最新刊期
卷 58 ， 期 2 ， 2024
- 摘要：Aiming at the issue of unstable operation caused by the fluctuating operation of air compressor in the combined compressed air and thermochemical energy storage system, a comprehensive mathematical model of thermochemical process is established to study the effects of different operating parameters on the heat transfer characteristics of the working fluids and methanol decomposition efficiency of the reactor. The operation control strategy of the reactor is further established to achieve the efficient and stable transformation from thermal energy to chemical energy. The results show that when the reactor operates under variable working conditions, the temperature of reactant and air increases and decreases respectively along the flow direction in the reactor. The methanol decomposition efficiency is improved by increasing the flow rate of air and inlet temperature on the air side of the reactor, and is reduced by increasing the flow rate of methanol. The disturbance of inlet temperature on the air side of the reactor has the greatest effect on the variation range of the methanol decomposition efficiency, while the reactor has the fastest response to the variation of the flow rate of methanol. Subsequently, by establishing the feedforward-feedback control strategy to regulate the flow rate of working fluid at the inlet of both reactor and air compressor, the methanol decomposition efficiency of reactor could achieve 95% within 1 000 seconds under the air compressor input load of 85%—110%, which proves the fast response and effectiveness of the proposed control strategy.关键词：compressed air;hybrid energy storage;methanol decomposition;dynamic performance;control strategy283|6|0更新时间：2025-05-13
- 摘要：Aiming at the issue of low accuracy in rapid prediction of flow field caused by errors in the standard POD-Galerkin reduced order model, an improved POD-Galerkin model using long short-term memory(LSTM)neural networks is proposed. In this method, based on the reduced order model obtained by dimensionality reduction and projection of the flow field using proper orthogonal decomposition(POD), two LSTM neural networks are introduced to establish a corrective mapping from the POD-Galerkin model to the actual POD coefficients, and an expansion mapping between the low-order mode time coefficients and the high-order mode time coefficients, so as to eliminate the error accumulation of the standard POD-Galerkin model and extend the order of reduced order model. This method enables the construction of a hybrid reduced order model that combines physics-driven and data-driven approaches. The improved POD-Galerkin model is applied to flow field prediction of a two-dimensional flow around a cylinder. A comparison with the original standard POD-Galerkin model is performed to analyze the model accuracy and computational speed. The results show that, with the addition of neural network correction terms, the accuracy of the reduced order model is effectively improved compared with the standard POD-Galerkin model. The root mean square error of the predicted mode time coefficients is reduced by one to two orders of magnitude compared with the original model, and the predicted flow field is closer to the original flow field. The improved model achieves a significant reduction in computation time while predicting the same order. The improved 8-order improved reduced order model based on 4- and 6-order expansions improves the prediction speed by approximately 56% and 25%, respectively, compared with the original 8-order POD-Galerkin model.关键词：proper orthogonal decomposition;reduced order model;neural network;flow prediction125|10|0更新时间：2025-05-13
- 摘要：In order to understand the impact of various coupled factors, such as hydrogen blending, on the dispersion of hydrogen-blended gas leakage in pipeline transportation is studied based on the underground comprehensive pipe galleries in three common gas transmission scenarios. The study starts from the feature that confined space is prone to cause gas cloud accumulation and combustion, with consideration given to factors such as different leakage directions, hydrogen doping ratios, and pipeline pressures, and the simulation of potential leakage scenarios within the comprehensive pipe galleries is conducted using Fluent software. The distribution characteristics of internal gases are examined, and a safety analysis of alarm probe positioning and spacing is performed. The simulation results show that the distribution of gas is significantly influenced by the directions of the leakage port, with a more obvious accumulation of gas observed in the near-wall region of secondary flows. The installation of probes at a distance of 30 cm from the top of the side walls effectively reduces alarm delays. With a 20% hydrogen blending, the leakage rate increases by 9.03%, leading to an intensification of gas accumulation near the leakage port and a slight increase in risk at the distant end of the port. The explosion concentration range(gas concentration >4%)at 5 seconds of gas leakage is found to be 1.54 m, and the addition of 10% and 20% hydrogen increases this distance by 16.2%(1.79 m)and 36.4%(2.10 m), respectively. Furthermore, as pipeline pressure increases to 0.8, 1.2, 1.6 MPa, the time required to reach the alarm concentration is respectively shortened by 18.9%, 28.3%, 32.1%. Valuable insights for the safe transportation of hydrogen-blended natural gas in comprehensive pipe galleries can be provided by this study.关键词：new energy resources;hydrogen safety;hydrogen additive;leak alarm66|5|0更新时间：2025-05-13
- 摘要：In order to improve the prediction ability of heat transfer performance on lantern-shaped pin-fin endwall, several deep learning surrogate models are constructed and their prediction performance compared. Based on data-driven thinking, five traditional surrogate models, namely polynomial response surface model(RSM), radial basis function model(RBF), radial basis function neural network(RBFNN), Kriging model and ensemble of surrogate model(Ensemble)are proposed. Additionally, five generative adversarial network surrogate models based on deep learning, namely pix2pix model, pix2pixHD model, CycleGAN model, StarGAN model all with residual network, and another pix2pix model without residual network are proposed. The training sets with various sample numbers of 50, 25, 12, 6 and 3 were obtained by Latin hypercube sampling, respectively, using the pin-fin cross-sectional shape as the design variables. According to the distribution characteristics of high heat transfer zone, the dataset with a training sample number of 50 is divided into a wide sample dataset and a narrow sample dataset. On this basis, the various heat transfer performance of different surrogate models are compared in terms of prediction accuracy, computational cost and generalization ability. The results show that, compared with the pix2pix model without residual network, the prediction accuracy of the pix2pix model with residual network is effectively improved, and the prediction error of the surface mean is reduced from 0.68% to 0.32%, and the averaged relative error is reduced from 6.89% to 6.41% when the sample number is 50. When the number of training samples decreases, the prediction performance of the models with residual network becomes more prominent. The time cost of traditional surrogate models is negligible, but the training time of deep learning models is long especially for models with residual network. When the number of training samples is 50, there is little difference in prediction accuracy between the traditional surrogate models and deep learning models. With gradual decrease in the number of training samples, deep learning surrogate models show higher prediction accuracy and generalization capabilities. Although the Kriging model has strong generalization ability, the prediction results tend to be similar. RSM model, RBF model, and Ensemble model have the lowest generalization ability, and the prediction results are severely distorted when there are fewer training samples. For the heat transfer distribution prediction of the pin-fin endwall, the deep learning models possess significant advantages in terms of both prediction accuracy and generalization ability, which are more suitable for small batch sample problems. This study has important reference value for improving the cross-sectional shape design efficiency of lantern-shaped pin-fin.关键词：gas turbine;surrogate model;deep learning;pin-fin;prediction of heat transfer performance94|5|0更新时间：2025-05-13
- 摘要：Aiming at the issue that conventional exergy analytic methods cannot disclose which part in the total exergy destruction of components is caused by their own irreversibility and how much can be avoided by improving the components, advanced exergy analysis of a supercritical CO2 power cycle for waste heat recovery is conducted to find out the cause of the exergy destruction and determine the actual improvement potential of components. Firstly, a multi-objective optimization of a recuperated layout waste heat recovery system is carried out from the aspects of thermodynamics, economy and compactness, and a thermoeconomic and exergy analyses are also performed. Then, the exergy destruction of each component is divided into four parts: endogenous avoidable, endogenous unavoidable, exogenous avoidable and exogenous unavoidable, and an advanced exergy analysis is performed. Finally, a comparison of the results of conventional and advanced exergy analyses shows the limitations of the conventional method. The results show that after optimization, the net electrical generation, LOCE and specific power heat transfer area are 6.24 MW, 4.48 cents/(kW·h)and 0.19 m2/kW, respectively. The exergy destruction rate of the recuperator is the highest, at about 37%. Due to technical limitations of key equipment, the exergy efficiency of the unavoidable cycle is reduced by about 7% compared to the ideal condition. The total exergy destruction is mainly caused by the irreversibility of the components themselves and can be reduced by about 43% by improving the efficiency of the components. The turbine has the highest endogenous avoidable exergy destruction rate under different gas turbine operating conditions.关键词：waste heat recovery;supercritical CO2 power cycle;multi-objective optimization;thermoeconomic analysis;advanced exergy analysis79|7|1更新时间：2025-05-13
- 摘要：In order to further explore the optimal design of high-performance centrifugal compressor, taking the impeller of a centrifugal refrigeration compressor with air bearing as the research object, combined with the multilayer BP neural network, a multi-objective impeller optimization strategy based on the nondominated neighbor immune algorithm is developed. Firstly, the hidden layer structure of the neural network is optimized using the immune algorithm, aiming to improve the nonlinear approximation ability of the neural network as a surrogate model. Secondly, the immune algorithm is applied to optimize the performance of impeller under all operating conditions with the polytropic efficiency of near surge point, design point and near choke point as the optimization target. The aerodynamic performance and internal flow characteristics of the impeller before and after the optimization are compared and analyzed through numerical simulation. The simulation results show that after the optimization based on the immune algorithm, the polytropic efficiency of the impeller increases by 1.8%, 1.9% and 4% at the near surge point, design point and near choke point, respectively, indicating that the stable operating range of impeller is widened. The flow field analysis shows that the loads distributed from LE to TE of the main blade and the splitter blade at 90% span increase obviously after the optimization, which reflects improved work capacity of the impeller. The shock loss decreases because of the reduced inclination angle of the splitter blade. The mixing phenomenon between the leakage flow and main flow in the passage is obviously weakened, and the flow field is more uniform, which verifies the effectiveness of the proposed multi-objective optimization strategy.关键词：centrifugal refrigeration compressor;multilayer back-propagation neural network;nondominated neighbor immune algorithm;aerodynamic performance;multi-objective optimization96|12|0更新时间：2025-05-13
- 摘要：Aiming at the issue that the combustion of gasoline in high-efficiency X-type rotary engine is insufficient, a method of cylinder hydrogen direct injection is proposed to improve the combustion efficiency and thermodynamic performance of the engine. The three-dimensional CFD numerical model of X-type rotary engine is established and validated via the experimental data of cylinder pressure, heat release rate and power. Under the same hydrogen injection total mass, pressure, and start time, the impact of hydrogen injection nozzle diameter on the in-cylinder flow, combustion, thermodynamic performance and pollutant emission of the engine when hydrogen in-cylinder direct injection and premixed gasoline are adopted. The advantages of hydrogen in-cylinder direct injection method are revealed by comparing with pure gasoline premixed engine. The results show that when the hydrogen injection nozzle diameter is small(2 mm), the flame propagation is more uniform, and relatively large symmetrical flames are found in the slits of both sides of combustion chamber, making the combustion more sufficient. The maximum indicated thermal efficiency of corresponding engine reaches of 37.07%, which is 10.23% and 7.85% higher than that of the engine without hydrogen injection and with a large hydrogen injection nozzle diameter(4 mm), respectively. In addition, compared with the large hydrogen injection nozzle diameter, although the NOx emissions increase by 21.12% when the hydrogen injection nozzle with small diameter is adopted, the HC and soot emissions decrease by 79.08% and 2.17%, respectively. Thus, the small hydrogen injection nozzle diameter(2 mm)is the optimal hydrogen injection strategy. This study provides guidelines for the design and optimization of the hydrogen injection strategy of X-type rotary engine.关键词：rotary engine;hydrogen direct injection;nozzle diameters;pollutant;thermal efficiency76|7|0更新时间：2025-05-13
- 摘要：In order to ensure the hydrogen supply of hydrogen refueling stations and lower the terminal price of hydrogen, the economic feasibility and application scenarios of different hydrogen supply paths of hydrogen refueling stations are explored. To study the economic feasibility of different hydrogen supply paths, the levelized cost of hydrogen is adopted to establish cost and price models for several typical hydrogen refueling stations with hydrogen supplied externally or hydrogen produced within the stations. The sensitivity analysis of key factors such as raw material cost of hydrogen production, hydrogen transportation distance and energy consumption are carried out to explore the pricing mechanism of hydrogen supplied from different sources and in different modes. In addition, a life cycle model was established to analyze the impact of carbon tax possibly imposed in the future on the terminal price of hydrogen consumption. The results show that the transportation distance and carrying capacity of single vehicle are the factors having major impact on the cost of hydrogen refueling stations with external hydrogen supply, and such influences are more significant if carbon tax is taken into consideration. The costs of self-produced hydrogen for hydrogen refueling station are mainly under the influence of raw material price and the energy used for hydrogen production. The economical distance for organic liquid hydrogen storage and transportation is 220—1 700 km, which is able to cover most scenarios of large-scale hydrogen transportation in China. Natural gas reforming in station has obvious advantages when the supply of natural gas is sufficient and the price is lower than RMB 4/m3. The combination of in-station water electrolysis and renewable power generation show economic and environmental advantages, and the hydrogen price can be maintained below RMB 35/kg. The study points out the future development direction of different hydrogen supply modes in China, and provides a reliable economic evaluation method for selection of hydrogen supply path. Hopefully the study can serve as reference for the construction of hydrogen refueling stations and policy making for regional hydrogen energy development.关键词：hydrogen refueling station;in-station hydrogen production;levelized cost;carbon tax79|7|0更新时间：2025-05-13
- 摘要：To explore the breakup characteristics of liquid nitrogen droplets in a cryogenic wind tunnel and determine the underlying mechanism, a two-dimensional liquid nitrogen droplet breakup model is established adopting the coupled level-set and volume of fluid(CLSVOF)method and adaptive local mesh refinement technology. The morphological evolution patterns of liquid nitrogen droplets and normal temperature droplets are compared, and the effects of We on the morphology, deformation coefficient and temporal features of liquid nitrogen droplets are analyzed. The results show that compared with normal temperature droplets, liquid nitrogen droplets have a higher We, which makes them more prone to deformation and fragmentation. As the We increases, the droplets sequentially undergo bag breakup, multimode breakup and shear breakup. For the three different breakup modes, the pressure difference between windward and leeward sides of the liquid nitrogen droplet increases first and then decreases with time. This is attributed to the formation of bag structures or the separation of droplets from the edge. Under different breakup modes of liquid nitrogen droplets, the pattern of deformation coefficient is distinctly different. The dimensionless initial breakup time of the droplet decreases with the increase of We. In the range of 0关键词：cryogenic wind tunnel;liquid nitrogen droplets;breakup characteristics;breakup modes;deformation coefficient66|4|0更新时间：2025-05-13
- 摘要：Considering the thermal contact resistance parameters of ODS MA754 alloy have a significant impact on the heat transfer of all solid-state core space reactor systems, high-temperature and high-pressure thermal contact resistance measuring devices are developed and designed to measure the ODS MA754 alloy heat transfer interface thermal contact resistance under different temperatures(20—800 ℃), different pressures(0—80 MPa), different roughness(1.6 and 3.2 μm)and in different gas environments(He and CO2). The thermal contact resistance database of ODS MA754 alloy is established accordingly. The experimental results show that the interface thermal contact resistance decreases with the increase of contact temperature and pressure, and the rate of thermal resistance reduction decreases gradually. The interface contact thermal resistance of the test piece with the roughness of 3.2 μm is apparently greater than that of roughness 1.6 μm. The obtained quantitative relationship can provide reference for the machining roughness requirements of subsequent engineering samples. The thermal contact resistance in Helium environment is far less than that in CO2 environment. Under 0.1 MPa and 100 ℃ working conditions, the thermal contact resistance in Helium environment is about one fourth of that in CO2 environment. The study results can provide data reference for the thermal design of space reactor.关键词：space nuclear reactor;ODS MA754 alloy;thermal contact resistance;high temperature and high pressure;roughness of contact surface39|6|0更新时间：2025-05-13
- 摘要：In order to conduct an in-depth study on the thermodynamic characteristics of the helium turbine expander during the cooling process and under low temperature conditions, an experimental system in the 80 K temperature range based on the ADS 500 W/4.5 K cryogenic refrigerator is constructed to conduct the low-temperature variable condition testing of helium turbine expander. The main shaft diameter of the tested helium turbine expander is 12.00 mm. The expander is supported by compliant foil bearings, and can reach a maximum rotational speed of 252 130 r·min-1. The maximum outlet temperature drop of the expander is 8.1 K when the expansion ratio is 1.88. When the expansion ratio is 2.07, the maximum isentropic efficiency reaches 71.2%. The numerical model of the tested helium turbine expander is established based on its dimensions and test conditions. The thermal performance and cooling characteristics of the turbine are simulated by using commercial software ANSYS CFX, and the corresponding theoretical temperature drop curve is obtained. The results show that the numerical model can predict the temperature drop process of the expander well, and the maximum relative deviation between the experimental value and the numerical calculation result is 0.45%. The tested helium turbine has good thermal performance and cooling characteristics, and the tested dynamic pressure helium gas bearing shows good stability. The numerical calculation and experimental results can provide reference for followed relevant researches and the application of large devices for scientific studies.关键词：helium refrigerator;turbine expander;cryogenic characteristic;gas bearing68|8|0更新时间：2025-05-13
- 摘要：In order to explore the law of electrostatic accumulation in liquid hydrogen transmission pipeline containing solid oxygen particles, the simulation of charging law of liquid hydrogen-solid oxygen system is carried out using COMSOL Multiphysics software. Lagrange particle orbit method and computational fluid dynamics are used to describe the motion of continuous liquid hydrogen flow and discrete solid oxygen particles, respectively. Materials Studio software is used to calculate the electrical properties of solid oxygen particles and the electricity-generating law of solid oxygen particles is described by capacitor method to realize the coupling solution of solid-liquid two-phase flow and electrostatic field. The simulation results show that when the flow rate of liquid hydrogen is 10 m·s-1 and the particle size of solid oxygen is 1 000 μm, the specific charge of solid oxygen particles reaches 10 μC·kg-1; the saturation charge of particles is about 84 pC; the charge density of two-phase flow is 2.84×10-4 C·m-3, which is 8 orders of magnitude larger than that of pure liquid hydrogen flow. With the increase of particle-wall collisions, the particle charge tends to be saturated. The parameters of pipe flow have significant influence on the charging law. The particle specific charge decreases slightly with the increase of particle mass flow rate, increases with the increase of tube length and the decrease of tube diameter. The particle specific charge decreases first and then increases with the increase of liquid hydrogen flow rate, so there is a minimum value. The particle property also has an effect on the charged energy. The particle specific charge has minimum and maximum value with the increase of particle size, and the particle Young's modulus, resistivity and density also have a certain effect on the charging law. The research work can provide theoretical support for the design and safety protection of liquid hydrogen transmission system.关键词：liquid hydrogen;solid oxygen particles;charge evolution;static accumulation42|9|0更新时间：2025-05-13
- 摘要：Aiming at the issue that conventional multi-scale convolutional neural networks in bearing fault diagnosis simply spliced features of different scales without considering the feature differences of different scales, a multi-scale adaptive selective convolutional neural network(MSASCNN)bearing fault diagnosis model is proposed. The features of the original bearing vibration signals are selected in the model through wide convolution of different sizes and combined into initial features. Multi-scale adaptive selective convolutional blocks are constructed to extract features of different scales, and the improved attention mechanism is used to adjust the feature weights of different scales adaptively, and residual connections are added to prevent model degradation. The bearing fault diagnosis is completed by the classifier. The experimental results on Case Western Reserve University bearing dataset and XJTU-SY bearing dataset show that in the model improving experiment, the bearing fault diagnosis accuracy of the proposed model increases by 1.98% compared with the model without improved attention mechanism. In the noise interference environment with different signal-to-noise ratios, the bearing fault diagnosis accuracy of the proposed model is higher than 93%.关键词：bearing fault diagnosis;convolutional neural network;adaptive fusion;attention mechanism;multiscale feature111|8|0更新时间：2025-05-13
- 摘要：Aiming at the issue that the improvement of quality factors is difficult and the traceability path of quality anomalies is unclear in quality anomaly trace of heavy gas turbine high-temperature turbine blades, a quality anomaly traceability path search method based on national quality infrastructure(NQI)data baseline model is proposed. The NQI data baseline model of heavy gas turbine high-temperature turbine blades manufacturing field is constructed, so as to provide the manufacturing logic standard and NQI quality control logic standard of heavy gas turbine blades manufacturing field. According to the complex logical relationship between quality events, the posterior probability and critical importance of basic events are solved by constructing the T-S quality risk tree and introducing the hyper-ellipsoid model. Considering the posterior probability, key importance and heuristic information value, the improved VIKOR algorithm is used to obtain the interval compromise value of each scheme, and the interval number ranking method of the possibility function of the binary connection number is combined to obtain the optimal scheme of quality anomaly traceability. Considering the update of attribute values with the search process, the optimal quality anomaly traceability search path is obtained. Taking a process of NQI data baseline model as an example for application verification, the results show that, compared with random search for incentives, the tracing efficiency is improved by 38% by using this tracing path and the causes of abnormal shell quality can be found faster, which provides a reference for quality improvement.关键词：high-temperature turbine blades;national quality infrastructure data baseline;manufacturing quality;anomaly tracing36|5|0更新时间：2025-05-13
- 摘要：Aiming at the issue of insufficient energy utilization efficiency of engineering machinery under complex working conditions, a collaborative control strategy for efficiency optimization of torque converter and gearbox is proposed. Firstly, based on the power and mechanical balance of loaders, a simulation platform of loader powertrain system is constructed based on the traction performance theory. The effectiveness and reliability of this platform are validated through data collected in the loader operational cycle experiment. Secondly, based on the test bench experiments of engine and hydraulic torque converter, the traction characteristics of ZL50 loader are studied, and the power performance of ZL50 loader in four different traction stages including starting, lifting, digging, and uniform speed is compared, and the influence of the hydraulic torque converter's lock-up point on the loader's power, smoothness and fuel efficiency is also studied. Finally, a collaborative control strategy for optimizing the efficiency of the hydraulic torque converter and gearbox under complex working conditions is proposed. A comparative analysis of the loader's performance before and after optimization is conducted. The results show that under the same V-cycle working conditions, the fuel consumption output energy of the loader increased from 372.69 kW·h·mL-1 to 420.51 kW·h·mL-1, and the overall efficiency of the entire loader increased by approximately 12.8%. The collaborative control strategy provides a solution to the problems of low transmission efficiency, high fuel consumption, and severe polluting emissions of large construction machinery.关键词：loader;drive system;torque converter;gearboxes;collaborative control86|6|0更新时间：2025-05-13
- 摘要：In this paper, the IGZO thin-film transistor biosensor based on functionalized human leukocyte antigen B27(HLA-B27)is developed for rapid detection of the HLA-B27, a serological molecular marker for ankylosing spondylitis. The fabrication of IGZO thin-film transistors(IGZO TFT)using radio-frequency magnetron sputtering technology and micro-nano-processing is described. The IGZO TFT is modified with 3-aminopropyltriethoxysilane(APTES)and antibodies to prepare biosensors for HLA-B27 detection. The experimental results show that the functionalized IGZO TFT biosensor has stable electrical characteristics and sensing performance. The sensor shows a detection limit of 1 pg/mL for HLA-B27, and its linear response within the concentration range of 1 pg/mL to 100 ng/mL is good. These results indicate that the proposed high-performance biosensor can effectively detect biomarker of ankylosing spondylitis. In addition, the IGZO TFT can be expanded into a sensor array platform to realize combined detection of multiple markers for a certain disease, which has great potential in the application of portable bedside diagnostic devices.关键词：indium gallium zinc oxide;thin film transistors;biosensors;ankylosing spondylitis;human leukocyte antigen B2744|4|0更新时间：2025-05-13
- 摘要：Aiming at the issue that the existing concept reduction algorithms are complex and the efficiency is low, a multi-thread concept reduction algorithm(MTCR)is proposed. MTCR takes improving the efficiency of concept reduction algorithms as the primary goal and employs multi-thread technology to parallelly calculate concept reduction in a multi-core environment. The MTCR algorithm initially uses two threads to calculate the object representative concept set of a single object and the attribute representative concept set of a single attribute, then puts the objects(attributes)into p queues in turn, and creates a thread for each queue. Finally, the object representative concept set of any object and the attribute representative concept set of any attribute are calculated parallelly using multi-threaded technology, and the representative concept matrix is constructed by computing the intersection of these two different types of representative concept sets, on the basis of which all the concept reducts are computed. In the MTCR algorithm, the data of each stage using multiple threads is relatively independent, which avoids frequent synchronization operations between multiple threads, thereby reducing the competition and waiting time between threads. This mechanism enables the full and effective utilization of computing resources, which greatly improves the performance of the algorithm. Experiments on UCI datasets and random datasets show that the MTCR algorithm can accurately obtain all concept reduction, and the running time is close to the existing SCR algorithm when using a single thread. Specially, when the number of threads is less than 8, the running time of the MTCR algorithm can be improved by more than 30% for each doubling of the number of threads.关键词：formal concept analysis;concept lattice;concept reduction;multi-thread parallel algorithm45|4|0更新时间：2025-05-13
- 摘要：Aiming at the inherent characteristics of lidar and the point cloud noise and redundant point cloud that are easily caused in complex environment, as well as the problem that the inherent features of point cloud are often ignored in conventional point cloud simplification algorithms, a point cloud simplification algorithm based on improved bald eagle search and K-means clustering(KMC)hybrid iteration(IBESSA)is proposed. Firstly, the convergence is accelerated and optimization accuracy is upgraded through the competitive fusion in the BES iteration stage(CFBES). Secondly, the point cloud data is clustered by the hybrid iteration of CFBES and KMC algorithm. Then, based on the implementation of point cloud density estimation with k-nearest neighbors(k-NN), point cloud information quantization is achieved combined Shannon entropy. Finally, the cluster with the information quantization value less than the threshold is deleted to complete the simplification of point cloud data. UCI international standard dataset and Stanford point cloud dataset are used to verify the clustering effect and point cloud simplification effect of CFBES-KMC. The results show that compared with hybrid iterative K-means clustering with improved moth-flame optimization, K-means++ and fuzzy C-means clustering algorithm, the clustering accuracy of CFBES-KMC is improved by 1.02%, 12.31%, 14.72% respectively. On the Stanford point cloud dataset, the IBESSA algorithm effectively filters out redundant point clouds while preserving the details and shape features of the original point cloud, which means it is an efficient point cloud simplification algorithm.关键词：bald eagle search algorithm;competitive fusion;K-means clustering hybrid iteration;Shannon entropy;point cloud simplification46|5|2更新时间：2025-05-13
- 摘要：Aiming at the issue that conventional algorithms cannot overcome the nonlinearity of switched reluctance motor(SRM)and effectively suppress the load disturbance of steering vane, thus being unable to achievefast and high precision position tracking control of the electromechanical actuator(EMA)driven by SRM, an adaptive PI controller with real-time current compensation is proposed. Firstly, the aerodynamic load exerting on the steering vane is estimated in real time by the load observer and the data is converted into the real-time compensation current to input the current loop to suppress the load disturbance. Secondly, the proposed adaptive controller is used to adjust the PI parameters of the speed loop optimally and adaptively based on the fitting curve of the torque-current characteristic and the real-time current of SRM, which weakens the nonlinearity of SRM and increases the speed regulation performance of the EMA. Finally, the position feedforward is adopted to improve the response speed and further enhance the position precision of EMA. Compared with the conventional PI controller, the adaptive PI controller, and the adaptive PI controller with position feedforward, the results of the simulation and experiment show that the proposed controller can improve the response speed and the position tracking precision of the EMA by 49.3%,44.4%, 30% and 54.8%,49.2%, 2.9% respectively, which makes the EMA possess better position tracking performance.关键词：electromechanical actuator;switched reluctance motor;position tracking control;current compensation;adaptive PI52|5|0更新时间：2025-05-13
- 摘要：Aiming at the issue that zero sequence inverse time current protection of non-faulty line occurs before the protection on the side with smaller zero sequence current in the faulty line when the system with large ground current has grounding fault, a zero sequence inverse time current protection scheme introducing zero sequence current effective value and phase mutation criterion is proposed. Firstly, the distribution characteristics of zero sequence current and the operating characteristics of zero sequence inverse time current protection in the case of grounding fault in single-circuit line and double-circuit line are analyzed. It is pointed out that the zero sequence current of adjacent non-faulty lines may be greater than the zero sequence current of the faulty line, causing the misoperation of zero sequence inverse time current protection. Then, through theoretical analysis, the changes of the effective value and direction of zero sequence current in other lines before and after the protection action on the side with larger zero sequence current in the faulty line are obtained. Finally, a zero sequence inverse time current protection scheme is proposed by introducing zero sequence current effective value and phase mutation criterion, and the zero sequence inverse time current protection of non-faulty lines is re-timed. The simulation results show that the proposed scheme can effectively prevent the misoperation of zero sequence inverse time current protection of non-faulty lines, thus improving the selectivity of protection, and the proposed scheme is still suitable for transitional grounding.关键词：relay protection;zero sequence current;inverse-time;mutation;selectivity54|5|0更新时间：2025-05-13
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