Search Results (488)

Rockets were launched from a freely ascending balloon, and the attitude dynamics of the rockoon system were investigated. Compared with ground-based or aircraft-based launches, rockoons offer reduced aerodynamic drag and pressure losses, leading to higher maximum altitudes of sub-orbital trajectory and improved launch capacity to earth orbits. To ensure trajectory accuracy and flight safety, an azimuth control system based on a control moment gyroscope (CMG) was implemented. The launcher, suspended beneath a helium balloon, was equipped with a CMG device for active azimuth control. Three model rocket launches were conducted, and attitude data were obtained using multiple accelerometers installed on the rocket and launcher. The results confirmed that azimuth control remained effective during free ascent, with the azimuth error at ignition within 7° of the target in all three launches. Oscillatory motion was observed in roll and yaw angles. It was identified as rotation about the launcher’s principal inertia axis, indicating no significant impact on the rocket’s flight trajectory. Additionally, pitch-up behavior during launch due to rail friction was observed, consistent with previous studies. Frequency analysis showed that a double-pendulum model reproduced the measured first-mode frequency within approximately 2%, while the measured second-mode frequencies were higher than the predictions, indicating an increase in the effective pendulum length due to the relaxed constraint of the balloon suspension. Under free-flight conditions, the first mode was no longer observed within the measurable frequency band, consistent with the removal of the ground constraint. These findings provide an experimental characterization of the attitude dynamics of rockoon launches with active azimuth control. Full article

Traditional RRT* methods can produce geometrically reachable but kinematically difficult-to-track paths when vehicle maneuverability constraints are not enforced during tree construction. To address this limitation, a kinematic-constraint-frontloaded RRT* algorithm with layered height-error-driven guidance is proposed for 3-D underwater path planning. Turn-angle and pitch constraints are embedded into tree expansion, parent selection, and rewiring. A curvature bound derived from the vehicle’s maximum yaw rate at nominal cruising speed limits the associated directional-change rate and the induced normal acceleration, while the pitch bound limits the vertical component of the reference velocity under the assumed nominal planning speed within the feasible range. A gravity-gain-modulated vertical guidance compensates for the height-convergence loss inherent to pitch limitation. Constraint-preserving post-processing further improves path continuity without breaking feasibility. Ablation experiments across three obstacle configurations with 50 runs per method—comparing Informed RRT*, Fillet-RRT*, a kinematic Informed RRT* variant without guidance, and the full method—demonstrate that the proposed method achieves 100% geometric planning success and 100% constraint satisfaction. Six-degree-of-freedom tracking simulations using the MSS REMUS 100 AUV model with 3-D ALOS guidance confirm a 100% successful-tracking rate, with lateral and vertical cross-track errors of 0.75 m and 0.2 m RMS, respectively, compared with 0% for the two baselines that do not enforce the full three-dimensional maneuverability constraints. The combined planning-to-tracking pipeline validates that kinematic-level pre-optimization can substantially improve trackability without modifying the downstream controller. Full article

The electric loading function of the active sidestick system introduces new safety risks, making the failure effects of the system uncertain. To clarify the failure effect characteristics of uncommanded oscillation signals in the active sidestick system, fault mechanism analysis and fault injection simulations were conducted. For the standalone active sidestick system, oscillation faults with different injection locations, waveforms, amplitudes, and frequencies were investigated, and their effects were evaluated from three aspects: surplus force, active sidestick deflection angle, and loading motor speed. The results show that oscillation faults cause the active sidestick deflection angle to oscillate, with the response amplitude depending on the fault injection location and signal characteristics. In addition, the pilot response to the fault was incorporated into the active sidestick system. The results show that the influence of pilot response on oscillation faults exhibits significant frequency dependent characteristics. When the fault frequency is lower than approximately 0.72 Hz, the additional pilot control force reduces the aircraft pitch angle tracking error and suppresses the oscillation fault. When the fault frequency is higher than 0.72 Hz, the pilot response increases the aircraft pitch angle tracking error, and its effect changes from a counteracting action to an amplifying action. Based on the standalone active sidestick system simulated by the experimental setup, a sinusoidal oscillation fault injection experiment was conducted at the torque sensor output. The variation trends observed in the experimental results were generally consistent with the corresponding simulation results, thereby providing indirect validation of the fault injection simulations. Full article

This paper addresses the real-time trajectory tracking problem for the Twin Rotor MIMO System (TRMS), a nonlinear, strongly coupled, open-loop unstable aerodynamic laboratory benchmark whose six-dimensional state space is only partially observable through pitch and yaw angle encoders. A High-Gain Observer (HGO) is designed to reconstruct the four unmeasured states, comprising angular velocities and rotor torques, from encoder measurements alone. Three observer-based backstepping control architectures are proposed and experimentally validated on the physical TRMS platform at a 1 kHz embedded sampling rate: (i) adaptive backstepping with tuning functions, which eliminates the over-parametrization inherent in conventional adaptive formulations through a single unified parameter update law; (ii) backstepping with online Brain Storm Optimization (BSO) of the design gains; and (iii) backstepping with online Artificial Bee Colony (ABC) gain optimization. All three architectures achieve stable 100 s trajectory tracking, whereas the conventional non-adaptive backstepping baseline diverges after 42 s due to progressive yaw-channel instability exceeding 4 rad. The BSO- and ABC-optimized controllers achieve the highest pitch-axis tracking precision (reducing pitch root-mean-square errors by 68% relative to the baseline), while the adaptive tuning functions architecture yields the best yaw-axis stability (0.2244 rad RMSE, a 91% reduction). The tuning functions architecture primarily resolves the yaw-channel instability caused by parametric over-parametrization, while the metaheuristic optimizers primarily improve pitch tracking precision through online gain refinement. Closed-loop stability is rigorously established via Lyapunov analysis and the nonlinear separation principle. The High-Gain Observer is directly validated on the two measured states through comparison of its pitch and yaw angle estimates against the incremental encoder signals over the full 100 s trial; the angular velocity and rotor torque estimates are only indirectly supported by the sustained stability of the closed loop, since no velocity or torque sensor is available on the rig. Comprehensive simulation and real-time experimental comparisons quantify the performance, robustness, and computational feasibility of each architecture under identical operating conditions. Full article

Low-altitude general aviation aircraft and unmanned aerial vehicles (UAVs) are widely deployed for complex operational tasks, yet low-altitude gusts and crosswind disturbances induce severe airspeed fluctuations, leading to variable lift, unstable flight altitude, and perturbed pitch attitude. Such aerodynamic fluctuations degrade flight smoothness and increase pilot control workload. To mitigate lift and altitude instability under unsteady incoming flow, this paper proposes a novel passive trailing-edge winglet configuration capable of self-regulating wing angle of attack (AOA) without active flight control systems. A quasi-static aerodynamic equilibrium analytical model based on moment balance about the wing pivot axis is established, combined with validated Computational Fluid Dynamics (CFD) simulations to characterize the passive AOA adjustment mechanism and quantify lift variations under velocity perturbations. Results demonstrate that the integrated wing-winglet layout generates passive aerodynamic feedback moments to automatically adjust the wing AOA when freestream speed varies. For airspeed disturbances within ±10% of the cruise velocity (102 m/s, 0.3 Ma), the total lift fluctuation of the wing-winglet assembly is suppressed within ±1.01%, whereas conventional fixed-wing configurations experience lift deviations between −16% and +22% under identical disturbance conditions. Notably, the present study only verifies quasi-static aerodynamic equilibrium under steady inflow; dynamic flight stability, unsteady aerodynamic effects, and stall-limit performance remain unexamined and require further investigation. The core novelty of this design lies in the passive negative-feedback aerodynamic moment generated by the trailing-edge winglet, which decouples fuselage attitude from wing pitching motion and stabilizes equilibrium lift under mild low-altitude gust perturbations. Full article

Dielectric Barrier Discharge (DBD) plasma actuators have shown considerable potential for aerodynamic flow control over fixed wings and helicopter rotors. However, their application to small unmanned aerial vehicle (UAV) propellers operating at high rotational speeds remains largely unexplored. This study experimentally investigates the effectiveness of leading-edge AC-DBD plasma actuators in improving the aerodynamic performance of rotating UAV propellers under hovering conditions. A custom-built experimental test stand was developed to measure thrust, rotational speed, and motor power consumption while supplying high voltage to the rotating blades through high-speed slip rings. A series of 3D-printed propellers with different blade pitch angles was tested at rotational speeds up to 4000 rpm. The results showed negligible performance changes for low-pitch propellers, whereas significant improvements were observed under separated-flow conditions. At nearly constant rotational speed and thrust, plasma actuation reduced the propeller power coefficient by up to 7.66%, resulting in a maximum 9.42% increase in Figure of Merit (FoM). The greatest benefits were obtained for intermediate blade pitch angles, while no measurable improvement was observed under severe separation conditions. These findings demonstrate that plasma actuation is most effective within an intermediate separated-flow regime and highlight its potential as a lightweight active flow-control technology for electrically powered UAVs. Full article

Ploughing constitutes a fundamental tillage practice for enhancing soil fertility as well as water and fertilizer utilization efficiency. The uniformity of tillage depth directly determines seedling emergence consistency and final crop yield. Conventional indirect tillage depth detection approaches based solely on the rotation angle of the tractor lift arm are susceptible to disturbances induced by uneven terrain and dynamic attitude fluctuations of the tractor-implement system. To compensate for disturbances induced by tractor pitch angle variations, existing pitch compensation models adopt cascaded output compensation to calculate tillage depth. Nevertheless, these models need recalibration after each modification to the three-point hitch linkage length and are incapable of simultaneously compensating for pitch variations in the tractor and attached implement. To reduce the sensitivity of the tillage depth model to structural changes in the three-point hitch, this work constructs a mapping between hitch structural geometric deviations and vertical projection offsets of key linkages via tractor–plough integrated distributed attitude sensing. In this paper, a distributed tillage depth model is developed, which takes the distributed attitude of the whole working unit and the pitch of the lower-link measured by a rotation angle sensor as independent input variables. Field validation was performed with a mounted moldboard plough, with ultrasonic ranging sensor tillage depth readings serving as the reference benchmark to assess the reliability and precision of the proposed distributed model. Experimental results show that compared with the pitch angle cascaded tillage depth model, the average root mean square error of the proposed method is reduced from 22.5 mm to 12.5 mm on bumpy fields and from 11.3 mm to 8.7 mm on flat fields. The distributed model can significantly improve the measurement accuracy and anti-interference capability of tillage depth detection on uneven farmland, and it is applicable to adaptive measurement and control of tillage depth in complex ploughing scenarios. Full article

This study focuses on the longitudinal dynamic stability of swifts in cruising forward flight, which is critical for their high maneuverability but remains insufficiently investigated. Understanding longitudinal dynamic stability is the essential prerequisite for revealing the physical mechanism underlying their maneuverability: it is the dynamic stability characteristics that determine how the flight state responds to disturbances and control inputs, thereby laying a foundation for subsequent flight control during agile maneuvers. Conventional studies mostly adopt steady or quasi-steady assumptions, which cannot accurately reflect the influence of periodic body vibration. This study combines CFD numerical simulation and dynamic modeling to systematically analyze the unsteady dynamic stability of swifts. A bio-inspired dynamic model is established using the BE3357B airfoil with a 5° sweep angle, and the flapping-wing motion is decomposed into three degrees of freedom: sweeping, pitching, and flapping. Numerical reliability is assessed through grid independence and time-step independence verification. Aerodynamic force and moment trimming are performed on fixed-DOF and free-DOF models, where the latter considers coupled heaving–pitching motion and adjusted trim parameters. Stability analysis is conducted using three aerodynamic derivative methods: fixed velocity, forced oscillation, and Floquet. By solving small perturbation equations, eigenvalues and eigenmodes are obtained. All three methods identify two stable modes: a short-period mode with damping coefficient 0.1236–0.1870 and oscillation period 0.1121 s–0.1380 s, and a long-period mode with damping coefficient 0.2456–0.6203 and damping half-life 3.5803 s–4.8890 s, verifying stability under periodic vibration and unsteady aerodynamic coupling. Flow field results show clear distinct dynamic pressure and drag fluctuation characteristics between the downstroke and the upstroke. The unsteady stability framework provides a theoretical reference for analyzing the longitudinal stability of biomimetic flapping-wing aircraft and offers useful insight for future bird-inspired flight dynamics studies. Full article

There is a growing industrial interest in the development of functional plastic surfaces with hydrophobic and easy-to-clean properties, particularly in manufacturing sectors where safety, hygiene, and durability are critical requirements. This work investigates the development of hydrophobic and superhydrophobic surfaces on acrylic resin components fabricated by vat photopolymerisation (VPP), using a high-performance Rigid 10K photopolymer. The influence of manufacturing parameters, namely layer thickness and build orientation, on initial wettability was first evaluated, showing that orientation plays a more relevant role than layer thickness in controlling the water contact angle. Subsequently, different surface modification strategies were explored, including femtosecond laser microtexturing, sandblasting, and physical vapour deposition (PVD) coatings. Preliminary results indicate that femtosecond laser texturing enables controlled modification of surface roughness and wettability, with strong dependence on laser fluence and pitch. Sandblasting significantly increases surface roughness, promoting hydrophobic behaviour through the generation of irregular topographies. In contrast, PVD coatings appear to modify wettability primarily through surface chemistry. Roughness analysis suggests that, although layer thickness governs the initial surface condition, post-processing treatments progressively dominate the final surface morphology. Ongoing work is focused on fully correlating roughness parameters, surface morphology, and wettability performance. Overall, the combination of VPP and tailored surface treatments presents a promising approach for functionalising polymeric surfaces for advanced engineering applications. Full article

To improve the unsteady aerodynamic response of the IAR 330 PUMA rotor, the present analysis provides a two-dimensional (2D) CFD-based framework for rotor blade sections integrated with trailing-edge flaps (TEFs). From a biomimetic perspective, the TEF is treated as an engineering abstraction of the adaptive aft-chord and camber variation observed in natural flyers, providing a controlled morphing envelope for aerodynamic-load regulation. The scientific contribution consists of an integrated assessment of the NACA 13112 section over an extended TEF deflection range, the comparison of several relative TEF chord lengths, and the transfer of the section-level framework to a four-section representation of the IAR 330 PUMA rotor. First, the effect of TEF deflection on the trajectory and strength of the dynamic stall vortex (DSV) is examined for a pitching NACA 13112 airfoil with a chord length of $c=0.6 \mathrm{m}$ and a pitching axis located at $x/c=0.25$. The pitching motion was prescribed in ANSYS Fluent through a user-defined function (UDF), imposing a hysteresis variation of the angle of attack (AoA) from $\alpha =-3°$ to $\alpha =23°$, while flap deflection angle ($\beta$) varied from $\beta =-20°$ to $\beta =8°$, corresponding to upward and downward TEF deflection, respectively. The second part of this study extends the same pitching law to real-scale rotor blade sections under hovering flight conditions. For the rotor simulations, the Multiple Reference Frame (MRF) model was used for the steady-state analysis, whereas a Sliding Mesh interface was adopted for the transient computations. A 2D pressure-based solver was employed, together with the SST k-ω turbulence model, the Unsteady Reynolds-Averaged Navier–Stokes (URANS) formulation, and a coupled pressure–velocity scheme. The rotational speed was set to $\omega =265 \mathrm{RPM}$, corresponding to a local tangential velocity of approximately $U=145 \mathrm{m}/\mathrm{s}$ at the analysed radius of $r=5.225 \mathrm{m}$ and to a local Mach number of $M\approx 0.43$. The ideal-gas assumption and energy equation were employed to account for compressibility effects. Among the investigated IAR 330 PUMA rotor-section configurations, the TEF with a chord length of $c_f=0.25c$ TEF provided the most balanced aerodynamic response, reducing the peak pitching-moment coefficient by approximately $32\%$ relative to the baseline airfoil. Full article

In this research, a signal-integrity control strategy of a through-silicon via (TSV) array for a Chiplet-based system is developed, based on the backpropagation neural network (BP-NN) model and particle swarm optimization algorithm with linear decreasing inertia weight (PSO-LDIW). Based on the HFSS software, the simulation results of the TSV array are obtained. The irregular relationship between design parameters (TSV pitches, height of TSV, radius of TSV, thickness of oxide layer, and offset angle) and signal indexes (return loss, insertion loss, near-end, and far-end crosstalk) is established by the BP-NN model. Then, the design parameters of the TSV array are optimized by the PSO-LDIW algorithm to obtain the desired signal indexes. Based on the optimized design parameters, the effectiveness of the developed signal-integrity control strategy is verified by HFSS simulations. For the three verification cases, the relative errors between the BP-NN-predicted values and the corresponding HFSS simulation values range from 0.31% to 5.02%. The relative deviations of the HFSS results from the desired NEXT, FEXT, and return-loss targets are no greater than 5.72%, while the maximum absolute deviation from the desired insertion-loss target is 0.0160 dB. These results demonstrate the feasibility of the developed strategy for controlling the signal indexes of the TSV array in the tested cases. Full article

Tracked deep-sea mining vehicles (DSMVs) interact strongly with soft seabed sediments during seafloor operations, which may cause excessive sinkage and vehicle instability. Variations in mineral loading and initial pitch angle are important factors affecting operational safety. In this study, the “Kunlong 500” tracked DSMV was selected as the prototype, and a coupled Eulerian–Lagrangian (CEL) numerical model was established to simulate vehicle–sediment interaction. The Drucker–Prager elastoplastic model was adopted to describe sediment yielding and plastic deformation. Different mineral loading levels and initial pitch angles were considered to investigate vehicle sinkage, local Mises stress in the track–sediment contact region, and attitude response. The results show that increasing mineral loading significantly increases body sinkage and rear-track Mises stress, causing the vehicle response to evolve from overall sinkage to rear-biased sinkage. Under the present model parameters, the reference critical loading for local rear-track sinkage was estimated to be approximately 5.8 t, with a sensitivity range of approximately 4.5–7.1 t under ±10% variation in the equivalent bearing term. Under the present model conditions, loading conditions of 8 t and above should therefore be treated as key risk-control cases. The initial pitch angle further aggravates asymmetric sinkage, especially under the 4 t loading and 4° pitch condition. These findings provide a reference for load control and attitude regulation of DSMVs. Full article

A capillary-driven microfluidic electrical screening platform was developed using silver nanoparticle (AgNP)-decorated laser-patterned villous microstructures on a glass substrate for the analysis of H3N2-infected A549 cells. The device integrated nanosecond laser patterning, AgNP conductive thin-film formation, passive capillary transport, and direct electrical readout within a single microfluidic sensing structure. Villous-like arrays were fabricated using a 1064 nm IR pulsed laser at a fluence of 4.35 J/cm², with a repetition rate of 300 kHz, pulse overlap of 96.7% and scanning speed of 500 mm/s. The fabricated structures exhibited a diameter of 60 μm, height of 80 μm and interpillar pitches ranging from 30 to 90 μm. After AgNP deposition, the surface showed a dominant Ag content of 59.2%, confirming successful formation of conductive microstructured electrodes. The 30 μm pitch structure produced the highest current response of 22 μA at 1 V and the highest ΔI_norm of 0.053 after introduction of H3N2-infected A549 samples. Wettability and capillary transport were tunable by pitch, with contact angles (CAs) decreasing from 140° to 30° and flow velocities decreasing from 0.1 mm/s to 0.03 mm/s. Formalin-fixed H3N2-infected A549 cells were electrically distinguished from non-infected A549 controls over 10¹–10⁶ PFU/μL, with detectable responses down to 10¹ PFU/μL. These results demonstrate a label-free, self-driven, and fabrication-oriented microfluidic strategy for electrical screening of virus-associated cellular samples. Full article

The inherent brittleness of cementitious materials presents a fundamental limitation for advanced structural applications. While bio-inspired Bouligand architectures have demonstrated remarkable damage tolerance in natural composites, their systematic translation to brittle inorganic binders via 3D concrete printing (3DCP)—and the development of high-fidelity meso-scale models to quantitatively map the resulting strength–toughness design space—remains underexplored. This study aims to decouple the intrinsic topological toughening potential of helicoidal Bouligand architectures from the stochastic defects inherent to additive manufacturing, through a meso-scale finite element (FE) framework. To physically validate the model, a nano-clay-assisted rheological strategy was utilized to enable the support-free fabrication of these helicoidal prototypes. Computationally, a meso-scale FE framework integrating the concrete damaged plasticity (CDP) model with three-dimensional cohesive zone elements was developed to explicitly resolve inter- and intra-layer interfacial crack kinematics. Coupled physical compression tests and numerical simulations indicate that the 15° Bouligand architecture achieves a computationally predicted 16.3-fold increase in volumetric energy absorption (experimentally: 13.7-fold) compared to the 0° unidirectional baseline, with a modest ~11% reduction in compressive strength (from ~33.0 MPa to ~29.5 MPa in simulations; ~12% experimentally). Furthermore, numerical parametric studies across the complete pitch-angle design space reveal an optimal topological window at 15–30°, wherein the competing effects of crack deflection and structural integrity are balanced. Imperfection sensitivity analysis demonstrates that the topological toughening mechanism is relatively robust: even with a 30% reduction in inter-filament bonding strength, the work of fracture remains 12.4 times higher than that of the 0° control. These findings suggest that spatial toolpath programming offers a viable, geometry-driven strategy for developing damage-tolerant cementitious composites, complementing conventional material-level reinforcement approaches. Full article

Modern logistics and manufacturing environments simultaneously demand mobility platforms that are compact enough to navigate narrow aisles and powerful enough to transport oversized or heavy components. We previously developed a compact Steering–Drive–Suspension (SDS) module that integrates steering, in-wheel drive, and suspension within a single wheel envelope, achieving $\pm {90}^{\circ }$ wide-angle steering with a single actuator. The present paper extends that hardware-centric work by treating the two-wheel (2WD) configuration assembled from two SDS modules as the unit module of the platform, building a four-wheel (4WD) operation by coupling two such 2WD units, and developing a unified balance and impedance-based control scheme. We derive a cart–pole inverted-pendulum model for the 2WD configuration and a planar 2-DOF bicycle model for the coupled and cooperative configurations, with full controllability proof and quantitative LQR robustness margins. Three Python 3.12 based scenarios validate the framework: (i) a 2WD inverted-pendulum tracking task, (ii) a forward and lateral relocation maneuver compared across SDS Crab, Ackermann, and four-wheel-steering modes, and (iii) cooperative transport of a $100\mathrm{kg}$ steel plate by two impedance-coupled 2WD units. Across all scenarios the proposed controllers achieve sub-centimetre tracking gap, pitch deviation within $\pm 2^{\circ }$, and well-damped cooperative behavior without payload sloshing. The results substantiate the central design claim that the SDS module’s compactness enables a single hardware platform to act simultaneously as an autonomous small-payload mover, a building block of a 4WD platform, and a cooperative agent for oversized loads. Full article