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Dynamics of buoyancy-driven microflow in a narrow annular space

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Journal of Zhejiang University-Science A(Applied Physics & engineering) 2023年第12期24卷 1131-1139页

作者： Yanzhong WANG Yaping ZHANG Kai YANG Boji LU Hao GAO school of mechanical engineering&automation Beihang UniversityBeijing 100191China Bejing Spacecraft Beijing 100094China school of mechanical and electrical engineering Sanming UniversitySanming 365001China

This paper aims to investigate the dynamics of buoyancy-driven microflow in a narrow annular space inside a liquid floated gyroscope(LFG). Several theoretical models with a non-uniform thermal boundary for fluid flow in annular channels are given to analyze the effects of various parameters, such as the clearance size h, roughness height re, and rough density ε, on the flow and temperature profiles as well as on the fluid-drag torque. In the narrow annular regime, the relationship between the temperature and the angular displacement of the outer wall is defined as a cosine function, and the surface roughness of the inner wall is structured as a series of surface protrusions with a circular shape. With the increase of clearance size h, the flow velocity gradually increases to a stable level, and the drag torque increases initially and then decreases to a stable level. Furthermore, the increase of roughness height re and roughness density ε intensifies the frictional effect of fluid on the inner-wall surface. However, these two parameters have no significant effect on the flow velocity. This study can provide theoretical references for precision manufacturing and precision improvement of gyro instruments.

关键词： Liquid floated gyroscope(LFG) Annular channel Roughness feature Fluid drag

Effect of Degree-of-Symmetry on Kinetostatic Characteristics of Flexure Mechanisms:A Comparative Case Study

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Chinese Journal of mechanical engineering 2018年第2期31卷 54-65页

作者： Xiao-Bing He Jing-Jun Yu Wan-Wan Zhang Guang-Bo Hao school of mechanical engineering and automation Beihang University school of engineering-electrical and Electronic engineering University College Cork

The current research of kinetostatic characteristics in flexure mechanisms mainly focus on the improvement of accuracy. To reduce or eliminate the parasitic motion is considered as an approach by using the common knowledge of symmetry. However, there is no study on designing the flexure mechanisms with symmetrical features as many as possible for better kinetostatic performance, when considering the resulting cost by the symmetry. In this paper, the concept of degree of symmetry(DoS) is proposed for the first time, which is committed to symmetry design in the phase of conceptual design. A class of flexure mechanisms with 0?DoS, 1?DoS, 2?DoS and 3?DoS are synthesized respectively based on the Freedom and Constraint Topology method. Their overall compliance matrices in an analytical form formulated within the framework of the screw theory are used to analyze and compare the effect of different number of DoS on the kinetostatic characteristics for flexure mechanisms. The finite element analysis(FEA) simulations are implemented to verify the analytical results. These results show that the higher the DoS is, the smaller the parasitic motion error will be. The flexure model with 3?DoS is optimized according to the overall compliance matrix and then tested by using the FEA simulation. The testing result shows that with the best combination parameters, the parasitic motion error for 3?DoS mechanism is almost eliminated. This research introduces a design principle which can alleviate the unwanted parasitic motion for better accuracy.

关键词： Flexure mechanism Symmetry Kinetostatic characteristics FEA simulation

Efficiency optimized fuel supply strategy of aircraft engine based on air-fuel ratio control

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Chinese Journal of Aeronautics 2019年第2期32卷 489-498页

作者： Yixuan WANG Yan SHI Maolin CAI Weiqing XU Qihui YU school of automation Science and electrical engineering Beihang University school of mechanical engineering Inner Mongolia University of Science & Technology

Accurate fuel injection control of aircraft engine can optimize the energy efficiency of UAV power system while meeting the propeller speed requirement. Traditional injection control method such as open-loop calibration causes instability of fuel supply which brings the risk of power loss of UAV. Considering that the closed-loop control of AFR can ensure a stable fuel feeding, this paper proposes an AFR control based fuel supply strategy in order to improve the efficiency of fuel-powered UAV while obtaining the required engine speed. According to the optimum fuel injection results, we implement fuzzy-PID method to control the set AFR in different situations. Through simulation and experiment studies, the results indicate that, to begin with, the calibrated mathematical model of the aircraft engine is effective. Next, this fuel supply strategy based on AFR control can normally realize the engine speed regulation, and the applied control algorithm can eliminate the overshoot of AFR throughout all the working progress. What is more,the fuel supply strategy can averagely shorten the response time of the engine speed by about two seconds. In addition, compared with the open-loop calibration, in this work the power efficiency is improved by 9% to 33%. Last but not the least, the endurance can be improved by 30 min with a normal engine speed. This paper can be a reference for the optimization of UAV aircraft engine.

关键词： AFR control Aircraft engines Efficiency optimization Fuel supply strategy Simulation and experiments

Research on Energy Efficiency Characteristics of Mining Shovel Hoisting and Slewing System Driven by Hydraulic-Electric Hybrid System

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Chinese Journal of mechanical engineering 2023年第6期36卷 197-211页

作者： Xiangyu Wang Lei Ge Yunhua Li Long Quan College of mechanical and Vehicle engineering Taiyuan University of TechnologyTaiyuan 030024China school of automation Science and electrical engineering Beihang UniversityBeijing 100191China

Mining shovel is a crucial piece of equipment for high-efficiency production in open-pit mining and stands as one of the largest energy consumption sources in mining.However,substantial energy waste occurs during the descent of the hoisting system or the deceleration of the slewing platform.To reduce the energy loss,an innovative hydrau-lic-electric hybrid drive system is proposed,in which a hydraulic pump/motor connected with an accumulator is added to assist the electric motor to drive the hoisting system or slewing platform,recycling kinetic and potential energy.The utilization of the kinetic and potential energy reduces the energy loss and installed power of the min-ing shovel.Meanwhile,the reliability of the mining shovel pure electric drive system also can be increased.In this paper,the hydraulic-electric hybrid driving principle is introduced,a small-scale testbed is set up to verify the feasibil-ity of the system,and a co-simulation model of the proposed system is established to clarify the system operation and energy characteristics.The test and simulation results show that,by adopting the proposed system,compared with the traditional purely electric driving system,the peak power and energy consumption of the hoisting electric motor are reduced by 36.7%and 29.7%,respectively.Similarly,the slewing electric motor experiences a significant decrease in peak power by 86.9%and a reduction in energy consumption by 59.4%.The proposed system expands the application area of the hydraulic electric hybrid drive system and provides a reference for its application in over-sized and super heavy equipment.

关键词： Mining shovel Hoisting and slewing system Hydraulic-electric hybrid drive Energy saving

Microstructure and wear-resistant properties of NiCr–Cr_3C_2 coating with Ni45 transition layer produced by laser cladding

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Rare Metals 2015年第7期34卷 491-497页

作者： Chun-Cheng Zang Yan-Zhong Wang Yi-Du Zhang Jin-Hua Li Hong Zeng De-Qiang Zhang school of mechanical engineering and automation Beihang University Institute of electrical engineering Chinese Academy of Sciences College of mechanical engineering and automation Liaoning University of Technology

NiCr–Cr3C2 metal–ceramic composite coating is commonly produced on metal substrate by laser cladding to be used as wear-resistant coating under medium- or high-temperature working conditions.The coating has high hardness, generally over three times that of the substrate.In order to make the hardness increase gradually from substrate to coating surface, the nickel-based alloy Ni45 was chosen as the transition layer and Ni Cr–Cr3C2 coating was indirectly cladded on 20Cr2Ni4 A substrate.Microstructure and composition of the coating were characterized by scanning electron microscope(SEM), energy-dispersive spectroscopy(EDS) and X-ray diffraction(XRD).Microhardness of the cross section of the coating was measured.Friction and wear behavior of Ni Cr–Cr3C2coating and substrate were investigated through sliding against the Si C ball at 20, 100 and 300 °C.The morphologies of worn surfaces were analyzed by SEM and EDS.The results show that the hardness of Ni45 transition layer is between that of the substrate and Ni Cr–Cr3C2coating, which avoids hardness jump and stress concentration of the coating.Ni Cr–Cr3C2coating contains hard phases of Cr3C2 and Cr7C3which enhance the wear resistance.With thetemperature increasing, friction coefficient and wear rate of the substrate increase significantly.Compared with the substrate, Ni Cr–Cr3C2coating has lower friction coefficient and wear rate at 100 and 300 °C, which verifies the good wear resistance of NiCr–Cr3C2 coating.

关键词： Laser cladding NiCr–Cr3C2 coating Hardness Wear re

Corrosion Resistance and Tribological Properties of Laser Cladding Layer of H13 Die Steel Strengthened by Ultrasonic Rolling

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Chinese Journal of mechanical engineering 2022年第6期35卷 415-426页

作者： Kaikui Zheng Youxi Lin Jianguo Cai Chengqian Lei school of mechanical engineering and automation Fuzhou UniversityFuzhou 350116China school of Advanced Manufacturing Fuzhou UniversityJinjiang 362251China mechanical and electrical engineering Practice Center Fuzhou UniversityFuzhou 350116China

Laser cladding is a new surface repair method that can improve the wear and corrosion resistance of substrate surfaces.However,the cladding layer typically exhibits a rough surface,high hardness and large residual tensile stress,and thus requires further machining and finishing.Ultrasonic rolling(U-rolling)is a highly efficient finishing and strengthening process that combines ultrasonic technology with traditional rolling(T-rolling).In this study,an ironbased alloy was coated onto the surface of H13 die steel using laser cladding,and the surface of the cladding layer was polished using U-rolling.The effects of U-rolling on the surface quality,corrosion resistance and friction and wear properties of the laser-cladding layer were investigated and compared with those obtained by T-rolling.The surface roughness of the U-rolled sample was only 1/4 that of the T-rolled sample.The hardness and residual compressive stress of the laser cladding layer after U-rolling were higher than those after T-rolling.Similarly,the surface corrosion resistance of the laser cladding layer after U-rolling was higher than that after T-rolling.U-rolling changed the surface roughness,grain size,and residual stress of the material and thus affected the corrosion resistance of the laser cladding layer.The friction coefficient and wear rate of the U-rolled surface of the cladding layer were lower than those of the T-rolled surface.In addition,the tribological properties of the cladding layer were found to be related to the rolling direction.When the friction direction of the sample was the same as the rolling direction,its friction and wear performance were higher than those when the two directions were perpendicular.

关键词： Laser cladding Ultrasonic rolling Surface quality Corrosion resistance Tribological properties

A robust solution for hesitate phenomenon in pick up process of aerospace electromagnetic relay

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Chinese Journal of Aeronautics 2013年第3期26卷 697-704页

作者： Ye Xuerong Deng Jie Ma Yue Zhai Guofu Yan Jihong school of electrical engineering and automation Harbin Institute of Technology school of mechanical and electrical engineering Harbin Institute of Technology

As for aerospace electromagnetic relay （AEMR） which is of small batches and having difficulty in automatic production, the uncertainty phenomenon is remarkable due to excessive manual work involved in the assembly and adjustment processes. This kind of uncertainty may increase the coil voltage difference （CVD） caused by hesitate phenomenon in the pick up process of AEMR. Taking a certain type of AEMR for example, the CVD problem in the actual producing process has been studied in this paper. The primary cause of this issue, two-steps of armature motion （namely hesitate phenomenon） in the pick up process, has been found by analyzing the matching characteristics of electromagnetic and mechanical torques of AEMR. Through the optimization of the matching characteristics, the two-steps of armature motion problem is solved by robust design of the return reed which is a key part of AEMR. The validity of this research has been proved by the comparison of characteristics of AMER before and after the optimization.

关键词： Aerospace Coil voltage difference Electromagnetic relay Hesitate phenomenon Robust design

Biological Eagle-eye Inspired Target Detection for Unmanned Aerial Vehicles Equipped with a Manipulator

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Machine Intelligence Research 2023年第5期20卷 741-752页

作者： Yi-Min Deng Si-Yuan Wang school of automation Science and electrical engineering Beihang UniversityBeijing 100191China

Inspired by eagle eye mechanisms,the structure and information processing characteristics of the eagle′s visual system are used for the target capture task of an unmanned aerial vehicle(UAV)with a mechanical arm.In this paper,a novel eagle-eye inspired multi-camera sensor and a saliency detection method are proposed.A combined camera system is built by simulating the double fovea structure on the eagle retina.A saliency target detection method based on the eagle midbrain inhibition mechanism is proposed by measuring the static saliency information and dynamic features.Thus,salient targets can be accurately detected through the collaborative work between different cameras of the proposed multi-camera sensor.Experimental results show that the eagle-eye inspired visual system is able to continuously detect targets in outdoor scenes and that the proposed algorithm has a strong inhibitory effect on moving background interference.

关键词： Unmanned aerial vehicle(UAV) eagle eye multi-camera sensor target detection saliency detection

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数字孪生增强的复合材料质量预测（英文）

engineering 2023年第3期 23-33页

作者：王雨澄陶飞左颖张萌戚庆林 school of automation Science and electrical engineering Beihang University Research Institute for Frontier Science Beihang University Department of automation Tsinghua University school of mechanical engineering and automation Beihang University

复合材料以其优异的性能被广泛应用于许多领域。复合材料的质量缺陷会导致其构件的性能下降，成为潜在的事故隐患。当前国内外研究者通常采用实验或仿真的方法对复合材料的质量进行预测。然而，由于固化环境的不确定性和动态、静态特征...

复合材料以其优异的性能被广泛应用于许多领域。复合材料的质量缺陷会导致其构件的性能下降，成为潜在的事故隐患。当前国内外研究者通常采用实验或仿真的方法对复合材料的质量进行预测。然而，由于固化环境的不确定性和动态、静态特征考虑不全面，因此难以准确预测复合材料的质量。为了解决这一问题，本文首先建立了复合材料的数字孪生（DT）模型，然后通过实现静态热压罐DT虚拟模型与可变复合材料DT虚拟模型的耦合，完成复合材料固化过程数字孪生模型的构建。基于该固化过程模型，生成模拟数据来增加动态特征，从而提高质量预测的准确性。最后基于获取的数据，使用极限学习机（ELM）构建复合材料质量预测模型，并通过结果分析验证了所提方法的有效性。

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