Search Results (1,949)

The visibility of vertical road signs is a crucial factor for driving safety, especially in low-light conditions. The retroreflectivity of signs is imperative to ensure that drivers are able to perceive the information in a timely manner. However, the effectiveness of signs can be compromised by factors such as material degradation, wear and tear, and dirt on the surface. The objective of this study is to analyze how different surface conditions and different levels of retroreflectivity of vertical signs affect users’ perception and driving behavior in a real controlled environment. A total of twenty-five volunteers undertook the same road test twice. During the initial trial, the subjects encountered signs with a Class II retro-reflective film (EN 12899-1:2007), and during the second trial, they encountered the same signs in the same positions as the first trial but with varied characteristics and additional factors such as dirt, water, and degradation. Through a Mobile Eye Tracker and a Racelogic Video Vbox, it was possible to investigate the alterations in the visual and kinematic behavior of participants across the two tests. The statistical analysis was conducted using the Wilcoxon test, Spearman’s correlation and regression analysis. The analysis revealed that the signal with a dirty surface had the most significant impact on participants’ perception, showing a substantial reduction in the distance of the first fixation (−15%), a decrease in the number of fixations (−37%), and an increase in the time required for it to be perceived (+40%). This study demonstrates that the maintenance of road sign surfaces is a critical factor in their effectiveness and is as influential as the level of retroreflectivity of the material. Full article

Soil compaction in grassland and agricultural soils reduces water infiltration, root growth and ecosystem services. Conventional deep tillage and coring can alleviate compaction but are energy intensive and strongly disturb the turf. This study proposes an earthworm-inspired subsurface robot as a low-disturbance loosening tool for compacted grassland soils. Design principles are abstracted from earthworm body segmentation, anchoring–propulsion peristaltic locomotion and corrugated body surface, and mapped onto a robotic body with anterior and posterior telescopic units, a flexible mid-body segment, a corrugated outer shell and a brace-wire steering mechanism. Kinematic simulations evaluate the peristaltic actuation mechanism and predict a forward displacement of approximately 15 mm/cycle. Using the finite element method and a Modified Cam–Clay soil model, different linkage layouts and outer-shell geometries are compared in terms of radial soil displacement and drag force in cohesive loam. The optimised corrugated outer shell combining circumferential and longitudinal waves lowers drag by up to 20.1% compared with a smooth cylinder. A 3D-printed prototype demonstrates peristaltic locomotion and steering in bench-top tests. The results indicate the potential of earthworm-inspired subsurface robots to provide low-disturbance loosening in conservation agriculture and grassland management, and highlight the need for field experiments to validate performance in real soils. Full article

Current small arch shed machine designs rely on manual pole placements, resulting in low construction efficiency and mechanized levels. These machines were not designed with key components tailored to the agronomic requirements of Xinjiang’s small arch shed cotton cultivation model. An automated rod-feeding mechanism for a small arch shed was designed using SolidWorks 2023 to bridge this gap. Its major components include rod separation and conveying units, enabling the separation and orderly transportation of tunnel rods. A kinematic simulation of the conveyor rod during the transport process using ADAMS 2024.1 software was performed to examine the effects of motor speed, synchronous belt stop block height, and horizontal distance on the conveyor rod. Using MATLAB 2023a to fit the center-of-mass distance curve yields the optimal values for the parameters (motor speed = 17.57 rpm, stop block height = 16.79 mm, and horizontal distance = 103.95 mm). Bench test results confirmed the simulation performance of the device with a motor speed of 17 rpm, a synchronous belt stop block height of 15 mm, and a horizontal distance of 100 mm. The automated rod-feeding device exhibited an 80.8% feeding rate. The prototype operates stably, and this design can serve as a reference for developing automated equipment for small arch sheds. Full article

Background/Objectives: Marker-based motion capture remains widely used for lower limb kinematics due to its high precision, although its application is often constrained by elevated operational costs and the requirement for controlled laboratory environments. Markerless methods, such as MediaPipe offer a promising alternative for extending biomechanical analyses beyond traditional laboratory settings, but evidence supporting their validity in controlled tasks is still limited. This study aimed to validate a pixel-based markerless pipeline for two-dimensional kinematic analysis of hip and knee motion during squatting. Methods: Ten healthy volunteers performed three squats with a maximum depth of 90°. Kinematic data were collected simultaneously using marker-based and markerless systems. For the marker-based method, hip and knee joint angles were calculated from marker trajectories within a fixed coordinate system. For the markerless approach, a custom pixel-based pipeline was developed in MediaPipe 0.10.26 to compute bidimensional joint angles from screen coordinates. A paired t-test was conducted using Statistical Parametric Mapping, and maximum flexion values were compared between systems with Bland–Altman analysis. Total range of motion was also analyzed. Results: The markerless pipeline provided valid estimates of hip and knee motion, despite a systematic tendency to overestimate joint angles compared to the marker-based system, with a mean bias of −17.49° for the right hip (95% LoA: −51.89° to 16.91°). Conclusions: These findings support the use of markerless tools in clinical contexts where cost and accessibility are priorities, provided that systematic biases are taken into account during interpretation. Overall, despite the systematic differences, the 2D MediaPipe-based markerless system demonstrated sufficient consistency to assist clinical decision-making in settings where traditional motion capture is not available. Full article

This study investigates fuel-induced oil dilution in hybrid powertrains using a combined assessment of kinematic viscosity and FTIR differential spectroscopy. Ten oil samples collected from hybrid vehicles operating under diverse real-world driving patterns were examined to determine how hybrid-specific operating conditions—such as frequent cold starts, extended start–stop phases and short, thermally unstable trips—influence lubricant ageing and, consequently, the energy efficiency of the combustion subsystem. In eight of the ten cases, a clear reduction in kinematic viscosity was observed, indicating the presence of volatile fuel fractions and confirming that fuel dilution is a dominant mechanism shaping the early stages of oil degradation in hybrid engines. FTIR analysis consistently revealed spectral shifts related to oxidation, nitration, sulfonation and additive depletion, together with hydrocarbon enrichment characteristic of fuel contamination. The co-occurrence of viscosity loss and FTIR band evolution demonstrates a strong and reproducible relationship between mechanical thinning of the lubricant and chemically driven transformation pathways, both of which can negatively affect frictional losses and energetic performance. Paper-based blot testing was used only as a supplementary qualitative tool and provided visual confirmation for samples exhibiting the strongest fuel-related FTIR signatures and viscosity changes. Although not mechanistically specific, the method reinforced the laboratory findings in cases of pronounced degradation. Overall, the results highlight the diagnostic value of combining viscosity data with FTIR spectral analysis to characterise fuel dilution and associated ageing mechanisms in hybrid combustion systems. This study contributes to a more comprehensive understanding of lubricant deterioration under real hybrid driving conditions and supports the development of practical monitoring strategies aimed at safeguarding both engine durability and the energy efficiency of hybrid powertrains. Full article

To counteract accuracy degradation in micrometer-scale precision marking—where the precision marking (PM) system denotes the precision marking platform and the Optical Microscope (OM) system denotes the camera-based visual guidance module—a genetic-algorithm-based framework for motion-system calibration and error control is introduced. A kinematic error model is established to capture multi-source coupled errors in the PM system, and the propagation mechanisms of axis misalignment, pose misregistration, and flatness-induced errors are analyzed. Building on this model, a GA-driven multi-objective calibration scheme and a coordinated optimization model jointly address axis-orthogonality correction, PM-OM extrinsic-pose calibration, and workpiece flatness compensation. Furthermore, a dynamic error-compensation framework leveraging real-time monitoring and adaptive adjustment sustains long-term high-precision marking. In post-calibration tests-after correcting axis orthogonality, aligning the PM-OM extrinsic pose, and compensating workpiece flatness, the PM system achieves dimensional accuracies of ±0.05, ±0.08, and ±0.10 μm for nominal 1, 2, and 3 μm marks, respectively, with positional accuracy better than ±0.2 μm. Marking consistency improves markedly, and the indentation force closely matches the target mark size, validating the approach. These techniques provide both theoretical and practical support for the engineering deployment of PM systems and are significant for improving the quality and productivity of micrometer-scale precision marking. Full article

The underwater hexapod robot has advantages such as lower energy consumption and reduced environmental interference compared to ROVs and AUVs. The foot-end contact detection with the seabed is the key technology for adapting to complex terrains. This paper focuses on the ‘Dragon Crab’ underwater hexapod robot developed by Shanghai Jiao Tong University and proposes an indirect detection method that does not require foot-end contact sensors. By establishing the kinematic and dynamic models of the robot’s legs, combined with multi-order polynomial trajectory planning to reduce non-contact force interference, the foot-contact determination condition is defined. Through simulation experiments and force analysis of the legs, the contact detection parameters are estimated. Then, single-leg contact tests are conducted to obtain joint motor torque variation curves and foot-end height variation curves through the kinematic model, verifying the proposed contact detection conditions and parameters. Finally, the method is applied to underwater obstacle-crossing experiments of the underwater hexapod robot using triangular and wave gait patterns. Experimental results show that the method can accurately identify the foot-end contact state and has high applicability in complex underwater terrains. Full article

This work presents a first-iteration bio-faithful dragonfly-inspired wing designed for future flapping micro air vehicle (MAV) applications. Using high-resolution imaging, the natural venation pattern of fore- and hindwings was reconstructed in CAD and reproduced through high-precision stereolithography at 1:1 and 3:1 scale. The printed polymeric wings successfully preserved the anisotropic stiffness distribution of the biological structure, enabling realistic bending and torsional responses. Modal analysis and dynamic testing confirmed that the lightweight designs operate within the biologically relevant 20–40 Hz range and that geometry and material choices allow predictable tuning of natural frequencies. Preliminary aerodynamic estimates captured the characteristic anti-phase lift behavior of four-wing flapping, while schlieren and infrared thermography demonstrated that heat dispersion and flow features follow the vein-driven structural pathways of the printed wings. Together, these results validate the feasibility and functional relevance of bio-faithful venation architectures and establish a solid foundation for future iterations incorporating membranes, full kinematic actuation, and higher-fidelity aeroelastic modeling. Full article

Background: Functional electrical stimulation (FES) is widely used in post-stroke rehabilitation to restore motor activity and improve walking. However, the immediate effects of a single FES session on gait biomechanics and muscle activity remain insufficiently studied. This pilot study aimed to evaluate the direct neuromotor effects of a single multichannel FES session during walking in patients with post-stroke hemiparesis. Methods: Eight patients with hemiparesis in the early or late recovery period after ischemic stroke underwent gait biomechanics and electromyography (EMG) assessment before and immediately after a single 30 min FES session. FES was applied to the tibialis anterior, gastrocnemius, quadriceps femoris, and hamstring muscles of the paretic limb during walking, synchronized with gait phases. Spatial-temporal, kinematic, and EMG parameters were recorded using an inertial system. Pre- and post-intervention data were compared using paired tests (a paired t-test or the Wilcoxon signed rank test, p < 0.05), while the standardized effect sizes (Cohen’s d) were calculated for all pre-post comparisons. Results: A significant decrease was observed in the single support phase of the paretic limb after FES (p < 0.05). Knee joint movement amplitude increased significantly in the nonparetic limb. Surface EMG amplitudes decreased in the tibialis anterior of the nonparetic limb and in the hamstring and gastrocnemius of the paretic limb (p < 0.05). No significant changes were detected in overall gait speed, rhythm, or phases of muscle activity peaks. Conclusions: A single session of multichannel FES induces neuromotor changes reflected by redistribution of muscle activity and compensatory adjustments in gait biomechanics without immediate improvement in global kinematic parameters. The direct biomechanical changes in the gait function can be interpreted as evidence of the onset of fatigue. The procedure demonstrated good tolerability and safety, confirming its feasibility for early post-stroke rehabilitation. Full article

Background: One of the main goals of rehabilitation after stroke is the restoration of motor function. Understanding movement patterns and compensatory strategies is essential to optimize therapy. This study analyzes upper limb kinematics during the Box and Block Test (BBT) to identify and quantify typical post-stroke compensation strategies. Methods: Thirty-one sub-acute stroke participants and thirty-one healthy controls were included. Kinematic data were collected using a 7-IMU system. Joint angles were analyzed with MATLAB R2023a, and 3D trajectories were reconstructed from calibrated quaternions and anthropometric data. Group differences were assessed with the Mann–Whitney test. Compensation strategies were quantified in percentage terms relative to healthy subjects. Results: Significant intergroup differences were observed in mean joint angles and ranges of motion. On the paretic side, participants overused the wrist and shoulder to compensate for reduced elbow and trunk activity. Similar overuse was also observed on the unaffected side. Quantification showed that 83.9% and 80.6% compensate, respectively, with wrist and trunk and 67.7% with the shoulder. Conclusions: Using IMUs during the BBT, this study identified specific compensation strategies that may hinder recovery. It also contributed to developing a quantification scale, supporting more personalized rehabilitation and improved quality of life. Full article

Paddy field leveling is the foundation of high-yield rice cultivation. In response to the current issues of low leveling accuracy and the lack of efficient multi-operation machinery, an Integrated Multi-operation Paddy Field Leveling Machine was designed in this study. This machine can complete soil crushing, stubble burying, mud stirring, and leveling in a single pass. Combined with an adaptive control system based on Global Navigation Satellite System—Real-Time Kinematic (GNSS-RTK) technology, it enables adaptive and precise paddy field leveling operations. To verify the operational performance of the equipment, field tests were conducted. The results showed that the machine achieved an average puddling depth of 14.21 cm, a surface levelness of 2.16 cm, an average stubble burial depth of 8.15 cm, and a vegetation coverage rate of 89.33%, demonstrating satisfactory leveling performance. Furthermore, to clarify the feasibility and superiority of applying this equipment in actual rice production, experiments were conducted to investigate the effects of different field leveling methods on early rice growth, yield, and its components. One-way analysis of variance was employed to examine the differences in agronomic indicators between the different field leveling treatments. The results indicated that using this equipment for paddy field leveling, compared to traditional methods and dry land preparation, can improve the seedling emergence rate, thereby laying a solid population foundation for the formation of effective panicles. It also promoted root growth and development and increased the total dry matter accumulation at maturity, thereby contributing to high yield formation. Over the two-year experimental period, the rice yield remained above 9.8 t·hm⁻². This research provides theoretical support and practical guidance for the further optimization and development of subsequent paddy field preparation equipment, thereby promoting the widespread application of this technology in rice production. Full article

Unmanned underwater vehicles (UUVs) capable of agile, high-speed maneuvering in complex environments require propulsion systems that can dynamically modulate three-dimensional forces. The California sea lion (Zalophus californianus) provides an exceptional biological model, using its foreflippers to achieve rapid turns and powerful propulsion. However, the specific kinematic mechanisms that govern instantaneous force generation from its powerful foreflippers remain poorly quantified. This study experimentally characterizes the time-varying thrust and lift produced by a bio-robotic sea lion foreflipper to determine how flipper twist, sweep, and phase overlap modulate propulsive forces. A three-degree-of-freedom bio-robotic flipper with a simplified, low-aspect-ratio planform and single compliant hinge was tested in a circulating flow tank, executing parameterized power and paddle strokes in both isolated and combined-phase trials. The time-resolved force data reveal that the propulsive stroke functions as a tunable hybrid system. The power phase acts as a force-vectoring mechanism, where the flipper’s twist angle reorients the resultant vector: thrust is maximized in a broad, robust range peaking near 45°, while lift increases monotonically to 90°. The paddle phase operates as a flow-insensitive, geometrically driven thruster, where twist angle (0° optimal) regulates thrust by altering the presented surface area. In the full stroke, a temporal-phase overlap governs thrust augmentation, while the power-phase twist provides robust steering control. Within the tested inertial flow regime (Re ≈ 10⁴–10⁵), this control map is highly consistent with propulsion dominated by geometric momentum redirection and impulse timing, rather than circulation-based lift. These findings establish a practical, experimentally derived control map linking kinematic inputs to propulsive force vectors, providing a foundation for the design and control of agile, bio-inspired underwater vehicles. Full article

Background/Objectives: Running is among the most prevalent forms of physical activity in preschool-aged children and constitutes a fundamental component for the effective execution of other motor patterns. The main aim of this study is to determine how fundamental running parameters change with age and whether there are differences between sexes. Methods: Four-hundred and five pre-school children with the mean (SD) age = 4.9 (1.1) years, height = 111.2 (9.3) cm, weight = 20.0 (4.2) kg, 53.5% girls were recruited from 34 kindergartens in four major cities. The inclusion criteria involved children aged 3–6 years with typical development and without any locomotor or mental disorders and diseases, who were enrolled in day care. Running performance was assessed in preschool children using a 10-m sprint test. Sprint parameters were measured with the OptoJump modular system, an infrared platform that accurately quantifies kinematic variables. Sex (boys vs. girls) and age (3 to 6 years old) differences were calculated by using analysis of variance (ANOVA) or Kruskal–Wallis H-test with post hoc comparison test between the groups. Results: In general, the results indicated that statistically significant differences between boys and girls were observed across the following levels: (1) temporal–kinematic step phase, (2) spatiotemporal movement characteristics, and (3) propulsive phase as an indicator of muscular activity. However, these differences were not consistent across all age groups. Conclusions: This study provides new insights into the spatiotemporal characteristics of running in preschool-aged children. The findings may assist in the early identification of potential motor deviations and in the planning of more effective strategies to promote physical activity during the preschool period. Full article

Drilling in aerospace one-up assembly demands high positional accuracy, strong clamping forces, and precise angular compensation to ensure quality in multi-layered stacks. Existing robotic solutions achieve these requirements but are costly, bulky, and unsuitable for flexible or collaborative environments. This work introduces the Advanced Collaborative Multifunctional End-Effector (ACME), a lightweight robotic drilling end-effector designed for integration with collaborative robots (cobots). ACME incorporates vacuum-assisted clamping capable of generating high forces, a passive self-normalization mechanism for angular alignment on double-curvature surfaces, and a compact 5-DoF positioning system for precise positioning and orientation. The system’s kinematics and dynamics were modeled and experimentally verified through frequency response function (FRF) testing, enabling precise behavior prediction. The tool is integrated within a cyber–physical system (CPS) featuring an interactive digital twin that, unlike passive monitoring systems, allows operators to configure workpieces, select drilling locations directly from rendered CAD, and supervise execution without programming expertise. Experiments demonstrated average positional errors of 0.19 mm and normality deviations of 0.29°, both within aerospace standards. The results confirm that ACME effectively extends cobot capabilities for aerospace-grade drilling while improving flexibility, safety, and operator accessibility. Full article

Background: The need to improve gait emulation in people with amputation has driven the development of customized prosthetic mechanisms. This study focuses on the design and validation of a mechanism for external knee joint prostheses, based on the trajectory of the Instantaneous Center of Rotation (ICR) of a healthy knee. Objective: The objective is to design a mechanism that accurately reproduces the evolution of the ICR trajectory, thereby improving stability and reducing the user’s muscular effort. Methods: An exploratory methodology was employed, utilizing computer-aided design (CAD), kinematic simulations, and rapid prototyping through 3D printing. Multiple configurations of four- and six-bar mechanisms were evaluated to determine the ICR trajectory and compare it with a reference model obtained in the laboratory from a specific subject, using MATLAB-2023a and the Fréchet distance as an error metric. Results: The results indicated that the four-bar mechanism, with the incorporation of a simple gear train, achieved a more accurate emulation of the ICR trajectory, reaching a minimum error of 6.87 mm. Functional tests confirmed the effectiveness of the design in terms of stability and voluntary control during gait. It can be concluded that integrating the mechanism with the gear train significantly enhances its functionality, making it a viable alternative for the development of external knee prostheses for people with transfemoral amputation, based on the ICR of the contralateral leg. Full article