Table of Content

25 March 2024, Volume 52 Issue 3

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Contents



2024, 52(3):  0. 

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Materials Science & Technology

Effect of Chitosan on the Hot-Extrusion 3D Printing Formability of Oxidized Starch Gel



CHEN Ling, LÜ Jiayu, QIU Zhipeng

2024, 52(3):  1-9.  doi:10.12141/j.issn.1000-565X.230433

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Oxidized starch gel material has become a hot material in fields such as food and biomedicine because of its advantages of hydrophilicity, chargeability, easy reaction and assembly in recent year. However, when used as a hot-extrusion 3D printing (HE-3DP) gel material, it has defects such as poor printability and low gel strength. This study investigated the influence of different chitosan addition amount on the rheological properties, printing formability and gel strength of oxidized starch-chitosan gel materials by adding different amounts of chitosan and utilizing non-covalent and chemical cross-linking between chitosan and oxidized starch. The results show that the oxidized starch-chitosan pastes exhibit typical shear-thinning characteristics. As chitosan is added in varying concentrations (0.5%~2%), non-covalent interactions such as hydrogen bonding and electrostatic attraction lead to an increase in the viscosity of the system. The thixotropic property initially increases and then decreases, while the flow stress (τ_f) first decreases, and then increases; and the yield stress (τ_y) increases first and then decreases. Compared with oxidized starch gel, oxidized starch-chitosan gel has good printing formability. Especially when the amount of chitosan added is 1%, the composite gel has the best thixotropic property, the minimum flow stress (τ_f) and the largest yield stress (τ_y), so the printing formability and printing accuracy is the best. Additionally, due to the non-covalent interaction between chitosan and oxidized starch and the schiff base chemical cross-linking, the oxidized starch-chitosan gel forms a dense network structure to improve gel stability and gel strength significantly. These effects are more significant with a higher chitosan content. The results can provide a theoretical basis and technical support for the performance improvement of oxidized starch gel material and the design and application of oxidized starch-chitosan gel materials suitable for HE-3DP.

Microstructure and Properties of Laser Cladding Hard Composite Coating on TC4 Surface



FU Yuming, MA Shunxin, LIU Shaofeng, et al

2024, 52(3):  10-17.  doi:10.12141/j.issn.1000-565X.230061

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TC4 is widely used in aerospace field due to its high specific strength, good corrosion resistance and light weight. However, its disadvantages such as large friction coefficient and poor wear resistance greatly limit its application range. In view of the shortcomings of low hardness and poor wear resistance of TC4, a 4 kW high-power Laser4000 semiconductor laser was used to prepare different proportions of steel-based metal-ceramic hard coatings on the surface of TC4 by laser cladding technology with transition family refractory carbides HfC, TaC and ZrC as reinforcing phases and H13 steel-based powder as base powder. Then, the macro morphology, microstructure, phase composition and coating element distribution of the coatings with different proportions were compared and analyzed by means of scanning electron microscopy (SEM), EDS energy spectrometer, D/max-2500/PC X-ray diffractometer (XDR) and other test methods. The hardness of the coating was tested by Qness Vickers microhardness tester and the variation law of the microhardness of the cross section of the cladding sample was analyzed. The friction and wear properties of the coatings with different material components were studied by MMU-5G end friction and wear tester. The results show that the cladding layer of the specimen forms a good metallurgical bonding with the substrate. The microstructure of the cladding layer is mainly dendritic structure and block structure. The main phases of each cladding layer all contain TiC, and as the content of ternary ceramic powder increases, the content of MC also increases. When the carbide mixed powder is 15% (mass fraction), Hf_0.8Ta_0.2Fe₂ ternary alloy phase is detected in the cladding layer. When the content of ternary ceramic powder is 10% (mass fraction), the cladding grain is the smallest, the average hardness of the coating layer is the highest, and the average hardness is about 763.43 HV, 2.29 times the hardness of the substrate. When the content of ternary ceramic powder is 5% (mass fraction), the coating has the best wear resistance, and the relative wear resistance is 25%.

Effect of Recycled Fine Aggregate and Clay Brick Powder on Properties of 3D Printed Concrete



ZHANG Haiyan, MA Jinyi, WU Bo, et al

2024, 52(3):  18-27.  doi:10.12141/j.issn.1000-565X.230020

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In order to reduce the amount of natural aggregates and cementitious material in 3D printed concrete, this study used recycled fine aggregate (RFA) to partially replace natural fine aggregate and clay brick powder (CBP) to replace cement. The fluidity and compressive strength test of cast-in-situ concretes with RFA only (0, 25%, 50%, 75% and 100% replacement ratio), with CBP only (0, 5%, 10%, 15%, 20% and 30% replacement ratio) and with both of them were firstly carried out to obtain the optimal replacement ratio of RFA and CBP. Then, it investigated the effect of the addition of 50%RFA and 10%CBP and the corresponding mix proportion adjustment methods (adding extra water and increasing water reducer dosage) on the fresh and harden properties of 3D printed concrete. The test results indicate that the decreasing amplitude of the compressive strength of cast-in-situ concrete is within 10% when the replacement ratio of RFA is less than 50%. With the increase of CBP replacement ratio from 0 to 30%, the compressive strength of cast-in-situ concrete increases first, then decreases and then slightly increases. The specimen with CBP content of 10% exhibits the highest compressive strength. Compared to the concrete with 50%RFA only, the concrete with 50%RFA and 10%CBP has higher strength, while the fluidity is almost kept unchanged. For 3D printed concrete, the addition of 50% recycled fine aggregate and 10% brick powder and additional water can keep the initial expansion of 3D printed concrete unchanged and improve the buildability of concrete, but it can decrease the slump, opening time, compressive and split tensile strength and increase intensity anisotropy. However, increasing water reducer dosage in the mixture can not only significantly improve the fluidity, opening time and compressive strength of 3D printed concrete, but also reduce the intensity anisotropy.

Study on Sodium β-glycerophosphate in Concrete Affects the Inhibited Behavior of Steel Bar



WANG Xiaoxian, LIU Jiaping, MU Song, et al

2024, 52(3):  28-40.  doi:10.12141/j.issn.1000-565X.230030

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In the high alkaline environment of concrete, in order to improve the resistance of steel bar in concrete to chloride ion erosion, this study adopted a new environmentally friendly organic rust inhibitor-β-glycerophosphate sodium to protect the steel bar and achieve the purpose of extending the service life of reinforced concrete structures. In this study, the electrochemical measurements were used to monitor the evolution properties of the steel embedded in concrete in real time. The corresponding key parameters were obtained to explore the relationship between sodium β-glycerophosphate and steel passive film in the passivation period, as well as the relationship among sodium β-glycerophosphate, steel passive film and chloride ions during the maintenance passivation period, and then the rust resistance mechanism of this kind of organic matter was revealed. The results obtained by OCP, LPR and EIS electrochemical testing methods show that: β-sodium glycerophosphate forms a more density protective film through physicochemically interacting with Fe oxides/hydroxides on the steel surface, so as to make the surface of the steel bar form a protective film with more inhibited behavior, which also improves the resistance of the steel bar under chloride ion erosion. The resistance of the steel bar in each of the four solutions is: NaOH + 0.1 mol/L sodium β-glycerophosphate > saturated clarified Ca(OH)₂ > NaOH > saturated clarified Ca(OH)₂ + 0.1 mol/L sodium β-glycerophosphate. Among them, the critical chloride ion concentrations (c_crit) of steel bars in NaOH, NaOH + 0.1 mol/L sodium β-glycerophosphate and saturated clarified Ca(OH)₂ solutions are: 0.02 mol/L, 0.07 mol/L, and 0.04 mol/L, respectively, while no effective passive film is generated on the steel bar in saturated clarified Ca(OH)₂ + 0.1 mol/L sodium β-glycerophosphate. In addition, the addition of sodium β-glycerophosphate to Na⁺ solutions can promote the formation of a more dense passive film on the steel bar surface with a faster passivation rate. That is, more than 80% passivation film can be formed in 72 h, and the rust inhibitor rate is as high as 99.80%. Furthermore, further comparative analyses of the effects the Na⁺ and Ca²⁺ solutions themselves on the resistance of the steel bar under chloride ions erosion show that Ca²⁺ solution is more conducive to the resistance to chloride ion erosion ability, and the corrosion inhibition efficiency is more than 90%.

Foaming Technology and Rheological Characteristics of Surfactant Additive-Foamed Asphalt



TAO Zhuohui, SHEN Shihui, SUN Yang, et al

2024, 52(3):  41-49.  doi:10.12141/j.issn.1000-565X.230121

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Warm mix asphalt technology can reduce the production and construction temperature of asphalt mixtures, and has great application potential in energy conservation and carbon reduction. The foamed warm mix asphalt technology has the advantage of low cost, but there are some problems such as the unsatisfactory foaming effect of modified asphalt and the insignificant warm mix effect, so it has potential application prospects. Surfactants have the effects of both “asphalt lubricant” and “foam stabilizer”, which makes it possible to improve the foaming characteristics and warm mix effect of foamed warm mixed asphalt. Based on this, this study prepared surfactant additive foamed asphalt (SAFB6, SAFB8, SAF10) with different mass fractions of surfactant additives and foaming temperatures. The foaming test, dynamic shear rheology test and bending beam rheology test were used to investigate foaming properties, high temperature performance, fatigue resistance and low temperature performance. The mechanism was analyzed by Fourier infrared spectroscopy test, and the synergistic effect of both surfactant and foaming process on the performance of foamed warm mix asphalt was revealed. The experimental results show that surfactant additives had a significant synergistic effect on the foaming properties of SBS modified asphalt, especially the half-life, which reached up to 69 s. The best foaming conditions can be achieved when the foaming temperature and surfactant additives content are 170 ℃ and 8%, respectively. No complex chemical reaction occurs during the preparation of SAFB asphalt, but the foaming process resulted in a certain degree of oxidation of SBS modified asphalt. The synergistic effect of the surfactant additives and foaming process improves the high temperature performance and fatigue resistance of the SBS modified asphalt, while the low temperature crack resistance is equivalent to that of SBS modified asphalt. Generally, the combination of surfactant and foaming technology is feasible, which improves the foaming effect and road performance of SBS modified asphalt.

Mechanical Engineering

Fatigue Test and Calculation Methods for Battery Package Based on Load Spectrum



SHANGGUAN Wenbin, YUE Lian, LÜ Hui, et al

2024, 52(3):  50-56.  doi:10.12141/j.issn.1000-565X.230063

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As one of the core components of electric vehicles, battery package has a critical impact on the overall performance of the electric vehicle. During the operation of electric vehicles, the battery package is constantly subjected to continuous impact from the road, causing fatigue damage to the battery package, which affects the safety of drivers and passengers as well as the performance of the whole vehicle. Taking battery package of electric vehicles as research object, this study established random vibration test method and calculation method for fatigue life of battery package. Firstly, it carried out frequency sweep analysis on Shaker table, fixture and battery package, and obtained the values of the acceleration sensors at shaker table surface, fixture unloaded end plate, and the connection end plate between battery package and fixture, which were consistent with the input frequency sweep acceleration values, verifying the effective transmission of the vibration signal and ensuring that the input vibration signal can be accurately transmitted to the battery package. After that, random vibration test of battery package was carried out. Cell performance testing, air tightness inspection, insulation resistance inspection, and resonance frequency inspection on the battery package were conducted and the damaged parts of battery package were obtained. The calculation method of battery pack fatigue damage was studied, and the battery box, battery module and battery pack were finely modeled. Based on the fine modeling, frequency response of battery package was analyzed. Based on the results of frequency response analysis and the random vibration load spectrum curve of the battery package obtained from the vehicle road spectrum acquisition test, and combined with the S-N curve of the battery pack material, random vibration fatigue life of battery package was analyzed under load spectrum by using Goodman fatigue life estimation method and Miner linear cumulative damage rule. The damage positions of battery package obtained from the test are in good agreement with the failure positions obtained from the analysis, which confirms the accuracy of the fatigue life calculation method proposed in this paper.

Research Progress Analysis of Laser-Arc Hybrid Welding of Aluminum Alloys



LUO Zhen, SU Jie, WANG Xiaohua, et al

2024, 52(3):  57-74.  doi:10.12141/j.issn.1000-565X.230112

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Lightweight manufacturing is the only way to achieve the carbon peaking and carbon neutrality goals as soon as possible. Aluminum alloy with its low density, high specific strength, recyclability and other advantages such as high shaping, excellent corrosion resistance can be widely used in all walks of life. However, due to its special thermophysical properties and complex alloy chemical composition, welding defects such as pores and hot cracks are prone to occur during the welding process, its further development in the path of lightweight is limited. Combining the advantages of laser welding and arc welding, laser-arc hybrid welding has gradually become an important fusion welding process for efficient and high-quality welding of aluminum alloys with its large welding penetration, high welding efficiency and high welding quality. To grasp the current status of research on laser-arc hybrid welding of aluminum alloys, this paper analyzed for the first time the published academic papers in this field from 1995—2021 in the Web of science database through bibliometrics, and visualized the data with VOSviewer software. The results show that the welded joint, microstructure, heat-affected zone, mechanical properties, and laser-arc interaction for the research hotspots, so this paper summarized and analyzed the laser-arc hybrid welding of aluminum alloys from the above areas, and came up with the selection of the type of joints, the distribution of the microstructure, the enhancement of the mechanical properties, and the mechanism of interaction of the hybrid heat source in the laser-arc hybrid welding of aluminum alloys. It aims to provide reference for subsequent research laser-arc hybrid welding. Finally, based on the current research situation, this paper presented the challenges and the prospect of future work in this field.

A GPS-Laser-IMU Fusion Mapping Algorithm Based on Iterated Kalman Filter



CONG Ming, WEN Xu, WANG Minghao, et al

2024, 52(3):  75-83.  doi:10.12141/j.issn.1000-565X.220667

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3D laser SLAM in outdoor large-scale scenes has been a challenging problem in the current field of robot navigation and environment sensing. Due to the instability of GPS signals in some environments and the error accumulation property of laser SLAM, traditional algorithms perform poorly in large-scale scenes. In order to solve the problems of error accumulation of 3D laser SLAM (simultaneous localization and mapping) in outdoor large-scale scenes, this paper proposed a GPS-Laser-IMU fusion mapping algorithm based on iterated Kalman filter, which improves the mapping accuracy and robustness. The algorithm used IMU to predict the robot state, while laser and GPS data were used as observations to update the robot state. The measurement equations and the related Jacobian matrix were derived. Integrating the absolute position information of GPS data in odometer can solve the problem of error accumulation in long-time operation. In the environment with sparse features, the algorithm may collapse due to insufficient constraints. The introduction of GPS can improve the robustness of the system. Additionally, gravity plays a crucial role in the prediction of robot state. Although gravity is a three-dimensional vector, the module length of gravity remains constant when the region does not change, so gravity was treated as a two-degree-of-freedom vector. Transforming gravity optimization into optimization on SO(3) successfully avoids over-parameterization issues, thereby improving precision. Its performance was compared with that of other algorithms in outdoor environments and the robustness and accuracy were verified in large scale scenes. The results show that the root mean square error of this algorithm is 0.089 m, which is 54% lower than that of other algorithms.

Robot Collision Detection Based on External Torque Observer



ZHANG Tie, CHEN Yijie, ZOU Yanbiao

2024, 52(3):  84-92.  doi:10.12141/j.issn.1000-565X.230086

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Collision detection technology can reduce the probability of equipment damage and personal injury and plays an important role in modern human-robot collaborative production. To realize the collision detection without external torque sensor, it is necessary to accurately estimate the external torque of industrial robots. However, the accuracy of external torque estimation can be affected by parameters identification error of dynamic model and measurement error of motor current. To solve these problems, this paper designed a disturbance Kalman filter external torque observer based on the disturbance principle. The observer takes the equivalent external torque of external collision as the disturbance term, defines the joint disturbance model, and introduces the generalized momentum of the robot to construct the state-space equation. Considering the parameters identification error of the dynamic model and the measurement error of the motor current, it carried out an iterative estimation based on Kalman filter algorithm to obtain the optimal external torque. In order to improve the sensitivity of collision detection, a time-varying symmetric threshold function which varies with joint velocity was proposed for collision detection. The proposed method can adjust the threshold according to the change of joint velocity to adapt to the observed values of external torques at different working speeds. Experimental results show that compared with the generalized momentum observer, the accuracy of external torque estimation of the proposed observer is improved by 52.03%. In order to verify the effectiveness of the proposed method, this paper used a 6-DOF series joint industrial robot to conduct collision detection experiments. The experimental results show that compared with the static threshold, the time-varying threshold method reduces the detection delay by 58.06%, which can improve the sensitivity of collision detection and is more conducive to the safe operation and collision protection of industrial robots.

Research on Topology Optimization of Compliant Mechanisms Based on Level Set Band Method



WEI Peng, HE Lei, XU Weipeng, et al

2024, 52(3):  93-101.  doi:10.12141/j.issn.1000-565X.230117

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The level set method uses a zero level set of the implicit level set function to describe the structure boundary in topology optimization problems. Since it can conveniently express structural topological changes and keep the structure boundary clear and smooth, the level set method has quickly become one of the important methods in the field of topology optimization. However, due to the discontinuity of topological changes during the optimization process, the level set method is prone to facing problems such as numerical instability and initial design dependence. In recent years, the level set band method has been proposed to effectively improve this phenomenon and has become an important means to improve the topological expression ability of the level set methods. This paper introduced the level set band into the parameterized level set-based topology optimization methods, and studied its application in compliant mechanism optimization design problems. The level set band method introduces a level set band area near the zero level set of the level set function. The level set function interpolation can be used to obtain the material density continuously distributed in the [0,1] interval within the bandwidth range. During the optimization process, the material density within the bandwidth range can gradually converge to a 0-1 distribution by gradually reducing the of the level set bandwidth. This method combines the advantages of the variable density method to maintain continuous material density changes during the optimization process, which can improve the stability of the parameterized level set method, obtain better objective function values, and effectively evaluate the initial design dependence of the level set method. This paper verified the effectiveness of the proposed method by studying various compliant mechanism optimization examples from the aspects of different initial designs, irregular design domain, geometric nonlinearity, etc. The optimization results show that the proposed method has good applicability for complex design problems in practical engineering.

Electronics, Communication & Automation Technology

Reconfigurable Intelligence Surface Channel Estimation Algorithm Based on RDN



ZHENG Juanyi, DONG Jiahao, ZHANG Qingjue, et al

2024, 52(3):  102-111.  doi:10.12141/j.issn.1000-565X.230081

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Channel estimation is a key technology in communication systems, which involves evaluating the channel characteristics experienced by signals during transmission, so that the receiver can effectively process and recover the received signals. In order to improve the quality of the communication system under the LOS channel occlusion communication, this study used an intelligent hypersurface to assist the existing communication system. In the smart hypersurface assisted wireless communication system, in addition to the line of sight channel between the base station and the user, there are also cascaded channels from the base station to the smart hypersurface and from the smart hypersurface to the user. The current channel estimation methods basically use traditional algorithms to estimate. In order to solve the problems of low accuracy and high computational complexity of the cascaded channel estimation with complex statistical distribution in the intelligent hypersurface assisted multi-user system, this paper proposed a channel estimation algorithm based on the combination of traditional algorithm and deep learning algorithm. The interpretability of traditional algorithms and the high performance of deep learning algorithms were utilized. On the basis of convolutional network, a denoising method based on residual dense network (RDN) was proposed. Firstly, the data set of the real environment was generated according to the simulation of the system parameters. And the traditional least squares (LS) method was used to rough estimate the channel, and the channel was regarded as a two-dimensional noisy image. Secondly, dense blocks (RDB) were used to fully extract the local features of noise data, and multi-channel convolution and residual network were used to fuse the data features. Finally, the trained model was used to estimate the data online and obtain the denoising channel. The proposed algorithm was verified from the channel estimation accuracy, and theoretical formula derivation and system simulation analysis were carried out on the Rician channel model. Simulation results show that the proposed algorithm improves the accuracy of channel estimation compared with the traditional algorithm.

Research on Transmission Scheme Based on Reconfigurable Intelligent Surface in Dense Urban Agglomeration



ZHUANG Ling, LIU Yuhang

2024, 52(3):  112-118.  doi:10.12141/j.issn.1000-565X.230016

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Due to the shortage of low-frequency resources, the future mobile communication network will gradually shift to higher frequency bands. The free space propagation loss, diffraction loss and penetration loss of electromagnetic waves are large, so it is easy to produce coverage blind spots and weak coverage areas. Reconfigurable Intelligent Surface (RIS) has become a new hot spot to solve the coverage problem of dense urban agglomerations by reconfiguring the propagation environment of signals to improve network performance and expand network coverage. Based on the multi-hop communication mode of the next generation mobile communication network with RIS participation in dense urban agglomerations, the multi-hop RIS transmission scheme was compared with a proposed decode-and-forward (DF) relay-assisted multi-hop RIS transmission scheme (DF-RIS). Firstly, the transmission loss, energy efficiency and system capacity of the two transmission schemes were theoretically derived and analyzed. Secondly, the simulation was carried out in the three-dimensional environment model of dense urban agglomeration. In order to improve the problem of reducing the efficiency of complex environment search and increasing the amount of calculation, an improved Lazy Theta * algorithm was proposed, and the search time and search path length of the improved algorithm and the common path search algorithm were simulated and compared. The improved algorithm was used to select the nodes required by the two transmission schemes in the same simulation environment. The different locations of the DF relay in the multi-hop DF-RIS transmission scheme were considered in the node selection. After determining the nodes, the transmission loss, energy efficiency and system capacity of the two transmission schemes were simulated and compared. The simulation results not only verify the effectiveness of the improved Lazy Theta * algorithm, but also illustrate the relationship between the number of RIS reflection elements and the performance of the two transmission schemes. It shows that the two transmission schemes have their own applicability, and the appropriate transmission scheme can be selected according to the actual requirements for performance.

Feature-Domain Proximal High-Dimensional Gradient Descent Network for Image Compressed Sensing



YANG Chunling, LIANG Ziwen

2024, 52(3):  119-130.  doi:10.12141/j.issn.1000-565X.230101

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Compressed sensing theory can be used to solve the problem of limited computing resources of information source acquisition equipment, but there is uncertainty in the signal reconstruction process. Traditional reconstruction algorithm is difficult to be applied in practice because of its high computational complexity. Recently, the reconstruction algorithm based on deep learning has broken the limitation of traditional algorithms, and has attracted wide attention with its fast reconstruction speed and high quality. Existing deep learning reconstruction algorithms can be divided into two types: “black box” and optimization-based inspired network. Compared with the “black box” network structure, the optimization-inspired deep network is easier to obtain high-precision recovery and more interpretable. However, the existing image compressed sensing reconstruction optimization-inspired networks only learn a single gradient in each optimization phase and has shortcomings such as insufficient use of measured information and difficulty in learning gradients, limiting the improvement of reconstruction performance. In order to make full use of the measurement and reduce the difficulty of gradient learning, the idea of high-dimensional space gradient learning was proposed to achieve more accurate gradient regression. On this basis, this paper proposed Feature-domain Proximal High-Dimensional Gradient Descent (FPHGD) algorithm, and designed a Feature-domain Proximal High-dimensional Gradient Descent Network (FPHGD-Net) to realize this algorithm, so as to obtain high-precision image reconstruction. In addition, three kinds of deep space proximal mapping network structures with different complexity were designed to meet different application. According to the spatial complexity from low to high, the corresponding models are respectively called FPHGD-Net-Tiny, FPHGD-Net and FPHGD-Net-Plus. Extensive experiment shows that, compared with OPINE-Net+, the average PSNR of the three proposed models on Set11 increase 1.34, 1.51 and 1.88 dB, and recover richer image details in the reconstruction of visual effects.

A Multi-Polarization Reconfigurable Antenna with Isoflux Pattern



JIN Guiping, PAN Weihao, HUANG Juehong, et al

2024, 52(3):  131-140.  doi:10.12141/j.issn.1000-565X.230295

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With the innovation of space technology, the demand for low earth orbit communication is increasing year by year. Low earth orbit satellites produced in this context are mainly used in remote sensing detection, weather forecasting and data communication fields. Because the earth surface covered by the antenna beam of low earth orbit satellite is spherical, the beam is usually designed as the equal flux form. Because of the problems of polarization mismatch and multipath effect in satellite communication, choosing multipolarization rather than circular polarization as the working state of low earth orbit satellite antenna can better adapt to the complex working environment and ensure the quality of communication. The combination of equal flux beam antenna and multipolarization reconfigurable technology has great application prospects. Based on the design principle of synthesizing linearly polarized waves from a pair of orthogonal circularly polarized waves, a multi-polarization reconfigurable antenna with isoflux beam was proposed in this paper. The antenna consists of a reconfigurable feeding network and a septum polarizer circular waveguide with choke rings. By changing the working states of SP4T switch and SP2T switches embedded in the feeding network, the feeding network will provide different feeding conditions to the circular waveguide, and the antenna can be reconfigured with two kinds of circular polarizations and two kinds of linear polarizations under the action of the septum in the circular waveguide. In addition, the beamforming was realized by introducing choke rings and T-shaped slots structures into the circular waveguide,which ensures that the antenna radiates isoflux pattern under different polarization states. The measured results show that the overlapping impedance bandwidth of -15 dB is 14.7%, covering 4.80~5.56 GHz, and the top of the radiation pattern has a flat effect in the range of θ from -24° to +24°. In the circular polarization states, the spatial axis ratio covers from -51° to +50°, and the coverage range is larger than the flat range at the top of the pattern. The measured results are in good agreement with the simulation results, and the antenna has the advantages of multi-polarization and flat top of the pattern, which can meet the needs of multi-polarization application scenarios in mobile communication and satellite communication.

Braking Transient Impact Suppression Strategy for Single Rope Winding Mine Hoist



XIE Hui, SHEN Gang, LIU Dong, et al

2024, 52(3):  141-150.  doi:10.12141/j.issn.1000-565X.230167

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In the braking control for mine hoists, braking transient impact is a key issue affecting the operational safety and reliability of mine hoists. Currently, due to the constraints of technology and economic costs, the braking process, including shoe-approaching and braking control, adopts force closed-loop control mode, which inevitably leads to the transient impact of braking pressure when the brake shoe is in rigid contact with the brake disc. Aiming at the problem of transient braking impact for mine hoists, this paper designed a hybrid shoe-approaching and braking control strategy by using the hysteretic-relay-based switching principle. Firstly, the non-singular fast terminal sliding mode control and backstepping control were adopted to design the controller for the shoe-approaching and braking system, respectively. Secondly, in order to achieve the purpose of fast shoe-approaching, it developed an online shoe-approaching trajectory re-planning method based on discrete integrator, which effectively reduces the shoe-approaching time of the system. Then, by using of the hysteretic switching principle, it developed an autonomous switching strategy from shoe-approaching control to braking control, which greatly reduces the transient impact of braking pressure. Finally, to verify the effectiveness of the proposed method, the traditional full-stroke pressure closed-loop control strategy C1 and hybrid shoe-approaching/pressure control strategy with direct switching C2 were selected as comparison methods, and comparative experiments were conducted on a single-rope winding hoisting test bench. The experimental results were analyzed from three aspects: braking time, maximum tracking error of braking force, and maximum tension of hoisting wire rope. The experimental results indicate that, compared with the C1 control strategy, the proposed braking control strategy reduces the braking time by 64.5% and the peak tension of the wire rope by 41 N. Compared with the C2 control strategy, the proposed braking control strategy reduces the braking force impact by 90.3% and the peak tension of the wire rope by 88 N. These results demonstrate that the proposed approach effectively improves the transient impact of braking, reduces shoe-approaching time, and improves the safety of the braking system. This study also provides an effective solution for a class of electro-hydraulic servo systems that require mixed force/position control.