Journal of Civil Aviation University of China

Interference impact on Beidou signal reception performance#br#

LIU Ruihua, WANG Jing

2019, 37(3): 1-4.

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Once the Beidou satellite receiving signal is interfered, its receiving performance will be greatly affected, even make it unable to astare signal. Based on equivalent carrier-to-noise ratio, a evaluation method of the signal reception performance of Beidou is presented, the influence of interference on reception performance of Beidou signal is studied, the relation between relevant evaluation parameters and the equivalent carrier-to-noise ratio and its calculation method are analyzed. Finally, through Matlab simulation, relation among the signal reception performance, the equivalent carrier-to-noise ratio and the pre-detection integration time are obtained. Comparison
results show that the greater the interference power is, the closer the center frequency of interference is to the center of the signal band, the smaller the equivalent carrier-to-noise ratio becomes, the poorer the signal is reception performance; under the same interference conditions, increasing the pre-detection integration time of the carrier tracking loop can reduce the influence of interference on the signal reception performance of Beidou.

Design and realization of satellite-based ADS-B signal simulation and display system#br#

HU Tieqiao, LI Yangbo, ZHANG Lulu

2019, 37(3): 5-10.

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Comparing with ground-based ADS-B, satellite-based ADS-B has the advantages of wider coverage and lower cost but the disadvantages of lower signal power and larger Doppler frequency shift. Through simulation of fourantenna satellite and target trajectory, satellite-based ADS-B signal power and its Doppler frequency shift are calculated. The corresponding software system is developed, which can simulate the Doppler frequency shift and signal power received from target, realizing display of satellite coverage, background map and target trajectory, as well as the digital communication with slave computer.

Departure aircraft altitude profile prediction based on aircraft mass estimation strategy#br#

KANG Nan, HAN Xiaolan, HU Yang, WEI Zhiqiang

2019, 37(3): 11-16.

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The aircraft weight cannot be obtained directly from departure aircraft altitude profile prediction, and thus the precision accuracy is affected. Aiming at this problem, the aircraft weight estimation model and the altitude profile prediction model based on the real-time track data are established. Using the actual departure trajectory of B737-800 recorded by SSR, the aircrafts’ weight and profile is predicted in real time from 500 m above the ground according to the historical track data at each time. Then the vertical track of follow -up departure is predicted and compared with the actual trajectory to analyze the prediction accuracy of departure time and flight distance. Results show that higher prediction accuracy of aircraft weight can be achieved with trajectory parameters on higher flight altitudes. If the weight estimation is started on and above 3 500 m, the subsequent error can be maintained within 5%

Precise altitude measuring method of flight-inspecting UAV based on fault-tolerant Kalman filter#br#

HU Dandan, GU Yuan, GAO Qingji

2019, 37(3): 17-21.

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In UAV fixed-point flight verification, the real-time height measurement accuracy determines the angle verification error of PAPI (precision approach path indicator). Aiming at the large information error of fusion height caused by signal mutation of rotor UAV multi-airborne height sensor, a precise height measuring method based on FTKFT (fault-tolerant Kalman filter) is proposed consisting of a main Kalman filter and three sub-filters (GPS/barometric altimeter/radar altimeter). Each height sensor is filtered by Kalman filter， calculating the height estimation and the error as detecting signal and the second-order integration of inertial navigation in short time as reference signal， conducting state Chi-square test and residual Chi-square test with error detector. Finally， optimal data fusion of multi height sensors basing on output error of each height sensor is realized with weighting.Simulation and flight experiment show that this method is capable to achieve the expected measuring accuracy and real-time fault-tolerant performance.

Airport pavement performance prediction based on Gray-Markov model#br#

DU Hao, YANG Ge, LIU Hailun

2019, 37(3): 22-26.

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Aiming at the lack of airport pavement original data and its stochastic variability, a new method that integrates Gray model and Markov chain is presented and is described in details by instance. Firstly, a GM (1, 1) model is built to conduct short-term PCI prediction and to expand the dataset. Secondly, least-square method is applied based on the expanded dataset to derive Markov state transition probability matrix. Using this matrix, middle and long term pavement performance is predicted by Markov chain. Thirdly, the precision sensitivity is analyzed,proving the high precision of this integrated model with big variability and sample data. This method can be used as an effective tool for airport pavement performance prediction.

Comparison of runway roughness evaluation methods under measured unevenness excitation#br#

LING Yingqi, LIU Shifu, LIN Sheng, WU Lei, BIN Xueyang

2019, 37(3): 27-32.

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In the latest version of runway evaluation, the evaluation index of runway roughness is revised as IRI and BBI without their adaptability. Currently, few studies focus on the actual application effect of these two methods. The comparison and analysis process of runway roughness evaluation methods based on Matlab is proposed, taking measured 3D roughness data of a certain airport runway in East China as instance, the relation between IRI and BBI indices and the dynamic responding characteristics of aircraft taxiing is explored in a multi-dimensional way. Results show that the correlation between BBI and IRI is poor, and the overall correlation coefficient is only about 0.1. From the prediction of aircraft acceleration RMS distribution trend, BBI is more capable than IRI by 3.6 times. It is suggested that in the latest version of the specification considers BBI as main evaluation index and IRI as auxiliary index. In the region with poor roughness, a more scientific and reasonable maintenance decision should be made by taking both of them into comprehensive consideration.

Landing gear load simulation of towbarless traction system on uneven road#br#

WANG Liwen, LIU Bing , SUN Yankun , ZHANG Wei

2019, 37(3): 33-37.

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Taking one C type aircraft as research target, the model of aircraft-towbarless tractor is established based on SolidWorks and Adams in order to study the load margin of towbarless wheel holding device Two kinds of uneven road models are summarized basing on theretical analysis. Dynamic simulation is carried out on the process of a towed tractor with a traction speed (5 km/h) based on dynamic theory analysis. The load of nose landing gear pillar is measured on uneven road; the maximum peak load is taken as load margin of the wheel lifting device. Simulation results show that the load of nose landing gear pillar increases with the depth enlargement of the pit or bulge, and the load curve firstly increases and then decreases with the width increase of the pit or bulge,then slowly increases, the load curve slowly changes with the width increase.

CFIT risk caused by human errors#br#

WANG Jiening, ZHONG Bin

2019, 37(3): 38-43.

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CFIT is one of the main types of civil aviation accidents. Aiming at CFIT risk during approaching and landing procedures, a system dynamics model is introduced to study the impact of human errors on CFIT. Cause-effect diagram is used to demonstrate the risk factors of CFIT and their interactive relations. Constructing the system dynamics model and simulating the change of the event chain, the risk value is obtained. By controlling variables like the pilots’ monthly average flight sorties, irregularities, etc, we observed the impact of each input scheme on the risk of CFIT. Results shows that pilot fatigue and routine violations have the greatest impact on the risk of
CFIT. Besides, it is verified feasibly to study safety risk by system dynamics in a given relationship, which not only reduces the complexity of risk assessment, but also provides a new approach for decision -making management to improve safety.

Application of distributed clustering algorithm in subdivision of airline ticket sales agents#br#

FAN Wei, ZHANG Wei

2019, 37(3): 44-48.

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In order to rapidly analyze the role of airline agents in ticket sales market and make corresponding cooperation plan as well as sales plan for different types of agents, aiming at the subjectivity of traditional classification methods and the difficulty of centralized system framework in massive data clustering and analyses, distributed Canopy-K-means algorithm is proposed in airline agents clustering, combining clustering results with actual market situation to obtain the agent’s role in market. Experimental results show that the final clustering result is in line with the actual evaluation results of relevant agents, and has practical significance. Finally, according to the clustering results, feasible suggestions for airlines are provided, helping airlines to manage sales agents.

Abnormal crowd event detection and event source localization algorithm#br#

LI Haifeng, JIANG Zizheng, FAN Longfei, CHEN Xinwei

2019, 37(3): 49-53.

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To improve the detection accuracy, an abnormal crowd event detection and localization method is proposed. This algorithm includes two phases: abnormal crowd event detection and event source localization. In the first phase,an algorithm combining with space and time is proposed. From the spatial perspective, the average kinetic energy distribution histogram is extracted to describe the crowd movement characteristics, and SVM classifier is used to classify the crowd movement characteristics; From the time perspective, the hidden Markov model is built to detect continuous crowd behaviors in the scene. In the second phase, under the framework of RANSAC, the event source location is realized by calculating the intersection point of the reverse extension line of abnormal behavior crowd movement, where the multiple event sources can be labeled simultaneously. Experimental results on UMN benchmarks show that this algorithm can effectively detect crowd anomaly behavior, and the value of AUC is 0.967, respectively increases by 0.127, 0.074 and 0.007 compared with traditional optical flow method,SIFT point detection method and social force method. Furthermore, this algorithm successfully localizes the event sources.

Sensor fault detection based on sliding mode observer#br#

TAO Liquan, LIU Cheng, WANG Wei, WANG Qian

2019, 37(3): 54-59.

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Aiming at the missing detection and erroneous detection in fault detection, a method based on residual and fault estimation is proposed. Firstly, with the application of Schur complementary lemma, the method of sliding-mode observer gain matrix is transformed into a multi-objective convex optimization problem under the restrict of LMI,and a reasonable gain is designed to solve the robustness problem. Secondly, according to the residual randomness, statistical theory is introduced to determine the fault detection threshold, which makes the fault detection results more credible. Then, in order to reduce missing detection and erroneous detection, the sliding mode observer is designed to generate the residual and realize the first fault detection, the fault estimation is conducted by equivalent output injection theory to realize the second fault detection. Finally, simulation instance proves the effectiveness of the proposed methods.

Carbon fiber fracture recognition based on electrical resistance method#br#

LU Xiang, ZHAO Zhenyao, LIN Yueguo, JIA Baohui

2019, 37(3): 60-64.

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Electrical resistance method is used to identify the internal fiber fracture of CFRP under tension. A preliminary theoretical exploration is carried out to realize on-line health monitoring on aircraft composite structure. Energized tension test and finite element simulation are conducted aiming at the unidirectional laminate [0]8 of T800 carbon fiber. It is proven that the electrical resistance method can soundly reflect fiber fracture. The judging standard of T800 fiber fracture by electrical resistance method is given: before resistance changing rate ΔR/R0 reaches 0.25, only fiber elastically deformation occurs; when ΔR/R0 reaches 0.25, fiber breaks; when ΔR/R0 reaches 3.5, the serious fiber damage occurs.

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