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Study of velocity effects on parachute inflation performance based on fluid-structure interaction method

Applied Mathematics and Mechanics(English Edition) 2014年第9期35卷 1177-1188页

作者：程涵张鑫华余莉陈猛 College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics Aviation Key Laboratory of Science and Technology on Aeronautical Life-Support AVIC Aerospace Life-Support Industries Ltd.

The inflation of a five-ring cone parachute with the airflow velocity of 18 m/s is studied based on the simplified arbitrary Lagrange Euler （SALE）/fluid-structure interaction （FSI） method. The numerical results of the canopy shape, stability, opening load, and drag area are obtained, and they are well consistent with the experimental data gained from wind tunnel tests. The method is then used to simulate the opening process under different velocities. It is found that the first load shock affected by the velocity often occurs at the end of the initial inflation stage. For the first time, the phenomena that the inflation distance proportion coefficient increases and the dynamic load coefficient decreases, respectively, with the increase in the velocity are revealed. The above proposed method is competent to solve the large deformation problem without empirial coefficients, and can collect more space-time details of fluid-structure-motion information when it is compared with the traditional method.

关键词： fluid-structure interaction （FSI） parachute inflation performance velocity,empirical coefficient opening shock load

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Measuring Center of Gravity of Pilot Helmet Based on Binocular Vision 4

Measuring Center of Gravity of Pilot Helmet Based on Binocul...

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4th International Conference on Advances in Computer technology, Information science and Communications, CTISC 2022

作者： Jun, Li Xie, Wujun Wan, Chuanqi Jia, Zixiao Yang, Junwei Avic Aerospace Life-Support Industries LTD. Aviation Key Laboratory of Science and Technology on Life-Support Technology Xiangyang China

ISBN: (数字)9781665458726

ISBN: (纸本)9781665458726

A variety of functions are integrated into the pilot helmet, making it an intelligent weapon platform for pilots to improve situational awareness and target attacks capabilities. However, the mass distribution of the helmet has also been changed, which has a negative impact on the pilot's health and safety. Accurate measurement of the Center of Gravity (CG) of pilot helmet is of great significance for the ergonomic design. Benefiting from the rapid development of 3D computer vision technology, a 3D coordinate of CG measurement scheme for pilot helmet based on binocular vision is proposed by adopting suspension method. The measuring equipment and program are introduced in detail, and the calculation model for the center of gravity is also established. The calibration results show that the proposed measurement scheme based on binocular vision is effective. © 2022 IEEE.

关键词： Binocular vision

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A Novel Cooperative MIMO Transmission Scheme Based on STBC for Event-Driven WSNs 3

A Novel Cooperative MIMO Transmission Scheme Based on STBC f...

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3rd IEEE International Conference on Electronics technology, ICET 2020

作者： Jun, Li Wujun, Xie AVIC Aerospace Life-support Industries LTD. Aviation Key Laboratory of Science and Technology on Life-support Technology Xiangyang China

ISBN: (纸本)9781728162836

The cooperative MIMO (CMIMO) technology having characteristics of low energy expended and high reliability can be very well suited to resource-constrained event-driven wireless sensor networks (WSNs), in which collecting date is unpredictable for space and time. A novel energy-efficient STBC-based CMIMO transmission scheme is put forward for event-driven WSNs in this letter, which adopts cross-layer design and dynamic event cluster. Detailed energy models are developed to maximize energy saving by the joint optimization for the number of cooperative nodes and constellation size. Through computer simulation, It can be found that the novel transmission scheme saves more energy in comparison with the traditional transmission protocol. © 2020 IEEE.

关键词： Wireless sensor networks

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Research on High Precision Measurement of Head Position and Posture

Research on High Precision Measurement of Head Position and ...

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2022 CSAA/IET International Conference on Aircraft Utility Systems, AUS 2022

作者： Luo, Guoxiong Liu, Xiang Gao, Hongyi Jin, Zhisheng Xie, Wujun Cui, Wenming Aviation Key Laboratory of Science and Technology on Life-support Technology Hubei Xiangyang China AVIC Aerospace Life-support Industries Ltd. Hubei Xiangyang China

ISBN: (数字)9781839537769

ISBN: (纸本)9781839537769

For the safety of pilots, it is necessary to explore the change process of ATD head spatial position and posture in the dynamic impact test of driver's seat. Therefore, a comprehensive position and posture solution method was proposed, which mainly including bundle adjustment method, forward intersection method and feature line projection method. This method achieves the high precision of the ATD head position and posture measurement requirements, and its measurement accuracy reaches the level of mm and degree respectively. © 2022 IET Conference Proceedings. All rights reserved.

关键词： attitude measurement biomechanics CCD image sensors computer vision impact testing position control position measurement vehicle dynamics

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Research on measurement method of six degree of freedom for head based on safetr of aircraft pilot seat

Research on measurement method of six degree of freedom for ...

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CSAA/IET International Conference on Aircraft Utility Systems 2020, AUS 2020

作者： Luo, Guo-Xiong Jin, Zhi-Sheng Xie, Wu-Jun Wang, Ru-Bing Aviation Key Laboratory of Science and Technology on Life-Support Technology Hubei Xiangyang China AVIC Aerospace Life-Support Industries Ltd. Hubei Xiangyang China

ISBN: (纸本)9781839535635

In order to ensure the safety of the pilot's life, the six degree of freedom data of the ATD head need to be obtained through dynamic impact test to evaluate the possibility of head injury in the cockpit. A binocular photogrammetry method by the simplified solution of normal equation based on bundle adjustment was proposed. On the basis of satisfying the imaging requirements of high-speed cameras, the 3D position and posture data of the head were obtained by shooting and analyzing the images of the test process. © 2020 Institution of Engineering and technology. All rights reserved.

关键词： Degrees of freedom (mechanics)

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Research on intelligent control technology for enhancing precision airdrop system autonomy 4

Research on intelligent control technology for enhancing pre...

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4th International Conference on Machine Learning and Computer Application, ICMLCA 2023

作者： Xu, Ronghua Yu, Gang Aerospace Life-Support Industries Ltd. Xiangyang China Aviation Key Laboratory of Science and Technology on Life-Support Technology Xiangyang China Hubei University of Arts and Science Xiangyang China

ISBN: (数字)9781510680265

ISBN: (纸本)9781510680258

The Precision Airdrop System (PADS) is widely used in the accurate recovery of spacecrafts and the precision delivery of supplies. The accuracy of control is the core of the PADS achieving the precision airdrop. To enhance control accuracy, an intelligent control technology for enhancing PADS autonomy based on simulation environment is developed. The dynamic model employed to calculate the PADS state is a 6-degree-of-freedom (6-DOF) model, and the reinforcement learning control training method is based on the A-C architecture. Through analysis of simulation results in both windless and windy environments, it is evident that the reinforcement learning control strategy based on the AC architecture outperforms the traditional PID strategy. The analysis highlights the challenges posed by wind in achieving precise control and presents an effective approach for enhancing PADS autonomy through intelligent control. © 2024 SPIE.

关键词： Intelligent control

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A hybrid piecewise FDD strategy for refrigeration charge fault of airborne vapor-compression cycle system

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INTERNATIONAL JOURNAL OF REFRIGERATION 2022年 135卷 164-173页

作者： Sun, Chengbin Wang, Hexu Jiang, Yanlong Gao, Zanjun Wang, Ju [a]Key Laboratory of Aircraft Environment Control and Life Support MIIT Nanjing University of Aeronautics and Astronautics 29 Yudao St. Nanjing 210016 China [b]Aviation Key Laboratory of Science and Technology on Aero Electromechanical System Integration Nanjing 211106 China

Many researchers have carried out study on refrigerant charge fault for variable refrigerant flow (VRF) airconditioning system, while few pay attention to refrigerant charge fault for vapor-compression refrigerant cycle system (VCS) of enhanced vapor injection (EVI) with a flash tank onboard. To develop a strategy for refrigerant charge fault of the above system, the optimization methods have been implemented to predict the refrigerant charge level (RCL) based on virtual refrigerant charge (VRC) models. Firstly, Pearson correlation coefficient analysis is employed to obtain the characteristic parameters. Secondly, a piecewise modified VRC model with the different characteristic parameters from VRC models is obtained for two cases of RCL < 75% and RCL > 75%. Meanwhile, combined with the principal component analysis (PCA) and the support vector machine (SVM) algorithm, a PCA-SVM model is developed to improve the prediction accuracy, and the average root mean squared error (RMSE) is only 7.8 compared to 14.9 of the modified VRC model when RCL > 75%, meanwhile, the correctly detected ratio is improved from 62.8% to 84.5%. Then, for solving the difficulty of fault detection and diagnosis (FDD) when RCL > 160%, the moving time window average (MA) algorithm is introduced and an online PCA-MA-SVM model is developed. Finally, a hybrid piecewise FDD strategy combined with three models for refrigeration charge fault in airborne VCS of EVI with a flash tank is obtained.

关键词： Vapor-compression refrigeration cycle system Enhanced vapor injection Refrigerant charge fault support vector machine Moving time window average

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RESEARCH ON AIRSPEED CORRECTION technologyOFEJECTION SEAT BASED ON CFD 34th

RESEARCH ON AIRSPEED CORRECTION TECHNOLOGYOFEJECTION SEAT BA...

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34th Congress of the International Council of the Aeronautical sciences, ICAS 2024

作者： Jin, Lou Feng, Guanghui Wu, Liang Aviation Key Laboratory of Science and Technology on Life-support Technology Xianyang441000 China Overall Technology R&D Department AVIC Aerospace Life-support Industries Ltd Xianyang441000 China

A certain ejection seat airspeed sensing system is located in the wake flow field of the seat, andtheperceived static pressure will produce a large error from the local standard static pressure, requiringaerodynamic corrections to the sensed static pressure to ensure the accuracy of the measured velocityandaltitude parameters. In this paper, a technique to correct the static pressure of ejection seats duringejectionfrom the cabin is proposed, which combines CFD simulation and successive iterative approximationalgorithm. CFD simulation method was used to simulate the dynamic flow field during the seat egressfromcabin, and the total and static pressure data measured by the pitot tube sensing systemat ejectionvelocitybelow 3 Ma were analyzed. The total and static pressure values at different ejection speeds werecalculatedwith the principle of "total pressure taking the maximum and static pressure taking the minimum", andtherelationship curves of the static pressure correction coefficient with ejection velocity were obtained. Asuccessive iterative approximation algorithm was used to correct the measured static pressure basedontherelationship between the static pressure correction coefficient and the ejection velocity (Mach number). Thecalculation results show that the maximum error of perceived total pressure and static pressuresimulationvalues with test values is 2.5% at different speeds, and the maximum error of felt static pressuresimulationis 1.9%. The CFD simulation accuracy is high, and the simulation results can be used as input foraerodynamic correction. When the ejection velocity is less than Mach 3, the static pressurecorrectioncoefficient decreases monotonically with the ejection velocity increasing, and the successiveiterativeapproximation calculation converges. The maximum error between the static pressure correctionvaluecalculated by the successive iterative approximation algorithm and the static pressure at the test siteis3.8%, and the maximum error betwe

关键词： Ejection seats

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Time-Frequency Characteristics of Parachute Gun Shockwave Based on VMD-HT 8

Time-Frequency Characteristics of Parachute Gun Shockwave Ba...

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8th International Conference on Communication, Image and Signal Processing, CCISP 2023

作者： Li, Jun Xie, Wujun Li, Hui Fang, Liyi AVIC Aerospace Life-support Industries LTD Key Laboratory of Science and Technology on Life-support Technology Xiangyang Hubei China

ISBN: (纸本)9798350305838

During the ejection process of the fighter pilot, the parachute is shot out by the life-saving seat gun, which generates a shockwave that endangers human safety. In order to accurately and stably extract the time-frequency distribution characteristics, the shockwave signal is obtained through parachute gun shooting experiments, and features of the shockwave signal is extracted by using Variational mode decomposition and Hilbert transform methods (VMD-HT). VMD is a high sampling rate shockwave signal decomposition technique, which is suitable for analysing unsteady airborne parachute gun shooting shockwave signals. The HT method is used to accurately extract the relationship between time, instantaneous frequency and energy for the decomposed signal, and to obtain the marginal spectra. The analytic results show that the shockwave signal lasting 3ms has a significant energy concentration in the low frequency band of 0∽1kHz, which is important for the better protection of pilots. © 2023 IEEE.

关键词： Variational mode decomposition

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Comparison of impulse noise energy distribution from two generations of parachute gun 2

Comparison of impulse noise energy distribution from two gen...

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2023 2nd International Conference on Acoustics, Fluid Mechanics and Engineering, AFME 2023

作者： Li, Jun Xie, Wujun Li, Hui Huang, Guangjun Key Laboratory of Science and Technology on Life-support Technology AVIC Aerospace Life-support Industries Ltd Hubei Xiangyang441100 China

The rocket ejection seat is an advanced life-saving device for fighter pilots. However, it can also produce damaging impulse noise during ejection, which could compromise the pilot's hearing health, and the manufacturer must assess the noise damage. This study uses Variational Mode Decomposition (VMD) and Hilbert-Huang transform (HHT) to analyze energy-instantaneous distribution over time and frequency-instantaneous and energy contribution of different modes of impulse noise generated by the parachute gun in two generations of rocket ejection seats. The results demonstrate considerable disparities in the energy distribution of impulse noise generated by the parachute gun in the new generation seat compared to the old generation seat. The new generation seat has higher overall energy, more concentrated action time, and a higher energy contribution in the 1-10 kHz frequency range. These findings provide valuable data for the design of the new generation of noise protection equipment for pilots. © Published under licence by IOP Publishing Ltd.

关键词： Mathematical transformations

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