Table of Content

31 December 2019, Volume 40 Issue 12

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Contents

2019, 40(12):  0. 

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Paper

Analysis of the Flow Instability of Supersonic Gaseous Jets for Submarine Vehicles Working in Deep Water

ZHANG Xiaoyuan， LI Shipeng， YANG Baoyu， WANG Yong， TONG Yue， WANG Ningfei

2019, 40(12):  2385-2398.  doi:10.3969/j.issn.1000-1093.2019.12.001

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The reliability and stability of underwater solid rocket motor propulsion system are crucial to the ballistic accuracy and flight stability of submarine vehicles. The working process of the motor is the flow process of typical supersonic gaseous jets underwater. A planar vertical two-dimensional jet geometric model is established, and the detached-eddy simulation turbulence model is used to simulate and analyze the flow field of supersonic gaseous jets in deep-water, and the oscillation characteristics of parameters in the flow field are monitored and analyzed. The underlying flow mechanism due to thrust oscillation of underwater solid rocket motor is addressed. The results show that a high-frequency oscillation occurs in the gas wake of the underwater solid rocket motor, and is accompanied by a high-amplitude intermittent oscillation. The oscillation is related to the unstable motion of shock waves along the central gas path, which leads to a sharp oscillation of pressure in the tail space, ultimately causing thrust instability. The analysis of thrust oscillation characteristics indicates that the deeper the water depth is, the larger the thrust oscillation amplitude is, and the higher the frequency is; and the larger the diameter of wall at nozzle exit is, the larger the thrust oscillation amplitude is, and the higher the frequency is. Key

Real-time LiDAR SLAM in Off-road Environment for UGV

LIU Zhongze, CHEN Huiyan, CUI Xing, XIONG Guangming, WANG Yuchun, TAO Yi

2019, 40(12):  2399-2406.  doi:10.3969/j.issn.1000-1093.2019.12.002

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Simultaneous localization and mapping (SLAM) plays a more and more important role in the environment perception system of unmanned ground vehicle (UGV). A hierarchical global topological map is proposed to solve the low real time capability problem during processing of 3D lidar point cloud map, which divides the entire map into many submaps consisting of large numbers of tree-structure-based voxels, and the submaps are organized with the help of topology. The probabilistic methods are used to represent the state of each voxel being occupied/null. A transitable area is extracted based on the submaps for the UGV's path planning. With the help of an inertial measurement unit (IMU) and two 3D lidars, a branch and bound search (BBS)-based loop detection algorithm called RHM-ICP algorithm is proposed to realize a real time 6-degrees-of-freedom global pose optimization with the help of Ceres, which is to process the sparse pose adjustment (SPA). Experimental results obtained from a real large-scale off-road environment shows an effective reduction of lidar odometry pose accumulative error with a global location error of less than 1 m and a good performance of 3D mapping. Key

Research on Directional Reflection Expansion Mechanism of Reducing Recoil Force of Rapid Fire Gun

DAI Jinsong, HE Fu, SU Xiaopeng, WANG Maosen, TAN Tian

2019, 40(12):  2407-2415.  doi:10.3969/j.issn.1000-1093.2019.12.003

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When the traditional rapid fire gun automatically fires at a high rate, the powder gas that is sprayed backward has a greater impact on the devices and personnel near gun emplacement. A mechanism of reducing the recoil force by directional reflection expansion is proposed. The powder gas is introduced into a directional reflection expansion cavity through several front inclined holes on the gun tube. The recoil force is reduced by a high pressure zone formed by powder gas in front of cavity and its impact on the reflecting surface of the device. The expansion mechanism is analyzed by using the computational fluid dynamics theory. The result shows that the maximum recoil force-reducing efficiency of the device can reach 48.3%, which is equivalent to the existing traditional muzzle attachment of rapid fire gun. The corresponding experimental research was made to verify the correctness of the theoretical analysis. Key

Life Prediction of Gun Barrel Based on Shear Fatigue Damage of Coating Interface

GENG Xuehao, ZHOU Kedong, HE Lei, FENG Guotong, LI Junsong

2019, 40(12):  2416-2424.  doi:10.3969/j.issn.1000-1093.2019.12.004

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According to the theories of coating shear failure mechanism and cumulative fatigue damage of gun barrel, a gun barrel life prediction method based on the shear fatigue damage accumulation at the interface of coating and substrate in barrel is proposed to study the bore damage mechanism of gun barrel and improve the gun barrel life. A shear failure model of coating interface under the effect of thermo-pressure coupling stress is built, and the shear stress of coating interface during continuous firing of 150 rounds is calculated by taking a 5.8 mm caliber gun barrel as study object. The barrel life is predicted by use of temperature dependent tensile strength of gun barrel material. The predicted results match well with life test results, which verifies the feasibility and validity of the proposed life prediction model. The research results show that the prediction of gun barrel life based on the shear fatigue life of coating is feasible and the shear fatigue failure of coating interface is an important reason to lead to the life end of gun barrel. Key

Robust Adaptive Control of Roll Position of Fixed Rudder for Dual-spin Projectile with Improved LuGre Friction Model

YIN Tingting, JIA Fangxiu, YU Jiyan, WANG Xiaoming

2019, 40(12):  2425-2432.  doi:10.3969/j.issn.1000-1093.2019.12.005

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A robust adaptive control strategy based on a continuously differentiable LuGre friction model is proposed for the roll position control of fixed rudder canard in dual-spin trajectory correction projectile with nonlinear friction, uncertain parameters and time-varying disturbance. A nonlinear mathematical model, including the improved continuous friction model, is established for the electromagnetic actuator based on the permanent-magnet synchronous generator (PMSG). A robust feedback compensation term based on the estimated upper bound of un-modeled disturbance is designed to reduce the influence of external disturbance on control performance. An adaptive control law is proposed by compensating for friction and adaptively estimating the system parameters and friction states online, which can effectively reduce the sensitivity of system to parameter uncertainties and nonlinear frictions. The global stability of closed-loop system is proved by Lyapunov analysis. Simulated results show that the proposed strategy can be used to accurately estimate and compensate for time varying parameter, uncertainties, nonlinearities and disturbances, and has the advantages of high accuracy and strong robustness.Key

Research on Jet Coherency of PTFE-based Energetic Liner

LI Yan, WANG Wei, ZHANG Leilei, WANG Zaicheng, JIANG Chunlan

2019, 40(12):  2433-2439.  doi:10.3969/j.issn.1000-1093.2019.12.006

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The jet cohesiveness of polytetrafluoroethylene (PTFE)-based energetic liner is related to the penetration and damage effect of jet. The numerical simulation and experimental verification were carried out to study the jet forming characteristics of PTFE/Ti/W energetic liner. The results show that there is a significant difference between the jets of energetic liner and inert aluminum liner. Due to the lower sound speed of energetic liner, the detached shock wave forms in the liner collapsed by the detonation wave, and the jet is radially diverged during flight. As the density of the liner increases, the jet coherency strengthens. The energetic penetrator continuously reacts and expands during forming. The contour of penetrator gradually becomes blurred and the density decreases with time. The numerical simulation method based on the inert material model can be used accurately to simulate the jet forming in a certain time frame. When the shape change caused by the reaction of penetrator cannot be ignored, the simulated results have certain disparity with the actual results. Key

Research on Changing Law of Resonance Acoustic Mixing Process of Plastic Bonded Explosive Simulant

MA Ning， ZHANG Zhe， SUN Xiaopeng， QIN Neng， XIE Zhongyuan， CHEN Song

2019, 40(12):  2440-2446.  doi:10.3969/j.issn.1000-1093.2019.12.007

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In order to obtain the resonance acoustic mixing process rule and achieve the efficient mixing of plastic bonded explosive (PBX) under the conditions of safety and low energy consumption, the effects of mixing acceleration and time on mixing process are studied for PBX simulant with 88% solid content. In the experiment, a 5 kg scale resonant acoustic mixer is used, the sample scale is 1 500 g, and the mixing acceleration varies from 0 g to 60 g (g=9.8 m/s²). The experimental results show that the material state changes with the mixing time, and the different minimum mixing accelerations are required for different material states. According to the typical material state in the mixing process, the mixing process is divided into five zones: granule mixing zone, granule-liquid mixing zone, cohesion spheroidizing zone, viscoelastic mixing zone and fluidizing zone. The material is premixed in previous three stages under a relatively safe condition, and is micro-mixed in viscoelastic and fluidizing mixing zones in the whole flow field; according to the required minimum mixing acceleration, three key points are defined: mixing point, aggregation point and fluidization point. Generally, the three key points increase successively, and they are about 10 g, 25 g and 40 g, respectively. The mixing process can be used to guide the resonance acoustic mixing process of PBX and other materials with highly viscous and highly solid content. Key

An Attitude Determination Algorithm Based on MEMS Inertial and Magnetic Measurement Unit

YAN Dan, DENG Zhihong, ZHANG Yanpeng

2019, 40(12):  2447-2456.  doi:10.3969/j.issn.1000-1093.2019.12.008

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Full-attitude determination methods are needed in many fields, such as UAV, robot, and human motion capture. Using MEMS inertial/magnetic sensors to determine the attitude of a object is a low cost, high performance, and commonly used scheme in these fields. To alleviate the problem that the magnetometer is susceptible to external ferromagnetic interference, the paper proposes a two-stage quaternion-based attitude update method: in the first stage, a cost function is constructed by establishing the gyroscope and accelerometer measurement models, which can be optimized by gradient descent to update the pitch and roll angles; in the second stage, a cost function is constructed by using the magnetometer measurement model, which can be optimized by gradient descent to update the yaw angle. The posteriori estimated quaternion is used to calculate the estimated ferromagnetic interference is regarded as the priori ferromagnetic interference at the next step. The experimental result shows that the proposed method can be used to effectively correct the cumulative error caused by angular rate integration and improve the attitude determination accuracy, and has the capability of anti-ferromagnetic interference, which can improve the environmental adaptability of the attitude determination system. Key

Design of Flight Control Law of Tilt-rotor Aircraft Based on Incremental Dynamic Inversion

ZHENG Chen, TANG Peng, LI Qiushi

2019, 40(12):  2457-2466.  doi:10.3969/j.issn.1000-1093.2019.12.009

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A flight control law of tilt-rotor aircraft based on incremental nonlinear dynamic inversion (INDI) is designed for the high precision and poor robustness of nonlinear dynamic inversion (NDI) control law. The incremental dynamic inversion control law is derived based on the dynamic model of tilt-rotor aircraft. In view of the redundancy of tilt-rotor aircraft, the control allocation algorithm of rudder surface is introduced based on the incremental dynamic inversion algorithm. A real-time solution to control the efficiency B-matrix is proposed, and a full-mode control law which can reduce the dependence on accurate mathematical model is designed. The effectiveness of the proposed algorithm for tilt-rotor aircraft is verified by simulation. Key

Wake Transition of the Hypersonic Vehicle and Its Influence on RCS

YU Zhefeng, CHEN Xuming, YANG Ying, BU Shaoqing, XIE Aimin, HUANG Jie, LIU Sen

2019, 40(12):  2467-2472.  doi:10.3969/j.issn.1000-1093.2019.12.010

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A long plasma wake is formed downstream when a hypersonic vehicle is flying in the atmosphere. It may cause a sudden increase in radar cross section (RCS), which affects the detection, tracking and identification of hypersonic vehicle. The flow field characteristics of hypersonic model in the free flight ballistic range is experimentally studied. The flow field structure and transition position of wake at different Mach numbers and chamber pressures were measured. The possible influence of transition position on the RCS characteristics of hypersonic vehicle is discussed. The results show that the model feature size, flight Mach number and chamber pressure are the main parameters affecting the transition position. The influence of the plasma wake on the hypersonic vehicle RCS is very complicated, which changes RCS and makes the radar imaging blurry, and even produce the fake targets. Key

Sea Clutter Parameter Estimation Based on BP Neural Network

HE Yaomin, HE Huafeng, XU Yongzhuang, SU Jing, WANG Yifan

2019, 40(12):  2473-2481.  doi:10.3969/j.issn.1000-1093.2019.12.011

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Sea clutter is studied and analyzed for evaluating the accuracy of missile-borne synthetic aperture radar under different sea conditions. A parameter estimation method based on BP neural network is proposed to solve the problem that the sea clutter parameter estimation based on traditional statistical methods is prone to be divorced from the actual sea clutter. The amplitude distribution characteristics and temporal correlation of sea clutter are used to establish a K-distribution-based sea clutter model. The influences of four model parameters, such as shape, scale, mean square root of clutter speed, and mean Doppler shift, on sea clutter chaos and fractal characteristics are analyzed, and the qualitative relationship among model parameters and physical characteristics is summarized. On this basis, BP neural network is used to fully explore the quantitative relationship among parameters and physical characteristics, and predict the chaos characteristics and fractal characteristics. The determinate coefficients are 0.985 and 0.952. The model parameters of BP neural network, maximum likelihood estimation and moment estimation method are compared by taking the measured sea clutter data as an example. The results show that the proposed model can be well close to the physical characteristics of actual sea clutter. Key

Influence of Cavity Mode on Lasing Wavelength of VCSEL

LIANG Jing, JIA Huimin, SU Ruigong, TANG Jilong, FANG Dan, FENG Haitong, ZHANG Baoshun, WEI Zhipeng

2019, 40(12):  2482-2487.  doi:10.3969/j.issn.1000-1093.2019.12.012

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The chips of vertical cavity surface emitting laser (VCSEL) with different positions of cavity mode were designed and prepared for 894.6 nm VCSEL with wavelength-stabilized output in high temperature environment. The influence of cavity mode position on lasing wavelength is studied by testing and analyzing the cavity mode position, output wavelength and temperature drift coefficient of VCSEL. It is found that the lasing wavelength of VCSEL has a linear relation with cavity mode. A structure of VCSEL with cavity mode at 890.5 nm was designed. VCSEL chips which output wavelength is 894.6 nm in 85 ℃ high temperature environment were prepared. The results show that the desired output wavelength of VCSEL chips can be obtained by controlling the position of cavity mode. Key

Application of SAR Ship Data Augmentation Based on Generative Adversarial Network in Improved SSD

YANG Long， SU Juan， LI Xiang

2019, 40(12):  2488-2496.  doi:10.3969/j.issn.1000-1093.2019.12.013

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For the high cost of data acquisition and few of datasets for ship detection in synthetic aperture radar (SAR) image, a data augmentation technology based on pix2pix is proposed. A dataset is set for pix2pix, and 800 SAR ship samples are obtained by training and testing the generative adversarial network (GAN). The objective evaluation is given for the generated typical samples. And for the problems that the accuracy of traditional ship detection in SAR images is susceptible to speckle noise and its generalization is poor, a ship detection algorithm based on single shot multibox detector (SSD) is proposed. An Inception module is added into the SSD detecting algorithm for enhancing its adaptability to multi-size target and improving the performance of detector. Finally, the SAR ship data generated by pix2pix GAN is marked and added to the improved SSD. A large number of comparison experiments were performed on the SSDD dataset. The experimental results show that the detection accuracy is improved by 4.3% when the generated samples are added to SSD. The detection accuracy is improved by 1.9% after the samples are added to the improved SSD; and the detection accuracy of the improved SSD is improved by 4.7% without the addition of the generated sample in the detector.Key

Research on Discharge Characteristics of Insulator-semiconductor Samples Based on Low-energy Electron Beam

HUO Zhisheng， PU Hongbin， YU Ningmei， LI Weiqin

2019, 40(12):  2497-2503.  doi:10.3969/j.issn.1000-1093.2019.12.014

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Research on elimination of negative charging effects caused by high-energy electron beam (EB) irradiation is of great significance for the fabrication, detection and imaging of microelectronic devices. The discharge characteristics and neutralizing mechanism of insulator-semiconductor sample based on low-energy energy electron beam are studied through numerical simulation and experimental measurement. A numerical model based on electron scattering, transport and trapping is established, and the space charge, space potential distribution and discharge characteristics are investigated. The relaxation characteristics of space charges under the low-energy EB irradiation and the influences of beam energy and beam current on neutralizing characteristics are analyzed. The results show that the negatively charged strength of sample decreases gradually after long-term placement, but it cannot be eliminated completely due to the trapping effect. Under low-energy EB irradiation lower than the second critical energy, the negative charges are neutralized quickly and the surface potential tends to zero with the accumulation of positive charges. The transient time of neutralization process is the shortest when the landing energy of EB approaches to that of maximizing the total electron yield. The larger the beam current is, the faster the transient process achieves the equilibrium.Key

Study of Characteristics Extraction of Underwater Bubbles Group Based on Hough Transform

QIN Ruolin， JIANG Xiaogang， JIN Liang'an， GAO Kexin

2019, 40(12):  2504-2512.  doi:10.3969/j.issn.1000-1093.2019.12.015

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Characteristics detection of ship bubble wake field is the basis of research on stealth performance of ship as well as guidance performance of wake-guided torpedo. The existing detection method of bubble characteristics is image acquisition based on high speed photography. A bubble characteristics extraction algorithm based on improved Hough transform is proposed. The proposed extraction algorithm can be used for the detection of bubble and the calculation of bubble radius distribution in the large-density and multi-overlapping bubbles images. The bubbles images were obtained in laboratory conditions, and the proposed algorithm was used to detect the number and size distribution of bubbles in these images. The detected result is highly accurate compared with the actual bubble number in the image. The result shows that the proposed algorithm can be used for the characteristics detection of ship bubble wake field. Key

Non-orthogonal Error Correction of Three-axis Magnetic Sensor Based on Improved IWO Algorithm

LUO Jingbo， CHEN Hao， ZHAO Miao， ZHAI Guojun

2019, 40(12):  2513-2518.  doi:10.3969/j.issn.1000-1093.2019.12.016

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The non-orthogonal error exists in a three-axis magnetic sensor due to the limitations of the machining and installation processes. A non-orthogonal error model of three-axis magnetic sensor is established to correct the error and obtain accurate triaxial magnetic data, and the model is solved by using the least squares method. Four intelligent optimization algorithms are used to solve the least-squares problem, and the invasive weed algorithm is improved. Simulated and experimental results show that the least squares error correction method based on the improved invasive weed optimization （IWO）algorithm can be used to effectively correct the non-orthogonal errors of three-axis magnetic sensors by reducing the motion noise of 85.42% and 86.5%, respectively.Key

Robust Adaptive Control for Nonlinear Path Tracking of Unmanned Surface Vehicles

LUO Fuyu, ZENG Jiangfeng, AI Ning

2019, 40(12):  2519-2528.  doi:10.3969/j.issn.1000-1093.2019.12.017

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A robust adaptive control approach based on cubic Hermite spline interpolation (CHSI) and neural network is proposed for the path tracking of underactuated unmanned surface vehicles (USVs). A smooth nonlinear desired path is obtained by using CHSI method to fit the way-point, which solves the problem of swing and twist of USV caused by traditional linear path. Based on the Serret-Frenet frame, an adaptive line-of-sight (ALOS) guidance law is setablished to improve the rate of convergence and reduce the oscillation. Considering the influence of model uncertainties of USV and environmental distur- bance, a concise robust adaptive neural network controller was developed. The proposed control strategy can effectively improve the accuracy and quality of path tracking control, and has the advantages of less learning parameters and computing load. The convergence of the system is proven through stability analysis, and the effectiveness of the proposed control scheme is verified by using the simulation examples. Key

Effect of Graphene Modification on the Detection Performance of Ag/AgCl Electrode in Undersea Electric Field

LI Hongxia, SONG Yusu, WANG Yexuan, CHEN Wenbo

2019, 40(12):  2529-2536.  doi:10.3969/j.issn.1000-1093.2019.12.018

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The electro-chemical properties and detection performance of Ag/AgCl electrode made of grapheme are studied. The influences of addition of graphene and its content on the detection performance of Ag/AgCl electrodes are analyzed from microstructure characterization, electrode potential drifts, amplitude-frequency response, self-noise, polarization curves, water absorption and microstructure of Ag/AgCl electrode. The study shows that the graphene-Ag/AgCl electrode has small potential drift, short stability time, and good electrochemical properties compared to Ag/AgCl electrode, which is suitable for the rapidly deploying measurement. The different contents of graphenes have different mechanisms of action for changing the interface contact properties of Ag/AgCl electrodes/solution. The porosity of electrode and the specific surface area increase with the graphene content of 1%, and the surface uniformity of electrode is improved and the permeation of solution medium is accelerated with the graphene content of 3%. Different mechanisms of action are the main reason for the difference of electrochemical properties of Ag/AgCl electrodes with different contents of graphene. Key

Research on Laser Cladding Processing for 38MnVS6 by PCA-TOPSIS Method

ZHAO Yao, YU Gang, HE Xiuli, LI Haiming, LI Shaoxia

2019, 40(12):  2537-2544.  doi:10.3969/j.issn.1000-1093.2019.12.019

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Preparing high performance coating on piston surface by laser cladding is of significance for prolonging the life of diesel engine. In laser cladding process, the selection of appropriate parameters is the key to improve the performance of cladding layer. Whereas the relationship between these factors is non-linear, stochastic and discrete, it is significant to optimize some of them, such as laser power, scanning speed, and powder feed rate. For the laser cladding of nickel-based alloy powder on 38MnVS6 medium carbon steel, L₉(3³) orthogonal array is designed. Taking cladding width, dilution rate and surface hardness as evaluation indicators, the weights of three parameters are obtained by the principal component analysis (PCA). The optimal combination of laser power, scanning speed, and powder feed rate is obtained by the technique for order preference by similarity to ideal solution (TOPSIS) based on Mahalanobis distance. The results show that, when the laser power is 850 W, the scanning speed is 3 mm/s, the powder feed rate is 3.13 g/min, and the coating has the best properties. The dilution rate of cladding layer is decreased by 1.13% and the average hardness of cladding layer is increased by 4.56% compared with those at the scanning speed of 3 mm/s. The range analysis shows that the laser power has the most important effect on the size and overall quality of cladding layer. Key

High Accuracy Flux Splitting Method for Numerical Solution of Euler Equation

ZHENG Qiuya, SU Ningya, LIANG Yihua

2019, 40(12):  2545-2550.  doi:10.3969/j.issn.1000-1093.2019.12.020

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A new scheme to couple the energy-convective upwind and split pressure (E-CUSP) scheme with the weighted essentially non-oscillatory (WENO) scheme is proposed for Euler equation. In the spatial direction, the flux of low dissipation E-CUSP scheme is reconstructed using high-precision WENO scheme. Fourth-order total variation reduction Runge-Kutta method is used for propulsion in time direction. On this base, a high accuracy flux splitting method for solving Euler equation is proposed. It is found through numerical simulation of shock tube that the proposed scheme can be used to simulate the shock tube problem and capture the shock wave and contact discontinuity more accurately compared to E-CUSP scheme. The numerical results show that the proposed scheme has higher accuracy and robustness. Key

Optimal Selection of Failure Samples Based on Multiple Impact Factors and Importance

QIU Wenhao, LIAN Guangyao, YANG Jinpeng, HUANG Kaoli

2019, 40(12):  2551-2559.  doi:10.3969/j.issn.1000-1093.2019.12.021

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A failure sample selection method based on multiple impact factors and importance of failure mode is proposed to solve the problem about the incomplete consideration of impact factors, the insufficient engineering application of sampling method and the strong subjectivity of impact factor weight in failure sample selection of testability test. On the basis of analyzing the necessity of sampling based on multiple influence factors, the impact factors are determined, and a calculation method of propagation intensity based on PageRank is proposed. A calculation method of similarity based on information entropy and support based on relative comparison is proposed, and then the impact factor weights are determined by using the game decision method, and finally the failure sample optimization based on relative importance is realized. The application of the proposed method in a control system shows that this method can be used to reduce the randomness of evaluation results of a single test. In the selection of samples, a variety of impact factors and their weights that are both objective and meet the requirements of test are taken into account comprehensively, which is more in line with the requirements of testability test and makes the selected failure samples more reasonable. Key

A Deep Fusion Method Based on Rough Sets and Evidence Theory for Local Conflict Evidence Synthesis

NI Longqiang, ZHANG Lihua, YAO Xintao, HU Gaoge, LIU Penghui

2019, 40(12):  2560-2569.  doi:10.3969/j.issn.1000-1093.2019.12.022

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A local conflict allocation evidence combination rule based on rough sets theory is proposed to reduce the computational complexity and improve the efficiency in conflict evidence combination. In this proposed method, the information system which is consisted of several evidences is reduced by rough sets, and the confidence of belief function is calculated based on the confidence of evidence and single focal elements individually. At last an example is given to prove the efficiency of this proposed method.Key

Control of Static Walking Gait of Load Carrying Quadruped Walking Vehicle Based on Virtual Components

TAN Yongying, CHAO Zhiqiang, JIN Yi, WANG Fei

2019, 40(12):  2570-2579.  doi:10.3969/j.issn.1000-1093.2019.12.023

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The traditional static gait control method based on inverse kinematics or inverse dynamics is liable to produce a large impact between the feet and the ground, which causes a large tracking error of vehicle body trajectory. A virtual-components-based static gait control method is proposed to achieve the static gait compliance of load-carrying quadruped walking vehicle. The proposed method is divided into two parts: vehicle body motion control and swinging leg control. The virtual spring damper elements are added to the vehicle body's and swing leg's degrees of freedom, respectively, so as to convert the control of vehicle body and the swing leg to the control of virtual forces. And the sequential quadratic programming method is used to assign the virtual forces of vehicle body to the supporting legs. Based on the Jacobian matrix of each leg, the joint torques of supporting legs and swing leg are obtained. A state machine of vehicle’s static gait is designed. MATLAB and ADAMS are used to establish the simulation models for the quadruped walking vehicle, and the co-simulations are carried out for the quadruped walking vehicle. The simulated results show that the virtual-components-based control method enables the vehicle to walk on rough terrain in a stable gait. The vehicle is able to adapt to the change of terrain, and a impact between the feet and the ground is reduced by using the proposed control method.Key

Research Notes

Research on Application of Vector Hydrophone onboard an Underwater Glider

WANG Wenlong, WANG Chao, HAN Mei, SUN Qindong, ZHANG Xiaochuan

2019, 40(12):  2580-2586.  doi:10.3969/j.issn.1000-1093.2019.12.024

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Underwater glider achieves floating and diving by changing its buoyancy, and realizes the forward gliding movement by virtue of hydrodynamic force. The use of underwater gliders for long-term, high concealment and large scale detection has become a current research focus. An underwater acoustic glider platform with target detection function was developed by integrating a single vector hydrophone in an existing underwater glider platform. The noises from vector hydrophone and underwater glider platform are test, and the self-noise level of vector hydrophone and the main noise source of underwater glider platform are analyzed. This study has significant guiding significance to reduce the vibration and noise and optimize the operating mode of acoustic system. The detection performance of underwater acoustic glider is analyzed from the experimental data collected in the experiment in the South China Sea in May 2018. The results show that the maximum detection distance of an underwater acoustic glider to detect a test surface vessel sailing at a speed 10 kn is longer than 14 km under good sea state in the deep sea.Key

Research on the Stealth Performance of Half-stealth Projectile against Radar

ZHANG Peizhong, NING Jingui, WANG Jianguo, WANG Xin

2019, 40(12):  2587-2592.  doi:10.3969/j.issn.1000-1093.2019.12.025

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The stealth technology of projectile is researched to develop a stealth projectile to counter hostile artillery locating and fire correction radar. The contour stealth design of projectile includes full-stealth and half-stealth structures. The full-stealth projectile structure is designed according to the full-stealthy design specifications. The full-stealth projectile is a subcaliber disc-type projectile. The full-stealth projectile has emarkable stealth performance, but it has the reduced power and hit accuracy. So a full-caliber stealth projectile structure is designed. The front bourrelet of projectile is not coated with radar absorbing materials and touches the bore directly to form a half-stealth projectile. The X and S band half-stealth projectiles were designed and manufactured. The half-stealth projectiles were searched and tracked by using an artillery locating and fire correction radar. Experimental results show that the half-stealth projectile has stealth performance. Key