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2021, 41(1): .

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2021, 41(1): .

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Overview of Big Data and Cloud Control Technologies in the Field of Unmanned Ground Vehicles

NI Jun, JIANG Xu, XIONG Zhoubing, ZHOU Bo

2021, 41(1): 1-8. doi:10.15918/j.tbit1001-0645.2020.068

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Abstract:
Unmanned ground vehicles(UGVs) refer to the vehicles that have full autonomous ability and replace humans to perform specific tasks. UGVs are supposed to be widely applied in the military and civilian fields,as well as making great contributions to the national defense and automotive industry. In recent years,the cloud control and big data technologies have provided new driving force for the development of various fields,and have become key technologies to promote the construction of intelligent transportation system and smart cities. In this paper,the development of big data and cloud control technologies and their application status in the vehicle field were reviewed first. Taking the series of multifunctional UGVs as an example,the development of typical UGVs and the research overview of key technologies were introduced. The application prospects of UGVs in military,logistics,patrol,transportation and other defense and civil fields were described. Based on the cloud control center of the UGVs developed by the team,the application prospect of cloud control and big data technologies in the field of UGVs was expected and its role in promoting the industrial application of UGVs was described.

A Modified Schnerr-Sauer Cavitation Model with Local Flow Properties

HU Jun, HOU Xiayi, YU Yong

2021, 41(1): 9-15. doi:10.15918/j.tbit1001-0645.2019.272

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Abstract:
In order to eliminate artificial choosing empirical parameters' influence on numerical simulation, the Schnerr-Sauer cavitation model, considering the effect of non-condensable gas, was modified based on the local flow properties. Choosing Mixture multiphase model and Realizablek-εturbulence model, the numerical simulation was carried out for steady cavitating flows over a 2D NACA0009 MOD hydrofoil by means of the modified and original Schnerr-Sauer model with the cavitation number 0.75 to 0.90,and the simulation results were compared with experimental data. The results show that, for the Schnerr-Sauer cavitation model, considering the effect of non-condensable gas, the densitynof non-condensable gas has a great influence on the simulation results before modifying, while the diameterd_nuchas little influence. The modified cavitation model which considers local shear strain rate can effectively eliminate the obvious effect of the empirical parameters and can improve the accuracy of numerical simulation. The saltation location of cavitation pressure gradient can be accurately predicted by the modified model.

Dynamic Characteristics of a Type of Vibration Isolator with Amplifying Mechanism

LIU Guoyong, ZHAO Pengpeng, LIU Haiping

2021, 41(1): 16-22. doi:10.15918/j.tbit1001-0645.2019.271

Abstract(836) PDF(403)

Abstract:
A new type of vibration isolator with amplifying mechanism was proposed by using a four-end articulated rod. Firstly, the analytical expression of the dynamic response of the vibration isolation system was obtained based on the harmonic balance method, and some parameters were got respectively, including the amplitude-frequency response, phase-frequency response, absolute displacement transmission rate, equivalent stiffness coefficient and equivalent damping coefficient of the vibration isolation system. The theoretical calculation results of the vibration isolation effect in the time domain and the frequency domain were compared with the conventional linear vibration isolator, and the verification test was carried out. Finally, the influence of system parameters on the dynamic performance of the vibration isolation system with amplification mechanism was analyzed, getting the influence mechanism. The results show that compared with the conventional linear isolators, the amplitude of the absolute displacement transfer rate of the inertial mass can be significantly attenuated by the vibration isolator with the amplification mechanism under the multi-frequency excitation in the time domain. Similarly, in the frequency domain, the amplitude of the absolute displacement transmission rate of the inertial mass can also be significantly attenuated, and the resonant frequency shifts slightly to the high frequency. The design parameters of the vibration isolation system have a great influence on the vibration isolation performance, and different vibration isolation targets can be realized by flexibly adjusting the design parameters of the vibration isolation system.

Determination Method of Sensitive Interval and Safety Dose for the Construction of Subway Tunnel Drilling and Blasting

JIA Haipeng, LIU Dianshu, FANG Zhengang, TIAN Shuaikang

2021, 41(1): 23-29. doi:10.15918/j.tbit1001-0645.2019.258

Abstract(768) PDF(393)

Abstract:
In order to strengthen the protection of the surrounding building during the tunnel drilling and excavation process, a t-distribution charge optimization formula and a sensitive interval calculation model were established based on the principle of statistics in this paper. Meanwhile, based on the practice of drilling and blasting excavation in Guiyang Metro Line 2, taking the proportional charge as a variable, the variation tendency of the optimized charge in the t-distribution with the proportional dose and the charge control of the explosion source in the forward movement process were studied. The study results present following conclusions. Firstly, the confidence probability with the traditional safety charge prediction formula is only 50%, the confidence probability based on the t-distribution formula can reach 99%. It is known that the t-distribution charge optimization formula can increase the protection degree to the surrounding building. Secondly, when the proportional charge is between 0 and 0.053,the asymptote of the critical charge approaches 0, therefore, this proportional dose interval cannot be used to guide the blasting construction. When the proportional charge is more than 0.053, the vertical vibration velocity is the largest, so the optimization charge formula can be used to guide the blasting construction. Finally, in the tunnel excavation direction line, the safety control charge is a process of gradually decreasing-reaching the minimum-rapidly increasing. When the working face is in the sensitive area, it is necessary to adjust the blasting design project in time to strengthen the protection to the surrounding buildings.

The Influence of OPC and PLU Protection on the Thermal System of Turbo-Generator Unit

HE Qing, LU Chang, LUO Ning, DU Dongmei

2021, 41(1): 30-36. doi:10.15918/j.tbit1001-0645.2018.163

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Abstract:
The unit's operating characteristics of power load unbalanced protection (PLU) and over-speed protection control (OPC) after load rejection and rotor overspeed was simulated. And the impact of overspeed protection action on the unit's thermal system was analyzed. The results show that: when the unit's power load unbalanced protection and rotor overspeed protection act, shutting the high-regulation valve and the intermediate-regulation valve quickly will cause the main steam pressure in front of the valve rising to 1.1415 times of the rated pressure rapidly. A certain impact force can take place on the valve of the unit, causing overpressure of the pressure-bearing components and the action of the safety valve, and ultimately leading to unstable combustion of the boiler. The only advantage of the power load imbalance protection is that, the unit can implement overspeed protection as early as the speed of the unit, but the two cases are all effective in the overspeed control. In comparison, the malfunction is more harmful.

A Virtual Assembly Process Simulation Method Based on Assembly Semantics

LIU Shaoli, WU Linlin, LIU Jianhua, DU Zenghui, MA Jiangtao

2021, 41(1): 37-42. doi:10.15918/j.tbit1001-0645.2019.285

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Abstract:
Aiming at the low efficiency caused by a large number of human-computer interaction operations in the virtual assembly simulation process, a virtual assembly process simulation method based on assembly semantics was proposed. Four typical assembly operations were extracted and the assembly characteristics were parameterized by analyzing the assembly process of complex aerospace products. Matching the assembly feature basic information and geometric primitive information of the assembly semantics, hierarchical analysis of assembly semantics was carried out from semantics layer to geometric feature layer. By solving the geometric constraints of the assembly features, according to the movement direction and order given by the assembly constraint relationship, the corresponding posture change matrix was generated to drive the execution object to complete the assembly process simulation. A prototype system was designed and developed based on Delmia, above process was verified by taking the assembly process simulation of a satellite navigator as an example.

Design and Research of Lower Limb Rehabilitation Robot Based on Flexible Joint

FU Tie, CAO Yuting

2021, 41(1): 43-47. doi:10.15918/j.tbit1001-0645.2019.283

Abstract(872) PDF(379)

Abstract:
Considering the achievement of the existing lower limb rehabilitation products, a sitting/horizontal lower limb rehabilitation robot with flexible joints was developed. A camera shooting instrumental analysis method was used to implement the gait analysis. And then, several procedures were carried out for the lower limb rehabilitation robot, including dynamics modeling, function analysis and simulation. The research results show that the lower limb rehabilitation robot can play a huge auxiliary role in the rehabilitation training for the stroke patients, spinal cord injury, paraplegia, and rewalking of fracture patients, and can make the patients move in a constant force and speed.

Spatial Domain Reconstruction of Road Roughness Based on White Noises Filtering

WANG Hanping, ZHANG Zhe, ZHANG Baozhen

2021, 41(1): 48-52. doi:10.15918/j.tbit1001-0645.2019.298

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Abstract:
Based on lower and upper triangular matrix (LU) decomposition of the power spectral density (PSD) matrix of road roughness for different wheel tracks, the transfer functions of road roughness was presented for different wheel tracks to two independent white noises signals. The coherent function in transfer functions was rationally approximated by Pade expansion. In addition, the complex transcendental function related to the coherent function in the transfer functions was rationally approximated by Chebyshev-Pade expansion. Based on white noises filtering (WNF) method, a 2D random road simulation model considering coherence function of different wheel tracks was constructed. The simulation results show that the Auto-PSD and the coherence function of different wheel tracks are in great agreement with the standard functions respectively. It is verified that the transfer functions derived from LU decomposition of PSD matrix of different wheel tracks and its Pade expansion and Chebyshev-Pade expansion possess high reliability in the simulation of 2D road roughness.

Numerical Study on Thermodynamic Effect of the Inducer Cavitation in Liquid Oxygen

HUANG Biao, FAN Yading, LIANG Wendong, WU Qin, WANG Guoyu

2021, 41(1): 53-58. doi:10.15918/j.tbit1001-0645.2019.250

Abstract(781) PDF(360)

Abstract:
To investigate thermodynamic effect of inducer with cryogenic fluids, FBM turbulence model and a revised Kubota cavitation model with thermodynamic correction were applied into the numerical investigation of inducer cavitation in normal temperature water and liquid oxygen. The numerical method was verified by general agreement between the numerical results and experimental data of suction performance of inducer in normal temperature water. The results show that, compared with normal temperature water, the inducer cavitation with liquid oxygen is supressed. There is intense heat transfer for evaporation in cavitation area with liquid oxygen which decreases the local temperature, causing depression of saturation pressure, and hence the development of cavitation is suppressed. For the different temperature of liquid oxygen, a method was proposed to theoretically predict the suction performance of cavitating inducer. Two cavitation performance curves were established as a reference to predict other inducer cavitation performance at different temperature of liquid oxygen. The agreement between theoretical prediction results and numerical results has verified the predicting method.

Estimation of Lithium Battery SOH Under Actual Operating Conditions Based on Particle Swarm Optimization

NAN Jinrui, SUN Lu

2021, 41(1): 59-64. doi:10.15918/j.tbit1001-0645.2019.211

Abstract(965) PDF(370)

Abstract:
A new method was proposed based on the particle swarm algorithm and the empirical capacity model of lithium batteries to estimate the state of health (SOH) of the battery under actual operating conditions. A linear model was established for charging curve characteristics and battery health under electric vehicle operating conditions. A battery empirical capacity model was supplied to make it conform to the actual situation of supervised learning and to be able to fit the parameters with a computer. Based on NASA's battery aging data, a training set and a validation set were established, training the model and verifying the trained model experimentally. Results show that, the SOH estimation error can reduce to less than 7%. In actual working conditions, the health of lithium batteries of electric vehicles can be accurately estimated quickly.

Thermodynamics Simulation and Analysis of Coaxial TSV with BCB Dielectric Layer

DING Yingtao, WU Zhaohu, YANG Baoyan, YANG Hengzhang

2021, 41(1): 65-69. doi:10.15918/j.tbit1001-0645.2019.195

Abstract(812) PDF(354)

Abstract:
Thermo-mechanical reliability of through silicon via (TSV) has become an important factor restricting the market application of TSV. In this paper, the thermodynamics characteristics of coaxial TSV with BCB dielectric layer were studied and analyzed. Meanwhile, in order to reduce the thermal stress of coaxial TSV, different parameters were simulated with various design geometries, including the thickness of SiO₂insulation layer and shielding ring, the pitch of TSVs as well as the radius of center signal line. The results show that, under the premise of the characteristic impedance match, the thermal stress of coaxial TSV can be effectively reduced by increasing the thickness of SiO₂insulation layer or decreasing the thickness of shielding ring,while the influence of the radius of the center signal line and the TSV pitch can be neglected.

A Reflectarray Antenna Design Based on Metasurface

REN Wu, ZHANG Yanan

2021, 41(1): 70-78. doi:10.15918/j.tbit1001-0645.2019.182

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Abstract:
A Ku band high gain reflectarray antenna was proposed based on metasurface. Firstly, adopting a "lantern meander-line" structure combined with an open square ring structure, a metasurface element was designed with a unit size of 0.3λ₀. The simulation analysis results show that, the unit can achieve a phase shift range 520° and a better phase shift characteristics. And then, a ku band high gain reflectarray antenna was designed with the unit. The reflectarray antenna was designed with a caliber size 160.8 mm×160.8 mm(7.2λ₀×7.2λ₀), fed by a pyramidal horn. The simulation analysis results show that, the reflectarray antenna can achieve higher gain and aperture efficiency. At the same time, it shows a better performance in the uplink frequency band 14.0~14.5 GHz and the downlink frequency band 12.25~12.75 GHz in the satellite communication. And the practical testing results are agreement with the simulated results, verifying the effectiveness of the design of the reflectarray antenna.

Sparse Nested Array Design for Virtual Aperture Extension

YAN Su

2021, 41(1): 79-83. doi:10.15918/j.tbit1001-0645.2019.282

Abstract(990) PDF(371)

Abstract:
A sparse nested array concept of distributing the right-side elements of two level augmented nested array (ANA) sparsely was proposed for degree of freedom (DOF) enhancement. The new strategy was arranged to make the distances between the right-side elements and the right most sensor in the middle subarray of ANA larger thanN₁to extend the furthest aperture successfully. In order to keep the continuity of virtual aperture, a new nested array, referred to as one side sparse nested array (OS-SNA), was proposed. Compared with the improved nested array ANAI-2 and maximum inter-element spacing constraint (MISC), the new nested array can generate more consecutive lags. Simulation results show the superiorities of the proposed OS-SNA in DOF and the precision estimation.

Research on Location Privacy Protection Methods for Mobile Users in 5G Environment

JIANG Haiyang, ZENG Jianqiu, HAN Ke, LIU Luan

2021, 41(1): 84-92. doi:10.15918/j.tbit1001-0645.2020.139

Abstract(942) PDF(327)

Abstract:
To solve the location privacy disclosure problem with location based service(LBS)applied frequently in 5G environment, the risks of mobile users' location privacy disclosure in 5G environment were analyzed, the existing privacy protection technologies were investigated, and three kinds of common privacy protection methods were summarized and compared. A new privacy protection method called fusion location privacy protection method was proposed, aiming at the new challenges of location privacy protection in 5G environment. By the combination of preliminary dimension reduction treatment, location privacy protection algorithm, and transmission encryption method,the method was arranged to reduce the risks during location dimension selecting, positioning and transmitting process without increasing the complexity. Simulation results indicate that the proposed method can perform well in mixed scenarios and be suitable for the dense, high frequency LBS in 5G environment.

A Convolution-Self Attention Abstractive Summarization Method Fusing Sequential Grammar Knowledge

LUO Senlin, WANG Ruiyi, WU Qian, PAN Limin, WU Zhouting

2021, 41(1): 93-101. doi:10.15918/j.tbit1001-0645.2019.188

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Abstract:
Abstractive summarization is to analyze the core ideas of the document, rephrase or use new words to generate a summary that can summarize the whole document. However, the encoder-decoder model can not fully extract the syntax, that cause the summary not to match the grammar rules. The recurrent neural network is easy to forget the historical information and can not perform parallel computation during training, that cause the main idea of the summary not significant and the coding speed slow. In view of the above problems, a new abstractive summarization method with fusing sequential syntax was proposed for the convolution-self attention model. First, constructing a phrase structure tree for the document and embeding sequential syntax into the encoder, the method could make better use of the syntax when encoding. Then, the convolution-self-attention model was used to replace the recurrent neural network model to encode, learnning the global and local information sufficiently from the document. Experimental results on the CNN/Daily Mail dataset show that, the proposed method is superior to the state-of-the-art methods. At the same time, the generated summaries are more grammatical, the main ideas are more obvious and the encoding speed of the model is faster.

WANG Chengliang, HUANG Liying, ZHAO Kai

2021, 41(1): 102-111. doi:10.15918/j.tbit1001-0645.2019.204

Abstract(881) PDF(383)

Abstract:
In the intelligent environment, by analyzing the similarity of the user's daily activity sequences, it is possible to group users with similar behaviors, detect abnormal behaviors of users and query other behavior sequences that are similar to a given sequence, so as to personalize the user finely. That can provide users with a perfect personalized information services. The existing research focuses on the activity similarity calculation without spatiotemporal information or with fixed spatiotemporal information, and does not measure the similarity of user behavior sequences from different levels. In order to realize the dynamic cognition of multi-granularity and multi-view of user behavior, a multi-granularity spatiotemporal sequence algorithm (MGSSA) based on Needleman-Wunsch algorithm was proposed. It was arranged to extend the score function of NW algorithm to combine the temporal information and spatial information, and to realize the similarity of spatiotemporal event sequences from different granularities through granular control. Finally, some experiments were carried out. The results show that the multi-granular spatiotemporal sequence alignment algorithm is effective and feasible.

Robust Boosting Method Combining Weighted KNN and Adaptive Newton Method

LUO Senlin, ZHAO Weixiao, PAN Limin

2021, 41(1): 112-120. doi:10.15918/j.tbit1001-0645.2019.174

Abstract(941) PDF(414)

Abstract:
Boosting is an essential ensemble learning method in the field of machine learning. continuously strengthening the attention of misclassified samples when combined with weak learners. Strengthening the attention continuously to misclassified samples with weak learners,the Boosting algorithms represented by AdaBoost are capable of building strong learners with excellent performance. However, there is an indiscriminate treatment of noise in the training mechanism, causing the learners likely to over-fit the noise and thus reducing the robustness of the algorithms. Aiming at the problem, a robust Boosting method combining weighted KNN and adaptive Newton method was proposed. Firstly, a weighted KNN method was used to estimate the noise prior probability of the sample. And then, the Logit loss was modified with the noise prior probability to construct a new loss function. Finally, the loss function was optimized based on an adaptive Newton method. The proposed method was arranged to give a corresponding penalty to the samples with a high probability of noise when the misclassified samples got a higher weight from the classifier, so as to make the weight of the noise samples be effectively reduced. The experiment results show that, compared with other robust Boosting methods, the proposed method has better robustness under different noise levels as well as under different evaluation criterions in a real medical data set, having obvious application value.

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