Search Results (47)

This paper proposes a robust navigation method based on a robust square-root cubature Kalman filter (RSRCKF) to address the accuracy divergence of integrated navigation systems caused by drilling-induced slippage and the mismatch between the tail-cable encoder and the robot motion during operations of a seafloor drilling robot in deep-sea soft sedimentary layers. Considering the large-deformation mechanical characteristics of the seabed under drilling conditions, a unified state-space model incorporating a time-varying odometer scale-factor error is first established. To alleviate the numerical instability of the nonlinear system in the presence of non-Gaussian noise, a square-root cubature Kalman filter (SRCKF) framework is employed, in which the positive definiteness of the error covariance matrix is dynamically preserved via QR decomposition. Subsequently, an online fault detection mechanism based on a modified chi-square test is developed. By introducing a two-segment IGG (a classical robust weighting scheme) weighting function, an adaptive variance inflation factor is constructed to enable real-time identification and down-weighting of abnormal observations induced by slippage. Field experiments, including drilling and turning tests conducted on tidal mudflats off the coast of Zhoushan, demonstrate that the proposed method can effectively mitigate the impact of “false displacement” disturbances caused by typical soft clay slippage conditions through enhanced statistical robustness. Taking the conventional SINS/OD integration scheme as the baseline, the proposed method achieves an approximate 82.4% reduction in positioning error. These results verify the robustness and engineering applicability of the proposed algorithm in complex seabed environments. Full article

The integration of glass fibre-reinforced polymer (GFRP) and steel reinforcement in hybrid RC beams offers durability benefits, yet the specific influence of GFRP surface treatments on bond mechanics remains critical. This study experimentally investigates the performance of hybrid GFRP-steel-reinforced beams under three-point bending, comparing sand-coated and ribbed GFRP bars, while maintaining a constant total reinforcement ratio of 1.4% to isolate interface mechanics. Due to the exploratory nature of the study and the specific specimen matrix, the results are interpreted as observed experimental trends rather than statistically generalised performance metrics. The results indicate that ribbed GFRP bars provide enhance mechanical interlocking; in this specific experimental program, the ribbed GFRP hybrid beam exhibits an observed load capacity approximately 11% greater than the sand-coated specimen in this study and surpassing comparable steel-only beams. Additionally, ribbed configurations demonstrated an observed 15% higher toughness. In contrast, sand-coated hybrid beams exhibited signs of premature bond degradation, quantitatively captured by strain gauge monitoring; sand-coated bars plateaued at 14,000 µε, reaching only 79% of their theoretical rupture capacity. This strain limitation indicates failure by internal slippage rather than material rupture, further evidenced by a 50% reduction in crack propagation compared to ribbed beams. While energy-based ductility indices suggest a marginal 6% advantage for sand-coated bars, both hybrid systems exhibited relatively low energy-based ductility indices (μ < 2), reflecting the linear-elastic nature of GFRP reinforcement. These findings suggest that the mechanical interlock of ribbed surface treatments is more resilient under the combined stress states typical of hybrid configurations, providing a foundational baseline for the development of future numerical models and reliability-based design frameworks for hybrid GFRP-steel-RC systems. Full article

A sucker rod pump is an artificial lift system widely used in oil wells to extract crude oil from deep underground. Due to the clearance between the barrel and the pump plunger, a phenomenon termed slippage occurs in which the annulus column of oil returns to the pump chamber due to the plunger motion and the pressure difference at the two ends of the plunger. Although it is important to maintain the clearance for lubrication between the plunger and the pump barrel in order to prevent excessive wear and tear along with galling, excessive clearance can also be a primary factor in the reduction of oil well production and must be managed. In this research, after briefly reviewing the Couette and Poiseuille flows within the annulus region, the relaxation time for the transients, and the eccentricity effects, we focus on the derivation of important system parameters such the effective mass, stiffness, and damping ratio based on the measurements of the sucker rod displacement and the pressures or loads. Analysis of experimental measurement data can provide better understanding of the sucker rod pump system parameters, helping to quantify and manage the so-called slippage issues. Full article

The reinforcement mechanism of functionalized graphene nanosheets (GNS) on the mechanical properties of polyetheretherketone (PEEK)/polytetrafluoroethylene (PTFE) composites was investigated. Composite specimens were fabricated using PGNS, as well as GNS grafted with hydroxyl, carboxyl (-COOH) and amino functional groups, and mechanical characterizations were conducted on the prepared specimens. The results demonstrated that carboxyl-functionalized GNS (COOH-GNS) exhibited the most remarkable reinforcing effect on PEEK/PTFE composites, with its elastic modulus, tensile strength, yield strength and compressive modulus increased by 47.09%, 31.1%, 45.16% and 20.91%, respectively, compared with PGNS-reinforced composites. Combined with experimental measurements and molecular dynamics simulations, the reinforcement mechanism of this composite system was elucidated. The functional groups on the surface of GNS can induce interfacial interactions with the PEEK/PTFE matrix, by which the mobility of polymer molecular chains is restricted, the deformation and slippage of molecular chains are suppressed, and the interfacial bonding between GNS and the polymer matrix is simultaneously strengthened. The enhancement of interfacial binding energy, the reduction in free volume in the composite system, and the restriction of polymer molecular chain mobility were identified as the critical atomic-scale mechanisms responsible for the improvement of the macroscopic mechanical properties of the composites. Full article

Improving the energy efficiency of rolling bearings requires a component-resolved understanding of loss mechanisms. While analytical models capture load-dependent losses, load-independent hydraulic losses demand a physics-based approach. This paper presents a computational fluid dynamics (CFD) methodology for the qualification of individual hydraulic loss contributions and to assess their sensitivity to operating conditions. The approach decomposes the total hydraulic loss of the spherical roller bearing 22320 into component-level shares and is benchmarked against dedicated experiments. The simulated results show good agreement with experimental measurements, supporting the validity of the methodology. The discrepancy between the measured and simulated friction torque values averaged at 2–7%, with a single outlier. Furthermore, CFD methods have been demonstrated to be capable of predicting trends in hydraulic losses resulting from variations in speed and temperature. A consistent finding across all investigated conditions is that the rolling elements dominate the hydraulic losses. Churning-induced losses of the rolling elements contribute for more than 50% of the hydraulic losses of the hole bearing in every test. The proposed methodology offers a reproducible way to assign losses individually, compare operating scenarios and guide targeted design measures for loss reduction in rolling bearings. Furthermore, dynamic kinematic simulations of rolling bearings can be equipped with component-resolved hydraulic losses. This is enabling more accurate predictive modelling of the bearing kinematics and detecting effects such as slippage. Full article

Sport horse feeding robots face significant challenges in achieving precise navigation within complex stable environments. Uneven terrain and frequently moist ground often cause drive wheel slippage, resulting in path deviation and cumulative pose errors that compromise feeding accuracy and operational efficiency. To address this challenge, an enhanced Dynamic Window Approach (DWA) path planning framework, which integrates an automatic drift correction module based on an Inertial Measurement Unit (IMU) and a two-stage cascade proportional–integral–derivative (PID) controller, is proposed in this paper. This enhanced DWA enables precise yaw adjustment while preserving the native velocity sampling and trajectory evaluation framework of conventional DWA. Field validations were conducted through ten independent trials along a fixed 28 m feeding route in an actual sport horse feeding environment to quantitatively evaluate the robot’s path deviation and yaw angle stability. The results demonstrated that the enhanced algorithm reduced the standard deviation of path deviation from 0.161 m to 0.144 m (10.56% improvement) and decreased yaw angle standard deviation from 2.19° to 1.74° (20.55% reduction in angular oscillation). These improvements validated the effectiveness of the proposed algorithm in mitigating slippage-induced pose drift and significantly improving the locomotion capability of robots for sport horse feeding within stable environments. Full article

Background: Winch-assisted harvesting is an alternative to traditional cable yarding on steep slopes, offering improved operational efficiency and fewer limitations. Knowledge on the effects of winch-assisted harvesting on soil disturbance are limited. This study aimed to assess the effects of winch-assisted and conventional tracked harvester operations on soil compaction and machine slippage in a clear-cut stand with sandy loam soil. Methods: We evaluated changes in soil physical properties, in depth and extent, along machine operating corridors with and without winch-assist across slope gradients ranging from 30% to 52% and up to three machine passes. Results: The relative increase in bulk density differed between treatments. In the non-assisted corridors, the bulk density increased by 18%, 12%, and 11% at depths of 0–10, 10–20, and 20–30 cm, respectively; the winch-assisted corridors showed smaller increases of 12%, 5%, and 3% at the corresponding depths. The winch-assisted plots did not show a significant reduction in rut depth compared with the non-assisted plots, a result likely influenced by site-specific dry soil conditions. Conclusions: These results highlight the potential of winch-assisted systems to reduce horizontal soil disturbance, though their effectiveness in limiting rutting remains variable under dry conditions. Full article

In modern robotics, actuator performance is fundamental to achieving efficient and durable motion, with compactness and torque density being especially critical. Compact actuators enable integration in space-constrained systems without compromising functionality, while high torque density ensures powerful output relative to size, enhancing efficiency and versatility. Harmonic gearboxes embody these qualities, offering lightweight design, zero backlash, and excellent torque density, which have made them a standard choice in robotics. However, their widespread adoption is limited by high manufacturing costs due to the precision machining required. To address this challenge, the authors previously introduced RM-Act, a Radial Modular Actuator employing two synchronous belts as harmonic speed reducers. Building on this concept, RM-Act 2.0 is introduced as an improved version that employs a single synchronous belt. This design reduces transmission slippage, improves torque density, and offers greater modularity with a wider range of reduction ratios. The work details the development and validation of RM-Act 2.0 through a functional prototype and performance model, highlighting its advancements over the original RM-Act in compactness and torque density. Full article

This paper investigates the use of reinforcement learning (RL) algorithms to learn adaptive hedging strategies for derivatives under realistic market conditions, incorporating permanent market impact, execution slippage, and transaction costs. Market frictions arising from trading have been explored in the optimal trade execution literature; however, their influence on derivative hedging strategies remains comparatively understudied within RL contexts. Traditional hedging methods have typically assumed frictionless markets with only transaction costs. We illustrate that the dynamic decision problem posed by hedging with frictions can be modelled effectively with RL, demonstrating efficacy across various market frictions to minimize hedging losses. The results include a comparative analysis of the performance of three RL models across simulated price paths, demonstrating their varying effectiveness and adaptability in these friction-intensive environments. We find that RL agents, specifically TD3 and SAC, can outperform traditional delta hedging strategies in both simplistic and complex, illiquid environments highlighted by 2/3rd reductions in expected hedging losses and over 50% reductions in 5th percentile conditional value at risk (CVaR). These findings demonstrate that DRL agents can serve as a valuable risk management tool for financial institutions, especially given their adaptability to different market conditions and securities. Full article

In modern agriculture, tractors play a crucial role in powering tools and implements. Proper operation of agricultural tractors in mechanized field operations can support sustainable agriculture and reduce emissions of pollutants such as carbon dioxide (CO₂). This has been a recurring concern associated with agricultural intensification for food production. This study aimed to evaluate the optimization of tractor gears and engine speed during crop operations to minimize CO₂ emissions and promote sustainability. The experiment was conducted using a strip plot design with subdivided sections and six replications, following a double factorial structure. The first factor evaluated was the type of agricultural implement (disc harrow, subsoiler, or sprayer), while the second factor was the engine speed setting (nominal or reduced). Operational and energy performance metrics were analyzed, including fuel consumption and CO₂ emissions, travel speed, effective working time, wheel slippage, and working depth. Optimized gear selection and engine speeds resulted in a 20 to 40% reduction in fuel consumption and CO₂ emissions. However, other evaluated parameters remain unaffected by the reduced engine speed, regardless of the implement used, ensuring the operation’s quality. Thus, optimizing operator training or configuring machines allows for environmental impact reduction, making agricultural practices more sustainable. Full article

To address the issue of interfacial shrinkage deformation in optical resin–cement-based composites, this study examined the effects of casting methods and coupling agent treatments on the interfacial deformation behavior and underlying mechanisms at the resin–cement interface. A self-developed interfacial shrinkage testing apparatus, combined with ABAQUS numerical simulations, was employed to facilitate this analysis. The results revealed that the interfacial shrinkage strain followed a characteristic distribution—higher at both ends and lower in the middle region—as the temperature increased. The experimental data showed a strong agreement with the simulation outcomes. A comparative analysis indicated that the pre-cast cement method reduced the interfacial shrinkage strain by 16% compared to the pre-cast resin method. Furthermore, treatment with a coupling agent resulted in a 31% reduction in the strain, while combining a serrated surface modification with a coupling agent treatment achieved a maximum reduction of 43.5%. Microscopic characterization confirmed that the synergy between the coupling agent and surface roughening significantly enhanced interfacial bonding by filling microcracks, improving adhesion, and increasing mechanical interlocking. This synergistic effect effectively suppressed the relative slippage caused by asynchronous shrinkage between dissimilar materials, thereby mitigating the interfacial cracking issue in optical resin–cement-based composites. These findings provide theoretical insights for optimizing the interface design in organic–inorganic composite systems. Full article

This study presents a detailed analysis of the influence of hole presence and size on the behavior of CFRP composite plates subjected to axial compression. The plates were manufactured by an autoclave method from eight-ply laminate in a symmetrical fiber arrangement [45°/−45°/90°/0°₂/90°/−45°/45°]. Four central hole plates of 0 mm (reference), 2 mm, 4 mm, and 8 mm in diameter were analyzed. Tests were conducted using a Cometech universal testing machine in combination with the ARAMIS digital image correlation (DIC) system, enabling the non-contact measurement of real-time displacements and local deformations in the region of interest. The novel feature of this work was its dual use of independent measurement methods—machine-based and DIC-based—allowing for the assessment of boundary condition effects and grip slippage on failure load accuracy. The experiments were carried out until complete structural failure, enabling a post-critical analysis of material behavior and failure modes for different geometric configurations. The study investigated load–deflection and load–shortening curves, failure mechanisms, and ultimate loads. The results showed that the presence of a hole leads to localized deformation, a change in the failure mode, and a nonlinear reduction in load-carrying capacity—by approximately 30% for the largest hole. These findings provide complementary data for the design of thin-walled composite components with technological openings and serve as a robust reference for numerical model validation. Full article

The CRTS III (China Railway Track System Type III)-girder is susceptible to fatigue damage under high-frequency train loads. However, existing research lacks sufficient focus on the CRTS III-girder and the transverse wheel–rail forces encountered during train operation. To better replicate the stress conditions experienced by high-speed railway track systems, a 1:4 scale CRTS III-girder was fabricated following the principle of mid-span concrete stress equivalence. Subsequently, 9 million transverse and vertical fatigue load cycles were applied to the specimen, leading to the following conclusions: First, no visible cracks appeared on the CRTS III-girder surface during the experiment, indicating strong fatigue resistance under train loads. Second, the box girder primarily exhibited a linear elastic response with minimal stiffness variation. Meanwhile, the upper ballastless track structure experienced a highly complex stress state, with significant variations observed across different layers under cyclic fatigue loading. Third, under fatigue loading, the longitudinal strain of the mid-span track slab and the self-compacting concrete (SCC) layer exhibited an overall decreasing trend, with reduction rates of −66% and −57.9%, respectively. Conversely, the longitudinal strain of the base plate and the top and bottom of the box girder gradually increased, with respective increases of 38.6%, 10.4%, and 12.2%. Finally, the connection between the base plate and the box girder remained robust, showing no relative slippage in the transverse, longitudinal, or vertical directions. The sliding layer exhibited stable performance in the longitudinal direction, with no significant degradation observed under cyclic fatigue loading. However, with increasing load cycles, the transverse relative displacement of the sliding layer gradually increased, reaching a maximum of 0.1 mm. This displacement, in turn, contributed to transverse rail movement, potentially affecting driving safety. Full article

This paper evaluated the structural behavior of shear-strengthened externally bonded FRCM composites. The additional shear strength of FRCM composites with three different types of textile grids (T1, T2, and T3) was analyzed for different crack patterns and failure modes. The influence of the internal transverse reinforcement ratio (ρ_w: 0.19%, 0.285%) and application method (SB: side bonding; UW: U-type wrapping) on the FRCM-strengthened beam was investigated. Furthermore, the interaction of FRCM composites with internal shear reinforcement was analyzed based on the strain distributions measured in the experiments. The experimental results showed that the failure modes (flexural, shear slippage, and shear debonding) changed depending on the type of textile grid applied. A reduction in shear reinforcement strain (interaction) due to FRCM strengthening was observed for all the strengthened beams, with differences depending on the shear reinforcement ratio and the type of textile grid. In addition, the ratio of the strain measured at the ultimate load to the strain of the textile grid in shear-failed reinforced beams was the lowest for the T3 grid, which had worse physical properties, and increased at lower shear reinforcement ratios. However, application methods (SB, UW) did not show significant differences. Full article

A well-known phenomenon in machinery systems is the easing of a blocked connection of mechanical parts after an impact hit close to the connection. Such impact hits may also arise in shaft–hub connections such as gears, crankshafts, or other parts. The objective of this study is to investigate the influence of local impact loads on the transmittable torque of smooth shaft–hub connections. In a specially designed test rig, it was demonstrated that the transmittable torque of the shaft–hub connection is reduced as a consequence of the impact, resulting in a reduction in the frictional force and slippage of the hub. Increasing the impact load leads to an increase in the reduction in the frictional force as well as the slippage and reduces the transmittable torque. By carrying out a modal analysis of the relevant parts and FE simulations of the impact, two possible reasons have been identified: (i) the impact load excites a vibration mode in the connection which reduces the frictional force and the transmittable torque; and (ii) the impact causes local deformation of the shaft, which results in local slip. Full article