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The computational fluid dynamic modeling of downwash flow field for a six-rotor UAV

Yongjun ZHENG, Shenghui YANG, Xingxing LIU, Jie WANG, Tomas NORTON, Jian CHEN, Yu TAN

《农业科学与工程前沿（英文）》 2018年 第5卷 第2期   页码 159-167 doi: 10.15302/J-FASE-2018216

摘要： The downwash flow field of the multi-rotor unmanned aerial vehicle (UAV), formed by propellers during operation, has a significant influence on the deposition, drift and distribution of droplets as well as the spray width of the UAV for plant protection. To study the general characteristics of the distribution of the downwash airflow and simulate the static wind field of multi-rotor UAVs in hovering state, a 3D full-size physical model of JF01-10 six-rotor plant protection UAV was constructed using SolidWorks. The entire flow field surrounding the UAV and the rotation flow fields around the six rotors were established in UG software. The physical model and flow fields were meshed using unstructured tetrahedral elements in ANSYS software. Finally, the downwash flow field of UAV was simulated. With an increased hovering height, the ground effect was reduced and the minimum current velocity increased initially and then decreased. In addition, the spatial proportion of the turbulence occupied decreased. Furthermore, the appropriate operational hovering height for the JF01-10 is considered to be 3 m. These results can be applied to six-rotor plant protection UAVs employed in pesticide spraying and spray width detection.

关键词： CFD simulation     downwash flow field     numerical analysis     plant protection     six-rotor UAV    

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A total torque index for dynamic performance evaluation of a radial symmetric six-legged robot

Kejia LI, Xilun DING, Marco CECCARELL

《机械工程前沿（英文）》 2012年 第7卷 第2期   页码 219-230 doi: 10.1007/s11465-012-0320-9

摘要：

This article focuses on the dynamic index and performance of a radial symmetric six-legged robot. At first the structure of the robot is described in brief and its inverse kinematics is presented. Then the dynamic model is formulated as based on the Lagrange equations. A novel index of total torque is proposed by considering the posture of the supporting legs. The new index can be used to optimize the leg’s structure and operation for consuming minimum power and avoiding unstable postures of the robot. A characterization of the proposed six-legged robot is obtained by a parametric analysis of robot performance through simulation using the presented dynamic model. Main influences are outlined as well as the usefulness of the proposed performance index.

关键词： six-legged robots     dynamic modeling     performance index    

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Effect of UAV prewetting application during the flowering period of cotton on pesticide droplet deposition

Weixiang YAO, Xianju WANG, Yubin LAN, Ji JIN

《农业科学与工程前沿（英文）》 2018年 第5卷 第4期   页码 455-461 doi: 10.15302/J-FASE-2018232

摘要：

Prewetting process can reduce the contact angle between the droplet and the leaf blade, so that the droplet can more easily wet and spread, thereby increasing the quantity of deposition. To improve the effectiveness of pesticides on cotton leaves, prewetting by single-rotor electric unmanned aerial vehicles (UAV) was studied, focusing on the effects of pesticide deposition on cotton leaves during the flowering period. Cotton leaves in 0°–30°, 30°–60°, 60°–90° leaf blade angle ranges (angle between the leaf blade and the horizontal plane) were examined. In the first experiment, four different prewetting volumes (0, 1.6, 3.2 and 4.8 L) were sprayed by a single-rotor electric UAV on four cotton plots (plots A to D) each with an area of 120 m , and then each area was sprayed with a 0.8% (w/v) ponceau 2R solution by another single-rotor electric UAV. The results revealed that with no prewetting, droplet deposition quantity decreased with increasing leaf blade inclination. After prewetting, the mean droplet deposition quantity on plots B, C and D increased by 39.8%, 9.7% and 24.9%, respectively. The prewetting rate of 1.6 L per 120 m had the most significant effect on improving the deposition of droplets. It was also found that the mean droplet deposition quantity in each leaf blade angle range increased after prewetting. For the leaf blade angle range 60° to 90°, this increase was the most pronounced, with 0.043, 0.062, 0.057 and 0.048 L·cm in plots A–D, respectively. Also, droplet deposition uniformity in the leaf blade angle range 60°–90° was better after prewetting. These results should provide a valuable reference for future research and practice to improve the effectiveness of pesticides applied to cotton by aerial applications.

关键词： aerial spray     cotton     deposition     flowering period     leaf angle     prewetting     UAV    

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Economic Growth Model Based on Six Basic Factors of Production—Xu Growth Rate Equation

Shou-bo Xu,Zong-yuan Huang

《工程管理前沿（英文）》 2014年 第1卷 第2期   页码 160-175 doi: 10.15302/J-FEM-2014024

摘要： This paper proposes an economic growth model based on the Six Basic Factors of Production and Xu Growth Rate Equation for the first time, which fills-in the deficits of the New Classical Economic Growth Model based on the Solow Model. The empirical analysis indicates that over the past three decades, the consumption of six basic factors of production had complicated relations with economic growth. In some years, the consumption rate of the basic factors of production was meager, but the economy witnessed relatively rocketing growth rate; in some years, the factors of production consumption rate was very high, but the economy growth rate slowed down. In general, economy grows at the expenses of huge consumption of four factors. There is an obvious characteristic of huge input and low efficiency. The average contribution rate of technological advance peaks in the middle, while it drops down at two ends. Noticeably, since 2004, the technology contribution rate generally shows a downward trend, reasons of which should be explored systematically in aspects like economic policy and industry structure with a view to boost further transformation of the macro-economy scientific growth model.

关键词： six basic factors of production     economic growth model     Xu Growth Rate Equation    

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A novel NN based rotor flux MRAS to overcome low speed problems for rotor resistance estimation in vector

Venkadesan ARUNACHALAM,Himavathi SRINIVASAN,A. MUTHURAMALINGAM

《能源前沿（英文）》 2016年 第10卷 第4期   页码 382-392 doi: 10.1007/s11708-016-0421-y

摘要： This paper presents a new neural network based model reference adaptive system (MRAS) to solve low speed problems for estimating rotor resistance in vector control of induction motor (IM). The MRAS using rotor flux as the state variable with a two layer online trained neural network rotor flux estimator as the adaptive model (FLUX-MRAS) for rotor resistance estimation is popularly used in vector control. In this scheme, the reference model used is the flux estimator using voltage model equations. The voltage model encounters major drawbacks at low speeds, namely, integrator drift and stator resistance variation problems. These lead to a significant error in the estimation of rotor resistance at low speed. To address these problems, an offline trained NN with data incorporating stator resistance variation is proposed to estimate flux, and used instead of the voltage model. The offline trained NN, modeled using the cascade neural network, is used as a reference model instead of the voltage model to form a new scheme named as “NN-FLUX-MRAS.” The NN-FLUX-MRAS uses two neural networks, namely, offline trained NN as the reference model and online trained NN as the adaptive model. The performance of the novel NN-FLUX-MRAS is compared with the FLUX-MRAS for low speed problems in terms of integral square error (ISE), integral time square error (ITSE), integral absolute error (IAE) and integral time absolute error (ITAE). The proposed NN-FLUX-MRAS is shown to overcome the low speed problems in Matlab simulation.
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Sorption and desorption of pymetrozine on six Chinese soils

Mingxing GAO,Yingying LI,Hong YANG,Yucheng GU

《环境科学与工程前沿（英文）》 2016年 第10卷 第1期   页码 1-10 doi: 10.1007/s11783-014-0715-4

摘要： Pymetrozine is a selective insecticide with a unique chemical structure and mode to control hemipteran and homopteran. While pymetrozine has brought great benefits to crop production by killing insects, its residues in soil may have a detrimental effect on environment. Therefore, it is of great importance to investigate its behaviors in soil. In this study, the sorption and desorption of pymetrozine on six Chinese soils were investigated using a batch equilibrium approach to understand its mobile behavior in the soils. Both sorption and desorption isotherms of pymetrozine were in good agreement with the Freundlich model. The sorption coefficient varied between 3.37 and 58.32 mL?g and the sorption isotherms were nonlinear, with 1/ ranging from 0.57 to 0.91. A regression equation was proposed to predict the sorption of pymetrozine on six different soil samples: log = 4.3708 − 4.5709 × log (pH in 0.01mol·L CaCl ) + 0.4700 × log OC% + 0.0057 × sand (%) + 0.0022 × CEC(clay), with = 0.9982. The organic carbon content of soil positively affected the sorption of pymetrozine, but soil pH had a negative effect on the sorption. Additionally, effects of CaCl concentration, soil to solution ratio and pesticide form were investigated. The sorption was promoted with an increase in soil to solution ratio and a decrease in CaCl concentration. The possible variation of the five formulated products of pymetrozine was also investigated.

关键词： desorption     pymetrozine     sorption     soil    

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Stability and dynamics of rotor system with 45° slant crack on shaft

Yanli LIN, Xiaohui SI, Fulei CHU

《机械工程前沿（英文）》 2011年 第6卷 第2期   页码 203-213 doi: 10.1007/s11465-011-0131-4

摘要：

Crack on a shaft is one of the common damages in a rotor system. In this paper, transverse vibrations are calculated to compare the influences of transverse crack and slant crack on the rotor system. Results show that the vibration amplitude of the rotor system with a 45° slant crack on the shaft is larger than that with a transverse crack when the two types of crack have the same depth and the rotor system runs in the same condition. Stability and dynamic characteristics of the rotor system with a 45° slant crack on the shaft under torsional excitation are analyzed by considering opening and closing of the crack. It is shown that the instability of the transverse vibration of the rotor system increases with increasing difference between the bending stiffness in two main directions, and the vibration is stable when the two bending stiffness are identical. The spectrum analysis of the steady-state response reveals that the gravity and the eccentricity produce different frequency components, and when the two bending stiffness are identical, the multiple frequency components of the torsional excitation disappear. Further investigation shows that the vibration amplitudes in combined frequencies increase rapidly in transversal, torsional, and axial vibration with increasing slant crack depth. The results are helpful for the understanding the dynamic behavior of a rotor system with a slant crack on a shaft and can be used for the detection of the slant crack on a shaft.

关键词： rotor dynamics     slant crack     stability     torsional excitation     open and close    

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Study on wave rotor refrigerators

Yuqiang DAI, Dapeng HU, Meixia DING

《化学科学与工程前沿（英文）》 2009年 第3卷 第1期   页码 83-87 doi: 10.1007/s11705-009-0075-y

摘要： As a novel generation of a rotational gas wave machine, the wave rotor refrigerator (WRR) is an unsteady flow device used for refrigeration, in whose passages pressured streams directly contact and exchange energy due to the movement of pressure waves. In this paper, the working mechanism and refrigeration principle are investigated based on the one-dimensional unsteady flow theory. A basic limitation on main structural parameters and operating parameters is deduced and the wave diagram of WRR to guide designing is sketched. The main influential factors are studied through an experiment. In the DUT Gas Wave Refrigeration Studying and Development Center (GWRSDC) lab, the isentropic efficiency can now reach about 65%. The results show that the WRR is a feasible and promising technology in pressured gas refrigeration cases.

关键词： wave rotor     refrigeration     unsteady flow theory     wave diagram    

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Optimization model for rotor blades of horizontal axis wind turbines

LIU Xiong, CHEN Yan, YE Zhiquan

《机械工程前沿（英文）》 2007年 第2卷 第4期   页码 483-488 doi: 10.1007/s11465-007-0084-9

摘要： This paper presents an optimization model for rotor blades of horizontal axis wind turbines. The model refers to the wind speed distribution function on the specific wind site, with an objective to satisfy the maximum annual energy output. To speed up the search process and guarantee a global optimal result, the extended compact genetic algorithm (ECGA) is used to carry out the search process. Compared with the simple genetic algorithm, ECGA runs much faster and can get more accurate results with a much smaller population size and fewer function evaluations. Using the developed optimization program, blades of a 1.3 MW stall-regulated wind turbine are designed. Compared with the existing blades, the designed blades have obviously better aerodynamic performance.

关键词： population     extended     algorithm     developed optimization     accurate    

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A novel six-legged walking machine tool for

Jimu LIU, Yuan TIAN, Feng GAO

《机械工程前沿（英文）》 2020年 第15卷 第3期   页码 351-364 doi: 10.1007/s11465-020-0594-2

摘要： The manufacture and maintenance of large parts in ships, trains, aircrafts, and so on create an increasing demand for mobile machine tools to perform operations. However, few mobile robots can accommodate the complex environment of industrial plants while performing machining tasks. This study proposes a novel six-legged walking machine tool consisting of a legged mobile robot and a portable parallel kinematic machine tool. The kinematic model of the entire system is presented, and the workspace of different components, including a leg, the body, and the head, is analyzed. A hierarchical motion planning scheme is proposed to take advantage of the large workspace of the legged mobile platform and the high precision of the parallel machine tool. The repeatability of the head motion, body motion, and walking distance is evaluated through experiments, which is 0.11, 1.0, and 3.4 mm, respectively. Finally, an application scenario is shown in which the walking machine tool steps successfully over a 250 mm-high obstacle and drills a hole in an aluminum plate. The experiments prove the rationality of the hierarchical motion planning scheme and demonstrate the extensive potential of the walking machine tool for operations on large parts.

关键词： legged robot     parallel mechanism     mobile machine tool     in-situ machining    

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Multi-UAV collaborative system with a feature fast matching algorithm

Tian-miao Wang, Yi-cheng Zhang, Jian-hong Liang, Yang Chen, Chao-lei Wang,zycet@126.com

《信息与电子工程前沿（英文）》 2020年 第21卷 第12期   页码 1671-1814 doi: 10.1631/FITEE.2000047

摘要： We present a real-time monocular system with a new distributed structure for multi-UAV tasks. The system is different from other general SLAM systems in two aspects: First, it does not aim to build a global map, but to estimate the latest relative position between nearby vehicles; Second, there is no centralized structure in the proposed system, and each vehicle owns an individual metric map and an ego-motion estimator to obtain the relative position between its own map and the neighboring vehicles’. To realize the above characteristics in real time, we demonstrate an innovative algorithm to avoid catastrophic expansion of feature point matching workload due to the increased number of UAVs. Based on the hash and principal component analysis, the matching time complexity of this algorithm can be reduced from (log ) to (1). To evaluate the performance, the algorithm is verified on the acknowledged multi-view stereo benchmark dataset, and excellent results are obtained. Finally, through the simulation and real flight experiments, this improved SLAM system with the proposed algorithm is validated.
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Structure improvement and strength finite element analysis of VHP welded rotor of 700°C USC steam turbine

Jinyuan SHI,Zhicheng DENG,Yong WANG,Yu YANG

《能源前沿（英文）》 2016年 第10卷 第1期   页码 88-104 doi: 10.1007/s11708-015-0387-1

摘要： The optimized structure strength design and finite element analysis method for very high pressure (VHP) rotors of the 700°C ultra-super-critical (USC) steam turbine are presented. The main parameters of steam and the steam thermal parameters of blade stages of VHP welded rotors as well as the start and shutdown curves of the steam turbine are determined. The structure design feature, the mechanical models and the typical position of stress analysis of the VHP welded rotors are introduced. The steady and transient finite element analysis are implemented for steady condition, start and shutdown process, including steady rated condition, 110% rated speed, 120% rated speed, cold start, warm start, hot start, very hot start, sliding-pressure shutdown, normal shutdown and emergency shutdown, to obtain the temperature and stress distribution as well as the stress ratio of the welded rotor. The strength design criteria and strength analysis results of the welded rotor are given. The results show that the strength design of improved structure of the VHP welded rotor of the 700°C USC steam turbine is safe at the steady condition and during the transient start or shutdown process.

关键词： 700°C ultra-super-critical unit     steam turbine     very high pressure rotor     structure strength design     strength design criteria     finite element analysis    

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Multi-UAV cooperative target tracking with bounded noise for connectivity preservation

Rui Zhou, Yu Feng, Bin Di, Jiang Zhao, Yan Hu,jzhao@buaa.edu.cn

《信息与电子工程前沿（英文）》 2020年 第21卷 第10期   页码 1413-1534 doi: 10.1631/FITEE.1900617

摘要： We investigate cooperative target tracking of multiple unmanned aerial vehicles (UAVs) with a limited communication range. This is an integration of UAV motion control, target state estimation, and network topology control. We first present the communication topology and basic notations for , and introduce the distributed . Then, convergence and boundedness of the estimation errors using the filter are analyzed, and potential functions are proposed for communication link maintenance and collision avoidance. By taking stable target tracking into account, a distributed potential function based UAV motion controller is discussed. Since only the estimation of the target state rather than the state itself is available for UAV motion control and UAV motion can also affect the accuracy of state estimation, it is clear that the UAV motion control and target state estimation are coupled. Finally, the stability and convergence properties of the coupled system under are analyzed in detail and demonstrated by simulations.
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Induction motors variable speed drives diagnosis through rotor resistance monitoring

K. YAHIA, S. ZOUZOU, F. BENCHABANE

《能源前沿（英文）》 2012年 第6卷 第4期   页码 420-426 doi: 10.1007/s11708-012-0192-z

摘要： Induction motor driven by vector control method makes high performance control of torque and speed possible. The decoupling of flux and electromagnetic torque obtained by field orientation depends on the precision and the accuracy of the estimated states. Rotor asymmetries lead to perturbations of air gap flux patterns in induction machines. These perturbations in flux components affect the electromagnetic torque, as well as stator currents and voltages. This paper first investigates the control of the induction motor using an extended Kalman filter (EKF) for a direct field-oriented control. It then studies the broken rotor bars (BRBs) fault by the monitoring the rotor resistance. The hypothesis on which the detection is based is that the apparent rotor resistance of the motor will increase when a rotor bar breaks. The rotor resistance is estimated and compared with its nominal value to detect BRBs fault. The EKF estimates the rotor flux, speed and rotor resistance on line by using only measurements of the stator voltages and currents. Simulation results show the effectiveness of the proposed method in the cases of load torque perturbation and speed reversion.

关键词： induction motor     vector control     broken rotor bars (BRBs) diagnostic     extended Kalman filter (EKF)    

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Impact analysis of compressor rotor blades of an aircraft engine

Y B SUDHIR SASTRY, B G KIROS, F HAILU, P R BUDARAPU

《结构与土木工程前沿（英文）》 2019年 第13卷 第3期   页码 505-514 doi: 10.1007/s11709-018-0493-3

摘要： Frequent failures due to foreign particle impacts are observed in compressor blades of the interceptor fighter MIG-23 aircraft engines in the Ethiopian air force, supplied by the Dejen Aviation Industry. In this paper, we made an attempt to identify the causes of failure and hence recommend the suitable materials to withstand the foreign particle impacts. Modal and stress analysis of one of the recently failed MIG-23 gas turbine compressor blades made up of the following Aluminum based alloys: 6061-T6, 7075-T6, and 2024-T4, has been performed, apart from the impact analysis of the rotor blades hit by a granite stone. The numerical results are correlated to the practical observations. Based on the modal, stress and impact analysis and the material properties of the three considered alloys, alloy 7075-T6 has been recommended as the blade material.

关键词： axial flow compressor     rotor and stator blades     aircraft engine     stress and impact analysis     aluminum alloys    

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标题 作者 时间 类型 操作

The computational fluid dynamic modeling of downwash flow field for a six-rotor UAV

Yongjun ZHENG, Shenghui YANG, Xingxing LIU, Jie WANG, Tomas NORTON, Jian CHEN, Yu TAN

期刊论文

A total torque index for dynamic performance evaluation of a radial symmetric six-legged robot

Kejia LI, Xilun DING, Marco CECCARELL

期刊论文

Effect of UAV prewetting application during the flowering period of cotton on pesticide droplet deposition

Weixiang YAO, Xianju WANG, Yubin LAN, Ji JIN

期刊论文

Economic Growth Model Based on Six Basic Factors of Production—Xu Growth Rate Equation

Shou-bo Xu,Zong-yuan Huang

期刊论文

A novel NN based rotor flux MRAS to overcome low speed problems for rotor resistance estimation in vector

Venkadesan ARUNACHALAM,Himavathi SRINIVASAN,A. MUTHURAMALINGAM

期刊论文

Sorption and desorption of pymetrozine on six Chinese soils

Mingxing GAO,Yingying LI,Hong YANG,Yucheng GU

期刊论文

Stability and dynamics of rotor system with 45° slant crack on shaft

Yanli LIN, Xiaohui SI, Fulei CHU

期刊论文

Study on wave rotor refrigerators

Yuqiang DAI, Dapeng HU, Meixia DING

期刊论文

Optimization model for rotor blades of horizontal axis wind turbines

LIU Xiong, CHEN Yan, YE Zhiquan

期刊论文

A novel six-legged walking machine tool for

Jimu LIU, Yuan TIAN, Feng GAO

期刊论文

Multi-UAV collaborative system with a feature fast matching algorithm

Tian-miao Wang, Yi-cheng Zhang, Jian-hong Liang, Yang Chen, Chao-lei Wang,zycet@126.com

期刊论文

Structure improvement and strength finite element analysis of VHP welded rotor of 700°C USC steam turbine

Jinyuan SHI,Zhicheng DENG,Yong WANG,Yu YANG

期刊论文

Multi-UAV cooperative target tracking with bounded noise for connectivity preservation

Rui Zhou, Yu Feng, Bin Di, Jiang Zhao, Yan Hu,jzhao@buaa.edu.cn

期刊论文

Induction motors variable speed drives diagnosis through rotor resistance monitoring

K. YAHIA, S. ZOUZOU, F. BENCHABANE

期刊论文

Impact analysis of compressor rotor blades of an aircraft engine

Y B SUDHIR SASTRY, B G KIROS, F HAILU, P R BUDARAPU

期刊论文