and robustness of the suggested controller. [ABSTRACT FROM AUTHOR]

High-precision indoor positioning technology is regarded as one of the core components of artificial intelligence (AI) and Internet of Things (IoT) applications. Over the past decades, society has observed a burgeoning demand for indoor location-based services (iLBSs). Concurrently, ongoing technological innovations have been instrumental in establishing more accurate, particularly meter-level indoor positioning systems. In scenarios where the penetration of satellite signals indoors proves problematic, research efforts focused on high-precision intelligent indoor positioning technology have seen a substantial increase. Consequently, a stable assortment of location sources and their respective positioning methods have emerged, characterizing modern technological resilience. This academic composition serves to illuminate the current status of meter-level indoor positioning technologies. An in-depth overview is provided in this paper, segmenting these technologies into distinct types based on specific positioning principles such as geometric relationships, fingerprint matching, incremental estimation, and quantum navigation. The purpose and principles underlying each method are elucidated, followed by a rigorous examination and analysis of their respective technological strides. Subsequently, we encapsulate the unique attributes and strengths of high-precision indoor positioning technology in a concise summary. This thorough investigation aspires to be a catalyst in the progression and refinement of indoor positioning technologies. Lastly, we broach prospective trends, including diversification, intelligence, and popularization, and we speculate on a bright future ripe with opportunities for these technological innovations. [ABSTRACT FROM AUTHOR]

Establishing a novel design and accurate analytical models for XY nanopositioning stages based on voice coil motor (VCM) actuators is critical to achieving an optimal working performance. To overcome the existing design challenges of 2-degree-of-freedom guiding mechanisms, a four-layer structure composed of L-shaped spatial double parallelogram flexure mechanisms was proposed for the magnetic stage, which exhibits light weight and inhibits parasitic and decoupled motions. The guiding mechanisms were modeled by the compliance matrix method. Thereafter, by combining an electromagnetic model for the VCMs with the equivalent magnetic network method, an electromagnetic–mechanical coupling optimization method with multiple constraints was proposed for the stage to achieve a millimeter-range motion with a maximized natural frequency. The mechanical and electromagnetic performances were then verified by finite element analysis software. The optimized prototype was tested with a stroke of ±3.41 and ±3.08 mm for X axis and Y axis, respectively, a closed-loop resolution of 100 nm for X axis and 150 nm for Y axis, and a resonant frequency of 11.75 Hz for both axes. The tracking of a 0.1 Hz spiral of Archimedes achieved a maximum tracking error of 2.9%. [ABSTRACT FROM AUTHOR]

This work describes the development of a vehicle state estimator, designed to be employed onboard in real-time, based on the data acquisitions already available within the vehicle CAN bus infrastructure. The proposed estimation algorithm, taking into account the suspension elasto-kinematics, the longitudinal, lateral and combined dynamics of the tyres as well as the aligning interaction torques at the ground, represents at the current stage a significantly complete tool, since it also provides an estimation of road slope and banking angles, generalising the adoption of the presented vehicle model even on highly inclined roads. A further advantage of the presented estimator consists of its capability to identify in real-time and with a good level of accuracy the tyre/road interaction physical characteristics in terms of grip and cornering stiffness. [ABSTRACT FROM AUTHOR]

Over the past decade, the demand and research for indoor localization have burgeoned and Wi-Fi fingerprinting approach has been widely considered because it is cheap and accessible. However, most existing methods lack in terms of positioning accuracy and high computational complexity. To cope with these issues, we formulate a two-stage, coarse and accurate positioning narrow-down approach (NDA). Furthermore, a three-step source domain refinement (SDR) scheme that involves outlier removal, stable AP's weight enhancement, and a data averaging technique by applying the K-means clustering algorithm is also proposed. The collaboration of SDR scheme with the training data selection, area division, and overlapping schemes reduces the computational complexity and improves coarse positioning accuracy. The effect of the proposed SDR scheme on the performance of the support vector machine (SVM) and random forest algorithms is also presented. In the final/accurate positioning phase, a set of lightweight neural networks (DNNs), trained on different sub-areas, predict the user's location. This approach significantly increases positioning accuracy while reducing the online computational complexity at the same time. The experimental results show that the proposed approach outperforms the best solutions presented in the literature. [ABSTRACT FROM AUTHOR]

Ionospheric delay is one of the most dominant error sources in GNSS fast relative positioning, especially for RTK positioning of medium and long baselines, which directly affects the ambiguity fixing successful rate and positioning accuracy. The strategy of combining ionospheric correction based on multi-reference station network with ionospheric weighted model is still one of the most effective methods for precise relative positioning. In this paper, a method of ionospheric weighted calibration model is presented. By using a large-scale reference station network at a certain period of time with ionospheric disturbance to obtain the prior ionospheric information required by the user, the GNSS precision relative positioning performance of the ionosphere-weighted calibration model in complex scenarios (the accuracy of prior ionospheric information will be reduced due to large-scale reference station network and ionospheric active scene) was systematically evaluated. The experimental results show that the ionosphere-weighted calibration (IWC) method can effectively reduce the influence of excessive ionospheric modeling residual on the positioning results, and significantly improve the fixed rate and positioning accuracy of RTK. Compared with the traditional ionosphere-fixed model based on virtual reference station (VRS) technology, the three-dimensional accuracy and fixed rate of the six rover stations are improved by 56% and 33.5% on average. Secondly, the prior ionospheric constraint intensity in IWC mode is controllable, which can effectively balance the relationship between initialization speed and positioning accuracy. On average, 94.3% of the time period of the six rover stations can complete the initialization and fixing within 10 epochs, which can basically meet the requirements of fast positioning. In addition, IWC model can ensure higher accuracy and better maintain fixed solution state after the ionospheric parameter convergence is completed. In the ionospheric disturbance stage, after a period of parameter convergence, high fixed rate and positioning accuracy can still be guaranteed. [ABSTRACT FROM AUTHOR]

Sustainable power supply via triboelectric nanogenerator (TENG) is attractive for self‐powered actuation systems in the era of the Internet of Things (IoTs). Herein, a low‐power actuation scheme enabled by the multilayered TENG for piezoelectric actuators, including the stack, unimorph, and micro‐fiber composite (MFC) actuator, is reported. The working principles of TENG‐powered piezoelectric actuators and their displacement characteristics in direct current (DC) and alternating current (AC) modes are theoretically investigated. Compared with conventional high‐voltage power sources, the multilayered TENG delivers a maximum power of only 10.17 mW, providing a low‐power alternative for piezoelectric actuator with self‐powered capability and operational safety. Meanwhile, the hysteresis of the stack actuator that is critical in precise positioning control is reduced by 58.1%. A precise positioning system is demonstrated by utilizing the TENG‐powered stack actuator as an object stage for microscope focusing applications. The feasibility of vibration control with a 76.7% reduction in vibration amplitude is also verified via two TENG‐powered MFC actuators. A rectifying control circuit comprising the rectifier and gas discharging tube is established to implement AC–DC conversion and discharging control, achieving a larger displacement of the unimorph actuator. The TENG‐powered piezoelectric micropump demonstrates its potential application in liquid transport through straightforward operation. [ABSTRACT FROM AUTHOR]

In the past few decades, the Time Difference of Arrival location technology in distributed high‐frequency surface wave radar has attracted wide attention due to its simple system, low cost, and higher positioning accuracy. Based on the time difference direction‐finding algorithm, this article presents new mathematical expressions of geometric dilution of precision in the Time Difference of Arrival positioning systems. The time difference direction‐finding reveals that the angle measurements are accurate for any length of baseline. Then the differences in geometric dilution of precision between the proposed algorithm and traditional method are analysed. Time difference direction‐finding algorithm can improve positioning accuracy without additional target information. Compared with the traditional method, the proposed algorithm can improve the positioning accuracy of partial observation areas under the same radar measurement system. The simulation results are presented to demonstrate the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Due to the blockage of satellite signals by the buildings and other structures, the high-accuracy, reliability and real-time indoor location-based services is one of the challenges for BeiDou navigation satellite system. As one of the core technologies of the spatio-temporal digital foundation for future artificial intelligence and super-intelligence applications, high-precision indoor positioning has long been a research hotspot in industry and academia. This paper first reviews the development status of existing high-precision indoor positioning technologies, and compares their advantages, disadvantages and difficulties. Then it analyzes the development trend of related technologies under typical applications, and looks forward to the fu ture development direction and application scenarios of indoor positioning technologies. [ABSTRACT FROM AUTHOR]

We establish a tunable open-access microcavity consisting of two planar distributed Bragg reflectors (DBRs) individually controlled by nanopositioners. By varying the cavity length, such configuration enables variation of the light–matter coupling strength by a factor of 2, while keeping in microresonators the same active region and cavity mirrors. Polariton condensation was demonstrated over a large range of Rabi splittings and the corresponding threshold diagram was derived as a function of cavity-exciton detuning, which fits well with theoretical simulations. The results show that for various light-matter coupling strengths, optimal detunings featured by the lowest condensation threshold always occur at a fixed depth of energy trap between the exciton reservoir and the polariton ground state, which enables the most efficient exciton–exciton scattering into the condensate state in the driven-dissipative polaritonic system. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to design and simulate a piezoelectric micropump using microelectromechanical systems technology for drug delivery applications. Design/methodology/approach: Two piezoelectric actuators are used to actuate and bend the diaphragms in the proposed structure. In this micropump, the liquid flow is rectified by two silicon check valves. Findings: The use of two piezoelectric transducer (PZT) actuators in the parallel mod not only reduces dead volume but also increases stroke volume as well. In addition to increasing the flow rate, this phenomenon enhances the operation of the micropump to have self-priming as smoothly as possible. Originality/value: This actuating method results in a 22% increase in flow rate and compression ratio, as well as a 15% reduction in function voltage. The fluid-solid interaction is simulated using COMSOL Multiphysics 5.3a. [ABSTRACT FROM AUTHOR]

For many years, the navigation team at the French Space Agency (CNES) has been developing its Precise Point Positioning project. The goal was initially to promote a technique called undifferenced ambiguity resolution. One of the main characteristics of this technique is the capability for a user receiver to perform centimeter-level accuracy in real time. To do so, a demonstrator has been built. Its architecture is composed of three main elements: a correction processing software called the server part, a means to transmit the corrections using standardized messages, and a user software capable of handling the corrections to compute an accurate positioning at the user level. In this paper, we present the recent advances in the CNES precise point positioning demonstrator. They are composed of some evolution of the network of stations and server software, the implementation of the new state space representation standard, a new method for instantaneous ambiguity resolution using uncombined four-frequency signals, its implementation in real-time at the server and the user level, and the use of high-rate Doppler measurements to improve the accuracy of the solution in harsh urban environments. On top of that, the computation of high-accuracy post-processed phase biases with the majority of current GNSS signals supported, compatible with the uncombined method and a new online positioning service to demonstrate the capacity of the user software, is demonstrated. [ABSTRACT FROM AUTHOR]

High-speed atomic force microscopy (HS-AFM) is a technique capable of revealing the dynamics of biomolecules and living organisms at the nanoscale with a remarkable temporal resolution. The phase delay in the feedback loop dictates the achievable speed of HS-AFM instruments that rely on fast nanopositioners operated predominantly in conjunction with piezoelectric actuators (PEAs). The high capacitance and high operating voltage of PEAs make them difficult to drive. The limited bandwidth of associated high-voltage piezo-amplifiers is one of the bottlenecks to higher scan speeds. In this study, we report a high-voltage, wideband voltage amplifier comprised of a separate amplification and novel voltage-follower power stage, requiring no global feedback. The reported amplifier can deliver a current over ±2 amps, offers a small-signal bandwidth of 1 MHz, and exhibits an exceptionally low phase lag, making it particularly well suited for the needs of next-generation HS-AFMs. We demonstrate its capabilities by reporting its achievable bandwidth under various PEA loads and showcasing its merit for HS-AFM by imaging tubulin protofilament dynamics at sub-second frame rates. [ABSTRACT FROM AUTHOR]

This paper presents the design and analysis of a novel piezoelectric-actuated compliant microgripper that mainly consists of a three-stage amplifier and a pair of parallelogram mechanism to achieve a large amplification ratio and a wide motion stroke. The three stages are configured as two bridge-type with one lever-type amplification mechanism, and a pair of parallelogram mechanisms are integrated into the lever-type amplification mechanism to provide advantages in terms of parallel gripping and large amplification ratio. The crucial structural parameters are optimized by the response surface optimization. The static model of the microgripper is established and finite element analysis is conducted to evaluate the characteristics of the microgripper. The performance of the microgripper is investigated by experimental studies on a fabricated prototype. Experimental results show that the microgripper obtains a large displacement amplification ratio of 45.58, a wide motion stroke of 683.70 μm, and it can successfully grasp different copper wires with diameters of 300 μm and 500 μm. [ABSTRACT FROM AUTHOR]

Among various types of precision stages, magnetically levitated precision positioning stages offer unique capabilities including frictionless motion, vacuum compatibility, and contamination-free operation, making them highly attractive for various applications such as photolithography scanners, micro-machining tools, and microscopes. However, today's magnetically levitated stages often only offer long-stroke motion in the planar directions, and typically have a limited motion range in the vertical axis. This fact limits their applicability in machines and instruments that require precision motion in all translational degrees of freedom (DOFs). Aiming to address this challenge, this paper presents the design, modeling, prototyping, and experimental evaluations for a novel magnetically levitated nanopositioning stage, which we call the LevCube, that can provide nano-precision positioning with a motion stroke of 10 mm in all translational DOFs. The LevCube prototype stage was successfully levitated with a positioning control bandwidth of 100 Hz in the translational DOFs and 70 Hz in the rotational DOFs. The maximum force of the stage is 25.5 N under 3.5 A current amplitude, which generates a maximum stage acceleration of 2.5 times the gravitational acceleration. These performances show the potential of the proposed stage to provide all-axis long-stroke precision positioning capability for future microscopes and manufacturing machines. [Display omitted] • A novel design for magnetically levitated precision stage with 10 mm motion stroke in XYZ DOFs. • Modeling and optimization for stage design to achieve constant force constant over full stroke • Design and built a LevCube prototype to validations for its positioning capability and performance [ABSTRACT FROM AUTHOR]

Piezoelectric actuators have been widely used in hard disk drives to form dual stage actuations for position control. Early designs, categorized as milli-actuators, typically place piezo elements on suspension base plate to swing suspension to induce motion of the head, located at the suspension tip. In recent years, micro-actuators with piezo elements next to the magnetic heads are introduced to improve positioning accuracy. These micro-actuators are first reviewed in this paper. An analytic model is then derived to understand key design parameters related to the micro-actuator performance and to compare designs. With the guidance of the model, the paper explores improvement directions for future micro-actuators. Combining the milli-actuator and micro-actuator to form triple stage actuations is shown to not only provide better position control accuracy than the dual stage actuations, but also expand micro-actuator design space for further performance enhancement, which provides a path for hard disk drive industry to keep growing track density for higher storage capacity. [ABSTRACT FROM AUTHOR]

This paper presents the design and implementation of a novel sliding mode control integrated with active disturbance rejection (SMCDR) for precise robust trajectory tracking of piezoelectric nanopositioning stages. The model uncertainties, nonlinearity, and external disturbances of the piezoelectric nanopositioning stage are regarded as a lumped disturbance, which is estimated by an extended state observer. The active disturbance rejection control (ADRC) strategy is used to realize a preliminary trajectory tracking, while the sliding mode control is adopted to handle the estimation error and residual uncertainties, and to improve the tracking performance. The exponential stability of the proposed SMCDR is proved using Lyapunov's direct method. The proposed SMCDR controller combines the strength of both ADRC and sliding mode control, exhibits a simple structure, requires only the position measurements, and does not require any information of model parameters except for an approximate constant gain. Experimental results reveal the robustness of the SMCDR approach in suppressing the hysteresis of piezoelectric actuator, and illustrate the superior performance over conventional ADRC, integral sliding mode controller (ISMC) and PID controller for trajectory tracking control of piezoelectric nanopositioning stages. [ABSTRACT FROM AUTHOR]

Piezoelectric nanogenerators have prospective uses for generating mechanical energy and powering electronic devices due to their high output and flexible behavior. In this research, the synthesis of the three-dimensional coral-like BaTiO3 (CBT) and its filling into a polyvinylidene fluoride (PVDF) matrix to obtain composites with excellent energy harvesting properties are reported. The CBT-based PENG has a 163 V voltage and a 16.7 µA current at a frequency of 4 Hz with 50 N compression. Simulations show that the high local stresses in the CBT coral branch structure are the main reason for the improved performance. The piezoelectric nanogenerator showed good durability at 5000 cycles, and 50 commercial light-emitting diodes were turned on. The piezoelectric nanogenerator generates a voltage of 4.68–12 V to capture the energy generated by the ball falling from different heights and a voltage of ≈0.55 V to capture the mechanical energy of the ball's movement as it passes. This study suggests a CBT-based piezoelectric nanogenerator for potential use in piezoelectric sensors that has dramatically improved energy harvesting characteristics. [ABSTRACT FROM AUTHOR]

Piezoelectric stick-slip driven nanopositioning stage (PSSNS) with nanometer resolution has been widely used in the field of micro-operation. However, it is difficult to achieve nanopositioning over large travel, and its positioning accuracy is affected by the hysteresis characteristics of the piezoelectric elements, external uncertain disturbances, and other nonlinear factors. To overcome the above-mentioned problems, a composite control strategy combining stepping mode and scanning mode is proposed in this paper, and an integral back-stepping linear active disturbance rejection control (IB-LADRC) strategy is proposed in the scanning mode control phase. First, the transfer function model of the system in the micromotion part was established, and then the unmodeled part of the system and the external disturbance were treated as the total disturbance and extended to a new system state variable. Second, a linear extended state observer was used as the core of the active disturbance rejection technique to estimate displacement, velocity, and total disturbance in real time. In addition, by introducing virtual control variables, a new control law was designed to replace the original linear control law and improve the positioning accuracy and robustness of the system. Furthermore, the effectiveness of the IB-LADRC algorithm was verified by simulation comparison experiments and experimentally validated on a PSSNS. Finally, experimental results show that the IB-LADRC is a practical solution for a controller capable of handling disturbances during the positioning of a PSSNS with a positioning accuracy of less than 20 nm, which essentially remains constant under load. [ABSTRACT FROM AUTHOR]

To overcome the limited stroke of existing micropositioning stages in precision engineering systems, this article proposes an optimal design of a new micropositioner based on the cricket-mimicked bistable mechanism. The suggested micropositioner is potential for polishing application. The proposed bistable mechanism is combined with a positive-stiffness mechanism to achieve a large stroke with centimeter range. The design targets of micropositioner are to deliver a large stroke, a high frequency, and a small parasitic motion but also ensure working safety. To solve three objective functions with four constraints, a hybrid optimization approach is proposed, namely fuzzy logic, teaching learning-based optimization (TLBO), and artificial neural network (ANN). The fuzzy logic is proposed to combine three objective functions into a single objective function, so-called output fuzzy. In the modeling, the TLBO is employed to determine the optimum ANN structure. Then, the multi-objective optimization problem of the micropositioner is converted into the single optimization task through the TLBO. Besides, the influences of the geometrical parameters on the performance qualities of the micropositioner are investigated. The results showed the performance indexes of TLBO-assisted ANN are reasonable and reliable. The optimum design parameters are found at l1 = 60.93 mm, l2 = 10.42 mm, t1 = 2.77 mm, t2 = 1.37 mm, and t3 = 9.28 mm. A prototype of ABS micropositioner is manufactured by fused deposition modeling 3D printer. The displacement and the parasitic motion were experimentally measured about 14.9513 mm and 0.0061 mm, respectively. The frequency and the stress were simulated in ANSYS software about 617.9227 Hz and 38.7659 MPa, respectively. The output stroke is over 1 cm which is potential for wide applications. [ABSTRACT FROM AUTHOR]

The compliant planar positioning stage actuated by voice coil motors can obtain nanoscale motion accuracy within a millimeter motion range and has received increasing attention in precision engineering. However, there is always a contradiction between the actuation force and the output stiffness in the design of the stage. This study presents the design of a novel redundant actuated planar 3-DOF-compliant nanopositioning stage. A redundant actuated configuration can increase the output stiffness of the stage and decrease the peak actuating force. The analytical stiffness model, kinetostatic model, and dynamic model of the stage are established, which illustrate the high force transmission efficiency and dynamic decoupling feature of the stage. The geometric parameters were optimized based on the established models, and model validation and performance evaluation of the stage were conducted via finite element analysis. Finally, a prototype positioning stage is fabricated. Experimental results show that the proposed stage can achieve a motion range of up to ±2.5 mm × ±2.5 mm × ±2.5° with a resolution of 80 nm and 0.28″, and the tracking error ratio for a composite Lissajous trajectory is within 0.102%. • A novel redundant actuated 4- P PR planar xyθ compliant nanopositioning stage with large motion range is proposed. • The analytical stiffness, kinetostatic and dynamic models of the stage is established. • The high force transmission efficiency of the stage is proved by the analytical models. • A prototype positioning stage is fabricated, nano-scale resolution and positioning accuracy are achieved. [ABSTRACT FROM AUTHOR]

Navigation/positioning systems have become critical to many applications, such as autonomous driving, Internet of Things (IoT), Unmanned Aerial Vehicle (UAV), and smart cities. However, it is difficult to provide a robust, accurate, and seamless solution with single navigation/positioning technology. For example, the Global Navigation Satellite System (GNSS) cannot perform satisfactorily indoors; consequently, multi-sensor integrated systems provide the solution, as they compensate for the limitations of single technology by using the complementary characteristics of different sensors. This article describes a thorough investigation into multi-sensor data fusion, which over the last ten years has been used for integrated positioning/navigation systems. In this article, different navigation/positioning systems are classified and elaborated upon from three aspects: (1) sources, (2) algorithms and architectures, and (3) scenarios, which we further divide into two categories: (i) analytics-based fusion and (ii) learning-based fusion. For analytics-based fusion, we discuss the Kalman filter and its variants, graph optimization methods, and integrated schemes. For learning-based fusion, several supervised, unsupervised, reinforcement learning, and deep learning techniques are illustrated in multi-sensor integrated positioning/navigation systems. Design consideration of these integrated systems is discussed in detail from several aspects and their application scenarios are categorized. Finally, future directions for their research and implementation are discussed. • Classifying integrated navigation systems with sources, algorithms, and scenarios. • Classifying multi-sensor fusion based on absolute and relative positioning sources. • Analytics-based and learning-based algorithms are discussed and classified. • Design considerations include state selection, observability, time synchronization. • Classifying application scenarios into 6 categories, including automated driving. [ABSTRACT FROM AUTHOR]

Wide-range application scenarios, such as industrial, medical, rescue, etc., are in various demand for human spatial positioning technology. However, the existing MEMS-based sensor positioning methods have many problems, such as large accuracy errors, poor real-time performance and a single scene. We focused on improving the accuracy of IMU-based both feet localization and path tracing, and analyzed three traditional methods. In this paper, a planar spatial human positioning method based on high-resolution pressure insoles and IMU sensors was improved, and a real-time position compensation method for walking modes was proposed. To validate the improved method, we added two high-resolution pressure insoles to our self-developed motion capture system with a wireless sensor network (WSN) system consisting of 12 IMUs. By multi-sensor data fusion, we implemented dynamic recognition and automatic matching of compensation values for five walking modes, with real-time spatial-position calculation of the touchdown foot, enhancing the 3D accuracy of its practical positioning. Finally, we compared the proposed algorithm with three old methods by statistical analysis of multiple sets of experimental data. The experimental results show that this method has higher positioning accuracy in real-time indoor positioning and path-tracking tasks. The methodology can have more extensive and effective applications in the future. [ABSTRACT FROM AUTHOR]

The inherent weakly damped resonant modes of the piezoelectric nanopositioning platform and the presence of model uncertainty seriously affect the performance of the system. A structured H∞ design is used in this paper to solve the accuracy and robustness problems respectively using a two-loop control structure. The multiple performance requirements of the system are constituted into an H∞ optimization matrix containing multi-dimensional performance diagonal decoupling outputs, and an inner damping controller d is set according to the damping of the resonant modes; the second-order robust feedback controller is preset in the inner loop to improve the robustness of the system; the tracking controller is connected in series in the outer loop to achieve high accuracy scanning; finally, the structured H∞ controller is designed to meet the multiple performance requirements. To verify the effectiveness of the proposed structured H∞ control, simulation comparison experiments are done with the integral resonant control (IRC) and H∞ controller. The results demonstrate that the designed structured H∞ controller achieves higher tracking accuracy compared to the IRC and H∞ controllers under grating input signals of 5, 10, and 20 Hz. Moreover, it has good robustness under 600g and 1000g loads and high frequency disturbances close to the resonant frequency of the system, meeting multiple performance requirements. Compared with the traditional H∞ control, yet with lower complexity and transparency, which is more suitable for engineering practice applications. [ABSTRACT FROM AUTHOR]

To meet the high requirements for positioning accuracy and multiple dimensions of positioning systems in the fields of precision measurement and precision machining, a new submicron-precision three-dimensional (3D) low cross-interference positioning system is designed and fabricated in this paper. The 3D motion stage mainly includes a mechanical structure, a support and guide system, and a driving system. The Abbe offset error is eliminated by adopting a coplanar structure in the X and Y directions, thus minimizing the mutual cross-interference of the motion stage. The X and Y motion stages are driven by a ball screw pair and an alternating current servo motor, which are supported and guided by an air-floating rail and slider. Moreover, the X and Y air-floating stages adopt a lateral structure and double rails, respectively. The Z-motion stage is directly driven by a high-precision piezoelectric motor. In addition, the system achieves high-precision motion by using the dual-loop control technology of secondary feedback combined with the high-resolution control characteristics of the servo motor. The performance of the positioning system is evaluated through a series of verification experiments. Results show that the stroke of the positioning system of the 3D air-floating motion stage can reach 100 × 100 × 100 mm3, and the repeated positioning accuracy is better than 0.41 μm (k = 2, k is defined by the International Organization for Standardization as the coverage factor). The maximum cross-interference of the X-stage is 180 nm, and the Y-stage reaches 320 nm when running with a full stroke of 100 mm in the Z-direction, demonstrating good repeatability, stable running, and high straightness. The submicron-precision 3D air-floating motion stage developed in this paper can be used as a suitable solution for coordinate measuring machines, microlithography, and micromachining applications when combined with an additional nanoprecision microstage. [ABSTRACT FROM AUTHOR]

Due to the characteristics of high accuracy and passivity, underwater matching navigation tech⁃ nology has become one of the main development directions of underwater vehicle navigation. To analyze the problems in gravity matching navigation, this paper introduces the development status of matching navigation based on gravity field products, and then discusses the constraints for positioning accuracy, including matching variables, gravity measurement precision, suitable matching areas and grid size. Gravity anomaly and gravity gradients of the two study regions are calculated by the spherical harmonic function based on a highly accurate gravity field model. And the influence of the grid size and the accuracy of gravity field product on the matching algorithm is evaluated. According to different kinds of indexes on gravity field charac⁃ teristics in the two study regions, it is easy to find that the study region of the South China Sea has much more abundant gravity field information and is more suitable for matching navigation than the Pacific Ocean. The gravity assisted matching navigation techno-logy is more suitable for use in the areas with obvious variations in gravity characteristics. If the grid size of the gravity field products is l, the highest precision of the matching navigation is 6l/6. [ABSTRACT FROM AUTHOR]

The commendable growth of portable and wearable electronics has taken the energy harvesting sector to new heights. Using the idea of nanogenerators for ambient nano-energy harvesting started with the emergence of the piezoelectric energy harvester reported in 2006. Three diverse types of nano-energy harvesters have developed: piezoelectric nanogenerators, triboelectric nanogenerators for harvesting mechanical energy, and pyroelectric nanogenerators for ambient heat energy harvesting. However, the efficiency of these nano-energy harvesters is limited to converting individual energy sources into electrical energy. Since technology is improving day by day, the requirement for efficient, sustainable hybrid energy harvesters is of great interest. Hybrid nanogenerators can be developed by combining two or more nanogenerators mentioned above. In this regard, hybrid tribo-piezoelectric nanogenerators, hybrid tribo-pyroelectric nanogenerators, and hybrid tribo-piezo-pyroelectric nanogenerators exist. The hybrid nanogenerators will have the essential characteristics of the individual nanogenerator with which it is developed, and a positive synergism can enhance the efficacy. This paper reviews the recent advancements in biocompatible energy harvesting materials that are efficient enough to be used as active layers in the tribo-, piezo-, and hybrid tribo-piezoelectric energy harvesters for wearable and biomedical applications. The article focuses on the properties, synthesis, development of materials, usage, hybrid tribo-piezoelectric energy harvesters, and their efficiency, which are made up of these materials, their applications, and finally, the conclusions and future perspectives of these materials. [ABSTRACT FROM AUTHOR]

The piezo-driven nanopositioning stage (PNS) is a key device to provide fast and precise motions for applications such as micromanipulation, microfabrication, and microscopy scanning. However, inherent nonlinearities associated with system perturbations bring difficulties to controller design. Regarding repetitive tasks for a PNS, existing control schemes are mainly dedicated to model inversion-based iterative learning control (ILC), which relies heavily on model accuracy. In this paper, a novel online identification and control scheme named neural network-based ILC (NN-ILC) is proposed for repetitive tracking of the PNS. The ILC scheme reduces repetitive errors due to the linear dynamics and invariable disturbance during each iteration. Neural networks are integrated into the ILC scheme to minimize the residual non-repetitive errors resulting from unknown nonlinear dynamics and model perturbations. Convergence results in both the time and iteration domains are demonstrated according to the Lyapunov stability theory. Comprehensive experiments of sinusoidal and triangular tracking references with different frequencies (5 ∼ 20 Hz) and different peak-to-peak amplitudes (5 ∼ 20 μ m) are conducted on a real-time control testbed. Results show that the root mean square error of the proposed NN-ILC for 20 μ m tracking cases is improved by up to 37% from feedback proportional-derivative (PD) control with neural networks and by up to 20% from feedforward PD-type ILC. • Developing a neural network-based iterative learning control scheme. • Demonstrating the stability in both time and iteration domain for the controller. • Figuring out the implementation procedure of the proposed NNILC scheme. • Conducting comprehensive comparisons between NNILC with typical controllers. [ABSTRACT FROM AUTHOR]

In Part II, we present the use and application of the Compliant Building Elements (CBE) method to generate practical designs for different multiple degree-of-freedom (DOF) compliant mechanisms. We first create a compliant mechanism library based on the combination of prismatic beams, which includes commonly used basic elements (BEs), serial elements (SEs), and parallel elements (PEs). Examples are given during the construction of the library. Based on the library and CBE method, we demonstrate the design of a six-axis nanopositioner, a compliant steering mechanism, and a one-dimensional mechanical metamaterial structure. The outcome of each design process yields a flexure topology that meets the design requirements as well as the corresponding parametric stiffness and compliance matrices, from which we can efficiently obtain the kinematic characteristics of the flexure system and optimize the stiffnesses in selected axes. • CBE is a new design methodology to generate practical designs for multiple degree-of-freedom mechanisms. • CBE combines the advantages of screw theory, matrix-based method, and practical experience to synthesize complex flexures. • A compliant mechanism library is provided based on the combination of prismatic beams to facilitate the design process. • We demonstrate the design process of compliant nanopositioners, steering mechanisms, and metamaterial structures via CBE. [ABSTRACT FROM AUTHOR]

Magnetoelectric (ME) composites that exhibit both ferroelectric and ferromagnetic properties have attracted significant attention, thanks to their potential applications, e.g., low-energy-consumption storage devices. Here, we study bulk composites based on Pb(Zr0.52Ti0.48)O3 (PZT) as a piezoelectric (PE) matrix and Fe3O4 nanoparticles (NPs) as soft ferromagnetic (FM) and magnetostrictive additives, in the form PZT-xFe3O4 with 0% ≤ x ≤ 50 wt. %, all sintered at T = 1000 °C for 2 h in air. We focus our study on a completely insulating sample x = 5% and measure its properties at room temperature upon an out-of-plane external electric field, Eex: namely, piezoelectric response [in-plane strain, S(Eex)], polarization [P(Eex)], and relaxation of the remanent magnetization, [mrem(t,Eex)], prepared upon application and removal of an external magnetic field. The peaks observed in the butterflylike S(Eex) curves at E±peak = ±6 kV/cm and the nucleation field recorded in the P(Eex) loops at the same range around E±nuc = ±6 kV/cm (both referring to the PZT PE matrix) are clearly imprinted on the relaxation behavior of the mrem(t,Eex) data (referring to the Fe3O4 FM NPs). This experimental fact proves the ME coupling between the PZT matrix and the embedded Fe3O4 NPs. We ascribe this feature to the comparable piezoelectricity of the PZT matrix and the magnetostriction of the Fe3O4 NPs that probably motivate and/or promote a strain transfer mechanism occurring at the PZT matrix-Fe3O4 NP interfaces. Our work proves that the low cost PZT-xFe3O4 composite is a promising candidate ME material for future studies, aiming to potential applications. [ABSTRACT FROM AUTHOR]

For high‐performance trajectory tracking at the nanometer scales, this paper presents a new fast terminal sliding mode controller, which combines a recursive integer‐order non‐singular high‐order sliding manifold and a fractional‐order fast fixed‐time reaching law to ensure globally fast convergence, and adopts a time‐delay‐estimation (TDE) based disturbance estimator deeming the designed controller robust to parameter uncertainty. Stability of the designed controller is verified through the Lyapunov framework, where the full analyses of convergence region and settling time are also presented. The tracking performance is experimentally verified on a piezo‐stack driven nano‐positioning platform. To showcase the performance improvements, measured closed‐loop performance of the proposed controller is contrasted with those obtained using three benchmark control approaches namely the basic Proportional‐Integral‐Derivative (PID), the popular Positive Position Feedback with Integral action (PPF+I), and the traditional linear sliding mode controller (LSMC). [ABSTRACT FROM AUTHOR]

Mark's precise positioning is critical for achieving wafer bonding accuracy. A Mark positioning algorithm is proposed to improve the accuracy and stability of Mark positioning. Shape template matching can effectively reduce the impact of image quality on positioning accuracy, but it can only achieve pixel precision Mark location. On the basis of this method, the algorithm uses the facet model method to extract the sub-pixel edge information for the Mark contour, and combines the sub-pixel traversal strategy to achieve accurate sub-pixel precision Mark location. Simultaneously, the composite template method is proposed for the first time to improve the template information's quality, which effectively improves the robustness of the algorithm to image quality. The simulation results indicate that the algorithm is capable of positioning with an accuracy of approximately 0.04 pixels. The experimental results indicate that the algorithm is capable of positioning with an accuracy of approximately 0.052 pixels and is resistant to image noise and blur, which meets the accuracy and stability requirements for Mark positioning in wafer bonding alignment. • A Mark positioning algorithm based on sub-pixel shape template matching is proposed that enables high-precision mark location during wafer bonding alignment. • The facet model method is used to introduce sub-pixel edge point information for shape template matching, and the sub-pixel positioning is realized combined with the search strategy of sub-pixel step size. • The composite template method is proposed to improve the template quality, which finally improves the reliability of template matching. • Simulation and experiments demonstrate that the algorithm has high positioning accuracy and robustness to image quality. [ABSTRACT FROM AUTHOR]

This study presents the design, implementation, and characterization of 1D resonant type micro-electro-mechanical-systems (MEMS) piezoelectric scanning mirrors with different actuator designs to investigate their influences on the figure of merits (FoMs) for automotive light detection and ranging application. The MEMS scanning mirrors are driven by lead zirconate titanate (PZT) thin film in this study owing to its outstanding piezoelectric properties. Three different beam-type piezoelectric actuators are designed, including the reference meander straight-beam actuator design, and the proposed meander curved-beam and straight-curved tapered beam actuator designs. Simulations show the scan angle enhancement for two proposed designs, yet the resonant scanning frequency of meander curved-beam design dropped to below the 2 kHz requirement. To evaluate the designs, scanning mirrors with two proposed actuators are fabricated and tested. Measurements show that the resonant frequencies for the two proposed MEMS scanning mirrors are 1735 Hz and 2578 Hz, respectively. Two proposed designs respectively have the maximum optical angles of 48.1° and 50.6° at the 20 Vpp driving voltage. Due to the much higher stress on the beam structure induced by the misalignment of PZT film, the actuator could not reach the predicted scanning angle of near 80°. In comparison of the two proposed designs, the straight-curved tapered beam actuator design could enhance the FoM for about 56%. In summary, the performances of piezoelectric MEMS scanning mirror can be improved by varying the designs of length and shape of actuator, and the distribution of PZT film on the suspended actuator is also a critical design concern. [ABSTRACT FROM AUTHOR]

A foldable compliant XY precision positioning stage with good decoupling property in both axes is developed for precision applications. The compliant rolling-contact element (CORE) is innovatively incorporated in the design of the stage to realize the folding function for compacting the mechanism structure. The input stiffness of the motion platform is determined using the matrix method and is verified by a conventional stiffness modeling method. Finite element analysis (FEA) simulations of three bridge-type amplifiers are conducted and compared to determine the preferable one for magnifying the limited output displacement of the actuator. A foldable stage is then assembled and its decoupling capability and dynamic performances are investigated with the ANSYS software. In addition, a prototype is fabricated to experimentally test the performance of the stage. Results demonstrate that the employed proportional-integral-derivative (PID) feedback controller can settle in 70 ms without overshooting. The closed-loop controlled stage is able to reach a resolution of 2 μm and has small tracking errors within ± 1 μm in the circular-contouring tests. [ABSTRACT FROM AUTHOR]

Location information is attracting more and more attention due to the increasing awareness of its importance for a wide range of applications. Whether it is for tracking valuable assets in the industrial context or monitoring the motion of elderly people and patients to prevent accidents or offering a better shopping experience using proximity and positioning marketing, an accurate and efficient indoor positioning has become crucial. Aware of this increasing need, we present in this paper "EIPSO" a new indoor 3D positioning algorithm based on Game Theory. An emphasis has been put on the energy efficiency of the proposed solution using "mGAPS" a hybrid micro-genetic and pattern search optimization process to reach the Nash equilibrium. A series of real experiments using Zigbee technology have been conducted on a testbed in LaRINa laboratory at the University of Carthage to evaluate the performances of the proposed solution. The obtained results prove the dynamic behavior of EIPSO which adapts the transmit power to both the signal quality and the battery level of the considered nodes. Moreover, a significant improvement of more than 40% of the network lifetime has been observed when using EIPSO while maintaining the positioning accuracy at a high level (≥ 90%). [ABSTRACT FROM AUTHOR]

The purpose of this paper is to combine machine learning to locate the 3D sensor network space. Real life is mostly a three-dimensional environment. Whether it is a factory in manufacturing or a vegetation base in agriculture, it needs to be monitored and positioned. In this paper, the localization algorithm is discussed to a certain extent. This paper firstly introduces the relevant background and organizes related work. It also wrote related algorithms, such as ranging-based positioning algorithms in the free space of wireless sensors. It shows the positioning link by introducing the wireless sensor network structure system and node structure. And this paper summarizes the Bounding-box Method positioning principle, TDOA algorithm principle, and TDOA positioning principle. It then describes the gradient boosting tree classification algorithm based on machine learning, and focuses on the admiral boosting tree classification algorithm related to the experiment. This paper also describes the ranging technology combining RSSI algorithm and DV-Hop algorithm in three-dimensional space, and mentions two algorithms of RSSI and DV-Hop. In the fourth part, the machine learning coordinate prediction accuracy improvement experiment and the three-dimensional space positioning algorithm optimization experiment and result analysis are carried out. It is proved by experiments that the model evaluation effect of the gradient boosting tree classification algorithm in machine learning is the best. It can be applied to the calculation of relative position coordinates of label nodes. It then carried out the three-dimensional positioning effect test experiment of IDV-Hop algorithm. This shows that when the network density in the experimental environment reaches more than 12, the localization coverage of IDV-Hop algorithm and DV-Hop algorithm are both higher than 91%. Finally, the hybrid algorithm of RSSI and DV-Hop algorithm is used to compare the positioning accuracy, positioning coverage and bad node rate with these two algorithms. It draws the stability of the hybrid algorithm and its effects, and finally discusses and summarizes the experiments. [ABSTRACT FROM AUTHOR]

Recent advances both in hardware and software have facilitated the embedded intelligence (EI) research field, and enabled machine learning and decision-making integration in resource-scarce IoT devices and systems, realizing "conscious" and self-explanatory objects (smart objects). In the context of the broad use of WSNs in advanced IoT applications, this is the first work to provide an extreme-edge system, to address structural health monitoring (SHM) on polymethyl methacrylate (PPMA) thin-plate. To the best of our knowledge, state-of-the-art solutions primarily utilize impact positioning methods based on the time of arrival of the stress wave, while in the last decade machine learning data analysis has been performed, by more expensive and resource-abundant equipment than general/development purpose IoT devices, both for the collection and the inference stages of the monitoring system. In contrast to the existing systems, we propose a methodology and a system, implemented by a low-cost device, with the benefit of performing an online and on-device impact localization service from an agnostic perspective, regarding the material and the sensors' location (as none of those attributes are used). Thus, a design of experiments and the corresponding methodology to build an experimental time-series dataset for impact detection and localization is proposed, using ceramic piezoelectric transducers (PZTs). The system is excited with a steel ball, varying the height from which it is released. Based on TinyML technology for embedding intelligence in low-power devices, we implement and validate random forest and shallow neural network models to localize in real-time (less than 400 ms latency) any occurring impacts on the structure, achieving higher than 90% accuracy. [ABSTRACT FROM AUTHOR]

The paper presents a framework to emulate spacecraft orbits using GNSS hardware in the loop that enables the evaluation of new orbital positioning algorithms. The framework software generates the spacecraft orbit and the GNSS signals, including the most common perturbations. These signals are modulated and transmitted by a software-defined radio and received by a commercial GPS receiver. The system is validated using a test orbit, where the GPS receiver accurately determines the spacecraft positions. Moreover, using raw data provided by the receiver, the spacecraft positions have also been determined by software for a low earth orbit, in which civil GPS receivers do not work. [ABSTRACT FROM AUTHOR]

One of the main challenges of Industry 4.0 is how advanced sensors and sensing technologies can be applied through the Internet of Things layers of existing manufacturing. This is the so-called Brownfield Industry 4.0, where the different types and ages of machines and processes need to be digitalized. Smart retrofitting is the umbrella term for solutions to show how we can digitalize manufacturing machines. This problem is critical in the case of solutions to support human workers. The Operator 4.0 concept shows how we can efficiently support workers on the shop floor. The key indicator is the readiness level of a company, and the main bottleneck is the technical knowledge of the employees. This study proposes an education framework and a related Operator 4.0 laboratory that prepares students for the development and application of Industry 5.0 technologies. The concept of intelligent space is proposed as a basis of the educational framework, which can solve the problem of monitoring the stochastic nature of operators in production processes. The components of the intelligent space are detailed through the layers of the IoT in the form of a case study conducted at the laboratory. The applicability of indoor positioning systems is described with the integration of machine-, operator- and environment-based sensor data to obtain real-time information from the shop floor. The digital twin of the laboratory is developed in a discrete event simulator, which integrates the data from the shop floor and can control the production based on the simulation results. The presented framework can be utilized to design education for the generation of Industry 5.0. [ABSTRACT FROM AUTHOR]

Objectives: BeiDou-3 navigation satellite system (BDS-3) has been fully completed and pro‐ vides reliable positioning, navigation, and timing services to global users. In order to achieve compatibility and interoperability with other global navigation satellite systems (GNSS), B1C and B2a signals have been modulated by BDS-3 based on BDS-2, which enable frequency multiplexing with E1 and E5a signals of Galileo. The inter-system biases (ISBs) are important for the fusion processing of different GNSS. Methods: This paper proposes an ISB estimation and application model based on the single-differenced observations and analyzes the ISBs between the overlapping frequencies of BDS-3 and Galileo. Based on several receivers of the new trackable BDS-3 signals, the characteristics of ISBs between BDS-3 and Galileo are revealed, and the real-time kinematic (RTK) positioning performance of BDS-3 and Galileo is analyzed. Results: The results show that the ISBs of B1C-E1 and B2a-E5a exist in different types of receivers but not in the same type of receivers. In addition, compared with BDS-3-only and Galileo-only, the combination of BDS-3 and Galileo has an improvement of more than 10% in both the success rate of ambiguity resolution and positioning accuracy. Conclusions: The multi-constellation RTK positioning performance with the introduction of ISBs is more advantageous than that of a single constellation [ABSTRACT FROM AUTHOR]

• Review recent landmark-based indoor positioning technologies. • Categorize them into four categories. • Wireless signals, built-in sensors, images, and multisource-based technologies. • Analyze them based on six evaluation criteria. • Present future directions on landmark-based indoor landmark positioning techniques. Owing to the increase in the time people spend indoors, coupled with the pervasiveness of high-performance smart devices, the importance of indoor positioning techniques has grown. Researchers have extensively studied indoor positioning techniques using wireless signals or mobile device built-in sensors because satellite signals are absent in indoor environments. However, the built-in sensor readings tend to be distorted by the surrounding indoor environments. Furthermore, wireless signal-based technology incurs substantial cost because of presurvey and maintenance. To address these drawbacks, landmark-based indoor positioning technologies have recently been developed. An indoor landmark is a unique point in a room that is distinguishable from other points based on its features. Because the indoor landmark itself underscores the unique features of a specific region, it acts as a reference point to help users navigate efficiently. In this paper, we review recent landmark-based indoor positioning technologies. We categorize the technologies according to whether they use wireless signals, built-in sensors, images, and multisource-based technologies. We analyze them based on six evaluation criteria, namely, accuracy, core technology, detection difficulty, cost, versatility, and robustness. Finally, we discuss future directions of research and applications on indoor landmark positioning techniques. We believe that this review provides useful viewpoints and necessary information regarding indoor positioning technology using landmarks. [ABSTRACT FROM AUTHOR]

Positioning systems are used in a wide range of applications which require determining the position of an object in space, such as locating and tracking assets, people and goods; assisting navigation systems; and mapping. Indoor Positioning Systems (IPSs) are used where satellite and other outdoor positioning technologies lack precision or fail. Ultra-WideBand (UWB) technology is especially suitable for an IPS, as it operates under high data transfer rates over short distances and at low power densities, although signals tend to be disrupted by various objects. This paper presents a comprehensive study of the precision, failure, and accuracy of 2D IPSs based on UWB technology and a pseudo-range multilateration algorithm using Time Difference of Arrival (TDoA) signals. As a case study, the positioning of a 4 × 4 m 2 area, four anchors (transceivers), and one tag (receiver) are considered using bitcraze's Loco Positioning System. A Cramér–Rao Lower Bound analysis identifies the convex hull of the anchors as the region with highest precision, taking into account the anisotropic radiation pattern of the anchors' antennas as opposed to ideal signal distributions, while bifurcation envelopes containing the anchors are defined to bound the regions in which the IPS is predicted to fail. This allows the formulation of a so-called flyable area, defined as the intersection between the convex hull and the region outside the bifurcation envelopes. Finally, the static bias is measured after applying a built-in Extended Kalman Filter (EKF) and mapped using a Radial Basis Function Network (RBFN). A debiasing filter is then developed to improve the accuracy. Findings and developments are experimentally validated, with the IPS observed to fail near the anchors, precision around ± 3 cm , and accuracy improved by about 15 cm for static and 5 cm for dynamic measurements, on average. [ABSTRACT FROM AUTHOR]

This paper presents a method of action location in three-dimensional motion teaching. The machine vision technology is used to solve the problems of low positioning accuracy and long positioning time in the traditional motion three-dimensional teaching method. The work of this method is as follows: (a) using machine vision method to determine the world coordinate system of the image; (b) using MRF algorithm to extract the features of 3D teaching action image; (c) determining the spatial correlation of 3D teaching action data. In the three-dimensional teaching action image, the smooth filtering technology is used to suppress and eliminate the noise. Then the convolution neural network (CNN) is used to reconstruct the three-dimensional teaching action image. The entropy of three-dimensional teaching behavior of physical education is determined by CNN. Through a large number of computer simulations, the effectiveness of the proposed system is confirmed. The results show that the system achieves 95% accuracy when the positioning time is 1.9 s. [ABSTRACT FROM AUTHOR]

Although there is a need to demonstrate reproducibility in light microscopy acquisitions, the lack of standardized guidelines monitoring microscope health status over time has so far impaired the widespread use of quality control (QC) measurements. As scientists from 10 imaging core facilities who encounter various types of projects, we provide affordable hardware and open source software tools, rigorous protocols, and define reference values to assess QC metrics for the most common fluorescence light microscopy modalities. Seven protocols specify metrics on the microscope resolution, field illumination flatness, chromatic aberrations, illumination power stability, stage drift, positioning repeatability, and spatial-temporal noise of camera sensors. We designed the MetroloJ_QC ImageJ/Fiji Java plugin to incorporate the metrics and automate analysis. Measurements allow us to propose an extensive characterization of the QC procedures that can be used by any seasoned microscope user, from research biologists with a specialized interest in fluorescence light microscopy through to core facility staff, to ensure reproducible and quantifiable microscopy results. [ABSTRACT FROM AUTHOR]