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Enhanced Reaction Time Measurement System Based on 3D Accelerometer in Athletics
Modular IoT Sensing and Data Pipeline for Digital Twin–Enabled Real-Time Aircraft Structural Health Monitoring
Flexible Sensor Foil Based on Polymer Optical Waveguide for Haptic Assessment
A Codesign Framework for the Development of Next Generation Wearable Computing Systems
Comparative Analysis of the Accuracy and Robustness of the Leap Motion Controller 2

Journal Description

Sensors

Sensors is an international, peer-reviewed, open access journal on the science and technology of sensors, published semimonthly online by MDPI. The Polish Society of Applied Electromagnetics (PTZE), Japan Society of Photogrammetry and Remote Sensing (JSPRS), Spanish Society of Biomedical Engineering (SEIB), International Society for the Measurement of Physical Behaviour (ISMPB), Chinese Society of Micro-Nano Technology (CSMNT) and more are affiliated with Sensors and their members receive discounts on the article processing charges.

Open Access — free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), PubMed, MEDLINE, PMC, Ei Compendex, Inspec, Astrophysics Data System, and other databases.
Journal Rank: JCR - Q2 (Instruments and Instrumentation) / CiteScore - Q1 (Instrumentation)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 17.8 days after submission; acceptance to publication is undertaken in 2.6 days (median values for papers published in this journal in the second half of 2025).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Testimonials: See what our editors and authors say about Sensors.
Companion journals for Sensors include: Chips, Targets, AI Sensors and IJMD.
Journal Cluster of Instruments and Instrumentation: Actuators, AI Sensors, Instruments, Metrology, Micromachines and Sensors.

Impact Factor: 3.5 (2024); 5-Year Impact Factor: 3.7 (2024)

Imprint Information Journal Flyer Open Access ISSN: 1424-8220

Latest Articles

25 pages, 1522 KB

Open AccessArticle

A Robust Deep Learning Framework for Skill Level Discrimination in Tennis Strokes Using Bilateral IMU Measurements

by Enes Halit Aydin and Onder Aydemir

Sensors 2026, 26(10), 3273; https://doi.org/10.3390/s26103273 (registering DOI) - 21 May 2026

In tennis, where performance is governed by complex kinetic chain interactions, objective skill classification is vital for coaching and talent identification. This study presents a hierarchical deep learning framework leveraging synchronized bilateral Inertial Measurement Unit (IMU) data from 39 participants (11 elite, 28 [...] Read more.

In tennis, where performance is governed by complex kinetic chain interactions, objective skill classification is vital for coaching and talent identification. This study presents a hierarchical deep learning framework leveraging synchronized bilateral Inertial Measurement Unit (IMU) data from 39 participants (11 elite, 28 amateur). The proposed system successfully distinguishes expertise levels across a total of 4594 strokes, including augmented samples.. A hybrid Convolutional Neural Network-Bidirectional Long Short-Term Memory (CNN-BiLSTM) architecture was developed to autonomously extract spatiotemporal features from the raw kinematic signals of forehand, backhand, service, and volley strokes. The proposed model achieved an accuracy of 95.54%, significantly outperforming both traditional machine learning and state-of-the-art deep learning benchmarks. Qualitative t-distributed Stochastic Neighbor Embedding (t-SNE) analyses revealed that elite athletes form highly homogeneous clusters in the feature space. Furthermore, quantitative Asymmetry Index assessments confirmed that professionals exhibit superior bilateral coordination stability. These findings demonstrate that the proposed end-to-end system offers a robust, field-applicable solution for identifying technical excellence. It provides coaches with reliable digital biomarkers, thereby overcoming the limitations of subjective visual observation. Full article

(This article belongs to the Section Intelligent Sensors)

17 pages, 873 KB

Open AccessArticle

Query-Efficient Hard-Label Attack: A Prior-Guided Adam Ray Search Optimization

by Tianyi Ding, Xinjie Xu, Qi Xuan, Hanzhe Yu and Chen Ma

Sensors 2026, 26(10), 3272; https://doi.org/10.3390/s26103272 (registering DOI) - 21 May 2026

Deep neural networks are vulnerable to adversarial examples, even in hard-label black-box settings where only the top-1 prediction is available. To address the challenges of high-dimensional optimization under limited query budgets, we propose two query-efficient attack methods: Adam-OPT, which integrates Adam-based adaptive optimization [...] Read more.

Deep neural networks are vulnerable to adversarial examples, even in hard-label black-box settings where only the top-1 prediction is available. To address the challenges of high-dimensional optimization under limited query budgets, we propose two query-efficient attack methods: Adam-OPT, which integrates Adam-based adaptive optimization into the ray-search framework to stabilize and accelerate zeroth-order gradient updates; Prior-Adam-OPT, which further incorporates transfer-based priors from surrogate models to enhance gradient estimation. Adam-OPT leverages historical gradient information and per-parameter adaptive updates to improve convergence, while Prior-Adam-OPT constructs a prior-guided orthogonal search basis that combines surrogate and random directions, enhancing both gradient accuracy and query efficiency. Our approach demonstrates superior performance across CIFAR-10, ImageNet, and zero-shot CLIP models, consistently reducing perturbation magnitudes and improving attack efficiency compared to state-of-the-art hard-label attacks. Ablation studies highlight the importance of the number of vectors used for gradient estimation and the quality of surrogate models, showing that combining adaptive optimization with transfer-based priors provides a scalable and robust framework for generating high-quality adversarial examples in challenging black-box scenarios. Full article

(This article belongs to the Special Issue Security of AI-Driven Sensing Systems)

21 pages, 6200 KB

Open AccessArticle

A Novel MSPLL-Based Method for Frequency Synthesis in Hydrogen MASER

by Dipika Simariya, Sheeba Rani Johnson, Dileep Dharmappa, Suresh Dakkumalla, Prem Ranjan Dubey, Roopa Malali Vasanthakumar, Deva Arul Daniel and Subramanya Ganesh Thirukkodi

Sensors 2026, 26(10), 3271; https://doi.org/10.3390/s26103271 (registering DOI) - 21 May 2026

Frequency synthesis is an important aspect of an atomic clock. It is also imperative that the synthesized frequency exhibits good short term stability or, in other words, exhibits good phase noise. Conventionally single-PLL-system-based approaches have been made for realizing the frequency synthesizers required [...] Read more.

Frequency synthesis is an important aspect of an atomic clock. It is also imperative that the synthesized frequency exhibits good short term stability or, in other words, exhibits good phase noise. Conventionally single-PLL-system-based approaches have been made for realizing the frequency synthesizers required for hydrogen maser atomic clocks. In this article, a novel approach involving a master–slave-based phase-locked loop (MSPLL) method is presented for frequency synthesis in a hydrogen maser atomic clock. The novelty of this paper lies in the fact that the way two phase-locked loops are coupled to obtain advantage in improving the master oscillator’s stability to match maser physics subsystem stability and at the same time achieving lower jitter by the design. The design involves the usage of a master and a slave phase-locked loop with coupled custom designed direct digital synthesizers for ensuring that the hydrogen maser’s frequency stability is transferred to the master oscillator. The slave PLL (SPLL) generates a low jitter clock for the master PLL (MPLL), thereby guaranteeing reliable tracking of the input reference of 10 MHz, obtained by down-converting the maser physics subsystem frequency of ∼1.4 GHz. A novel mathematical model was derived for the proposed MSPLL design which aids in determination of the settling time of phase, which in turn, leads to the investigation of jitter variance in time domain. A detailed study and analysis of the settling time, phase noise in frequency domain, phase jitter in time domain. and stability performance is presented. The results were validated by the experimental data. The realized frequency synthesizer deduced a settling time of phase that can be adjusted between 689

μ

s to 811

μ

s. The synthesized frequency’s phase noise is ≤−114 dBc/Hz at 1 Hz offset, and it was observed that this design induces a very low phase noise to the output signal with respect to the physics subsystem. The achieved short-term stability of the output signal at 1 s is approximately (7.66 ×

10^{- 12}

)

τ^{- 1 / 2}

, which is very close to the physics subsystem stability. In terms of stability degradation factor, the proposed MSPLL design exhibits an excellent short-term stability that is one order better than that of the existing methods. Full article

(This article belongs to the Topic Navigation and Positioning System: Opportunities and Obstacles)

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30 pages, 17171 KB

Open AccessArticle

Optical Gas Imaging with Cooled and Uncooled Thermal Infrared Cameras

by Gabriel Jobert, Nicolas Vannier, Charlène Lefèvre, Eléa Bourliaud, Adrien Bertrand, Emmanuelle Chazelle and Eric Mallet

Sensors 2026, 26(10), 3270; https://doi.org/10.3390/s26103270 (registering DOI) - 21 May 2026

In a context of greenhouse-gas-reduction for climate-change mitigation, Optical Gas Imaging (OGI) is cited by US and EU regulations as a key technology for detecting methane leaks in the oil and gas industry. The paper outlines the principles of OGI, covering specificity of [...] Read more.

In a context of greenhouse-gas-reduction for climate-change mitigation, Optical Gas Imaging (OGI) is cited by US and EU regulations as a key technology for detecting methane leaks in the oil and gas industry. The paper outlines the principles of OGI, covering specificity of both high-performance cooled cameras and cost-effective thermal infrared uncooled cameras. It explains camera design, the optical-radiometric theory of contrast and sensitivity, and provides a comprehensive description of the key performance indicators (KPIs) such as NETD, NECL, and MDLR; together with parameters that influence them. These theoretical concepts are supported by measurements taken under laboratory conditions and outdoors, with wind and complex scenes. Finally, video-processing methods for visualizing gas leaks are presented, showing how they increase visual sensitivity and reduce the user’s cognitive load. Full article

(This article belongs to the Section Optical Sensors)

42 pages, 3786 KB

Open AccessArticle

Hybrid Validation of a Quality-Controlled, Waveform-Centered AI Framework with Optional Multi-Sensor Support for Seismic Monitoring

by Askar Abdykadyrov, Yerik Alipuly, Maxat Mamadiyarov, Bekbolat Tashev, Akerke Yerkinova and Kalmukhamed Tazhen

Sensors 2026, 26(10), 3269; https://doi.org/10.3390/s26103269 (registering DOI) - 21 May 2026

Rapid and reliable seismic monitoring requires accurate waveform inference, together with robustness to noise, incomplete sensing, and unstable predictions. This study investigates a quality-controlled, waveform-centered, AI-assisted framework for seismic event detection, P- and S-phase picking, graph-aware inter-station refinement, and rapid hazard-related characterization. The [...] Read more.

Rapid and reliable seismic monitoring requires accurate waveform inference, together with robustness to noise, incomplete sensing, and unstable predictions. This study investigates a quality-controlled, waveform-centered, AI-assisted framework for seismic event detection, P- and S-phase picking, graph-aware inter-station refinement, and rapid hazard-related characterization. The framework includes optional DAS, MEMS, and high-rate GNSS branches; however, the primary empirical validation is based on real waveform-centered IRIS records from the Almaty seismic region, not on a fully synchronized multimodal field deployment. The dataset includes seven seismic stations, HHZ waveforms sampled at 100 Hz, 219 seismic events, 1260 event traces, and 240 s P-centered windows from 1 January 2023 to 31 December 2024. Optional auxiliary branches are evaluated through controlled branch-availability, reduced-input, fallback, and stress-test scenarios. Under the standard-condition benchmark, the proposed framework achieved a precision of 0.941, recall of 0.932, F1 score of 0.936, false-alarm rate of 0.051, detection latency of 173 ms, and P- and S-pick mean absolute errors of 31 ms and 54 ms. Under controlled low-SNR testing, it retained an F1 score of 0.846. The findings support waveform-centered, quality-controlled monitoring, while broader cross-domain and fully synchronized multimodal validation remain necessary. Full article

(This article belongs to the Section Intelligent Sensors)

36 pages, 683 KB

Open AccessArticle

An FPGA-Based Event-Timing Front-End for Time-Resolved Sensing with Dual-Mode Experimental Characterization

by Juan Núñez and Rafaella Fiorelli

Sensors 2026, 26(10), 3268; https://doi.org/10.3390/s26103268 (registering DOI) - 21 May 2026

This work presents an FPGA-based edge-event timing front-end for time-resolved sensing and event-driven measurement scenarios. The proposed design is intended as a detector-independent timing subsystem whose architectural choices are motivated by constraints that are common in single-photon avalanche diode (SPAD)-based and other asynchronous [...] Read more.

This work presents an FPGA-based edge-event timing front-end for time-resolved sensing and event-driven measurement scenarios. The proposed design is intended as a detector-independent timing subsystem whose architectural choices are motivated by constraints that are common in single-photon avalanche diode (SPAD)-based and other asynchronous time-resolved sensing workflows, including event trustworthiness, dead-time sensitivity, and constrained downstream readout. Rather than treating the implementation as an isolated interpolation macro, this work evaluates it as an experimentally observable timing subsystem that combines carry-chain-based fine interpolation, coarse–fine timestamp formation, explicit event-quality assessment, dead-time-aware handling, and lightweight host-visible export. The experimental validation is organized around two complementary modes. An internal ILA-based mode is used to verify coherent front-end behavior under MHz-range short-pulse excitation, while a UART-based campaign identifies practical host-visible operating regions through baseline, repeatability, pulse-width, safe-versus-aggressive, and intermediate frequency-sweep experiments. The results identify a safe export-compatible operating point, a more exploratory high-rate regime, and an experimentally interpretable transition between them that, while not strictly monotonic in all metrics, does not exhibit catastrophic degradation across the explored frequency range. Taken together, the measurements indicate that the proposed architecture is best understood not as a best-case standalone time-to-digital (TDC) benchmark but as an experimentally characterized timing front-end whose practical behavior can be interpreted across complementary internal and export-visible operating regimes. Full article

(This article belongs to the Special Issue SPAD-Based Sensors and Techniques for Enhanced Sensing Applications)

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29 pages, 11781 KB

Open AccessArticle

MOCA-Net: A Model for Automatic Segmentation of Retrogressive Thaw Slumps from Sentinel-2 Imagery Along the Qinghai–Tibet Engineering Corridor

by Yijiang Li, Qiong Li, Guoxin Chen, Wenqi Li and Changyan Bao

Sensors 2026, 26(10), 3267; https://doi.org/10.3390/s26103267 (registering DOI) - 21 May 2026

Retrogressive thaw slumps (RTSs) serve as key indicators of global climate change and also pose significant risks to critical infrastructure along the Qinghai–Tibet Engineering Corridor (QTEC). Accurate automatic segmentation of RTSs using Sentinel-2 imagery is of great value for climate change research and [...] Read more.

Retrogressive thaw slumps (RTSs) serve as key indicators of global climate change and also pose significant risks to critical infrastructure along the Qinghai–Tibet Engineering Corridor (QTEC). Accurate automatic segmentation of RTSs using Sentinel-2 imagery is of great value for climate change research and risk assessment, owing to the dataset’s ready availability and extensive spatiotemporal coverage. However, this segmentation task remains challenging due to the complex morphology and variable sizes of RTSs, as well as their low contrast and fuzzy boundaries against the surrounding landscape in medium-resolution satellite imagery. To deal with these challenges, this study proposes the Multi-Scale Object-aware Context Attention Network (MOCA-Net), which enhances the Swin Transformer backbone through two critical components: the Feature Enhancement Network and Enhanced Decoder. Evaluation metrics show that MOCA-Net outperforms seven mainstream baseline models, achieving a Mean Intersection over Union (mIoU) of 0.8609 and an RTS-class IoU of 0.7473. The qualitative visual evaluation further confirms MOCA-Net’s improved performance in delineating RTSs through more accurate morphologies and boundaries. Ablation studies confirm that each designed component contributes to the MOCA-Net’s segmentation performance, and their combination yields more balanced results. This model unlocks the capability of Sentinel-2 imagery for accurate RTS segmentation, making it promising for applications over large spatiotemporal extents. Full article

(This article belongs to the Section Remote Sensors)

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22 pages, 3307 KB

Open AccessArticle

Geometry-Aware Enhanced 6DRepNet for Single-RGB Head Pose Estimation

by Hua Yang, Yuanyuan Li, Mingzhi Mu and Ming Zhao

Sensors 2026, 26(10), 3266; https://doi.org/10.3390/s26103266 - 21 May 2026

Head pose estimation is a fundamental task in facial analysis and behavior understanding. To address the limitations of 6DRepNet in single-RGB scenarios, particularly in high-level spatial discriminative region modeling, global feature-to-6D rotation representation mapping, and the optimization of large-pose challenging samples, this paper [...] Read more.

Head pose estimation is a fundamental task in facial analysis and behavior understanding. To address the limitations of 6DRepNet in single-RGB scenarios, particularly in high-level spatial discriminative region modeling, global feature-to-6D rotation representation mapping, and the optimization of large-pose challenging samples, this paper proposes a geometry-aware enhanced framework for head pose estimation. While preserving the 6D continuous rotation representation and its SO(3)-based geometric supervision mechanism, the proposed method improves the baseline model through the joint design of a Spatial Recalibration Module, a Residual Pose Mapping Head, and a Pose-Aware Weighted Geodesic Loss. Experiments are conducted using 300W-LP for training and AFLW2000 and BIWI for evaluation. The results show that the proposed method consistently outperforms the baseline 6DRepNet on both datasets, reducing the overall MAE from 3.97 to 3.72 on AFLW2000 and from 3.54 to 3.26 on BIWI. Ablation studies further verify the effectiveness and complementarity of the proposed components. These results demonstrate that the proposed method can effectively improve the accuracy and robustness of single-RGB head pose estimation without introducing additional modalities. Full article

(This article belongs to the Section Sensing and Imaging)

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36 pages, 9783 KB

Open AccessArticle

Spectral-YOLOv13: A Dual-Domain Vision-Mamba Sensing Framework for Fine-Grained Coral Health Assessment and Continuous Ecological Forecasting

by Litian Yang, Wenkun Chen, Zhuoyue Mo, Xin Gao, Minzhi Mo, Chunlei Xia and Liankuan Zhang

Sensors 2026, 26(10), 3265; https://doi.org/10.3390/s26103265 - 21 May 2026

Coral reefs are among the most important and vulnerable marine ecosystems worldwide. AI-powered underwater visual monitoring has become essential for effective reef conservation, yet current methods still face severe limitations: spectral ambiguity caused by underwater turbidity, fine-grained confusion in early coral health assessment, [...] Read more.

Coral reefs are among the most important and vulnerable marine ecosystems worldwide. AI-powered underwater visual monitoring has become essential for effective reef conservation, yet current methods still face severe limitations: spectral ambiguity caused by underwater turbidity, fine-grained confusion in early coral health assessment, and discrete forecasting models that cannot represent continuous ecological degradation dynamics. To address these issues, we propose Spectral-YOLOv13, a dual-domain vision-Mamba sensing framework for high-precision coral health evaluation and continuous ecological forecasting. The framework incorporates three novel components: a Wavelet-Integrated Omni-Neck (WIO-Neck) to perform multi-scale spectral filtering and suppress turbidity-induced noise; a Contrastive Prototype Head (CP-Head) to enhance discriminability between visually similar health states; and a Bio-Mamba Predictor based on state-space models to capture long-term continuous health trajectories. Extensive experiments on the CR-Mix++ dataset demonstrate that Spectral-YOLOv13 achieves 53.8% mAP with strong robustness in turbid underwater environments. It reduces four-week forecasting error by 26.8% and maintains real-time inference speed at 112 FPS. This work provides a reliable and high-performance vision framework for practical underwater coral reef monitoring and proactive conservation management. Full article

(This article belongs to the Special Issue AI-Based Computer Vision Sensors & Systems—2nd Edition)

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29 pages, 19163 KB

Open AccessArticle

Real-Time Small Retail Product Detection in Low-Light Intelligent Cabinets Under Complex Backgrounds

by Moushiqi Yang, Junjie Cai, Yuanyuan Yang, Jian Chen and Kai Xie

Sensors 2026, 26(10), 3264; https://doi.org/10.3390/s26103264 - 21 May 2026

Intelligent retail cabinets require accurate and real-time detection of small retail products in complex environments, particularly under low-light conditions and large-scale variations. However, existing object detection methods often suffer from insufficient feature representation and unstable performance in small-object retail commodity recognition tasks under [...] Read more.

Intelligent retail cabinets require accurate and real-time detection of small retail products in complex environments, particularly under low-light conditions and large-scale variations. However, existing object detection methods often suffer from insufficient feature representation and unstable performance in small-object retail commodity recognition tasks under low illumination and complex backgrounds. To address these challenges, this paper proposes a real-time small retail product detection framework based on YOLOv26 for low-light intelligent cabinet environments, aiming to improve detection accuracy, robustness, and deployment efficiency. A C3k2-enhanced multi-scale feature extraction module is introduced to strengthen feature representation for small retail products, while a novel detection head integrates minimum-resolution feature layers and an Efficient Multi-scale Attention (EMA) mechanism to enhance feature fitting ability under low-light conditions. In addition, convolution-based downsampling and Content-Aware ReAssembly of Features module (CARAFE) is adopted to improve feature fusion efficiency and reduce computational overhead. Experimental results on the RPC commodity dataset and the 6th Commodity Recognition Competition dataset demonstrate that the proposed method achieves improved detection performance compared with baseline models, with a 0.9% increase in Recall and a 0.2% improvement in mean Average Precision at IoU threshold 0.50 (mAP@50) while maintaining competitive mean Average Precision averaged over IoU thresholds from 0.50 to 0.95 (mAP@50-95). While the GFLOPS value rose from 5.8 to 6.3, deployment on the Jetson Nano platform achieves 25 FPS, demonstrating real-time detection capability in intelligent retail environments. The proposed framework provides a reliable and deployable solution for small retail product detection in low-light intelligent cabinet systems. Full article

(This article belongs to the Special Issue Real-Time Object Detection and Classification Using Advanced Sensing Techniques)

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23 pages, 32417 KB

Open AccessArticle

Vision-Based Person-Following Algorithm for Assistive Elderly-Care Quadruped Robots

by Vishnudev Kurumbaparambil, Subashkumar Rajanayagam and Stefan Twieg

Sensors 2026, 26(10), 3263; https://doi.org/10.3390/s26103263 - 21 May 2026

The demographic shift towards an aging population necessitates innovative solutions for care and mobility support. While commercial quadruped robots like the Unitree Go1 offer dynamic stability, their native following modes often lack the safety margins and predictability required, and they do not consistently [...] Read more.

The demographic shift towards an aging population necessitates innovative solutions for care and mobility support. While commercial quadruped robots like the Unitree Go1 offer dynamic stability, their native following modes often lack the safety margins and predictability required, and they do not consistently follow the user, at times deviating and navigating independently. This paper presents a robust, vision-based, person-following algorithm designed to address these limitations. Utilizing a ZED 2 stereo camera and Robot Operating System (ROS), the system employs a finite state machine to ensure deterministic target tracking. A velocity control strategy partitions the robot’s motion into distinct stability, proportional, and braking zones based on depth data to ensure fluid interaction. The framework was validated on a Unitree Go1 quadruped platform in an outdoor environment involving 90-degree turns to evaluate tracking robustness. By operating in a headless mode, the system achieved a mean processing latency of

66.5 \pm 4.3

ms. Experimental results demonstrated consistent operational stability, 0.0% intrusion into the intimate safety zone, and effective velocity synchronization between

0.47

and

0.54

m/s. While this study establishes a robust technical baseline using healthy subjects, it serves as a preliminary development platform; further iterative testing with elderly users in clinical settings is required to move toward deployment. Beyond the evaluated trials, the framework maintained reliable functional performance across various care facility workshops, successfully following the target in all deployment scenarios. These findings establish a stable technical foundation for the future development of robotic walking partners. Full article

(This article belongs to the Special Issue Intelligent Sensing for Robotic Control and Visual Perception)

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36 pages, 6977 KB

Open AccessArticle

SparseTrack: A Physics-Informed Transformer Framework for Real-Time Human Motion Reconstruction from Sparse IMUs

by Adithya Balasubramanyam, Suchir Murali Velpanur, Sushma Edhala Jeevarathnam, Tejasree Chekuri Jayachandra, Prasad Honnavalli and Gowri Srinivasa

Sensors 2026, 26(10), 3262; https://doi.org/10.3390/s26103262 - 21 May 2026

Wearable inertial measurement units are widely used for human motion analysis due to their portability; however, most IMU-based motion capture systems rely on dense sensor configurations that increase cost, complexity, and usability challenges in real-world applications. To address this limitation, this paper presents [...] Read more.

Wearable inertial measurement units are widely used for human motion analysis due to their portability; however, most IMU-based motion capture systems rely on dense sensor configurations that increase cost, complexity, and usability challenges in real-world applications. To address this limitation, this paper presents a sparse inertial human motion reconstruction framework that uses only five wearable sensors while maintaining real-time performance and biomechanical plausibility. The proposed framework integrates Movella Xsens DOT IMUs with a learning-based inverse kinematics pipeline and a real-time biomechanical digital twin for motion reconstruction and visualization. The evaluation was conducted in two phases: first, a real-time motion streaming system was established to validate sensor alignment, coordinate frame consistency, and end-to-end latency; second, a sparse inference framework was trained using the Virginia Tech Natural Motion Dataset combined with a custom dataset containing hard negative samples. Experimental results show that the system can accurately reconstruct full-body human motion, excluding head movement, with a local Mean Per-Joint Position Error of 5.96 cm using only five sensors. Comparative ablation studies demonstrate that Transformer-based temporal modeling achieves better geometric accuracy and temporal smoothness than recurrent and convolutional baselines, while physics-informed regularization and hard negative mining significantly improve biomechanical consistency and reduce motion jitter. Real-time experiments further demonstrate that the framework operates within interactive latency limits, highlighting its potential for biomechanical digital twin applications. Full article

(This article belongs to the Section Intelligent Sensors)

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18 pages, 5622 KB

Open AccessArticle

MscaVPR: Multi-Scale Coordinate Attention Network for Robust Visual Place Recognition

by Xiaohan Gao, Zhinong Zhong, Yongjian Tan, Ning Jing, Anran Yang and Qingren Jia

Sensors 2026, 26(10), 3261; https://doi.org/10.3390/s26103261 - 21 May 2026

Visual place recognition (VPR) aims to localize a query image by matching its visual representation against a geotagged database. One major challenge in VPR is to learn place representations that remain robust under appearance changes, viewpoint variations, and perceptual aliasing. However, existing VPR [...] Read more.

Visual place recognition (VPR) aims to localize a query image by matching its visual representation against a geotagged database. One major challenge in VPR is to learn place representations that remain robust under appearance changes, viewpoint variations, and perceptual aliasing. However, existing VPR methods still show limitations in adaptive multi-scale feature fusion and viewpoint-aware training supervision, which may hinder robustness under severe viewpoint changes. In this paper, we propose MscaVPR, a VPR framework that combines multi-scale feature enhancement with azimuth-aware training. Specifically, a Multi-Scale Spatial Pyramid Attention (MSPA) module is incorporated to aggregate regional features across different spatial scales, and Coordinate Attention (CA) is used to encode positional cues for spatially refined feature learning. To further enhance viewpoint robustness, we design an azimuth-guided training strategy that selects hard positive samples with significant viewpoint discrepancies and optimizes them using an azimuth-aware auxiliary loss function.Experimental results on multiple benchmark datasets indicate that MscaVPR generally outperforms the strong baseline and demonstrates improved performance under challenging conditions. In particular, Recall@1 is improved by 2.1%, 1.9%, and 1.9% on the AmsterTime, SVOX-Night, and SVOX-Sun datasets, respectively. The results demonstrate that explicitly incorporating azimuth cues provides an effective complement to existing multi-scale and attention-based VPR methods. Full article

(This article belongs to the Section Navigation and Positioning)

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32 pages, 1124 KB

Open AccessArticle

An Inverse Generalized Conversion Filter for State Estimation in Nonlinear Adversarial Sensing Systems

by Yi-An Xi, Xin-Hao Dong and Sun-Yong Wu

Sensors 2026, 26(10), 3260; https://doi.org/10.3390/s26103260 - 21 May 2026

In adversarial games involving intelligent sensing systems, inverse filtering plays an important role in the defender’s decision-making by estimating the opponent’s perception based on the defender’s sensor observations. Existing inverse nonlinear filters, such as the inverse quadrature Kalman filter and the inverse extended [...] Read more.

In adversarial games involving intelligent sensing systems, inverse filtering plays an important role in the defender’s decision-making by estimating the opponent’s perception based on the defender’s sensor observations. Existing inverse nonlinear filters, such as the inverse quadrature Kalman filter and the inverse extended Kalman filter, are limited in their ability to fully exploit higher-order nonlinear information contained in sensor observations. To address this issue, this paper proposes an inverse generalized-conversion-based filter (I-GCF). Unlike conventional inverse filters, the proposed method not only extracts nonlinear information through deterministic sampling but also constructs a generalized optimal decorrelating transformation function to capture nonlinear observation information that cannot be obtained by the linear minimum mean-square error (LMMSE) estimator. As a result, it enhances the exploitation of higher-order nonlinear sensor information and improves the estimation accuracy and stability of inverse filtering in nonlinear sensing environments. Furthermore, this paper derives general expressions for the time complexities of both GCF and I-GCF, thereby further enriching their theoretical framework. Numerical results demonstrate that, in nonlinear environments, the proposed I-GCF achieves higher estimation accuracy and better stability than conventional inverse filters. Full article

(This article belongs to the Section Electronic Sensors)

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15 pages, 2746 KB

Open AccessArticle

DGrA: Lightweight Modulation Recognition Based on Hybrid Neural Networks

by Xu Chen, Rui Gao, Ding Xu and Hongbo Zhu

Sensors 2026, 26(10), 3259; https://doi.org/10.3390/s26103259 - 21 May 2026

Automatic modulation recognition has been recognized as an effective technique for non-cooperative communication and intelligent transmission. In this paper, we propose a new lightweight method for automatic modulation recognition, aiming to extract crucial discriminative features of signals for higher recognition accuracy while reducing [...] Read more.

Automatic modulation recognition has been recognized as an effective technique for non-cooperative communication and intelligent transmission. In this paper, we propose a new lightweight method for automatic modulation recognition, aiming to extract crucial discriminative features of signals for higher recognition accuracy while reducing spatial costs. To enhance the dissimilarity between samples, this paper combines an improved attention block and convolutional operations with the recurrent neural network, focusing on key features during the training phase to efficiently differentiate signal sequences. By replacing standard convolutions with depthwise separable convolutions, the model’s computational complexity is reduced while enhancing its feature extraction capability. Furthermore, the method incorporates pruning to reduce ineffective features, decreasing the model size while maintaining performance. Experimental results on RadioML2016.10a demonstrate that the proposed method outperforms other comparative methods, exhibiting both higher recognition accuracy and smaller model size. To validate real-world applicability, the algorithm was implemented on a software-defined radio platform for signal transmission and reception under practical conditions, achieving an accuracy of 87.22% in the presence of environmental noise, thus confirming its effectiveness in real-world scenarios. Full article

(This article belongs to the Special Issue Intelligent Signal Processing Techniques for Wireless Communications)

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22 pages, 2625 KB

Open AccessArticle

Lens Antenna Arrays for THz Superconducting HEB Mixers: A Review and a Metasurface Coupling Approach

by Yuner Gan, Ruiguang Peng, Shijia Feng, Maimai Mu and Qian Wang

Sensors 2026, 26(10), 3258; https://doi.org/10.3390/s26103258 - 21 May 2026

Terahertz hot electron bolometer (HEB) mixers, which offer the highest sensitivity in the frequency range above 1.5 THz, are equipped on space observatories to detect the terahertz radiation emitted from the interstellar medium within galaxies. To increase the mapping speed, it is essential [...] Read more.

Terahertz hot electron bolometer (HEB) mixers, which offer the highest sensitivity in the frequency range above 1.5 THz, are equipped on space observatories to detect the terahertz radiation emitted from the interstellar medium within galaxies. To increase the mapping speed, it is essential to develop large HEB mixer arrays. However, conventional quasi-optical coupling methods, including single large silicon lens approaches and silicon lens array approaches, suffer from the conflict of achieving high filling factor and uniform illumination on the HEB mixer array. This paper reviews the research progress on quasi-optical coupled HEB mixer arrays and proposes an innovative array coupling scheme to overcome the existing limitation. We designed a metasurface beam shaper based on the Gerchberg–Saxton algorithm and COMSOL simulation to transform an incoming Gaussian beam into a flattop beam in the focal plane, thereby forming uniform illumination for an antenna-coupled HEB mixer array. The metasurface is intended primarily for uniform local oscillator (LO) distribution across the array. The simulation of the metasurface beam shaper at 0.6 THz demonstrates a flattop beam with a flat region approximately 3 mm wide, and the intensity across this region varies by only 4.2%. The same simulation is also performed at 1.6 THz, and the flat region is 1.5 mm wide with a 5.5% intensity variation. This work demonstrates the feasibility of using a metasurface to convert a Gaussian beam into a flattop beam at terahertz frequencies as well as a pathway for array-level coupling schemes for HEB mixer arrays with high filling factor and uniform illumination. Full article

(This article belongs to the Section Physical Sensors)

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24 pages, 6719 KB

Open AccessArticle

Design and Initial Evaluation of a Low-Cost Microprocessor-Controlled Ankle Prosthesis

by Zhanar Bigaliyeva, Abu-Alim Ayazbay, Sayat Akhmejanov, Nursultan Zhetenbayev, Aidos Sultan, Yerkebulan Nurgizat, Abu Jazar Ussam, Gulzhamal Tursunbayeva, Arman Uzbekbayev, Kassymbek Ozhikenov, Gani Sergazin and Yelubayeva Lazzat

Sensors 2026, 26(10), 3257; https://doi.org/10.3390/s26103257 - 21 May 2026

Lower-limb amputation remains a significant clinical and socio-economic challenge, while the high cost of microprocessor-controlled prostheses (MPKs) limits their widespread accessibility. This paper presents the design and preliminary laboratory-scale evaluation of a low-cost microprocessor-controlled ankle prosthesis intended as a feasibility-oriented alternative platform for [...] Read more.

Lower-limb amputation remains a significant clinical and socio-economic challenge, while the high cost of microprocessor-controlled prostheses (MPKs) limits their widespread accessibility. This paper presents the design and preliminary laboratory-scale evaluation of a low-cost microprocessor-controlled ankle prosthesis intended as a feasibility-oriented alternative platform for future active prosthetic system development. Building upon the previously developed V1 mechanical architecture, an updated CAD model was created in the SolidWorks 2024 environment, and the kinematic configuration was refined using a ball-screw transmission (SFU1204-300) driven by a NEMA 17 stepper motor. The electronic control system integrates an ESP32 microcontroller, an MPU9250 inertial measurement unit (IMU), a limit switch for initial-position detection, and a WiFi-based REST API interface for communication and control. Laboratory no-load experiments demonstrated controlled positional behavior, repeatable angular response, and successful operation of the homing procedure within a motion range of 0–4200 motor steps. The prototype actively generated dorsiflexion–plantar flexion motion in the sagittal plane, while a passive inversion–eversion mechanism was incorporated and intended to improve structural adaptability. IMU-based measurements enabled preliminary monitoring of angular displacement and positional behavior during the experiments. The presented prototype represents an initial engineering feasibility study of a low-cost active ankle actuation architecture and provides a foundation for future investigations involving load-bearing experiments, biomechanical gait analysis, and closed-loop control implementation. Full article

(This article belongs to the Section Sensors and Robotics)

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13 pages, 233 KB

Open AccessArticle

Wearable-Measured Physical Activity Goal Adherence and Body Composition Change in a 12-Month mHealth Weight Loss Trial

by Zhadyra Bizhanova, Lora E. Burke, Maria M. Brooks, Bonny Rockette-Wagner, Jacob K. Kariuki and Susan M. Sereika

Sensors 2026, 26(10), 3256; https://doi.org/10.3390/s26103256 - 21 May 2026

Background: Wearable activity trackers are commonly used in mHealth weight loss interventions, but evidence linking adherence to moderate-to-vigorous physical activity (MVPA) goals with changes in body composition is limited. We examined associations between adherence to study-prescribed MVPA goals and changes in percent body [...] Read more.

Background: Wearable activity trackers are commonly used in mHealth weight loss interventions, but evidence linking adherence to moderate-to-vigorous physical activity (MVPA) goals with changes in body composition is limited. We examined associations between adherence to study-prescribed MVPA goals and changes in percent body fat and sex-specific waist circumference (WC) over 12 months in the SMARTER trial. Methods: Participants (N = 502, 79.5% female; mean age 45 years; mean BMI 33.7 kg/m²) were randomized to self-monitoring of diet, PA, and weight (SM) or SM plus daily tailored feedback messages (SM + FB). Weekly adherence to ≥300 min/week of MVPA was quantified using Fitbit-derived equivalents. Associations between MVPA adherence and changes in percent body fat and sex-specific WC over 12 months were examined using linear mixed models. Results: Among the full sample, greater MVPA adherence was associated with reductions in body fat (b = −0.01; 95% CI: −0.02, −0.005), but not in WC (women: b = −0.01; −0.03, 0.01; men: b = −0.03; −0.05, 0.0002). Among the completers, higher adherence was associated with decreases in body fat (b = −0.01; −0.02, −0.004) and WC (women: b = −0.02; −0.04, −0.004; men: b = −0.04; −0.08, −0.003). Conclusions: Higher MVPA adherence was associated with favorable changes in adiposity over 12 months, supporting the use of wearable-derived PA measures in long-term mHealth behavioral interventions. Full article

(This article belongs to the Special Issue Wearable Sensors and Signal Processing Technology for Digital Health Applications)

24 pages, 12170 KB

Open AccessArticle

SA-YOLOv11s: A Slicing-Attention YOLOv11s with U-IoU for Oil Leakage Detection in Power Equipment

by Daoyuan Liu, Chenlei Liu, Zhijuan Wang, Shiji Zhang, Yulong Yang, Tong Zhao and Xiaolong Wang

Sensors 2026, 26(10), 3255; https://doi.org/10.3390/s26103255 - 20 May 2026

To address the challenges of low detection accuracy and high missed detection rates in insulating oil leakage detection for power equipment—arising from small and densely distributed oil stains, structural occlusion, and complex background interference—this paper proposes a detection method based on an enhanced [...] Read more.

To address the challenges of low detection accuracy and high missed detection rates in insulating oil leakage detection for power equipment—arising from small and densely distributed oil stains, structural occlusion, and complex background interference—this paper proposes a detection method based on an enhanced YOLOv11s (You Only Look Once version 11 small) architecture. First, a dedicated dataset is constructed, encompassing four representative scenarios—small object detection, complex background, multi-object detection and equipment occlusion—to evaluate detection performance. Second, in terms of network design, a proposed attention module, SimAMWS (Simple Attention Module With Slicing), is introduced. This module enhances the model’s sensitivity to subtle and irregular oil stains by utilizing slicing operations and localized energy-based weighting. For bounding box regression, a U-IoU (Unified Intersection over Union) loss is adopted, which incorporates a dynamic scaling mechanism during training to enable the model to focus more effectively on high-quality candidate boxes—leading to improved localization accuracy, particularly suited to the characteristics of oil leakage. Finally, comparative experiments are conducted against mainstream object detectors including SSD (Single Shot MultiBox Detector), Faster R-CNN (Region-based Convolutional Neural Network), YOLOv5s, YOLOv8s, and the baseline YOLOv11s. The proposed method achieves an mAP@0.5 (mean Average Precision at IoU = 0.5) of 97.7% and an mAP@0.5:0.95 of 66.9%, with an inference speed of 96.4 FPS. These results demonstrate that the proposed model delivers higher detection accuracy while maintaining high inference efficiency, making it well-suited for real-time oil leak detection in power equipment and supporting the development of intelligent operation and maintenance systems in the power industry. Full article

(This article belongs to the Special Issue Advances in Sensors and Metering Solutions for Smart Grids)

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18 pages, 1577 KB

Open AccessArticle

Deep Learning-Based Heartbeat Detection from 3D Seismocardiography for Robust Heart Rate Monitoring

by Sobuz Rana, Jukka A. Lipponen and Mika P. Tarvainen

Sensors 2026, 26(10), 3254; https://doi.org/10.3390/s26103254 - 20 May 2026

Accurate monitoring of heart rate (HR) is critical for assessing cardiac functions in a wide range of health and wellness applications. Seismocardiography (SCG), which captures subtle chest vibrations using wearable accelerometers, provides a non-invasive and cost-effective approach for resting and nocturnal HR monitoring. [...] Read more.

Accurate monitoring of heart rate (HR) is critical for assessing cardiac functions in a wide range of health and wellness applications. Seismocardiography (SCG), which captures subtle chest vibrations using wearable accelerometers, provides a non-invasive and cost-effective approach for resting and nocturnal HR monitoring. This study presents a deep learning-based approach for accurate heartbeat detection and HR estimation from three-dimensional SCG signals. The model was trained on a large-scale dataset of resting SCG signals collected from 6600 subjects and evaluated on an independent cohort of 947 individuals. For short-term (≤5 min) resting SCG recordings, the model achieved robust performance in heartbeat detection (PPV: 0.979, sensitivity: 0.916, F1-score: 0.946). HR estimation showed high accuracy, with a mean absolute error (MAE) of 0.27 bpm, root mean square error (RMSE) of 1.02 bpm, and correlation of 0.996 with the reference HR. To assess real-world applicability, the model was further evaluated on 28 nocturnal recordings acquired using Apple Watch accelerometer, yielding an MAE of 1.10 bpm, an RMSE of 1.88 bpm, and a correlation of 0.982. The proposed SCG-based deep learning model demonstrates robust and highly accurate HR monitoring in both resting and nocturnal conditions, highlighting its potential for integration with consumer-grade wearable devices in a server-based analysis pipeline. Full article

(This article belongs to the Special Issue Human Signal Processing Based on Wearable Non-Invasive Device: 2nd Edition)

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