Table of Content

30 September 2016, Volume 37 Issue 9

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Paper

Research on Influence of Breakwater on Hydrodynamic Characterisitics of Displacement Amphibious Vehicles

MAO Ming, WANG Jian-bing

2016, 37(9):  1553-1560.  doi:10.3969/j.issn.1000-1093.2016.09.001

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Breakwater is one of important parts which affect the performance of amphibious vehicle on water. A hydrodynamics model of displacement amphibious vehicle is established to research the influence of breakwater on its hydrodynamics. The hydrodynamics performance of displacement amphibious vehicle is simulated in terms of different shapes and sizes of breakwaters and their positions relative to vehicle body. The effect of breakwater on navigation resistance, lift force and longitudinal pitching moment is analyzed. The research results show that segmented breakwater is better engineering structure in shape, which has the advantages of arc-shaped and flat-plate breakwaters; the increase in width has small influence on resistance and lift force, but the longitudinal pitching moment increases a lot; with the increase in distance between breakwater and vehicle body, the resistance increases, the lift force decreases, and the longitudinal pitching moment increases greatly; with the increase in angle between breakwater and underbody plane, the resistance and lift force have a little change, but the longitudinal pitching moment increases significantly.

Research on Feedforward-feedback Speed Control of Turbocharged Diesel Engine

XIA Meng, ZHAO Chang-lu, HUANG Ying, ZHANG Fu-jun, LI Gang

2016, 37(9):  1561-1569.  doi:10.3969/j.issn.1000-1093.2016.09.002

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In order to improve the load disturbance rejection and rotating speed control effect for the tracked vehicle engine, a feedforward-feedback speed control algorithm is proposed according to the torque-based architecture. A load estimation algorithm is designed based on mean value model and crankshaft dynamic model. The estimation accuracy of the proposed load estimation algorithm is validated under steady and transient conditions. The feedforward-feedback speed control algorithm can significantly improve the capability of load disturbance rejection in the simulation of powertrain. The reseach results show that a rapid speed control effect can be achieved and repetitive calibration of speed control parameters can be avoided during acceleration process of tracked vehicle. The improvement in pedal-rotating speed following characteristics leads to the reduction in unexpected gear shifting of tracked vehicle in a driving cycle.

FEA Method for Analysis of SINS Error Caused by Vibration Isolation System

GAO Jun-qiang, TANG Xia-qing, HUANG Xiang-yuan, CHENG Xu-wei

2016, 37(9):  1570-1577.  doi:10.3969/j.issn.1000-1093.2016.09.003

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In order to study the strapdown inertial navigation system (SINS) error caused by vibration isolation system which breaks the fixed connection between SINS and carrier, the error mechanism is analyzed, and an analysis method based on finite element analysis (FEA) is proposed. A model of SINS with vibration isolation system is constructed in FEA software. The motion parameters generated by trajectory generator are used to simulate the motion processes of carrier and SINS. The measured data of inertial devices obtained from the FEA results can be used to resolve and acquire the SINS error caused by vibration isolation system. The research results show that the FEA-based method can realize the quantitative analysis of SINS error caused by vibration isolation system, which is very important for optimization design of vibration isolation system.

Numerical Simulation on Pressure Wave in a 30mm Electrothermal-chemical Gun

NI Yan-jie， CHENG Nian-kai, JIN Yong， YANG Chun-xia， LI Hai-yuan， LI Bao-ming

2016, 37(9):  1578-1584.  doi:10.3969/j.issn.1000-1093.2016.09.004

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A one-dimensional internal ballistic model including the transient burning rate law is used to simulate the 30 mm electrothermal-chemical (ETC) launch. The accuracy of the model is proved by experimental data. Compared with classical ignition, the pressure wave decreases obviously while propellant is ignited by plasma. The effects of the initial parameters, such as input electric power, discharging timing sequence, propellant web thickness and loading density, on in-bore pressure wave are analyzed. In the condition of synchronous discharging, the peak value of pressure wave can be controlled while the electric energy ratio is less than 0.042. If the electric energy ratio is larger than 0.042, the peak value of pressure wave increases rapidly with the electric energy ratio. The first negative wave value is proportional to the electric energy ratio. Compared with the peak value of pressure wave, the first negative wave value is less affected by the electric energy ratio. In the condition of timing discharging, the allowed input electric energy ratio to control the pressure wave is proportional to the current pulse duration. At the high electric energy ratio, the peak value of pressure wave is inverse proportional to the current pulse duration. The pressure wave increases with the increase in loading density. But the allowed electric energy ratio to control the pressure wave showed no significant change, and the variation trend of the first negative wave value is unchanged. The influence of propellant web thickness on pressure wave in ETC launch can be ignored.

Research on Influence of Muzzle Brake Efficiency on a New Large Caliber Machine Gun Based on Floating Principle

LU Ye, ZHOU Ke-dong, HE Lei, LI Jun-song, HUANG Xue-ying

2016, 37(9):  1585-1591.  doi:10.3969/j.issn.1000-1093.2016.09.005

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A rigid-flexible coupling multi-body dynamic model of a new large caliber machine gun based on floating principle is established, in which the influences of soil and human body on machine gun were considered. The dynamics simulation of the machine gun with muzzle brake is conducted, and the simulated results are compared to the experimental results, and the availability of the proposed model is verified. The range of values allowed for the muzzle brake efficiency of machine gun based floating principle is obtained. The study results show that the proposed rigid-flexible coupling multi-body dynamic model including muzzle brake is accurate and reliable, and the efficiency of the designed muzzle brake is 35.9%. The theoretical range of values for the muzzle brake efficiency of machine gun is 22.5~50.0%.

The Study of Bullet-Barrel Matching Design Method of High Precision Sniper Rifle

LIU Guo-qing， XU Cheng

2016, 37(9):  1592-1598.  doi:10.3969/j.issn.1000-1093.2016.09.006

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A numerical calculation model of interaction between bullet and barrel is established to deeply study a matching design method of sniper rifle, which is based on nonlinear finite element theory. The proposed model is a comprehensive theory model to analyze launch process. Validation experiments were conducted. The experimental results are in agreement with the calculated results. The orthogonal experimental method is used to study the robustness of the main design parameters of bullet and barrel, in which the design parameters of bullet and barrel, the eccentric mass of bullet and the swing angle are taken as control factors, noise factor and performance measure, respectively. The calculated results of design parameter robustness in two levels are obtained. The calculated results of four groups of matching parameters of barrel and bullet with or without noise factor are agreed with the experimental results, which proves the correctness and feasibility of the robust design for matching design of bullet and barrel.

Analysis on the Influence of Turn-off Characteristics of Thyristor on Augmented Railgun

LI Zhen-xiao， ZHANG Ya-zhou， NI Yan-Jie， LI Bao-ming

2016, 37(9):  1599-1605.  doi:10.3969/j.issn.1000-1093.2016.09.007

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Based on the load characteristic of an augmented railgun, the influence of turn-off characteristics of high power thyristor is analyzed. The research shows that part of electric energy in pulse forming network cannot be used effectively in the process of launching experiment. The major reason is that the initial inductance of augmented railgun is larger and the rail current is of trapezoidal wave. Thus the breech voltage of augmented railgun is higher at the initial phase of launch, leading to the situations when the high power thyristor is shut off due to reverse voltage and the stored electric energy of pulse forming unit is not released entirely during discharging. The above conclusions are verified by the simulation and experiment of augmented railgun. According to the actual state of the pulse forming network in augmented railgun, the reuse of remaining energy is discussed. The research conclusion has a guiding role for the application of high power thyristor in augmented railgun system.

Estimation Method for Storage Life of Magnetorheological Fluid Fuze Arming Device

HU Ming, WANG Jiong, WU Xiao-lang

2016, 37(9):  1606-1611.  doi:10.3969/j.issn.1000-1093.2016.09.008

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An estimation method is proposed to study the safety and reliability of magnetorheological fluid (MRF) arming device using after a long-term storage, by which the storage life of MRF fuze arming device is estimated. The effect of harsh environment on the yield stress and viscosity of MRF and the performance of fuze arming device is analyzed through storage stability experiment. The experimental results show that a long-time high temperature results in sedimentating and aggregating the ferromagnetic particles in MRF, and speeding up the failure of MRF fuze arming device. An estimation method for the storage life of MRF fuze arming device is presented by establishing an accelerated storage life model. The reliable storage life of MRF fuze arming device under normal storage condition is estimated by the proposed method. The estimated results indicate that the reliable storage life of MRF fuze arming device is 15.2 years.

Analysis of Interior Ballistic Characteristics and Muzzle Flow Field of High-pressure Gas Launcher

ZHOU Peng， CAO Cong-yong， DONG Hao

2016, 37(9):  1612-1616.  doi:10.3969/j.issn.1000-1093.2016.09.009

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According to Navier-Stokes equation and Spalart-Allmaras turbulence model，the motion law of projectile under the action of high- pressure gas and its flow characteristics are simulated by using the dynamic mesh method based on CFD software. The change rules of in-bore average pressure， projectile base pressure， chamber base pressure and projectile motion parameters at the four kinds of initial pressure in the chamber are mainly studied. The changes of Mach number contours at different time at initial pressure up to 2.5 MPa are analyzed. Research results show that a flow oscillation phenomenon occurs in the bore，and the changes of chamber base pressure and projectile base pressure are fluctuating. Initial gas chamber has the effect on the pressure oscillation amplitudes of chamber base and projectile base and the projectile in the muzzle velocity. The relationship between projectile motion velocity or motion time and motion distance in the barrel is approximately parabolic.

Influence of Injection Pressure Change on Expansion Characteristics of Pulsed Plasma Jet

ZHAO Xue-wei， YU Yong-gang， MANG Shan-shan

2016, 37(9):  1617-1623.  doi:10.3969/j.issn.1000-1093.2016.09.010

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To analyze the influence of injection pressure on the expansion characteristics of pulsed plasma jet, a two-dimensional axisymmetric unsteady model for pulsed plasma jet expansion in air is established, and the numerical simulation of this process is carried out. The evolution characteristics of two-phase interface and the variation of flow field parameters of pulsed plasma jet in air are studied in the range of 1.5~ 3.5 MPa jet pressure, then compared with the experiments. Results show that the simulation values of axial expansion displacement of pulsed plasma jet are in good agreement with the experimental results. The parameters of the jet field are mutated at the nozzle exit, the pulse decays near the nozzle, and then it gradually decays to environmental parameters. When the injection pressure increases, the parameters of flow field, such as the expansion volume of pulsed plasma jet, the size of Mach disk and the pressure, increase, and the turbulent mixing in the expansion process is also enhanced, which is characterized by the more fracture of the interface of the plasma and air. When the injection pressure reduces to 1 MPa, no Maher disk appears at nozzle.

Research on Control of Hypersonic Shock Wave/boundary Layer Interactions by Double Micro-ramps

DONG Xiang-rui， CHEN Yao-hui， DONG Gang， LIU Yi-xin

2016, 37(9):  1624-1632.  doi:10.3969/j.issn.1000-1093.2016.09.011

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Shock wave/boundary layer interaction (SWBLI) is a ubiquitous phenomenon encountered in hypersonic flow field, and a flow separation induced by SWBLI leads to the performance degradation of hypersonic inlet. Detached-eddy simulation model and finite volume method are used with adaptive mesh refinement to simulate the flow separation controlled by micro-ramps, which is induced by SWBLIs in hypersonic flow for Ma=7. The control effect of micro-ramps on flow separation is discussed based on flow velocity, pressure gradient, transformed form factor and total pressure loss, and the control mechanism of double micro-ramps is investigated. The research results indicate that the reciprocal induction between streamwise vortex pairs generated by two micro-ramps accelerates the entrainment of vortex pairs generated by each micro-ramp, consequently the effect of two micro-ramps for eliminating the separation bubble is better than that of a single micro-ramp. As the height of micro-ramps decrease, the total pressure loss shows a trend of first decrease and then increase. The effects of streamwise vortex intensity and form resistance are synthetically discussed. The micro-ramps with 35%δ′ in height (separation bubble thickness) have the best effect on controlling the separation bubble, by which the separation bubble is decreased to disappear the reversed flow, and the peak of transformed form factor and the total pressure loss are reduced by about 86% and 1.9%, respectively.

Formation Mechanism of Pore Structure of Ball Propellant with Micro-pores Made by Double Emulsion Method

LIN Xiang-yang, LI Han, ZHENG Wen-fang, PAN Ren-ming

2016, 37(9):  1633-1638.  doi:10.3969/j.issn.1000-1093.2016.09.012

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The formation mechanism of pore structure of ball propellant with micro-pores made by double emulsion method is revealed. The formation and changing rule of pore structure are studied through sampling, microscopic observation and image analysis during emulsifying, balling and solvent distilling. The results show that the major parameters influencing the shape forming of pore structure are the conditions of emulsion and solvent distillation. The shape and size distribution of dispersed droplets in nitrocellulose emulsion are in basic agreement with the pore structure and pore size distribution in finished ball propellant. As a result, the pore morphology of ball propellant is determined by the emulsification conditions. The conditions of shape forming process have no significant effect on the size and morphology of the pores, while the solvent evaporation conditions have greater influence on the pore size distribution. The faster the solvent is distilled, the worse the pore structure uniformity is due to the agglomeration of pores. The pore structure uniformity of finished particles is improved effectively by reducing the speed of solvent distillation. The pore structure of nitrocellulose ball propellant with micro-pores made by double emulsion method is substantially determined by the morphology of the disperse phase droplets in nitrocellulose emulsion.

Numerical Simulation of Dynamic Brazilian Test of Polymer Bonded Explosive Simulant Based on Cohesive Crack Model

CUI Yun-xiao, CHEN Peng-wan, David A. Cendón, DAI Kai-da, ZHONG Fang-ping

2016, 37(9):  1639-1645.  doi:10.3969/j.issn.1000-1093.2016.09.013

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Polymer bonded explosive (PBX) is the key component of warhead. The dynamic behaviors of PBX, especially dynamic fracture behavior, are crucial issues on the safety and reliability of warhead. By introducing cohesive crack model (CCM), the dynamic explicit software LS-DYNA is used to simulate the dynamic Brazilian experiment on polymer bonded explosive simulant (PBX-M). By comparing with time history of tensile stress obtained by the strain gauge glued on the Hopkinson bar, the displacement fields and strain fields obtained by digital image correlation and high-speed camera, it is found that the tensile stress peak value obtained by numerical simulation is 5% smaller than the experimental result, and the deviation of the concentration zone of tensile strain from experimental data is less than 15%. Thus the validity of CCM is confirmed. The law of crack initiation and propagation of PBX-M sample during dynamic Brazilian experiment is studied from the results of numerical simulation. The quantitative information about crack width in sample is given.

Research on Containment Control of Second-order Nonlinear Multi-agent with Collision Avoidance Mechanism

CAO Hao-zhe， WU Yan-xuan， ZHOU Feng， WANG Zheng-jie

2016, 37(9):  1646-1654.  doi:10.3969/j.issn.1000-1093.2016.09.014

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The containment protocol proposed in the previous researches does not take the collision among followers into consideration under certain conditions. The containment of second-order nonlinear multi-agent system with collision avoidance mechanism around formation is studied based on the graph theory, matrix analysis and nonlinear analysis. The static and adaptive protocols are proposed, respectively. Lyapunov method is used to obtain the sufficient condition for stability of protocols. The simulations are used to verify the effectiveness of the containment control protocols. The protocols can make followers’ trajectories finally converge to a finite radius from the convex hull spanned by leaders’ trajectories, and keep the distances among followers being more than the safe distances all the time.

Experimental Research on Exhaust Plume Radiation of Scramjet

ZENG Xue-jun, SHI An-hua , HAN Dong, LI Xiang-dong, HU Hua-yu, ZHANG Jun

2016, 37(9):  1655-1661.  doi:10.3969/j.issn.1000-1093.2016.09.015

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The radiation measurement methods and test of scramjet exhaust plume are introduced. The exhaust plume radiation intensity and spectrum from 1m scale level scramjet are obtained for the aerial kerosene fuel under the test state of Mach number 6 with equivalent fuel-to-air ratio of 0.8. The radiation intensities of near ultraviolet band, near ultraviolet to visible light band, and mid-infrared band are reduced slowly along the exhaust direction near the exit of the scramjet. The high frequency instability and low frequency stability of radiation intensity reflect the micro instability and macro stability of combustion. According to the spectrum of plume, the radiation energy concentrates around the band of 4.364 3 μm. The main radiation component is identified to be CO₂.

Research on Topologically Optimized Anti-jamming Technology for Tactical MANETs

LOU Li, FAN Jian-hua, XU Cheng

2016, 37(9):  1662-1669.  doi:10.3969/j.issn.1000-1093.2016.09.016

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The military wireless communication network based on MANET architecture is characterized by a variety of communication modes and flexible self-organizations of nodes, but the multi-hop wireless transmission links are vulnerable to interference. In addition to using a series of traditional anti-jamming technologies at physical and link layers, the control and optimization means of network topology for getting better invulnerability and survivability become key issues in the research of anti-jamming policy of network layer. In dynamic electromagnetic interference environment, the tolerance of node or link failures is the basis of improving the survivability of the upper layer protocols, as well as the network recovery capability. According to the complex system theory, graph theory and random process theory, the influence of dynamic communication condition in battlefield is analyzed, and then a topology optimization method based on the measures of local stability is proposed in view of the importance of nodes and the connectivity of topology in order to construct a more reliable network. Simulated results show that the proposed method provides satisfactory efficiency and can improve the anti-jamming and self-optimizing performances of military communication networks under dynamic transmission.

Modulation Recognition Method of Non-cooperation Underwater Acoustic Communication Signals Using Principal ComponentAnalysis

JIANG Wei-hua, TONG Feng, WANG Bin, LIU Shi-gang

2016, 37(9):  1670-1676.  doi:10.3969/j.issn.1000-1093.2016.09.017

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The modulation classification of the non-cooperation underwater acoustic communication signals is extremely challenging due to channel transmission characteristics and low signal-to-noise ratio. The principal component analysis (PCA) is used to analyze the power spectra and square spectrum features of signals, which is capable of extracting the principal components associated with different modulated signals as input vector, thus reducing the feature dimension and suppressing the influence of noise. An artificial neural network (ANN) classifier is proposed for modulation recognition. The experimental modulation classification results obtained from field signals in 4 different underwater acoustic channels show that the proposed modulation recognition method has good classification performance.

Research on Single Carrier Underwater Acoustic Communication Based on Multiband Transmission

HAN Xiao, GUO Long-xiang, YIN Jing-wei, SHENG Xue-li

2016, 37(9):  1677-1683.  doi:10.3969/j.issn.1000-1093.2016.09.018

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For the high peak-to-average power ratio and the sensitivity of orthogonal frequency division multiplexing system to Doppler shift, a single carrier underwater acoustic (UWA) communication method based on multiband transmission is proposed, providing a feasible approach for high-rate UWA communication. The communication band is divided into some sub-bands with several kilohertz in bandwidth, and a guard band is inserted between sub-bands to eliminate inter-carrier interference at the receiver. A UWA communication experiment was conducted at sea. The available band is divided into two sub-bands, of which has 2.25 kHz in bandwidth and a 0.75 kHz guard band, and the carrier frequencies are 3 kHz and 6 kHz, respectively. Passive time reversal mirror combined with decision feedback equalizer is used to suppress inter-symbol interference. Transmissions of test data at communication distances of 3 km, 5 km, and 7 km are implemented at low bit error rate with communication rate of 9 kbit/s when modulated by 8-PSK, proving the effectiveness and robustness of the proposed method.

Cooperative Engagement-based Differential Guidance Law for Underwater Interceptor

LIU Wei-dong, CHENG Rui-feng, GAO Li-e, ZHANG Jian-jun

2016, 37(9):  1684-1691.  doi:10.3969/j.issn.1000-1093.2016.09.019

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A differential game guidance law based on game theory is developed for the underwater interceptor in order to improve the ability to intercept an unknown target in collaborative defense. A tripartite maneuvering game model is established, in which the homing constraint information can be obtained using the line-of-sight command. The method of solving the terminal problem by the adjoint mathematics is used to get the zero effort miss distance of the differential strategy by taking terminal miss distance and control energy as the performance indexes, which can be applied to arbitrary order control situation for tripartite strategies. The receding horizon control is used to predict the guidance law parameters in real time. The differential game strategy is simple to implement in practical applications under the conditions of homing. The performance of the guidance law is analyzed, and the effects of intercepting the targets by using different guidance laws are compared. The simulated results show that the differential game guidance law is robust adaptability and stability, which is not restricted by the maneuvering forms of targets under the condition of same constraints, and is of better trajectory characteristics.

Independent Component Analysis Based on Machining Error Separation

ZHANG Fa-ping, WU Di, ZHANG Ti-guang, ZHANG Ling-yun, YANG Ji-bin

2016, 37(9):  1692-1699.  doi:10.3969/j.issn.1000-1093.2016.09.020

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For the unsuccessful separation of the multiple systematic errors with similar scales by current machining error separation method, a new method to separate the machining errors is proposed based on independent component analysis. An error transfer model is built to describe the relationship between the systematic error caused by individual error source and the final systematic error measured from the machining surface. Then according to the theory of blind signal separation, an optimization model is used for the machining error separation where the negative entropy of the estimated error is used as the optimization objective function, and the fixed point algorithm is used as the optimization method. A method to determine the number of machining error sources is also given by means of the principal component analysis. A study case of a certain gyroscope surface is tested to verify the efficiency of the error separation method. The proposed method provides a new way for separation of machining errors and tracing of error sources.

A Reverse Direction Iterative Planning Algorithm of Clamping Forces in Entire Active Region Based on Workpiece Stability

QIN Guo-hua, SUN Shuo, WANG Hua-min, ZUO Dun-wen, WU Tie-jun, LU Yu-ming

2016, 37(9):  1700-1707.  doi:10.3969/j.issn.1000-1093.2016.09.021

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The reasonable planning of clamping forces in the machining process is a key issue for guaranteeing the machining quality, which is of great significance to ensure the machining reliability and accuracy. For this purpose, a reverse direction iterative planning algorithm of clamping forces in entire active region is established. In addition to the direction constraint to contact force between workpiece and fixture, the force state of workpiece in fixturing layout is analyzed. According to unknown and known conditions of magnitude of clamping forces and clamping placement, the analysis methods of force existence and force feasibility are established based on the linear programming technology. Under the condition of existence of clamping forces, a clamping surface is discretized into points, and the magnitude of clamping force is chosen, beginning with the minimum value at each point with a certain step length along the positive direction. The selection of the next magnitude of clamping force depends on the difference between the feasibilities of clamping forces at two adjacent points. According to the difference between the feasibilities of the current clamping force and the last one, the step length and its direction can be determined for the next selection. If the feasibility of the current magnitude is same as the feasibility of the previous magnitude, the step length and its direction for the next magnitude are the same as those for the current magnitude. Otherwise, a half of step length along the negative direction is chosen. The selection procedure for the magnitude of clamping force is exceeded until the absolute value of the current step length is within the given threshold value. The proposed method can be used to transform the continuous design issue of clamping forces into a discrete one. It can be used for the development of computer aided clamping force design as well as the determination of clamping forces for workpieces with complex surfaces.

A Nonsingularity Modification Method of Angular Deviation in Azimuth-elevation Tracking Frame

CHEN Jia-hong, XIANG Jie, WANG Er-jian

2016, 37(9):  1708-1714.  doi:10.3969/j.issn.1000-1093.2016.09.022

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The secant compensation method for correcting an angular deviation of radar tracking measurement system in azimuth-elevation polar coordinate frame is reviewed, and its pros and cons are analyzed. To overcome the complexity of derivation process and singularity, a tracking pointing coordinate system, i.e., line-of-sight coordinate system, and a simple and practical nonsingularity compensation method based on coordinate transform principle are proposed. The equipollency between the proposed method and the universal secant compensation method based on solid geometry reasoning results is proven. The application of the proposed method in typical deviation correction of shafting and its effect on the tracking and measurement accuracies of radar system are also analyzed. For elevation angle of 89°, and azimuth and elevation angular deviations of 3 mrad, the azimuth error and elevation error calculated by the secant compensation method are 6 759.2″and 63.5″, respectively. The proposed method is benefit for the high precision tracking and measurement of space targets in the polar coordinate frame, especially to effectively improve the zenith tracking performance and the pointing accuracy with high elevation.

Storage and Computation of Markov Reliability Model for Large-scale Phased-mission System

YAN Hua， GAO Li， WANG Kui， QI Lei

2016, 37(9):  1715-1720.  doi:10.3969/j.issn.1000-1093.2016.09.023

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When Markov model is used to analyzed the reliability of phased-mission system, the system state grows exponentially with the increase in the number of components, thus resulting in a huge storage space and calculated amount resolved by the model. According to the element value rules and sparsity of the transition rate matrix Q in Markov model, the formula of computing the elements q_ij is derived based on binary description of states, and a Q-matrix compressed storage scheme (QMCS) is proposed. A reliability computing algorithm using Krylov subspace method is proposed based on the model compressed storage scheme. Taking a practical phased-mission system for example, the required storage spaces, computation times and reliability results of different compressed storage schemes and different algorithms are compared. The analysis results show that the method combining QMCS and Krylov subspace method has higher efficiency in storage and computation. Especially in the case of a large matrix, the QMCS-Krylov method is superior to other methods both in computation time and accuracy.

Implementation of Active Disturbance Rejection Control of Robot by Tracking Differentiator

LI Dian-qi， DUAN Yong

2016, 37(9):  1721-1729.  doi:10.3969/j.issn.1000-1093.2016.09.024

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A disturbance estimation-based nonlinear feedback control system for robots is presented, and its stability is demonstrated. On the basis of result, a novel active disturbance rejection controller (ARDC) is proposed, which avoids the burdensome online computation of robot inverse dynamics and implement the trajectory tracking of robots. The controller comprises two tracking differentiators (TDs) , one is used to arrange the transient process of system，and the other is used to estimate velocity and acceleration. TD can attenuate measurement noise due to its filtering characteristic. “Extended state”, comprising the control input of controlled object and the feedback of estimated acceleration, is used to detect the real time effects of system model and the external disturbances, and then dynamically compensate their real-time effects. The proposed ARDC has the same good adaptability and expected robustness as previous ADRC, and it also has the characteristic of less parameters adjustment. Numerical results show that the control system has less overshoot, rapid response, and robustness.

Capturing Dynamics of Flexible Ropes for Space Large-scale End Effector

RONG Ji-li, XIN Peng-fei, ZHUGE Xun, YANG Yong-tai, XIANG Da-lin

2016, 37(9):  1730-1737.  doi:10.3969/j.issn.1000-1093.2016.09.025

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The problems of dynamics during winding and capturing a satellite by the space manipulator end-effector are studied. The winding movement of transverse isotropic flexible wire ropes is described by absolute nodal coordinate formulation (ANCF), and Cardan angles are applied to describe the attitude of the rigid satellite. A rigid-flexible coupling dynamic model containing a stationary ring and a rotation ring fixed on the end-effector, three ropes and a shaft of the captured satellite is established. Nonlinear contact force is introduced to reveal the interaction between shaft and wire ropes. The generalized-α method and the scaling technique are employed to develop a numerical calculation program for solving the dynamic equations precisely and efficiently. Simulation results show that the proposed dynamic model can preferably simulate the processes of flexible wire rope winding and satellite capturing. The change of satellite attitude and rope movement during capturing are obtained, which could provide reference basis for design and test of capturing mechanism.

Research Notes

Analysis about Thermal-structure Coupling Effect of High Firing Rate Automatic Mechanism of a Gun

DAI Yong, QIAN Lin-fang, WU Xiao-jin, XU Ya-dong

2016, 37(9):  1738-1743.  doi:10.3969/j.issn.1000-1093.2016.09.026

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The prototype of a high firing rate automatic mechanism of a gun has a periodic fire stop failure during firing. The classical thermal expansion theory and the finite element method are used for the thermal-structure coupling analysis of high firing rate automatic mechanism. The analysis results show that the size of its structure can be appropriately adjusted to meet the requirement of the current firing rate and further improve the rate of fire. The improved structural design of demonstration prototype has non periodic fire stop phenomenon after several rounds of live ammunition tests. Thermal-structure coupling method can be used to solve similar failures in engineering practice.

Crack Fault Diagnosis of Automatic Mechanism Based on Shock Response Spectrum Features Extraction

LI Hai-guang， PAN Hong-xia， REN Hai-feng

2016, 37(9):  1744-1752.  doi:10.3969/j.issn.1000-1093.2016.09.027

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A new crack fault diagnosis method is presented for the automatic mechanism of high-speed gun. The method uses shock response spectrum (SRS) for features extraction. Impact vibration data are acquired in the weapon firing test in which different cracked parts are used. These data are separated according to gun operation status. The shock response spectra of the separated data are computed. Two new definitions of relative peak ratio and relative peak frequency ratio of response spectrum are proposed based on different response characteristics of response spectrum area. The relative peak ratio and relative peak frequency ratio as fault features are extracted. The various faults are recognized by comparing the Statistical distribution pattern of fault characteristic values under different crack conditions. The experimental result shows the proposed method can be used effectively and accurately to diagnose the crack failures of gun automatic mechanism and is particularly applicable for on-line monitoring.

Small Target Detection in a Single Infrared Image Based on RPCA

WANG Zhong-mei, YANG Xiao-mei , GU Xing-fa

2016, 37(9):  1753-1760.  doi:10.3969/j.issn.1000-1093.2016.09.028

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The robust infrared small target detection is one of the key techniques of infrared search and track systems. An improved algorithm is presented for small target detection in single-frame infrared image. The infrared image model is generalized to a new infrared patch-image model, and based on the new model, the small target detection is formulated as an optimal robust principal component analysis (RPCA) problem of separating low-rank and sparse matrices. Considering the presence of noises and clutter in infrared image, an alternating direction algorithm is used for solving the RPCA problem to obtain sparse target image, and a simple image segmentation method is used to segment the target image for target detection. The small infrared targets in different scenes, such as sky, sea-sky, cloud and sea surface, are detected and simulated. Experimental results demonstrate the effectiveness of the proposed method.