最新刊期
卷 55 ， 期 8 ， 2021
- 摘要：To solve the problem of improper segmentation in vibration signal spectrum by empirical wavelet transform, an empirical wavelet transform based on the adaptive energy peak location is proposed, where Teager energy operator is used to concentrate the energy of Fourier spectrum to reduce the influence of noise and independent components. The spectrum segmentation boundary is determined adaptively by multi-scale peak-finding algorithm. Modal components are extracted by the constructed wavelet filter bank. According to kurtosis index, the modal component with maximum fault information is selected. The fault feature frequency of the bearing is extracted by Hilbert envelope demodulation. The simulation and experiment show that the proposed method is more robust from the perspective of energy. Considering the shape of frequency spectrum, fault frequency band can be identified adaptively. Compared with the original EWT method, this proposed method enables to obviously enhance the early weak fault features and improve the early fault diagnosis performance of bearings.关键词：empirical wavelet transform;rolling bearing;fault diagnosis;multi-scale energy peak location906|5|0更新时间：2025-07-09
- 摘要：Aiming at the shortcomings in the existing three-point thickness derivation method for sliding shoe pair of piston pump, a higher-precision double-sided average 6-point derivation method is proposed, and the related pressure field distribution, power loss and leakage theory are improved. Furthermore, under constant temperature vibration conditions, the experimental system for the fluid lubrication characteristics of sliding shoe pair is designed. By this test system, it is possible to accurately measure the oil film thickness, pressure, temperature and leakage of the axial piston pump at different speeds, input pressures and structural forms under the conditions of constant temperature or variable temperature and with or without vibration, then the laws of power loss, temperature distribution, pressure distribution and leakage of the sliding shoe pair are obtained, and the applicability of existing theory for fluid lubrication characteristics under vibration conditions is verified. This test system enables to accurately measure the thickness of the sliding shoe pair oil film in real time. During the temperature control test, with a measurement error of less than 1 μm, the target temperature error required by the test system is ensured to keep less than 0.1 ℃. An electro-hydraulic controlled three-way vibration system is adopted, and the frequency is adjusted within the range of 0-200 Hz, which basically meets the testing requirements of vibration frequency under all working conditions. This test system provides a platform for investigating fluid lubrication characteristics of piston pumps under constant temperature and vibration conditions.关键词：piston pump;sliding shoe pair;lubrication characteristics;test system121|4|0更新时间：2025-07-09
- 摘要：To reveal the effect of tip clearance on compressor performance during the scaled modeling process, the performance variation with different scaled model is numerically investigated by taking the first 1.5 stages compressor as the object. It is found that the performance of the scaled model is weakened if the tip clearance size is kept constant during the scaling process, resulting in a decrease of about 1.4%-3.38% for the peak variable efficiency and a decrease of 0.88%-3.17% for the pressure ratio of converted prototype. The influence of tip clearance on the flow field similarity is mainly concentrated in the flow passage area at the blade tip, resulting in a flow out of the similar conditions there. The flow field analysis indicates that with the increasing model shrinkage, the relative leakage flow rate of the tip clearance increases, the range of low-speed zone in the tip passage expands, and the radial influence range and intensity of leakage vortex also increase. This is the main reason for the aggravation of flow clogging and performance degradation after the scale modeling. The increasing model shrinkage ratio also facilitates weakening shock wave for the tip leakage flow.关键词：axial compressor;model shrinkage;blade tip clearance;leakage vortex;shock wave148|4|0更新时间：2025-07-09
- 摘要：To realize kinematics modeling of continuum robot and realize its position control, under the assumptions that the self-weight and load are ignored and the curvature of each part on the center line of the continuum structure is consistent after deformation, a self-developed pneumatic trunk-type continuum robot is taken as an example and the relationship of deformation parameters(s, k, φ)with length of continuum nodes(l1, l2, l3)is obtained. The kinematic model of the robot is constructed by referring to D-H method after discretizing continuum components as joint variables. The robot pneumatic system is designed and its motion data are collected. The actually collected data are substituted into the above model to determine model parameters, which can offset the model error caused by ignoring the robot weight and load and improve the control precision to some extent. The grabbing experiments show that this constant curvature model with parameters determined by the collected data can be applied to control the continuum robot. Compared with the simulated trajectory with the actual trajectory of this robot actuator, the maximum motion error reaches 6.3 cm, and the deference mainly comes from three aspects: system error, model error and measurement error. The approach has reference significance for application and position control of this kind of continuum robot.关键词：continuum robot;constant curvature;kinematic model;position control107|4|0更新时间：2025-07-09
- 摘要：A two-step visual positioning method based on template matching for rough positioning and edge detection for fine positioning is proposed to solve the problem of locating microholes of bonding wedges. In the step of rough positioning, a rough positioning method based on shape template matching and support vector machine is proposed. Firstly, the template with mask is established, and then it is based on shape template matching that the matching process is accelerated by an early termination strategy, image pyramid and reducing search area. After extracting the histogram features of oriented gradient from matching results, the classification is carried out based on support vector machine to prevent mismatching. In the fine positioning stage, an edge detection algorithm with angle constraints is proposed to accurately locate the edge of the outer contour. The sub-pixel edge positioning is realized by using a quadratic function to fit the maximum gradient, and the least square method is used to the contour edge to locate the machining location of microholes. In the experimental stage, the SVM is trained with a small number of samples, and the accuracy reaches 99.76%. On this basis, the intersection of union of the proposed coarse positioning method reaches 82.9%, while that of the traditional template matching method is only 36.5%. The fine positioning experiment is carried out by placing the bonding wedges in different positions with different postures and adding Gaussian noise under different light intensities. The maximum positioning error of the proposed fine positioning method is 2.20 microns, while the maximum positioning error based on Canny edge detection method is 5.99 microns. The proposed whole algorithm only takes 328 ms.关键词：chip packaging;bonding wedges;micro-plane;microhole;template matching;edge detection92|4|0更新时间：2025-07-09
- 摘要：To improve the transient performance of servo systems and satisfy the high-precision processing requirements of industrial production lines, a fuzzy adaptive deep reinforcement learning algorithm is proposed to optimize the control performance of permanent magnet synchronous motor servo system. According to the rapidity and stability requirements of transient response, the reward function and Actor-Critic networks are constructed, the transient optimization link for servo controller is introduced, and the learning rate fuzzy controller for real-time computing requirements is designed. A servo system Simulink simulation model is established and fitted in with the actual servo system, the optimized parameters are obtained via transient performance optimization simulation and then applied to a Siemens 840D computerized numerical control system. The verification of simulation calculation by system experiment shows that the proposed method of transient performance optimization shortens the servo system adjustment time by more than 10%, significantly heightens the system transient response rate without introducing an obvious overshoot. This method has strong versatility to provide a new way for the intelligent control optimization of the servo system.关键词：servo system;control optimization;transient performance;deep reinforcement learning;fuzzy control98|4|0更新时间：2025-07-09
- 摘要：Analogy of transfer processes is an important and creative method in many interdisciplinary studies. Appropriate analogy of transfer processes facilitates the recognition and even the similar problem-solving between disciplines and further drives the development of interdisciplines. In this paper, we compare the development and connection of heat transfer and electrology. It is acknowledged that the mutual reference and learning of theories among disciplines can promote the development of heat transfer and electrology and verify the feasibility of thermal-electric analogy study. According to the fundamental theories of heat transfer and electrology, similarities and differences between heat transfer and electrology are analyzed in detail. It is found that there are similarities of the heat transfer and electrology in-between central physical quantities, derived quantities of central physical quantities, field functions and boundary conditions, and differences exist in some physical quantities, such as heat charge and charge, as well as the mechanism of heat transfer and conduction. Based on the antithetical relations of physical parameters between heat transfer and electrology, we obtain thermal circuit analysis model by the analogy investigation of electric circuit. This approach to the theoretical fundamentals on thermal-electrical analogy is expected to provide enlightenments for solving heat transfer problems in electrical engineering.关键词：heat transfer;electrology;analogical transfer;thermal-electrical analog mode51|4|0更新时间：2025-07-09
- 摘要：A self-heating effect model for vacuum gate dielectric vertical-stacked silicon nanowires(SiNWs)gate-all-around field-effect transistors(GAA FETs)considering scale effect is proposed to address intensified influences of thermal transport scale effect on self-heating effect in nanoscale MOSFETs. Firstly, the relationships between phonon scattering free paths in silicon film and SiNW are analyzed, and the SiNW thermal conductivity attenuation factor used to measure the revealing phonon boundary scattering is quantified. Then an analytical model of the thermal conductivity of SiNW considering the influence of scale effect is derived based on the current international analytical model for nanoscale silicon films. Finally, the self-heating effect model considering the scale effect is established for GAA SiNWs FET by combining with the critical path of heat transfer in nanoscale devices. The proposed model is used to realize numerical simulation of the self-heating effect of GAA SiNWs FET in TCAD software. Simulation results show that the vacuum gate dielectric with low thermal conductivity, vertical stacked multiple heat sources and thermal transport scale effect lead to more complex heat generation and diffusion processes in vacuum gate dielectric GAA SiNWs FET, and aggravate the self-heating effect of devices. The thermal transport capacity of gate can be maximized through the compromise design between vacuum gate gap and surrounding gas pressure and the self-heating effect of the device can be inhibited to improve the performance and reliability of device. Compared with the hot spot temperature estimated by the traditional self-heating effect model, the hot spot temperature in the vacuum gate device predicted by the proposed model increases by 30%, indicating that the proposed model can effectively reveal the thermal transport scale effect of SiNW in GAA FET.关键词：field-effect transistor;thermal conductivity;thermal transport;silicon nanowires;self-heating effect70|6|0更新时间：2025-07-09
- 摘要：Aiming at the problem that the mutual interferences among different antennas from the desired user in the spatial multiplexing system reduce the communication quality, a new adaptive space-frequency anti-interference equalization method is proposed. Firstly, signals to be transmitted are sent to the receive antennas in the form of spatial multiplexing at the transmitter; Then, the adaptive equalizer is first designed based on the minimum mean square error(MMSE)criterion by exploiting the pilot signal received by each receive antenna; Finally, parameters estimated from the designed adaptive equalizer are used to detect the data through iterative optimization. In the process of parameter estimation, the proposed method makes use of the mutual interferences among different antennas from the desired user rather than attempts to completely remove them, thereby reducing its impact on system performance. Simulation results show that the proposed method can achieve significant gain in performance over the traditional adaptive space-time or space-frequency equalization methods. When the bit error rate is 10-5, the proposed method achieves around 2.5 dB performance gain as compared with the existing competitors. Moreover, in the presence of interference, the proposed method also exhibits much stronger anti-interference capability compared with existing schemes, and there is no obvious performance platform.关键词：spatial multiplexing;multiple antenna;adaptive space-frequency equalization;anti-interference68|4|0更新时间：2025-07-09
- 摘要：In order to solve the problem of complex operation mode and difficult parameter design of the interleaved-control double-input Buck converter due to the difference of the two input voltages, three cases of the two input voltages of the converter are analyzed and discussed. Mathematical models of critical load, inductance current and output ripple voltage of the converter operating in continuous conduction mode(CCM)and discontinuous conduction mode(DCM)are established. It is found that the critical load of the converter increases as the difference between the two input voltages decreases, and the inductor current ripple and output ripple voltages decrease as the voltage difference between the two input voltages decreases. When the two input voltages are equal, the critical load of the converter reaches the maximum, and the inductor current ripple and output ripple voltages reach the minimum. Finally, an experimental platform for double-input Buck converter is built, and three groups of different input voltages are given for experimental study. The experimental results verify the correctness of the operation mode of the converter and the mathematical models of the output ripple voltage. The research results provide a theoretical basis for the parameter optimization design of the double-input Buck converter with interleaved control.关键词：double-input Buck converter;interleaved control;working mode;ripple voltage75|5|1更新时间：2025-07-09
- 摘要：A scheme of applying a large-scale cryogenic refrigerator to cryogenic distillation is proposed to solve the problem that the current cryogenic distillation mostly uses regenerative refrigerator as the cold source of the condenser, and it is difficult to meet the needs of industrial applications for large-scale processing of distillation materials. A simulation experiment platform of cryogenic distillation based on the reverse Brayton cycle is designed and built, which simultaneously meets the load simulation requirements of the condenser, reboiler and cold shield, and solves the problem that the process of recovering the cooling power of the reboiler is difficult to simulate. The simulation experiment platform is tested. It provides refrigeration capacity of about 600-1 200 W for the condenser in the temperature range of 20 K, recovers the cooling power of the reboiler, and provides cooling power of more than 500 W for the cold shield. The efficiency of the turbine expander is more than 70%. Feasibility of applying the large-scale cryogenic refrigeration system to cryogenic distillation technology is verified.关键词：large-scale cryogenic refrigeration system;cryogenic distillation;simulation experiment platform;reverse Brayton cycle45|4|0更新时间：2025-07-09
- 摘要：A direct location algorithm of pulse train radiation source in nonuniform noise is proposed to solve the problem that the accuracy of the direct location algorithm is reduced due to the different noise power of each reconnaissance station in the process of passive location. Firstly, Fourier transform is used to construct the incoming wave signal, and then the problem of positioning solution is transformed into a maximum eigenvalue problem of generalized cross ambiguity matrix by matrix transformation. Finally, the location of the target radiation source is obtained, and the Cramer-Rao bound(CRB)of the algorithm is derived under the condition of nonuniform noise power. Simulation results show that the positioning accuracy of the proposed algorithm is effectively improved with the increase of the number of observed pulses and the signal-to-noise ratio(SNR). Compared with the existing DPD algorithm under the same boise background, the positioning accuracy of the proposed algorithm improves by about 50% when the number of observed pulses is 120 and SNR is 5 dB.关键词：direct position determination;nonuniform noise power;cross ambiguity matrix;Cramer-Rao bound;pulse train radiation source52|4|0更新时间：2025-07-09
- 摘要：A session recommendation model based on dual encoders(SR-BE)is proposed to solve the problem that it is difficult to accurately capture the global dependencies between items in the existing session recommendation models. The dual encoder consists of a global encoder based on self-attention network and a local encoder based on graph neural network. The global encoder can adaptively capture the global dependencies among all items by using the attention mechanism regardless of their time intervals and encode them into global latent vectors. In order to make up for the lack of local dependencies in self-attention network, the local encoder first constructs the session sequences into a session graphs, then the graph neural networks are used to capture the local dependencies among adjacent items and encode them into local latent vectors. Finally, the linear combination of global and local latent vectors obtained from the dual encoder is used to obtain the session representations and the click probability of each candidate item is obtained by decoding the session representions through the prediction layer. Experimental results and comparisons with a single global encoder and a single local encoder show that the combination of the global encoder based on self-attention networks and the local encoder based on graph neural networks improves the hit rate by 3.11% and 6.55%, respectively. Comparisons with state-of-the-art methods on two public datasets validate the effectiveness and feasibility of the proposed method.关键词：session-based recommendation;self-attention network;graph neural network;encoder;recommendation model83|4|0更新时间：2025-07-09
- 摘要：A tolerance allocation method based on evolutionary game is proposed to solve the influence of complex and diverse manufacturing resources on the tolerance allocation of product assembly dimension chain in cloud manufacturing(CMfg). Firstly, all tolerance elements in the same dimension chain are taken as the game parties, and an evolutionary game model is established with the selection of manufacturing resources. The game strategy comprehensively considers the quality loss and the resource price of the tolerance design scheme, and the assembly quality requirements and cost are converted into the total payment benefit after the selection of manufacturing resources by the tolerance element. Secondly, a replication dynamics equation of the model is constructed to simulate the strategy adaptation process of different users. Finally, the Lyapunov's second method is used to prove the convergence of the model to evolutionary equilibrium, and the distributed iterative algorithm is used to find its solution. The feasibility and effectiveness of the model and algorithm are verified by a tolerance design example of the front end assembly. Experimental results show that the quality loss coefficient has no effect on the resource selection strategy, but affects the total payment. Comparisons with the non-cooperative game method and the linear weighting method show that the proposed evolutionary game method reduces the quality loss and total payment of the tolerance allocation scheme by 28.3% to 54.0% and 18.2% to 63.6% on average, respectively. The proposed method can be applied to the tolerance allocation design of assembly dimensional chain and to realize the selection of manufacturing resources according to tolerance design in cloud manufacturing environment.关键词：tolerance allocation;evolutionary game theory;evolutionary equilibrium;distributed iterative algorithm;cloud manufacturing62|4|0更新时间：2025-07-09
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