Lightweight Requirements Research Articles

Unsupervised motor incipient fault detection using lightweight network and orthogonal low-rank embedding

Abstract Electrical motor is a key component in industrial systems. Detecting incipient fault of motor is critical to system reliability. However, the characteristics of faults and normal stages are difficult to distinguish, Meanwhile, the lightweight requirements of the model and the imbalance of the samples also make incipient fault detection challenged. To address these problems, this paper proposes an unsupervised fault detection method combines lightweight network and orthogonal low-rank embedding (OLE). The raw signals are firstly transformed into time-frequency images and fed into lightweight convolution network for feature extraction. Then, the features are clustered into orthogonal subspaces to enhance inter-class separability. Finally, a detection module based on distance metric is designed to identify the incipient fault of motor. The effectiveness of the proposed method is validated on four industrial motor dataset and compared with other methods.

Modular design and structural optimization of CubeSat separation mechanism

In order to achieve the design requirements of light weight and high stiffness of the CubeSat modular separation mechanism, a BPNN-GA-PSO size optimization method is proposed to optimize the design of the separation mechanism. Firstly, the separation mechanism of modularization and standardization is analyzed to select the optimization objects. Then, a hierarchical optimization strategy of topology optimization followed by size optimization is adopted to find the global optimum using a hybrid GA-PSO optimization algorithm. Meanwhile, the BPNN surrogate model is introduced to improve the optimization efficiency. The results show that the mass proportion of the optimized separation mechanism is reduced to 18 %, and the maximum deformation of the separation mechanism is 0.123 mm, which meets the design requirements of light weight and high stiffness of the separation mechanism. It proves the applicability of the optimization method to the optimal design of the separation mechanism. The CubeSat modular separation mechanism designed in this paper has been verified by ground verification with overload, vibration, and shock mechanical tests, and successfully deployed the BY-03 satellite in-orbit, which can provide reference for the design and development of subsequent CubeSat modular separation mechanisms.

Enhanced heat transfer performance in vapor chambers via fabrication of novel regular composite porous wick structures using selective laser melting

The composite structure wick has been proven to significantly enhance the heat transfer performance of vapor chambers. Aluminum vapor chambers offer advantages such as being lightweight and cost-effective, meeting the requirements for lightweight cooling in fields like aviation. This study presented two novel composite porous wick structures with regular-shaped pores, designed and controlled via selective laser melting (SLM): the vertical square pore composite wick structure and the round-vertical square pore composite wick structure. A water-cooling test platform was built to investigate the effects of parameters such as wick structure thickness, round pore diameter, and round pore depth on the heat transfer performance and thermal resistance of the vapor chambers. The results indicate that the optimal thickness for the vertical square pore composite wick structure was 1.5 mm, yielding a minimum thermal resistance of 0.04 K/W. When the thickness was below 1.5 mm, it caused a reduction in the density of the vaporized core and insufficient liquid transport capacity. Conversely, when the thickness exceeded 1.5 mm, the primary limiting factor for heat transfer shifts to vapor-liquid flow resistance. Furthermore, the round-vertical square pore composite wick structure can provide further improvements in vapor-liquid transport within the structure.

Energy absorption characteristics of STF impregnated Kevlar fabric coating GFRP composite structure by projectile high-velocity impact

The new STF impregnated Kevlar fabric coated GFRP (glass fiber reinforced polymer) composite structure obtained by combining STF（shear thickening fluid） impregnated Kevlar fabric and GFRP can obtain strong energy absorption capacity with light weight compared with two separate structures, so it has strong impact resistance. In this paper, the experiments of STF impregnated Kevlar fabric, GFRP laminated plate and STF impregnated Kevlar fabric coating GFRP laminated structure were carried out, respectively. Based on reliable numerical simulation, the macroscopic damage and energy absorption characteristics of the same material in STF impregnated Kevlar fabric, GFRP laminated plate and STF impregnated Kevlar fabric coating GFRP laminated structure were analyzed. The results show that the GFRP laminate and the rear Kevlar fabric in the STF-impregnated Kevlar fabric coating GFRP laminate structure show a larger damage area than that of GFRP laminate and STF impregnated Kevlar fabric alone, and a larger deflection is generated during the process of impact. The increase of the number of layers of Kevlar fabric in the front and back of the laminate and the increase of the thickness of the laminate make the Kevlar fabric absorb more energy. If the energy absorption capacity of GFRP laminates is increased, the number of layers of the front Kevlar fabric can be reduced, the thickness of the laminates can be increased, and materials with greater strength can be added to the front ply of the laminates. However, increasing the thickness of GFRP laminates will reduce the lightweight requirements of laminated structures.

Design of Broadband Phased Array Feed Using Stereolithographic Additive Manufacturing Heterogeneous Integrating Technology for Fast Radio Burst Observation

Herein, a stereolithography appearance 3‐D printed phased array feed (PAF) on radio telescopes based on broadband Vivaldi antenna elements covering 4–10 GHz, which meets the requirements of low cost, lightweight, and compact volume, is designed and proposed. The prototype is integrated with two orthogonal linear polarized 4 × 5 arrays, each of which is composed of 20 Vivaldi antenna elements. The distance between adjacent antenna elements is 1/2 λ in both E‐plane and H‐plane. By increasing thickness of the slice elements compared with traditional end‐fire arrays on printed circuit board, the wide‐band impedance matching is realized. The mutual impedance matrix of the dual‐polarization array is calculated and the equivalent circuit of the active and parasitic elements is demonstrated. Due to the orthogonal parasitic elements inserted between the adjacent active antennas, equivalent capacitance is introduced in the tightly coupled array. The measured active voltage standing wave ratio of the manufactured PAF exhibits 4–10 GHz operating bandwidth for both broadside radiation and 45° scan in both E‐ and H‐plane polarization. The proposed wideband PAF has a promising potential application prospect in fast radio burst and other astronomic observation.

A novel design of energy absorption branch for HVDC circuit breakers

Metal oxide varistors (MOV) used for energy absorption branch in DC circuit breakers are complex enough to meet the requirements for small volume, light weight, and reliability in future high-voltage direct current (HVDC) grids. Therefore, a new energy absorption branch circuit that combines MOV and a liquid metal alloy energy absorber (LMEA) is proposed. Based on the constructed equivalent mathematical model of LMEA, the working principle and energy absorption process of MOV and LMEA in DC breaking process are analysed in PSCAD/EMTDC simulation software. Results demonstrate that LMEA, in contrast to MOV alone, absorbs 2.12 MJ of energy, constituting 35.6% of the total energy. Moreover, LMEA enhances energy dissipation density while reducing volume. Experimental analysis reveals MOV’s energy absorption mechanism via achieving residual voltage with ZnO varistor’s non-linear properties, swiftly transitioning from high to low resistance states to absorb energy. Conversely, LMEA relies on pulse current amplitude to initiate internal arcing, sharply increasing internal resistance for effective energy absorption. Experimental findings validate LMEA’s contribution of one-third of total energy absorption when pulse current amplitude reaches critical arcing threshold, consistent with simulation results. The results provide theoretical support for the engineering application of the new liquid metal alloy energy absorption in DC circuit breakers.

Design, fabrication and vibration characteristics of a novel composite auxetic structure embedded with resonators

With the rapid development of shipbuilding and aerospace industries, the mechanical performance requirements for structures are becoming increasingly demanding. Conventional vibration reduction structures cannot meet the requirements for lightweight, high load capacity, low frequency and broadband vibration reduction. Therefore, it is necessary to consider new structural topologies and material systems. Inspired by the lightweight and high strength characteristics of composite materials, the negative Poisson's ratio characteristics and the locally resonating phononic crystal, the carbon fiber composite auxetic structure embedded with resonators is proposed. Embedded resonators within composite auxetic structures can be strategically positioned to introduce gaps, thereby enhancing the vibration damping performance. The basic auxetic structure is prepared by simpler methods including molding and bonding, and the outer shell of resonator is made by 3D printing technology. The method enables the design of appropriate outer shell based on various cavity types within the structure, ensuring a stable connection between resonators and the structure itself. The range of the band gap can be predicted based on the negative effective mass. Vibration behavior and band gap characteristics of the structure are proved through vibration experiments and numerical simulations. It is revealed that the structure can generate local resonant band gaps at lower frequencies. Meanwhile, the coupling relationship between the auxetic structure and the resonator makes an impact to the band gap range. Therefore, the proposed structure can meet the required multi-functional integrated performance requirements. Furthermore, the parametric analysis is carried out, and the relevant conclusions can provide theoretical guidance for designing porous composite structures with effective low-broadband vibration reduction capabilities.

A Lightweight Real-Time Recognition Algorithm for Tomato Leaf Disease Based on Improved YOLOv8

To address the real-time detection challenge of deploying deep learning-based tomato leaf disease detection algorithms on embedded devices, an improved tomato leaf disease detection algorithm based on YOLOv8n is proposed in this paper. It is able to achieve the efficient, real-time detection of tomato leaf diseases while maintaining model’s lightweight requirements. The algorithm incorporated the LMSM (lightweight multi-scale module) and ALSA (Attention Lightweight Subsampling Module) to improve the ability to extract lightweight and multi-scale semantic information for the specific characteristics of tomato leaf disease, which include irregular spot size and lush tomato leaves. The head network was redesigned utilizing partial and group convolution along with a parameter-sharing method. Scalable auxiliary bounding box and loss function optimization strategies were introduced to further enhance performance. After undergoing the pruning technique, computation decreased by 61.7%, the model size decreased by 55.6%, and the FPS increased by 44.8%, all while a high level of accuracy was maintained. A detection speed of 19.70FPS on the Jetson Nano was obtained after undergoing TensorRT quantization, showing a 64.85% improvement compared to the initial detection speed. This method met the high real-time performance and small model size requirements for embedded tomato leaf disease detection systems, indirectly reducing the energy consumption of online detection. It provided an effective solution for the online detection of tomato leaf disease.

Interface of AlCrTiN/6061 laminated composite fabricated by one-pass rolling and its tribological properties

Inspired by the bionic idea, the AlCrTiN/6061 laminated composite material with “mortar and brick” structure was fabricated by one-pass rolling. And the interface characteristics, dry friction process and wear mechanism of the nacre-like AlCrTiN/6061 laminated composite were systematically studied. Scanning electron microscopy (SEM) confirmed the successful construction of the “mortar-brick” structure in the composite. And high resolution transmission electron microscopy (HRTEM) revealed that Al18Cr2Mg3 phase is formed at the interface of AlCrTiN/6061 laminated composite. Electron back scatter diffraction (EBSD) analysis showed that there are 〈110〉 silk texture in the RD direction. Moreover, the tribological tests indicated that the friction coefficient (COF) of the laminated composites ranged from 0.379 to 0.437, which can meet the requirements of lightweight and high-performance braking of automobiles.

MPNet: A lightweight fault diagnosis network for rotating machinery

Rotating machinery is prone to faults, especially bearing faults. Existing machinery fault diagnosis methods suffer from low accuracy and poor robustness under actual complex working conditions. To address these problems, this paper proposes a sound signal-based rotating machinery fault diagnosis method and designs a lightweight fault diagnosis network called MPNet. A multi-branch feature fusion module is constructed to capture the multi-scale correlation information of the sound features. A residual attention pyramid module is designed to adaptively learn abstract fault information at different levels, then the feature-enhanced attention maps at multi-scale generated by hierarchical fusion. Experimental results on a public bearing dataset and a self-made idler dataset reveal that the proposed method achieves 95.83% and 94.81% accuracy, respectively, meeting the requirements of lightweight and real-time detection. Compared with conventional methods, the proposed method has better diagnostic precision and robustness under strong noise. The code library is available at: https://github.com/xgli411/MPNet.

Investigation of the static and low‐velocity impact performance of 3D braided spacer composites

AbstractTo meet the lightweight requirements of advanced composite materials, the ultralightweight three‐dimensional (3D) braided spacer composites were designed and manufactured by ultra‐high molecular weight polyethylene (UHMWPE). The key structural effects of core column distances and core column heights on the static bending, compression, and low‐velocity impact properties of the composites were further investigated. Results indicated that the mechanical properties of 3D braided spacer composites was closely depended on their structural parameters. The flexure and compression of 3D braided spacer composites decreased with increasing core column distance and core column height. W1/H1 specimen showed the optimal bending and compressive performance. The maximum flexural strength and flexural modulus were approximately 54.77 MPa and 4.95 GPa, respectively. The low‐velocity impact properties were further investigated where the stiffness, energy absorption, and impact resistance of the composite decreased with increasing core column distance. The peak load and energy absorption of the W1 specimen were 2.39 kN and 7.99 J, respectively. While the low‐velocity impact properties increased with increasing core column distance. The H3 specimen exhibited the greatest stiffness, impact resistance and energy absorption with peak loads and energy absorption of 2.81 kN and 8.49 J, respectively. In addition, the macro morphology and scanning electron microscopy (SEM)micrographs were examined to investigate the damage morphology and failure mechanism of the composites. The main failure modes were matrix cracking, interface debonding, fiber buckling, and dislocation, as well as tilting, and failure of the core columns. This work provides guidance for structural design and engineering application of 3D lightweight braided spacer composite.

A Lightweight CER-YOLOv5s Algorithm for Detection of Construction Vehicles at Power Transmission Lines

In the context of power-line scenarios characterized by complex backgrounds and diverse scales and shapes of targets, and addressing issues such as large model parameter sizes, insufficient feature extraction, and the susceptibility to missing small targets in engineering-vehicle detection tasks, a lightweight detection algorithm termed CER-YOLOv5s is firstly proposed. The C3 module was restructured by embedding a lightweight Ghost bottleneck structure and convolutional attention module, enhancing the model’s ability to extract key features while reducing computational costs. Secondly, an E-BiFPN feature pyramid network is proposed, utilizing channel attention mechanisms to effectively suppress background noise and enhance the model’s focus on important regions. Bidirectional connections were introduced to optimize the feature fusion paths, improving the efficiency of multi-scale feature fusion. At the same time, in the feature fusion part, an ERM (enhanced receptive module) was added to expand the receptive field of shallow feature maps through multiple convolution repetitions, enhancing the global information perception capability in relation to small targets. Lastly, a Soft-DIoU-NMS suppression algorithm is proposed to improve the candidate box selection mechanism, addressing the issue of suboptimal detection of occluded targets. The experimental results indicated that compared with the baseline YOLOv5s algorithm, the improved algorithm reduced parameters and computations by 27.8% and 31.9%, respectively. The mean average precision (mAP) increased by 2.9%, reaching 98.3%. This improvement surpasses recent mainstream algorithms and suggests stronger robustness across various scenarios. The algorithm meets the lightweight requirements for embedded devices in power-line scenarios.

Fabrication characterization and compression failure analysis of Ni-based alloy ABD-900AM TMPS structures via laser powder bed fusion

The novel high-strength and high-temperature nickel-based alloy developed for additive manufacturing, i.e., ABD-900AM, shows great potential in next-generation aircraft engines. However, there are limited investigations about the printing capability of ABD-900AM with complex structure as well as compression behaviors of this new alloy system. To meet the lightweight requirement, ABD-900AM with triply periodic minimal surface (TPMS) is fabricated by selective laser melting (SLM) in the present work, and the printing quality and compression performance of different TPMS structures are analyzed utilizing both experimental and computational methods. First, six types of TPMS structures are designed, and the external contours fabricated by SLMed ABD-900AM are detected through 3D optical scanning. In general, high fabrication quality is achieved with the proper process parameters, while the positive deviations are observed at the lateral surfaces and edges, and the negative deviations are observed at the upper regions of the cellular structures. Further, compression tests of SLMed ABD-900AM TPMS structures are conducted, and the failure mechanisms are evaluated. The equivalent elastic modulus is ranked as Diamond > Split-P > Primitive > Gyroid > I-WP > Lidinoid. The SLMed ABD-900AM TPMS structures shows advantages compared to these TPMS structures fabricated using typical metal alloys. Finally, the computational models of SLMed ABD-900AM TPMS structures are built up in the commercial software ABAQUS. The stress-strain behaviors and the failure process of different SLMed ABD-900AM TPMS structures are successfully reproduced.

Effects of Recycled Polyethylene on Natural Rubber Composite Blends Filled with Aluminum Trihydroxide and Polyurethane Waste: Mechanical and Dynamic Mechanical Properties, Flammability.

This research studies natural rubber (NR) composite blends prepared with recycled polyethylene (PE), polyurethane waste (PU), silica (SiO2), and aluminum trihydroxide (ATH) under the proper mixing conditions using an internal mixer and a two-roll mill. The mechanical, impact, dynamic mechanical, and thermal properties, together with flammability, were investigated. NR/PU composites filled with a specific SiO2/ATH concentration resulted in excellent flame-retardant properties without using PE. Adding PE causes poor flammability, while using PU and SiO2 prevents flame extensibility of the composites. In addition, SiO2 and ATH synergistically improved both mechanical and dynamical mechanical properties. This is attributed to the reinforcement of SiO2 particles inside the matrix, whereas the ATH releases water as a flame retardant. The V-0 composites tested with UL-94 showed acceptable heat resistance, strength, and durability, making them suitable for interior and exterior applications in buildings without the lightweight requirement.

Encapsulating Si particles in multiple carbon shells with pore-rich for constructing free-standing anodes of lithium storage

Silicon based (Si-based) materials are considered to be the most promising anode materials for lithium-ion batteries (LIBs) due to their high specific capacity. However, the issues of poor electrical conductivity and volume expansion during cycling have not been effectively addressed. The optimum remedy is to select specific materials to establish an exceptional conductive and volume buffer structure to assist the Si materials to develop its excellent lithium storage properties. Here, Si particles were encapsulated into porous carbon fibers containing ultrafine Co particles (CP) to obtained Si-x@CP-y film. Among them, the addition of Si particles and the void structure was precisely regulated to achieve a superior electrode with a high specific capacity. Subsequently, the two-dimensional conductive material reduced graphene oxide (rGO) nanosheets were further incorporated to obtain Si-2@CP-2@rGO films with core@multi-shell structure. The final electrode was equipped with one-, two-, and three-dimensional electronic pathways to allow rapid electron transport, and featured with multi-layer buffer structure and reserved pores that could effectively mitigate volume changes. As expected, the free-standing Si-2@CP-2@rGO electrode delivered a high specific capacity of 1221.2 mAh/g after 100 cycles at 0.1 A/g in a half cell, and the assembled full cell showed 249.0 mAh/g after 200 cycles at 0.2 A/g, which fulfilled the lightweight requirement for new energy storage devices.

Free vibration analysis of CNT reinforced plates using higher order shear deformation theory

With the stringent requirements of lightweight and high stiffness in space technology and spacecraft, the research on frequency characters of carbon nanotubes (CNTs) reinforced structures is particularly urgent. In this paper, based on the Reissner-Mindlin higher-order shear deformation theory (HSDT), a vibration model for a CNT functionally graded (FG) plate is developed, and influences of the reinforcements distribution form, reinforcement volume fractions, and various boundary conditions of the structure are considered in this established model. Subsequently, the model’s convergence test was presented first with a rectangular plate structure. Finally, the vibration characteristics and modal shapes of the CNT-FG plate structure are carried out by using this model.

Study on insulator defect detection based on improved YOLOv8

Given the problems of poor detection effect in aerial insulator images resulting in poor detection effect, a multi-defect detection algorithm for aerial insulators based on improved YOLOv8 is proposed. The algorithm first changed the FPN structure to BiFPN by introducing the upsampling and downsampling connections in the upstream and downstream of the feature pyramid, to enhance the interaction and information flow between characteristics at different scales. Secondly, the SPPF is improved by using the LSKA attention mechanism to enhance the ability to extract multi-scale features. Finally, for the detection of tiny fine particles, this paper reheavys the decoupling head and the lightweight decoupling head, extracts the key information above the space and channels, and implements a lower inference latency while maintaining accuracy. The algorithm detects the normal glass insulator, glass sheet dirt, glass sheet defect, polymer sheet dirt, polymer sheet defect, and polymer insulator in the aerial image, and simultaneously detects the flashover of the insulator. The experimental results show that the network used in the insulator defect data set detection accuracy (mAP) reached 87.8%, which increased by 2.6% compared to the benchmark model, and the calculation amount (GFLOPs) decreased by 24%. At the same time, after lightweight model parameters are reduced by 32%, based on the accuracy of the subsequent deployment of lightweight requirements, we can better detect insulators of different scales and different conditions.

Expanding THz Vortex Generation Functionality with Advanced Spiral Zone Plates Based on Single‐Walled Carbon Nanotube Films

AbstractOptical elements based on nanomaterials are becoming major avenues to satisfy the technological requirements of compact, lightweight, and tunable elements of the emerging terahertz (THz) field. A new generation of diffractive components integrating specific geometry with additional features (flexibility, stretchability, rotation, and other approaches for tuning properties) extends the functionality of wavefront control. Here, an innovative approach is demonstrated to control the THz wavefront via a layered composition of spiral zone plates (SZPs) with tunable mutual orientation and scaling. As a proof of concept, the SZP is designed using Laguerre‐Gauss mode analysis with further fabrication and experimental characterization of the resultant vortex beams. For each single SZP, a flexible element is proposed based on a thin film of single‐walled carbon nanotubes deposited on a stretchable substrate. Thus, this diffraction element can be tuned not only by rotation (along the azimuthal direction), but also by its stretching (in the radial direction). The spatial tuning of the developed SZPs (spiral zone plates) opens up an efficient, convenient, and highly customizable approach for the manipulation of vortex beams.

Automatic generation method for long-focal-length unobscured freeform optical systems with small volume

The existing design methods for long-focal-length unobscured freeform systems rarely consider the imaging quality requirements and volume constraints simultaneously, causing most of the final designs to not fulfill the requirement of light weight. This study proposes a method to automatically design a long-focal-length unobscured reflective system that satisfies volume constraints while maintaining high imaging quality. First, a method to adaptively set the structural parameter range is proposed, and multiple parameters for different systemic specifications can be effectively calculated within it. Subsequently, the systemic volume and area functions are constructed using the ray tracing method, where the tilt angles, distances between mirrors, and radii of curvature of the mirrors are chosen as the optimization parameters. Third, a comprehensive objective function is jointly established combining ray obscuration and convergence as performance evaluation factors. Then, the structural parameters of a long-focal-length unobscured system with small volume are easily obtained via the simulated annealing method. Finally, the improved W-W method is used to further enhance the imaging quality of the system, and an unobscured freeform reflective optical system with three mirrors is automatically generated. Experimental results demonstrate that our method can automatically calculate the parameter ranges to facilitate the search for structural parameters, and effectively design the long-focal-length unobscured freeform systems with small volume and high imaging quality.

Fabrication of MOF-rGO aerogels to enhance electromagnetic wave absorption by adjusting the morphology and structure of MOFs by electron transfer

Graphene and its derivatives have become the star materials in the field of electromagnetic wave (EMW) absorption, and have been widely studied because of their unique structure and excellent properties. However, the high electrical conductivity of graphene-based material leads to poor impedance matching performances, so it often needs to be annealed at high temperatures, which is a intricate procedure and cause the waste of energy. Herein, we develop a convenient strategy to synthesize metal organic framework-reduced graphene oxide (MOF-rGO) aerogels through facile hydrothermal and freeze drying procedure. Firstly, the excessive electrons on graphene can be transferred to MOF, in this way, no annealing is needed. Secondly, the morphology and structure of MOF can be regulated electronically to endow the material with rich heterojunction interfaces and enhance its interfacial polarization. Thirdly, the synthesized aerogels satisfy the requirements of thin thickness, low density and light weight. The fabricated Ni-MOF-rGO and FeNi-MOF-rGO aerogels exhibit remarkable EMW absorption performances with strong reflection loss (RL) and broad effective absorption band (EAB) at the thickness of 2.4 (−47.8 dB and 7.84 GHz) and 2.9 mm (−48.3 dB and 8.32 GHz) whereas the filling contents are just 5 %. Moreover, the attenuation capacity of the fabricated aerogels are verified through the radar-section simulation and the interfacial polarization loss are confirmed by the COMSOL analogue simulation. In a word, this work provides a new afflatus and inspiration for the design of graphene-based EMW absorption materials.