Search Results (540)

The Absolute Nodal Coordinate Formulation (ANCF) is extensively utilized in the field of flexible multibody dynamics because it offers a constant mass matrix and inherently eliminates Coriolis forces. However, ANCF requires the computation of complex nonlinear elastic internal forces and thermal deformation forces at each time step, which imposes a significant computational burden. To alleviate this burden, researchers have developed local linearization (LL) methods. The local linearization method constructs constant elastic and thermal stiffness matrices within a small range by means of Taylor expansion, effectively reducing the number of stiffness matrix updates. But the method suffers from error accumulation and relies on displacement-based update criteria that are inefficient for systems with large rigid-body motion. This paper proposes an improved local linearization (I-LL) method to address these issues. Two key enhancements are introduced: (1) the update criterion for the elastic and thermal stiffness matrices is modified from displacement-based to total strain-based, enabling more accurate and size-independent updates; (2) accurate elastic or thermal deformation force calculations are inserted within the local linearization iteration cycle to mitigate error accumulation. These two improvements reduce the number of calculations of the nonlinear internal forces and, at the same time, lessen the error accumulation in the simplified model. The accuracy and effectiveness of the I-LL algorithm are demonstrated through three numerical examples. Full article

Robotic belt grinding is an effective and widely adopted finishing method for superalloys, offering notable advantages such as high material removal capability, low heat input, and reduced workpiece damage. In addition, robots can readily integrate multiple sensors—such as infrared radiation cameras, force sensors, and high-speed cameras—which facilitate real-time monitoring of the grinding process and thereby enhance grinding quality control. With the establishment and continuous advancement of large-scale artificial intelligence (AI) data models, new breakthroughs have emerged in the optimization of robotic grinding processes. Owing to its dexterous workspace and advantages in high flexibility and cost-effectiveness, robotic belt grinding has become a critical process for the precision forming of complex curved components such as aero-engine blades and blisks. However, factors such as the limited absolute accuracy of industrial robots, time-varying grinding contact states, and significant transient boundary effects make it difficult for the current constant-parameter open-loop machining mode to simultaneously meet the demands for high material removal efficiency and high surface integrity on complex profiles. This paper systematically reviews the technologies for precision control and process optimization of robotic belt grinding aimed at pointwise precise material removal. First, the structural composition of the robotic belt grinding system and the material removal mechanism are analyzed. Then, centered on the compensation concept, a hierarchical progressive technical framework is outlined, covering geometric calibration compensation, force/position hybrid online compensation, transient entry boundary compensation, and system-level comprehensive compensation of multi-source errors, with a comparison of the applicable scenarios and the effects on shape and property control at each level. Furthermore, under the support of effective compensation, the collaborative optimization methods of material removal modeling, multi-objective optimization of process parameters, force-constrained trajectory planning, and intelligent adaptive processes are elaborated. Finally, current technical bottlenecks are summarized, and future trends in next-generation adaptive grinding technology driven by digital twins and embodied intelligence are envisioned. This review aims to provide a systematic theoretical reference for the high-precision and intelligent upgrading of robotic precision grinding systems. Full article

Optimizing the structural stability of foundations is challenging in modern geotechnical engineering. This study investigated the mechanism of geocell-reinforced foundations through discrete element modeling based on transparent soil model tests. A three-dimensional particle flow code (PFC^3D) model was developed to investigate the micromechanical soil–geocell interactions in both unreinforced and geocell-reinforced foundations under strip loading. Particle displacement, contact force distribution, and structural deformation within the foundation system were analyzed to quantify the performance of geocell reinforcement. The results show that geocell inclusion enhances structural performance by 2.1 times compared to an unreinforced foundation, increasing the bearing capacity from 60.6 to 126.8 kPa at a defined bearing capacity criterion. The geocell walls act as rigid physical boundaries that microscopically intercept the lateral migration and horizontal extrusion of soil particles. The kinematic trajectories of soil particles beneath the loading plate are forced into a downward realignment, decreasing the displacement vector rotation angle from 42° in the unreinforced soil to 27° in the reinforced soil and effectively mitigating the heave of adjacent surfaces. Furthermore, the quasi-rigid three-dimensional network completely interrupts the continuous steep contact force chains inherent in unreinforced foundations. Concentrated vertical stresses are converted into horizontal components through interfacial friction and mechanical interlocking, resulting in the lateral redistribution of the applied load by a distance of approximately 0.06 m. The geocell–soil composite considered as a flexible raft foundation extends load dispersion and reduces average subsoil pressure. A coupled tension and compression stress state in the horizontal plane is developed within the geocell structure. Forces are channeled along rigid paths by elevated bending moments and stress concentrations at the cell junctions. These findings provide micromechanical insights into the performance of geocell-reinforced-foundation systems. Full article

In electricity–hydrogen coupling systems (EHCSs), the uncertainty of renewable energy generation (REG) tends to impact electrolyzers (ELs) in the following ways: (1) input powers of ELs are prone to fluctuations; (2) ELs are forced to operate under variable load states. Consequently, both impacts will reduce the service life of ELs. In this paper, considering the start–stop characteristics and combined operation modes of multiple ELs, a two-stage multi-time-scale energy allocation strategy (MSEAS) is proposed to mitigate the impacts of REG uncertainty and optimize the energy allocation for EHCSs. First, five refined operating states of ELs, such as shutdown, cold standby, low-load, variable-load and overload, are formulated as mixed-integer constraints and embedded into the system-level energy optimization model. Second, to mitigate power fluctuations caused by REG, a day-ahead optimization is employed to plan the power allocations of ELs, lithium batteries, fuel cells, and the grid with a 1 h time step; and then an intra-day rolling optimization is employed to adjust the operating states and power outputs of the above units with a 4 h window and 15 min step. Third, by enabling multiple ELs to flexibly operate in a combined mode, power-sharing mode and switching mode, the proposed MSEAS can refine the operation powers of ELs and reduce their start-up frequency. Comparative case studies are conducted in the off-grid and grid-connected operation tests, and the relevant results verify that the proposed MSEAS can effectively prevent the frequent start–stop of ELs, which contributes to extending the service life of ELs and reducing the system operating cost. Full article

Achieving precise docking, reliable locking and damage-free emergency unlocking under complex ocean current conditions remains a key challenge for deep-water multi-way quick connectors (MQCs). This study proposes a novel MQC prototype characterised by a tiered tolerance guidance mechanism, an innovative L-shaped spatial helical cam locking system, and a real-time visual attitude indicator. Using Ansys 2023 R2 and its tools, the safe operating limits were determined through explicit non-linear finite element collision analysis. The results demonstrate that, under a controlled docking speed of 10 mm/s, the hierarchical guidance mechanism successfully accommodated extreme initial misalignments (25 mm lateral offset, 5° horizontal rotation and 15° axial rotation), whilst keeping the peak collision stress within the elastic limit. Furthermore, the L-shaped locking guide was analysed using a fifth-order polynomial motion law and a macro-micro elastoplastic Hertzian contact mechanics model, effectively eliminating rigid-flexible impact forces. Under extreme separation loads of 10,000 psi, the maximum equivalent plastic strain at the base of the locking shaft was strictly controlled at 0.00926. This is well below the failure threshold of 0.0865 specified by ASME, providing a substantial safety margin and completely preventing local yielding. Crucially, the emergency release strategy based on precision locating pins was validated through full-scale prototype testing. Destructive tests conducted under simulated severe jamming conditions demonstrated clean, damage-free disengagement under shear torques ranging from 2100 Nm to 2200 Nm. This threshold ensures that accidental triggering will absolutely not occur during routine operations (1400 Nm) and establishes a safe underwater robotic (ROV) operating speed of ≤4 r/min. This study provides a robust theoretical framework and empirical data for the future design of yield-resistant subsea connectors and safe emergency recovery. Full article

To address the issues of low efficiency, high labor intensity, and susceptibility to damage during the manual harvesting of Volvariella volvacea, a mechanized harvesting device was developed to accommodate the growth characteristics of Volvariella volvacea. Thin-film sensors were used to measure the harvesting force values under both the bending method and the rotating method, incorporating two-finger and three-finger operation modes. The results indicated that the maximum force for the bending method was 4.60 N, while that for the twisting method was 2.91 N (peak values, n = 20 per method). The twisting method required less effort and posed a lower risk of damage. A four-suction-cup flexible end-effector was designed using silicone rubber material and equipped with a rotary cylinder. ANSYS 2022 R1 finite element simulation verified that under an applied force of 8 N, the surface stress on the Volvariella volvacea was less than 1.1489 MPa, meeting low-damage requirements. A Volvariella volvacea harvesting test rig was constructed, and performance tests were conducted. The results showed that the overall harvesting success rate was 96.65%, the damage rate was 2.03%, and the average time per harvest by the end-effector was 5.9 s. This study provides a theoretical foundation and technical support for the mechanized and intelligent harvesting of Volvariella volvacea, and is significant for promoting the high-quality development of the Volvariella volvacea industry. Full article

Sea anemones detect external stimuli through the deformation of their soft tentacles, which exhibit multi-directional force sensitivity. Inspired by this mechanism, we designed a capacitive three-dimensional force flexible tactile sensor composed of a hollow hemisphere and a hollow cylinder. The device was fabricated using 3D printing combined with a Layer-By-Layer assembly process. For normal forces, the sensor achieved sensitivities of approximately 0.66 N⁻¹ in the 0–1 N range and 0.15 N⁻¹ in the 2–10 N range. For tangential forces, the four symmetrically distributed electrodes exhibited opposite monotonic capacitance variation trends. The sensor exhibited a force resolution of 0.02 N, a lower detection limit of 0.04 N, a hysteresis error as low as 3.5%, and a response/recovery time of up to 50 ms under a 0–10 N load. Moreover, the device demonstrated good stability under 1000 load–unload cycles and over a temperature range from 20 °C to 100 °C. Its utility was further validated through multi-scenario applications, including game controller manipulation, gripper-based object recognition, Morse code and Huffman coding transmission, as well as multi-joint human motion detection. These results demonstrate that the proposed bioinspired sensor offers a promising solution for flexible force sensing, human–machine interaction, and wearable health monitoring. Full article

Seismic isolation systems are widely adopted in bridge engineering to reduce earthquake-induced force transfer and improve structural resilience. Conventional lead rubber bearings (LRBs) provide effective energy dissipation and period elongation; however, their limited recentering capability may result in significant residual displacement after strong ground motions. This study investigates the seismic performance of a two-level shape memory alloy–lead rubber bearing (TL-LRB-SMA) hybrid isolation system for multi-span bridges considering structural flexibility, support compliance, and geometric irregularity. A nonlinear analytical model of the hybrid isolator was developed and validated under cyclic loading using benchmark hysteretic behavior from the literature. Subsequently, a multi-degree-of-freedom numerical model of an eleven-span benchmark bridge was established and verified through modal analysis, equivalent static analysis, and comparison with MSBridge software (MSBridge Beta 1.0.1). Nonlinear time-history analyses were performed using multiple excitation scenarios, including the 1940 El-Centro record, Kobe ground motion, oblique seismic incidence, and combined loading cases. Flexible foundation conditions were represented using equivalent translational soil springs. The results indicate that the TL-LRB-SMA system consistently improves self-centering performance and significantly reduces residual displacement relative to conventional LRBs. For the regular bridge with 48 ft piers, residual displacement decreased from 0.786 inches to 0.268 inches under El-Centro excitation, while under combined excitation it reduced from 0.264 inches to 0.087 inches. For irregular bridge configurations, substantial residual displacement reductions were also observed under both longitudinal and oblique loading. Although moderate increases in peak displacement occurred in some cases due to staged SMA activation, the overall recentering performance improved markedly. Overall, the proposed TL-LRB-SMA system demonstrates strong potential for enhancing seismic resilience and post-earthquake serviceability of bridge structures, particularly in flexible and irregular configurations. Full article

This paper aims to develop an on-board shock absorber detection method for general aviation aircraft. The effects of common gas and oleo leakage are analyzed in this paper. Based on the principle of landing gear dynamics, it is found that gas leakage and oleo leakage would mainly affect air spring force of shock absorbers in various ways. A rigid–flexible coupled landing gear multi-body system (MBS) model is developed by considering strut flexibility, aiming to offer more accurate simulated responses. A database is developed that considers common leakage faults and typical landing conditions using the developed landing gear model. A deep learning model is proposed in this paper. The proposed model is trained and tested using the database simulated from the rigid–flexible coupling landing gear model. The proposed method demonstrates robust detection performance, achieving over 95% precision for most fault types. This work provides a practical, sensor-efficient solution for real-time health monitoring of landing gear shock absorbers, contributing to improved maintenance strategies and operational safety for general aviation aircraft. As this is a preliminary feasibility study, full validation requires future drop tests or instrumented flight tests. Full article

Extreme orbital thermal cycling and temperature-dependent clearance nonlinearity make it difficult to predict contact–impact, stick–slip, and bifurcation responses of flexible deployable space structures with sufficient stability, accuracy, and computational efficiency. An Adaptive Dissipation–Precision Coordinated Multi-Scale Implicit Integration Algorithm (ADPC-MSIIA) is proposed. First, an absolute nodal coordinate formulation (ANCF)-based thermo-mechanical clearance-joint model with thermal-viscosity-modified contact and frictional/impact heat feedback is established; second, a dual-time-scale implicit integration scheme with dual-$\alpha$ stability–dissipation control and third-order compensation is developed; finally, numerical validation is performed using a linear single-degree-of-freedom (SDOF) benchmark, a temperature-dependent clearance impact oscillator, finite-element and published benchmark comparisons, and a deployable annular truss antenna case. Simulation results show that ADPC-MSIIA achieves a high-frequency spectral radius of $0.867$, an effective convergence order of $2.98$, a maximum contact force error of $3.1\%$, and a $51.7\%$ reduction in the global cumulative error compared with the generalized-$\alpha$ method. This study contributes to knowledge by linking temperature-driven clearance evolution, frictional heat feedback, and adaptive numerical dissipation within a unified framework for predicting non-smooth thermo-mechanical deployment dynamics of large flexible space structures with clearance joints. Full article

Poly(trimethylene ether) glycol (PO3G), a bio-based polyether polyol with excellent flexibility and superior hydrolytic stability, has emerged as a critical raw material for the preparation of high-performance polymer materials. This work optimized the sulfuric acid-catalyzed polymerization process and assessed the feasibility of using p-toluenesulfonic acid (PTSA) as an alternative catalyst. A parametric study was conducted to establish a reliable operating window for the sulfuric acid system. DFT calculations demonstrated that the driving force for chain growth decreases with increasing chain length, that recombination between chains of significantly different lengths is more favorable than between chains of equal length, and that the formation of disulfate esters is thermodynamically more favorable. Although PTSA required a higher catalyst loading, the resulting polymer had a markedly lower yellowness index. Prolonged reaction times lead to a molecular weight plateau, especially at high PTSA concentrations, while the yellowness index continues to increase after reaching the plateau. ¹H NMR analysis indicated the formation of benzenesulfonate monoester intermediates during PTSA catalysis, suggesting a potentially milder pathway and possibly fewer side reactions compared to the sulfuric acid system. This paper provides theoretical and experimental foundations for the green, efficient synthesis of PO3G and the catalyst optimization for analogous bio-based polyether polyols. Full article

As extreme-scale manufacturing evolves, the dynamic response of heavy moving components under ultra-high loads becomes a critical design challenge. This study focuses on friction-induced vibration of a more than 30-ton movable mass during the mold-opening stage in a two-platen machine with a clamping force >17,000 kN. A mathematical model and a validated rigid/flexible multibody dynamics model with PID co-simulation were developed to analyze transient vibration using maximum acceleration amplitude and stability time as core metrics. The results show vibration stems from imbalance between anti-opening resistance and hydraulic driving force, amplified by vacuum collapse, static-to-dynamic friction transition at slide feet/rail interface and PID overshoot, featuring high amplitude density (>0.75 g), transience (<50 ms) and high impact (>60,000 N). The maximum vibration acceleration amplitude remains 79.22% even after there is no mold vacuum suction, indicating that a static friction force other than the vacuum suction is the dominant factor resulting in a severe friction-induced vibration. These mechanistic insights establish an applicable framework for the dynamic optimization of the heavy components in extreme-large-scale manufacturing equipment. Full article

Flow-induced vibration of high-speed pantographs becomes increasingly important as train speed approaches and exceeds 400 km/h. This paper develops an efficient computational framework that couples component-resolved unsteady aerodynamic loads from improved delayed detached eddy simulation (IDDES) with a dynamic-stiffness-method (DSM) flexible model of a high-speed pantograph. Two operating orientations, namely, knuckle-downstream and knuckle-upstream, are compared at 400 km/h, and the more unfavorable knuckle-upstream orientation is further investigated over 400 km/h to 600 km/h. The DSM model contains 49 beam elements and 42 nodes and shows good agreement with a refined three-dimensional solid-element finite element model in the low-order frequency range. For a 2 s transient analysis, the proposed model predicts the panhead displacement response with peak errors below 5% relative to the finite element model while reducing the computational time from 53 min 22 s to 35 s on the same platform. The results show that vertical vibration dominates the structural response, with the panhead peak vertical displacement reaching about 20 mm in the studied 400 km/h open-line case. Frequency-domain inspection of the panhead aerodynamic lift and vertical displacement shows that broadband aerodynamic excitation mainly activates the low-order structural modes, with a low-frequency aerodynamic component around 3 Hz to 4 Hz and additional energy mainly over the 20 Hz to 30 Hz range. The knuckle-upstream orientation increases the standard deviation of the equivalent contact-force response by 46% compared with the knuckle-downstream orientation at 400 km/h. For the knuckle-upstream orientation, increasing speed from 400 km/h to 600 km/h raises the standard deviation by 189%. The proposed framework provides an efficient tool for rapid comparative evaluation of pantograph flow-induced vibration under multiple operating conditions. Full article

The increasing demand for personalized conservative treatment of idiopathic scoliosis (IS) highlights the need for objective and continuous monitoring of corrective forces during brace therapy. This study aims to evaluate the feasibility and clinical relevance of a smart orthopedic brace equipped with integrated force sensors for long-term biomechanical assessment. Three female patients with different types of idiopathic scoliosis were treated using a custom-designed thoracolumbosacral orthosis incorporating four flexible pressure sensors, enabling real-time and long-term recording of corrective forces at key anatomical locations. Sensor data were analyzed in relation to brace-wearing adherence, patient activity, and radiological outcomes assessed using Cobb angle measurements. The results demonstrated substantial variability in force distribution and wearing patterns among patients, which was associated with differences in treatment effectiveness. Higher and more stable corrective forces near curve apices were generally accompanied by improved radiological outcomes, whereas irregular brace use and uneven pressure distribution limited therapeutic effects. Long-term monitoring enabled identification of insufficient correction zones and adherence issues. In conclusion, the proposed sensor-based orthotic system provides clinically relevant information on force distribution and brace use, supporting individualized therapy optimization. These findings indicate that smart braces can enhance clinical decision-making and contribute to more effective and personalized scoliosis management. Full article

To enhance immersion in virtual reality (VR) environments and improve the fidelity of virtual tactile interaction, this study proposes a perceptually grounded haptic-rendering framework for fine surface-texture simulation. The framework is centred on a Perceptual Haptic Spectrum Model (PHSM), which maps virtual surface attributes, including hardness, elasticity, roughness, friction, and microtexture periodicity, to multi-band tactile targets in perceptual frequency space. A Just Noticeable Difference (JND)-inspired parameterisation strategy is used as a design guideline to avoid imperceptible or redundant actuation, while region-specific response functions adapt the output to the fingertip centre, finger pad, and lateral edge. To improve reproducibility, the revised manuscript now specifies the flexible thin-film force/strain-sensor cell, array quantity, 320 Hz per-cell acquisition setting, signal-conditioning pipeline, contact-state classification rules, delay budget, and dual-actuation scheduling logic. The sensing design is based on a commercial flexible piezoresistive force-sensor cell with microsecond-level response time and a 12-bit ADC acquisition chain that provides a sufficient aggregate sampling margin for a 7–21 cell array. Manufacturer-supported sensor performance and prototype-level acceptance criteria are reported for response time, linearity, repeatability, hysteresis, drift, SNR, contact-state detection, latency, and durability. The system remains a proof-of-concept platform rather than a completed large-scale psychophysical validation. Within these boundaries, the results show coherent integration of perceptual modelling, multi-rate sensing, state monitoring, predictive feedforward control, and coordinated haptic actuation for fine VR texture rendering. Full article