Journal of Civil Aviation University of China

Research on change point detection and recognition of aircraft trajectory

SU Zhigang, LI Zhiqiang, HAO Jingtang

2017, 35(4): 1-6.

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Effective division of aircraft flight phase is an important technical measure of supporting active monitoring of aviation emission, which can be realized via change point detection and recognition. According to the characteristics of multivariate T²statistics, under the assumption of variance consistency of overall data parameters, a method with sequential double sliding window is proposed for detecting and estimating the change points. Simulation and experimental results show that the proposed method is more sensitive to the size of the window, change point detecting problem of trajectory can be effectively solved with well selected window length. According to the characteristics of aircraft trajectory, the proposed method is validated effective under the premise of appropriate window length.

FPGA implementation of matrix inversion based on configurable Cholesky decomposition

HU Tieqiao, ZHANG Maomao, LI Yangbo

2017, 35(4): 7-10,15.

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As a simple and effective interference suppression algorithm, power inversion algorithm is widely used in various array signalprocessing algorithms. The keyofthe algorithmisto find the inverse matrix of corresponding covariance matrix. Given the high speed of FPGA, array signal anti-jamming processing algorithm is mostly accomplished by FPGA at present. In order to realize the commonly used system of array signal anti-jamming system, a Cholesky matrix decomposition based on FPGA is designed, which can be applied to the inversion of 3~8 positive definite Hermitian matrixes. Test results show that this algorithm can save hardware resource without affecting calculation precision.

Coverage analysis on ADS-B station based on measured data

BAI Yujun

2017, 35(4): 11-15.

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According to the factors such as topography, earth curvature, headspace blind zone and equipment performance,theoretical coverage of ADS-B ground station is calculated. Based on ADS-B data, Lambert projection method is used to project the generation algorithm of concave hull. Based on measured data, the coverage of ADS-B under different layers of height is calculated. An ADS-B continuity calculation method is proposed to calculate the leakage rate and continuity level. Results show that the proposed method can provide theoretical maximum coverage under the influence of terrain shelter and can be used to assist ADS-B ground station's location decision.

Experimental analysis on bending strength and uniaxial compression strength of glaze ice

YANG Kun, ZHAI Biyao, JI Shunying

2017, 35(4): 16-20.

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Aircraft icing is a significant hazard requiring extra attention in winter, and the shed ice can cause engine damage if it impacts an engine surface with enough mass and velocity. Glaze ice is more susceptible to aerodynamic forces that result in shedding. The experimental analysis of bending strength and uniaxial compression strength for glaze ice helps to analyze the ice shedding from the blade. Thus, the ice sample is generated with spraying to simulate the ice buildup on the engine blade during icing environment encounter. A compression test instrument is designed to measure the compression strength of glaze ice. A linear function is established between temperature and compression strength based on experimental data. The current experimental study can be applied for the analysis of mechanical properties of glaze ice and help to evaluate any engine compressor damage that results from ice shedding.

Numerical study of new thermal protection structure on turbine blade

ZHOU Feng

2017, 35(4): 21-24.

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According to front-line feedback, turbine blade erosion is increasing, bringing huge pressure to the maintenance and operation of airlines. The root cause of blade ablation is that the traditional cooling structure cannot meet the needs of gas temperature rise. A new type of slit cooling structure is proposed and its structure cooling effect is verified through numerical calculation on both cooling efficiency and pneumatic loss. Results show that in appropriate range of blowing ratio, the seam type structure makes obvious uniform cooling effect in both spanwise and extending direction of blade. It significantly reduces thermal stress generated by uneven cooling on blade surface, so the extent of blade ablation is reduced and the service life of blade is extended. Simultaneously the seam structure is also superior to traditional structure in the pressure loss, cleaning and maintenance.

Ground pressure distribution of B737 main landing gear tire

LIAO Zhigao, YUAN Jie, LEI Xiaoping, SHI Enhui, LIU Shifu

2017, 35(4): 25-30,40.

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Aircraft load is generally assumed as uniform distribution in airport pavement structure response simulation, but ground pressure of aircraft tire is obviously non-uniformly distributed. An image analysis method is developed based on pressure sensitive paper, and is applied to B737- 800 main landing gear tire static ground pressure distribution measurement under different pressure and load conditions. Results indicate that there is a linear relation between effective ground area and load; pressure distribution on cross section is more similar to concave type; on vertical section it is more similar to bell-type; under the same tire pressure, high pressure section would move outward, therefore ground pressure distribution could be convex type under high tire pressure and low load.

Research on calculation method of effective width of aircraft tire loads on asphalt pavement

SHI Xingna, WANG Yadong

2017, 35(4): 31-35.

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The effective width of aircraft tire loads at the top of subgrade has a significant effect on calculating the load repetitions in designing an airport asphalt pavement. The relationship between the effective width of aircraft tire loads and subgrade strength, equivalent surface thickness is researched basing on a single wheel by ANSYS. For a complex main gear, multiple tires will lead to load interaction. How to approach the effect of load interaction on effective width of tire loads of complex main gear is also discussed. According to these analyses, calculation method of tire loads‘effective width of complex main gear is achieved.

Crashworthiness simulation analysis and evaluation of wide-body aircraft fuselage section

ZHANG Xiaomin, MA Congyao, HUO Yujia, MOU Haolei

2017, 35(4): 36-40.

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For the requirements of crashworthiness design, verification and certification of wide-body aircraft, different failure modes of fuselage sections are analyzed. Finite element model of double decks wide-body aircraft fuselage section is developed and the dynamic responses of wide-body fuselage section subjected to vertical impact velocity of 9.14 m/s are analyzed. The failure modes, acceleration responses and energy -absorbing characteristics are obtained and analyzed. Simulation results show that the cabins of wide-body aircrafts are well maintained for the two different cases, and the acceleration responses of junctions between seats and floor are within the limits of human tolerance. The energy absorbed by the same fuselage structures are different for two cases, the energy-absorbing capability of cargo floor structures can be improved by optimizing design, and thus the wide-body aircraft crashworthiness performance can be enhanced, which has a certain reference value for crashworthiness design, analysis and evaluation of wide-body aircraft fuselage section.

Temperature control system simulation of bridge air conditioning based on single neuron PID

LIN Jiaquan, LI Bo

2017, 35(4): 41-45.

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During the process of using bridge air conditioning instead of airborne APU, controlling of bridge air conditioning has become the focus of operation and management. By modeling the bridge air conditioning, temperature control system transfer function is established. In order to improve the accuracy of the temperature control, an improved single neuron PID controller combined with the traditional PID control method is taken. And on the basis of single neuron, the weight and K value are improved, and the S function is written to establish the Simulink model of controlled system. Matlab is used to simulate the temperature control system of bridge air conditioning system, and the control effect of traditional PID and the improved single neuron PID are compared. Simulation results
show that the improved algorithm can effectively improve the speed and stability of bridge air conditioning system, and has good application prospect.

Task assignment of electric and fuel special vehicles based on decision tree

FEI Chunguo, SHANG Dexuan

2017, 35(4): 46-50.

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One of the main reasons of flight delay is the failure of airport ground vehicle allocation. With the airport ground special vehicle change from oil-driven to electricity-driven, electric vehicles and charging pile will be introduced, and the electric vehicle assignment and scheduling process will face new problems. In early stage of the introduction of electric vehicles, it is necessary to study a new scheme to solve the problem of task allocation under the coexistence of special oil vehicles and special electricity vehicles. The ID3 decision tree algorithm of two kinds of special vehicle state data are analyzed and summarized, and decision tree is constructed to generate decision rules set as well as decision model of task allocation for two kinds of characteristics of the vehicle. Results show that the proposed method can effectively and accurately solve the task assignment problem of special vehicles. Compared with the traditional methods, this method can effectively reduce the errors caused by human factors and improve the operation efficiency of special vehicles.

Design of low-voltage current reference circuit in RF front-end with high electromagnetic interference immunity

BAI Huixin, MA Zhenyang, WANG Zhiwu, YANG Ke, ZENG Peipei

2017, 35(4): 51-53,61.

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Based on CMOS bulk-driven structure, a low-voltage current reference circuit with high electromagnetic interference (EMI)immunity is proposed, improving the reliability of RF front-end receiver circuit in primary surveillance radar. In the circuit, bulk-driven structure realizes low-voltage supply and sensitive isolation structure improves EMI immunity. The design is implemented in a 0.35 μm standard CMOS process using 1V power supply. Theoretical analysis and simulation results for EMI robustness are presented and compared with the classical bulk-driven structure. Results show that the current shift of the proposed design is less than 0.3 μA when a 3 times of EMI referred to the reference current is presented in the input.

Human factor analyses on dispatch based on AHP

TAN Zhaoyang

2017, 35(4): 54-57.

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In order to further reduce the rate of aviation accidents caused by human factors during dispatch, AHP(analytic hierarchy process)is used to analyze the human factors on dispatch. The weight of personal, organizational and environmental factors are obtained, and the effective evaluation model of human factors on dispatchers is set up.Among human factors during dispatch, the dispatch qualification is the most important one; workload of dispatchers, establishment of system and association are the following ones; self-efficacy of dispatchers, work environment and management efficiency are thirdly important factors; social environment, teamwork and organizational climate impact are relatively weaker factors. According to the evaluation results, effective prevention measures of aviation accidents caused by human factors on dispatch are further put forward.

Study on delay cost of block time in China

WU Yongyan, YU Haiyang, HU Huaqing

2017, 35(4): 58-62.

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Since air delay is a current hotspot of social concern, it is necessary to accurately estimate flight delays and loss based on air traffic data. Logarithmic model is used to fit the relationship between speed and distance and the trend of flight time in China is drawn. With the relationship between speed and distance in 2005, flight delays of airlines, passengers, cargoes and mails are estimated. Based on the unit value of time-related activities, the flight delay cost is estimated. The delay costs of passengers, cargoes and mails, and airlines are respectively ￥2.20 billion, ￥1.15 billion and ￥23.60 billion in 2015.

Research on airport rescue resource scheduling based on dynamic programming

WANG Yuanzhuo, ZHENG Jiao

2017, 35(4): 62-64.

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