Search Results (711)

To address the challenges of limited storage space and mobile launch-and-landing operations for vehicle-mounted multirotor UAV swarms, this paper proposes a stackable Cone-Sleeve UAV swarm system. The UAV airframe incorporates a through-body central sleeve integrated with conical guidance structures, which cooperate with a vertical guide rod mounted at the center of the mobile platform to achieve geometric passive pose correction during landing. In addition, a UWB-based onboard local positioning and navigation system is developed, in which a tightly coupled UWB/IMU estimator is employed to achieve high-precision relative state estimation for the UAV swarm. A five-stage finite state machine (FSM) schedules the landing sequence. During terminal landing, a motion feedforward control strategy is introduced for dynamic motion compensation and to ensure seamless state transitions. Simulation and vehicle-mounted experimental results demonstrate that, strictly under low-speed (≤0.5 m/s), constant-velocity straight-line motion conditions, the proposed system enables autonomous vertical takeoff and landing as well as rapid stacked launch-and-landing operations for multiple UAVs. The cooperative guidance strategy integrating active control and the Geometric Passive Guidance (GPG) mechanism improves the precision and speed of swarm landing operations. The proposed system provides a feasible system-level solution for the storage, transportation, and autonomous rapid launch-and-landing of high-density UAV swarms. Full article

Static wake steering can increase wind-farm power production, but its application to floating offshore wind farms requires assessment of the coupled wake, platform, structural, and station-keeping response. This study evaluates whether power-maximizing static yaw setpoints identified using the steady, control-oriented FLORIS model retain their benefit when transferred without re-optimization to a coupled FAST.Farm floating wind-farm model. The reference farm comprises four IEA Wind 15 MW turbines mounted on VolturnUS-S semi-submersible platforms. Greedy and static wake-steering operations are compared at three below-rated wind speeds, three sea states, and five matched turbulent-inflow realizations, resulting in 90 farm-level FAST.Farm simulations. Wake behavior is characterized through wake-center deflection, meandering, and velocity-deficit profiles, while turbine and mooring fatigue responses are evaluated using paired damage-equivalent-load statistics. Static wake steering increases mean farm power under all nine investigated wind–wave conditions. The gains are approximately 5.1–$5.2\%$ at $7\mathrm{m}{\mathrm{s}}^{-1}$, $5.0$–$5.1\%$ at $8\mathrm{m}{\mathrm{s}}^{-1}$, and $4.0$–$4.2\%$ at $9\mathrm{m}{\mathrm{s}}^{-1}$, with all paired $95\%$ confidence intervals remaining above zero. The gain results from a power redistribution in which the intentionally yawed upstream turbine incurs a local loss that is exceeded by the combined recovery of the downstream turbines. The fatigue response is strongly component- and turbine-dependent. The paired farm-mean blade-root DEL decreases by $0.82$–$2.24\%$, whereas the tower-base DEL increases by $0.76$–$2.78\%$, and the FairTen1 response generally increases by $0.88$–$2.92\%$. The farm-mean yaw-bearing response is mixed, ranging from a $1.15\%$ reduction to a $4.32\%$ increase. Turbine-level analysis reveals larger localized penalties, reaching approximately $10.4\%$ for the yaw-bearing DEL and $12.8\%$ for FairTen1. Spectral analysis associates the yaw-bearing response with yaw-induced aerodynamic and structural excitation, while the tower-base response is strongly influenced by low-frequency wave–platform dynamics. A complementary FLORIS sensitivity analysis demonstrates that the optimized aerodynamic benefit depends strongly on wind direction, spacing, wind speed, and turbulence intensity. For a Tampen-derived 11-turbine layout, resource weighting over the modeled 4–$13\mathrm{m}{\mathrm{s}}^{-1}$ interval produces an annual energy-contribution increase of $3.653\mathrm{GWh}{\mathrm{year}}^{-1}$, or $0.921\%$. These results provide numerical evidence that static wake steering can retain a positive power benefit in a coupled floating wind-farm environment, but controller assessment must include turbine- and component-specific dynamic loads rather than farm power alone. Full article

Accurate crack width measurement is essential for the condition assessment of reinforced concrete (RC) bridges, yet most unmanned aerial vehicle (UAV) inspections remain limited to pixel-level observations that cannot be converted into reliable metric units without an external scale reference. This paper presents a lightweight, drone-agnostic UAV-mounted metrology system that enables standards-aligned metric crack width measurement directly from inspection imagery. The payload integrates a focusable diffractive optical element (DOE) red laser that projects a cross pattern of known angular geometry, three TF-Luna time-of-flight (ToF) distance sensors, and an ESP-WROOM-32 microcontroller that provides dual-rate sampling, Bluetooth Low Energy (BLE) streaming, and on-board logging. A two-stage calibration links the synchronized distance measurements to the physical length of the projected cross, yielding an image-specific pixel-to-millimeter scale that is applied to pixel-level crack widths obtained from a vision-based segmentation pipeline. The system is field-deployed on the Puente Huamani Bridge in Pisco, Peru, where measurements of 39 cracks classified under AASHTO MBEI condition states are compared against independent manual measurements by six inspectors. The proposed system reduces measurement variability across all condition states (CS), lowering the average coefficient of variation from 0.36 to 0.10 for fine CS1 cracks, from 0.27 to 0.11 for CS2, and from 0.22 to 0.07 for CS3. Cross-platform adaptability is demonstrated through an additional deployment on a DJI Matrice 350 RTK at the Low Level Bridge in Edmonton, Canada. The results indicate that the system provides a practical, low-cost, and scalable solution for repeatable, standards-aligned UAV-based bridge crack assessment. Full article

To harness the terrain adaptability of legged systems and the high-speed efficiency of wheeled platforms, this paper presents the design of a novel leg-wheel hybrid mobile platform intended for enhanced obstacle negotiation. The proposed system comprises six identical leg-wheel modules, each integrating a closed-chain mechanical leg with an independently driven wheel mounted at the tip. The platform operates in two distinct modalities: a pure leg mode and a leg-wheel composite mode. In the leg mode, locomotion is driven by crank motors, providing exceptional mobility across uneven terrain. Conversely, the composite mode utilizes both crank and pitch link motors to facilitate obstacle surmounting, while hub motors ensure high-efficiency propulsion. Comprehensive gait planning for both modes is conducted, accompanied by a detailed analysis of the platform’s obstacle-negotiation capabilities. Kinematic analysis and gait simulations validate the platform’s superior mobility and efficient obstacle-crossing performance under the dual-mode strategy. Prototype experiments further confirm the feasibility of the mechanical design, demonstrating significant proficiency in traversing obstacles. This research contributes a novel design exploration by serially combining a closed-chain leg mechanism with an actuated wheel. The adopted closed-chain architecture offers the distinct advantages of high foot clearance and a single degree of freedom (DoF), which are critical for achieving reliable and effective obstacle-surmounting capabilities. Full article

This paper presents the design and simulation-based validation of an acoustic navigation system intended for operation within a swarm of underwater vehicles. The system is deployed on a mobile leader unit, while the remaining vehicles, referred to as followers, navigate relative to the leader. The proposed solution utilises two or three acoustic transmitters mounted at the front and rear, and, in the option with three transmitters, also in the middle of the leader platform. These transmitters periodically emit acoustic signals that are received by the follower vehicles. By measuring the time-of-flight of the received signals, followers estimate their distances to the transmitters. This dual(triple)-range information, combined with Kalman filter dead-reckoning, enables relative position estimation with respect to the leader, supporting coordinated swarm movement without reliance on external positioning infrastructure such as GPS, which is unavailable underwater. The system was evaluated in a simulation environment across multiple scenarios with varying levels of distance-measurement error. Rather than modelling detailed acoustic signal propagation, the study focuses on assessing the robustness of the positioning method to measurement inaccuracies. The results demonstrate that the proposed configuration provides useful relative positioning accuracy under a range of error conditions and identifies the operating conditions in which its performance deteriorates, supporting the feasibility of the proposed approach for leader–follower coordination in underwater swarms. Full article

Optical coherence tomography (OCT) and photoacoustic imaging (PAI) provide complementary structural and absorption contrasts but require different coupling conditions: 1310 nm swept-source OCT is attenuated by water, whereas PAI requires acoustic coupling. We developed a large-field dual-modal imaging system combining temporal medium separation with hardware-based coordinate locking. The OCT head, linear-array ultrasound transducer, and photoacoustic excitation fiber bundle were mounted on a rigid common platform, and a one-time calibration established a two-dimensional affine transformation between the modality coordinate systems. OCT was acquired in air and PAI in deionized water within a common large-field coordinate range. In five paired air–water measurements with an approximately 23 mm water path, the displayed OCT peak level decreased from 98.4 ± 1.5 dB in air to 79.4 ± 1.8 dB in water, corresponding to a mean reduction of 19.0 ± 1.4 dB. Quantitative registration was evaluated using a 5 × 5 dual-modal landmark phantom, with nine landmarks used for affine calibration and 16 excluded landmarks reserved for independent validation. The mean two-dimensional validation error was 0.235 ± 0.128 mm, with an RMSE of 0.266 mm and a maximum error of 0.446 mm. Five additional medium-switching cycles performed without recalibration yielded an overall registration error of 0.369 ± 0.163 mm across 80 validation measurements. PA spatial resolution was further characterized using six thin hair targets, yielding lateral and axial FWHM values of 0.342 ± 0.069 mm and 0.394 ± 0.073 mm, respectively. These results demonstrate reproducible two-dimensional en face OCT–PA coordinate mapping under modality-specific coupling conditions and support the proposed workflow as a phantom-based technical validation for large-field multimodal imaging. Full article

Nd laser posterior capsulotomy is the standard treatment for posterior capsule opacification following cataract surgery. Although generally considered safe, inadvertent laser impacts on the intraocular lens (IOL) optic may induce permanent surface defects that contribute to postoperative dysphotopsias and reduced visual quality. This experimental study investigated the optical consequences of Nd laser-induced damage on two commercially available hydrophobic acrylic IOLs, focusing on retinal light distribution and optical image quality. Two hydrophobic acrylic monofocal IOL models, the CT LUCIA (Carl Zeiss Meditec) and the AcrySof IQ (Alcon), were mounted on a customized experimental holder and exposed to standardized Nd laser applications consisting of 5, 10, or 15 laser shots. Laser interactions were documented using the PhysioGo.Lite laser platform combined with infrared thermal imaging. Untreated IOLs served as controls. Optical performance was subsequently evaluated using a standardized optical bench according to ISO recommendations. Point spread function (PSF) and modulation transfer function (MTF) analyses were performed to quantify retinal image quality, light scattering, and optical degradation. Retinal light distribution was assessed using a high-resolution projection screen simulating the retinal image. Laser exposure produced permanent focal defects on the anterior optical surface of both IOL models, resulting in measurable optical degradation. Even the lowest laser exposure (five shots) generated detectable alterations in light propagation, characterized by increased peripheral light scattering, enlargement of the PSF halo, reduced central peak intensity, and irregular light distribution across the simulated retinal plane. Descriptively, increasing numbers of laser impacts were associated with more pronounced optical disturbances, particularly in the AcrySof IQ samples. MTF analysis demonstrated a reduction in optical performance across multiple spatial frequencies, indicating deterioration of image contrast and resolving power. Although both hydrophobic acrylic IOL models exhibited optical alterations after laser exposure, descriptive differences in the magnitude and distribution of light scatter suggested a possible influence of material composition, refractive index, and surface microarchitecture. These observations should be considered preliminary because of the limited sample size and absence of inferential statistical analysis. Under the present experimental conditions, Nd:YAG laser-induced pitting was associated with measurable structural and optical alterations in two hydrophobic acrylic IOL models. Surface defects alter retinal light distribution, increase forward light scatter, and reduce optical quality, providing a possible optical mechanism that may contribute to postoperative dysphotopsias, although clinical visual symptoms were not directly evaluated in this study. These findings highlight the importance of meticulous laser focusing on the posterior capsule to minimize inadvertent IOL damage and preserve postoperative visual quality. Further investigations combining optical bench analyses with patient-reported visual outcomes are warranted to better define the clinical significance of laser-induced IOL pitting. Full article

The perception abilities of autonomous vehicles are highly dependent on the configuration of various sensors installed in the vehicle. However, sensor placement often comes from a manual process. This research paper introduces an optimization model to address sensor placement as a multi-objective problem where the objectives consist of the maximization of weighted coverage of Regions of Interest (ROIs) and the minimization of sensor cost, subject to physical and perceptual constraints such as mounting bounds, directional balance, redundancy, and self-occlusion. The introduced method combines NSGA-II algorithm with visibility analysis by means of ray casting and weighted coverage of ROIs near the vehicle. The developed framework has been tested on three different vehicle types: a small car, a light commercial transporter, and a large bus. It has been found that the suggested optimization technique outperforms the baseline solution in case of the car and the bus, whereas the transporters pose much harder optimization problems characterized by high variance between runs. Thus, the results show that the sensor suite design heavily depends on the platform type and geometrical symmetry hinders the convergence of an evolutionary search method. Full article

Achieving uniform agrochemical deposition in coffee is challenging because canopy structure, terrain, and wind conditions influence spray movement and retention. This study compared an unmanned aerial spray system (UASS), backpack sprayer, and tractor-mounted sprayers across three commercial coffee farms on Hawai‘i Island. Spray coverage, droplet density, droplet size metrics, and operational efficiency were evaluated using water-sensitive cards positioned throughout the canopy and analyzed using mixed-effects models. UASS produced significantly lower spray coverage and droplet density than the ground-based application systems, whereas backpack and tractor sprayers did not differ. Deposition patterns varied with canopy position, with application method effects depending on canopy height, depth, and aspect. Volume median diameter decreased in the upper canopy and with increasing wind speed, while relative span varied modestly among methods and was greater within the canopy interior. Canopy position and wind strongly shaped agrochemical deposition across spray platforms. Although UASS required less field labor and improved accessibility in terrain-limited systems, these operational advantages were accompanied by reduced deposition relative to ground-based sprayers. These findings demonstrate that canopy position and environmental conditions strongly influence agrochemical deposition and support UASS as a complementary application platform rather than a direct replacement for conventional sprayers under the conditions evaluated. Full article

This paper presents WSMAQ (WEC-Sim-MoorDyn-AeroelasticQ), a coupled aero-hydro-elastic-mooring simulation framework for floating offshore multi-rotor wind turbines. The framework integrates WEC-Sim for platform hydrodynamics; MoorDyn-C for mooring-line dynamics; and in-house aeroelastic code, AeroelasticQ, for rotor-level aerodynamic and blade structural calculations. These modules are coupled within MATLAB/Simulink/Simscape 2023a. The novelty of WSMAQ lies in three coupling-oriented methodological extensions. First, for deep-draft spar platforms, the WEC-Sim body is configured using the physical mass and inertia at the true center of gravity, the full unadjusted added-mass matrix is retained in the radiation-load calculation, and a three-block integrator filter is used to break the added-mass–acceleration algebraic loop. Second, the WEC-Sim mooring class is extended to pass the non-zero initial platform orientation to MoorDyn-C. Third, AeroelasticQ is integrated with the multibody wind turbine model through a rotor-count-parameterized Level-2 C++ MEX S-function. The framework was benchmarked against OpenFAST through aeroelastic, platform-mooring, and full-wind-turbine tests on the OC3 spar with the 5 MW reference turbine developed by the National Renewable Energy Laboratory. Across the primary response channels, the mean relative error remained below 2% in most cases. Multi-rotor capacity was demonstrated using three NREL WindPACT 1.5 MW turbines mounted on the OC3 spar. In this case study, an asymmetric rotor-parked condition generated a mean yaw offset of approximately 4°, which did not appear in the symmetric-load cases. Full article

Conventional methods of plant distance and volume measurements are limited by low efficiency, limited spatial coverage, and high measurement error. LiDAR and RGB-D imaging offer cost-effective, precise, and non-destructive techniques for plant distance and volume measurements. This study aimed to measure cabbage height, volume, and distance using LiDAR and RGB-D imaging. The sensors were mounted on a 1.6 kW electric field scouting platform (EFSP) for data collection. Point cloud (PCD) data were collected using LiDAR, whereas data processing, visualization, and measurements were done using commercial software and open-source programming scripts. A total of 20 cabbage plants were analyzed. LiDAR data processing included data frame screening, outlier removal, denoising, voxelization, and generation of 3D PCD density maps. Depth image processing included importing raw data and metadata shaping using intrinsic camera parameters, visualization, extraction of depth points, and pixel-level measurements of distances and volume. RGB image processing involved image conversion, segmentation, normalization, binary masking, mask cleaning, region extraction of cabbages, separation of ROI and preparation of contours, Delaunay triangulation and convex hull preparation, ROI overlay, bounding box preparation, sharing boundary between two boxes, conversion to pixel distances, and for visualization, plant height, volume measurements, and center to center distance measurement for measuring the plant distance. LiDAR demonstrated higher measurement accuracy for cabbage plant height, circumferential volume (geometric canopy volume), and plant distance, followed by RGB-D imaging, while RGB imagery showed comparatively lower performance under the study field conditions. Overall, LiDAR and RGB-D imaging provided reliable and non-destructive approaches for cabbage geometric characterization under field conditions, although accurately capturing complex plant geometry remains challenging. Positive and negative values of bias represent the over- and under-estimated results, respectively. Future studies should include larger and more diverse plant datasets exhibiting diversified size, shape, and geometric structure to further improve the robustness and general applicability of the proposed sensing approaches. Full article

This study maps the dynamic response of the IEA 15 MW reference wind turbine mounted on the UMaine VolturnUS-S semi-submersible platform across seven wave headings, spanning $\beta$ = 0–180°. A fully coupled aero–hydro–servo–elastic OpenFAST model with lumped-mass catenary mooring is simulated over three environmental groups: below-rated operation, a severe sea state at rated wind, and a parked extreme, combined with seven wave headings and supplemented by a 77-case operational envelope sweep across hub wind speeds of 4–24 m/s. Responses are analyzed through time-domain and frequency-domain statistics, drift kinematics, and exceedance curves. At operating states, the maximum side-to-side moment rises from 80.44 to 273.60 MNm between following and beam seas, while the maximum fore–aft moment reduces from 566.90 MNm to 485.23 MNm, respectively. The parked extreme LC-C maximum pitch response (2.77° at following seas, 2.59° at beam seas) is roughly half that of the severe operating LC-B (6.29° and 5.38°, respectively). This directional coupling is robust across environmental severities. In the parked group, the lateral motions (sway, roll) are amplified, as feathering reduces the rotor’s aerodynamic contribution to lateral damping. The developed wind speed misalignment response atlas condenses the aforementioned data, providing a compact basis for rapid early screening of ultra-large floating offshore wind turbines. Full article

Enteric methane measurement from ruminant livestock faces fundamental trade-offs between accuracy and operational feasibility. Existing methods quantify methane after eructation and atmospheric dilution, limiting temporal resolution and confounding biological signals with environmental variables. We present the Smart Cannula-mounted Optical Unit for Trace methane (SCOUT), an autonomous system for continuous in vivo monitoring of ruminal headspace methane concentrations. SCOUT uses a closed-loop gas recirculation circuit that samples the headspace continuously without venting gas to the atmosphere and mounts onto a standard cannula plug without degrading its seal integrity. SCOUT was deployed on cannulated Simmental heifers under contrasting dietary treatments. Headspace concentrations were two to three orders of magnitude above concurrent ambient sniffer readings, providing substantially greater signal resolution for characterizing methane dynamics. High-frequency monitoring revealed concentration changes associated with postural transitions and feeding on timescales inaccessible to ambient methods. Cross-platform comparison with ambient sniffers showed that eructation events produced the expected inverse concentration signature, supporting the validity of the in vivo concentration signal. These results demonstrate that the rumen headspace contains continuous, biologically interpretable methane signals that SCOUT can reliably access, establishing the measurement infrastructure necessary for developing concentration-to-flux models that would support precision phenotyping, emission proxy calibration, and mitigation strategy evaluation. Full article

Traditional liquid-resistive mounts are widely used in vehicle powertrain vibration isolation because of their favorable low-frequency damping characteristics. However, they usually suffer from pronounced high-frequency dynamic stiffening, which significantly degrades their vibration-isolation performance in the high-frequency range and remains a critical limitation in passive mount design. To address this problem, this study presents the systematic modeling, comparative analysis, and structural optimization of liquid-resistive mounts with different internal configurations. Three representative mount structures, namely the decoupler-membrane type, the conventional bell-plate type, and a novel bell-plate configuration, are first described in terms of their structural characteristics and working mechanisms. Based on the lumped-parameter method, mathematical models of the three mounts are established, and their low- and high-frequency dynamic characteristics are comparatively investigated. The vibration isolation performance of the mounts is further evaluated under various excitation conditions to clarify the influence of structural modifications on the dynamic response and transmitted force. In addition, sensitivity analysis is performed using the ISIGHT software platform (ISIGHT 5.6 Design Gateway) to identify the key parameters governing high-frequency performance. Subsequently, structural optimization is conducted using nonlinear programming under the quadratic Lagrangian algorithm and the Six Sigma method. The results indicate that the introduction of a bell plate has little influence on the low-frequency dynamic characteristics, while it effectively suppresses high-frequency hardening and improves high-frequency vibration isolation. Moreover, the Six Sigma optimization method achieves better performance improvement than the NLPQL approach, providing a useful reference for the design and optimization of passive liquid-resistive mounts. Full article

The transition from Industry 4.0 to Industry 5.0 is increasing the need for design approaches that place human centrality, safety, and ergonomics at the core of system development. In this context, immersive simulation is evolving from a training-oriented technology into a controlled environment for the observation of human behaviour and task execution. However, many Virtual Reality applications still rely on generic interaction devices that are not sufficiently representative of real tool-mediated operations, limiting the reliability of ergonomic and behavioural assessment. This paper proposes an anthropocentric framework for human-centred assessment in immersive simulation. The framework integrates four main components: a task-oriented Scenario Digital Twin, a Physical-Tool-in-the-Loop module based on a real instrument synchronised with its virtual counterpart, an Interaction Engine for state-dependent action management, and an Operator-in-the-Loop module coupled with a Human-Centred Assessment Layer. The framework is instantiated through an immersive hazelnut pruning simulator, selected as a representative case study because pruning involves non-neutral postures, irreversible actions, and strong dependence on tool handling. The reference implementation combines reality-based reconstruction of hazelnut trees, interactive branch-cutting logic, an instrumented electric pruning shear, full upper-body embodiment, and multimodal data acquisition. In particular, the proposed architecture supports the extraction of body motion through markerless multi-camera pose estimation and the acquisition of eye-related variables through the head-mounted display. A preliminary experimental session demonstrates the technical feasibility of the proposed architecture by showing that multimodal data, including reconstructed 3D body kinematics and eye-tracking signals, can be successfully acquired during immersive task execution, providing a basis for subsequent ergonomic analysis. The results show that a real instrumented tool, a task-oriented digital twin, and a continuous monitoring pipeline can be integrated within a single immersive platform, as well as that the assessment pipeline is sensitive to differing postural configurations during simulated task execution. They do not establish equivalence between behaviour in the simulator and behaviour during real-world pruning; dedicated cross-modal validation is therefore required. The framework is intended to support the evolution of immersive simulation toward assessment-oriented applications, contributing to a broader Safety-by-Design perspective in which human behaviour and interaction quality are considered as early-stage design inputs. Full article