Table of Content

29 October 2023, Volume 41 Issue 1

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Civil Aviation

Numerical study on attack angle characteristics of nacelle inlet based on airworthiness standard

BAI Jie, GUO Chongjia , FU Wenguang , SUN Peng

2023, 41(1):  1-6. 

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In order to study the effect of flow separation in the nacelle inlet caused by high attack angle of transport aircraft during climbing stage on the intake performance, the nacelle inlet of large bypass ratio turbofan engine DGEN380 is taken as the research object. The flow field at 0 °- 40 ° attack angle is simulated respectively. It is found that the low momentum fluid accumulation and flow separation in the nacelle inlet caused by the increase of attack angle are the main reasons for the total pressure distortion. The results show that with the increase of attack angle, the total pressure recovery coefficient decreases and the inlet distortion index increases. In the range of 28°-40 ° attack angle, the total pressure recovery coefficient and inlet distortion index are more sensitive to the changes of angle of attack(AOA) and Mach number due to different intensity of separation of air flow in the nacelle inlet. In this range, at the same attack angle, the greater the Mach number, the easier the separation of flow.

Research on reliability test scheme of restoration task of civil aircraft landing gear

WU Xiao, SU Maogen, PENG Chaofeng

2023, 41(1):  7-11. 

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In order to meet the requirements of airworthiness authorities concerned about the civil aircraft landing gear reli鄄 ability test, the conversion relationship between landing gear restoration task interval and corresponding failure rate is analyzed based on the fault law of civil aircraft landing gear. Then, the reliability test scheme of civil air鄄 craft landing gear based on Bayes theorem is formulated. Prior information is properly used to determine the prior distribution of product failure rate. On this basis, the improved scheme is proposed, referred to the calculated posterior distribution and the given user risk. The experimental results show that the improved scheme can re鄄 duce the required sample size and test time on the premise of meeting the requirements proposed by airworthi鄄 ness authorities, as well as maintaining the test confidence, compared with the classical statistical test scheme.

Quantitative analysis of control efficiency of arrival aircraft in terminal area

DU Shi , YAN Dan , REN Jingrui , CHU Xinyu

2023, 41(1):  12-21. 

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The flight density and complexity of aircraft in terminal area are relatively high, and the processing capacity of this controlled area is the bottleneck restricting the efficiency of aviation system. Quantitative research on the control efficiency of arrival aircraft will help to enhance the control capacity and quality. Firstly, the standard mileage of regional area navigation(RNAV) standard instrument arrival procedure is proposed as the calcula tion basis of quantifying arrival control efficiency. Through the results of clustering algorithm based on random ized search, the aircraft RNAV standard instrument arrival procedures are obtained, taking the aircraft landing at Beijing Capital International Airport as the analysis object, the arrival control efficiency of the aircraft is calcu lated. Combined with the trajectory, the operation mode and characteristics of the aircraft under different RNAV standard instrument arrival procedures are discussed. Secondly, the influence factors of arrival control efficiency are discussed, and the gray correlation analysis method is used to quantify the influence degree and weight of each factor. The results show that the degree of radar vectoring and the change numbers of the three factors of navigation have a significant impact on the arrival control efficiency, while the flight flow and the standard mileage of RNAV standard instrument arrival procedure have a relatively small impact on the arrival control effi ciency. From the perspective of influence factors, more comprehensive and objective overall arrival control effi ciency is evaluated. Finally, from two aspects of the RNAV arrival procedure path and excellent control behavior mode, the approaches and methods to improve the arrival control efficiency are explored.

A detection method for small UAVs in the strong moving clutter environment

WU Renbiao, WANG Jiangang, WANG Xiaoliang, HE Weikun

2023, 41(1):  22-29. 

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Affected by the strong moving clutter such as the civil aircraft in the airport environment, the detection probability of radar for the weak and small unmanned aerial vehicle (UAV) will decrease. A method of detecting the small UAV target by suppressing strong moving clutter is proposed to cope with the problem mentioned above. The method employs the feature that the new UAV surveillance radar can obtain long coherent pulse interval. Firstly, the strong moving clutter is detected, the spectral center compensation method based on reassigned spectrogram is adopted to accurately estimate the spectral center of the strong moving clutter and compensate its spectrum center to zero frequency position. Then, the strong moving clutter is suppressed by adaptive moving target indication filter and the weak and small UAV is further detected by the constant false alarm rate detection method. The experiment results show that the proposed method has higher target detection probability and lower error detection rate compared with current better-performanced singular value decomposition reconstruction method when the weak and small UAV target echo is disturbed by the strong moving clutter

Optimization of modulation strategy for multilevel cascaded H-bridge inverter

GAO Jianshu, LIU Letao , TIAN Yimeng

2023, 41(1):  30-34. 

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Aiming at the problem of high harmonic content and poor waveform quality in output voltage of traditional carrier amplitude shift modulation strategy of intermediate frequency inverter, the improved carrier amplitude shift sinusoidal pulse width modulation (SPWM) strategy is proposed based on the multilevel cascaded H-bridge inverter topology. In this strategy, the triangle carrier is improved on the basis of in-phase stack amplitude shift modulation. Traditional triangle wave and the line are comprised to form a combined carrier, and the intersection position of the carrier and the modulation wave is changed, so that the pulse width of the switching device is wider, which effectively reduce the total harmonic distortion (THD) value of output voltage and improve the quality of output waveform. The simulation model of cascaded H-bridge inverter is built in Simulink of Matlab, and THD value of output voltage under the control of traditional and improved modulation strategy is compared through simulation, which verifies the feasibility of the improved carrier amplitude shift modulation strategy.

Research on fault diagnosis of aircraft elevator hydraulic system based on CNN

ZHANG Peng , LI Guangdao

2023, 41(1):  35-40. 

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Aiming at the dependence of expert experience on fault diagnosis of civil aircraft hydraulic system and the degradation of deep network diagnosis model, an improved one-dimensional convolutional neural network algorithm is proposed. Firstly, the simulated fault data is directly inputted into the one-dimensional convolutional neural network, and then the residual block mechanism is used to improve the utilization of information in the convolutional layer. The squeeze and excitation network is introduced to weight the feature vectors of the convo lutional layer, so as to reduce the invalid information and achieve anti-interference effect. Then one-dimension al global average pooling layer is used to process the information of last layer to reduce the neural network parameters and diagnosis time. Finally, in order to verify the effectiveness and practicability of the proposed method, this method is tested by the fault data of the aircraft elevator hydraulic system obtained by the laboratory simulation platform, and compared with the mainstream algorithm. The experimental results show that the test set accuracy of the proposed method is as high as 99.3%. Compared with other networks, the accuracy and generalization of fault diagnosis of hydraulic system are significantly improved. With 20% noise added environment, the accuracy of the proposed network is 4.4% higher than that of the traditional convolutional network, and it has strong practicability.

Evaluation of fatigue life of asphalt overlay based on reflective crack induced by aircraft loads

SHI Chao, ZHANG Lei , TIAN Shuaituan , YAO Pengfei

2023, 41(1):  41-46. 

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Reflective crack is one of the primary pavement distresses leading to the failure of composite pavement. To study the fatigue life of asphalt overlay controlled by reflective crack induced by large aircraft, composite stress intensity factor was firstly taken as the mechanical index to establish the fatigue life prediction model of the asphalt overlay based on propagation law of reflective crack. The distribution of stress on the asphalt overlay under the critical locations of gear loads with different interface conditions was then simulated by finite element method.

Then, the regular pattern of the composite stress intensity factor was also obtained and applied to establish a formula between the fatigue life and the mechanical & geometrical parameters of different overlay structures. Finally, the formula was applied to optimize the asphalt overlay structure of the runway in a civil hub airport and the result turned out to be 6 cm SMA(stone mastic asphalt) + 9 cm AC(asphalt concrete).

Study on the snowdrift of Xialaoba interchange subgrade of G7 expressway

MUHADEER Yeermulati

2023, 41(1):  47-52. 

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In order to understand the snowdrift characteristics on the subgrade of expressway interchange sections and provide a theoretical basis for future snow fence setting, wind information and snow distribution characteristics of Xialaoba interchange subgrade, which is a section of newly built Jingxin expressway (G7) from Barkol to Mori, were analyzed using wind field monitoring, on-site snow investigation and numerical simulation methods. The wind field monitoring system showed that the wind direction of Xiahaoba interchange area was unstable and the dominant wind direction in this area was northwest wind. Numerical simulation results showed that the height and distance difference between the adjacent two ramps of the subgrade in the interchange section affected the wind speed and snow distribution on downwind subgrade. Under two conditions of 10 m distance and 2 m height difference or 50 m distance and 7 m height difference between adjacent two ramps, the wind velocity of downwind subgrade has decreased about 35% and 53% respectively, while the snow on subgrade increased 14.0% and 18.5%. Accumulated snow survey showed that the snow cover law on the ramp was consistent with the numerical simulation results. Snow prevention facilities should be reasonably arranged outside the interchange according to the snow on the downwind ramp.

Fault self-repair method of modular robot based on reinforcement learning algorithm

Guan Enguang , Wang Yao , Cao Jiabin, Zhao Yanzheng

2023, 41(1):  52-57. 

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A fault self-repair method based on reinforcement learning algorithm is proposed for the robust design issue of lattice modular robot. The method transforms the self-repair process with the goal of filling empty spaces into a self-reconfiguration process by means of the movements of meta-modules containing empty nodes. Based on the reinforcement learning algorithm, a discrete path planning for the movement of empty nodes is proposed, and the empty nodes are accordingly guided to travel through the system. The simulation test results show that the effectiveness of this fault self-repair method is verified on the lattice modular robotic system and can be widely applied to other isomorphic modular robotic systems

Research on the coordination level evaluation of regional general aviation emergency rescue

GAO Jinmin , LE Meilong

2023, 41(1):  58-64. 

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In order to objectively evaluate the coordination level of regional general aviation rescue, a comprehensive evaluation index system is constructed from five aspects: emergency management, emergency goals, emergency processes, emergency information, and emergency resources. The interval analytic hierarchy process (IAHP) and the multi -level fuzzy comprehensive evaluation method are applied comprehensively to evaluate the coordination level of regional general aviation rescue. Finally, the constructed evaluation system is verified by taking the region of Yangtze River Delta as an example. The comprehensive evaluation results and the evaluation results of each subsystem show that the model and method proposed in the study can better reflect the current coordination situation of regional general aviation emergency rescue, and have a good feasibility and practicality. The research conclusions can provide decision-making basis for cross-regional emergency rescue activities in various regions.