Table of Content

23 June 2014, Volume 35 Issue 6

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Paper

Dynamics Characteristics of Automatic Mechanism for Gas Operated and Floating Barrel Operated Automatic Action

SONG Jie, LIAO Zhen-qiang, LI Jia-sheng, XIAO Jun-bo

2014, 35(6):  753-761.  doi:10.3969/j.issn.1000-1093.2014.06.001

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In order to perform the feasibility study on the application of automatic mechanism for gas and floating barrel operated automatic action in high muzzle velocity grenade launcher(HMVGL) and reduce the recoil of weapon system, the structure parameters of gas operated device is adjusted, and the recoil energies of the barrel and bolt carrier assembly are matched. The basic equations of interior ballistic and flow problems which consider the effects of heat loss and floating barrel are derived based on aerodynamics and thermodynamics. The performance characteristics of automatic mechanism and the recoil-time curve are obtained by the calculation and simulation of launch dynamics of HMVGL. The reliability of the model is validated by comparing the simulation and experimental results. The pressure fluctuation of gas chamber is discussed with regard to gasport diameter, gas-port position and initial gas volume. The speed curves of automatic mechanism and the recoil curve are also analyzed. By means of automatic mechanism based on the gas and floating barrel operated automatic action, the maximum recoil of HMVGL can be limited within 1 100 N to achieve a low recoil launching.

Research on Velocity Measurement of Solid Armature in Electromagnetic Launch Based on B-dot Probes

LIU Fu-cai, LI Huan, WANG Da-zheng, WANG Zhen-chun, HE Suo-chun

2014, 35(6):  762-768.  doi:10.3969/j.issn.1000-1093.2014.06.002

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The measurement of projectile velocity and displacement is one of the railgun test parameters. The multiple high-speed data acquisition channels are required in the velocity measurement of distributed probes. The new probe in-series and waveform combination methods for measuring the velocity of solid armature in enhanced electromagnetic railgun bore are proposed according to the velocity measuring principle of the B probe. The induced voltage of the probe of enhanced electromagnetic railgun is calculated by using the driving current data and the fitting speed data, and then the probe in-series and waveform combination methods are used to measure the armature velocity, respectively. The simulation and experimental results show that the calculated waveform is basically in agreement with the measured waveform. The proposed methods are compared with the distributed probe measurement method. The two methods need only one high-speed data acquisition port. They have the advantages of low cost and high reliability.

Application of Adaptive Fuzzy Wavelet Neural Sliding Mode Control in AC Servo System

HOU Run-min， LIU Rong-zhong， HOU Yuan-Long， GAO Qiang， YANG Guo-lai

2014, 35(6):  769-775.  doi:10.3969/j.issn.1000-1093.2014.06.003

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An adaptive fuzzy wavelet neural network fast terminal sliding mode control (AFWN-FTSMC) approach is proposed to control the position of high power AC servo system in a certain weapon. An adaptive fuzzy wavelet neural network controller (AFWNC) is introduced to approach the equivalent control of sliding mode control, which solves the problem that the equivalent control can not be obtained accurately because of the uncertain parameter and external disturbances of the system. The controller can be designed without accurate mode. An adaptive proportional-integral (A-PI) law is used to eliminate system chattering. The stability of the closed loop system is guaranteed by using the Lyapunov method. Simulation results show that the proposed approach can not only improve the steady state performance and control accuracy, but also avoid the chattering problem effectively, and the structural parameter uncertainty has strong robustness.

Optimization Design of Positioning Precision for Howitzer Shell Transfer Arm with Parameter Uncertainity

GAO Xue-xing, SU Zhe-zi, SUN Hua-gang, HOU Bao-lin

2014, 35(6):  776-781.  doi:10.3969/j.issn.1000-1093.2014.06.004

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An optimization design method is proposed to indirectly improve the reliability of positioning precision for shell transfer arm in ammunition automatic loading system with uncertain parameters. The main uncertain factors that influence the positioning performance are analyzed. Space is transformed, and Latin hypercube sampling is applied for the uncertain variables. The error weights are calculated according to the distances from sampling points to the mean point in the transformed space. An electromechanical model is established with MATLAB/Simulink, and the simulations are run for every sampling point to get the positioning errors. The weighted sum of these errors is calculated as a performance index. This performance index is optimized using particle swarm algorithm. This method has remarkable optimization effect and good computational efficiency.

Research on the Chamber Parameters Measurement Based on Vision Sequence Image Analyses

WANG Hui-feng， WANG Xiao-yan, WANG Bing-jian, GUAN Li-min, WANG Gui-ping

2014, 35(6):  782-788.  doi:10.3969/j.issn.1000-1093.2014.06.005

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A new idea of reading data target using vision cross diameter is put forward for the high-accuracy measurement of chamber parameters, and a measured data reading method that is based on the target sequence image is designed. In this method, a special rule target measurement equipment is designed to read the cross diameter data in a single image sence. The rule targe

Experimental Research on Technical Approaches for Reducing Firing Energy of SCB/LTNR

YAN Nan, WANG Gang, HE Ai-jun, BAO Bing-liang

2014, 35(6):  789-794.  doi:10.3969/j.issn.1000-1093.2014.06.006

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Further reduction in the firing energy of SCB/LTNR firing device has long been a bottleneck of micro initiation system in MEMS fuze.Technical approaches for reducing the firing energy of SCB firing device are obtained by testing the firing sensitivity, such as decrease in dimensions, proper aspect ratio, addition of V-notch angle, reduction in particle size of ignition composition, atc. In the experimental process, 3.83 V of the minimum all-firing voltage, 0.073 mJ of firing energy and 229.88 mA of the maximum no-firing current are achieved. Two ignition mechanisms can be found by analyzing firing phenomenon and electrical characteristics curve. One critical ignition mechanism is electrothermal ignition, of which corresponding bridge area of SCB transducer element is 7.65×10² μm² and the mass is 3.55×10^-6 mg. The other is electro-explosive ignition, of which corresponding area is 5.68×10² μm² and the mass is 2.64×10^-6 mg.

High-frequency Measurement and Calculation Study of Systematic Errors of High-rolling Projectile Roll AngleBased on a Combination of MR/GNSS

CAO Peng, YU Ji-yan, WANG Xiao-ming, YAO wen-jin, WU You-long

2014, 35(6):  795-800.  doi:10.3969/j.issn.1000-1093.2014.06.007

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In order to study the systematic errors of MR/GNSS measurement system and improve its measuring frequency, a high-frequency measuring method for the projectile roll angle and angular rate, which is based on the assumptions of small angle-of-attack and single axis rotation, is established by using the flight characteristics of high-spin projectile. The systematic error equations of roll angle and angular rate are derived. The real-time systematic error of this combined measuring system in the global scope is calculated by establishing the simulation model with pitch angle as a variable. The results of 6-DOF exterior ballistic simulation show that the overall roll angle error is less than ±5° and the angular rate error is less than ±5°/s after the region of smaller angle between projectile axis and geomagnetic vector is excluded. In the condition of medium or small launching angle, the roll angle calculation method based on MR/GNSS can meet the needs of high-frequency and high-accuracy roll angle measurement for the high- spin projectile.

Self-adaptive Cabin Opening Method Based on Firing Data Error of Shrapnel

YANG Rui-wei, YIN Yue-qiang, LI Dong-guang, YANG Deng-hong

2014, 35(6):  801-807.  doi:10.3969/j.issn.1000-1093.2014.06.008

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In order to increase the impact dispersion accuracy of submunitions, a method of self-adaptive cabin opening is put forward. A trajectory model of submunition is built based on the research on the flight dynamics of spin-stabilized shrapnel. The impact dispersion of subminution is simulated by using this model. According to the errors got from the theoretical and practical trajectory results of a certain ejection point of the shrapnel, the effects of the errors on the impact dispersion of submunition are analyzed through simulation comprehensively. With the help of the simulation results, a shrapnel self-adaptive cabin opening method with modified ejection point is proposed to improve the impact dispersion accuracy of submunition. A modified formula for the best cabin opening point of spin-stabilized shrapnel is deduced. The results show that the method used in this paper can be used to increase the impact dispersion of submunitions by 26.3% in horizontal and 53.8% in vertical.

Research on Muzzle Shock Wave in Low Pressure Environment

ZHU Guan-nan, WANG Zheng-lun, MA Jia-jia， WANG Qiao

2014, 35(6):  808-813.  doi:10.3969/j.issn.1000-1093.2014.06.009

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A pressure test of muzzle shock wave is carried out to understand the propagation of muzzle shock wave in low pressure environment. Low pressure environment is established in a cabin through vacuum pumping system. Pressure curves of muzzle shock wave at different pressures are got by the pressure test system. The results show that the distribution of muzzle shock wave in low pressure environment is the same as that in atmospheric environment. With the decrease in the ambient pressure, the intensity of shock wave decreases linearly. The intensity of shock wave at 10 km altitude is roughly half of that in ground. These results lay the foundation for the research on muzzle flow field and its control technology of aircraft gun in real high altitude environment.

Terminal Ballistics Study of Deformable Projectile Penetrating Brittle Material Targets for Free-surface andCrack Region Effects

KONG Xiang-zhen, FANG Qin, WU Hao

2014, 35(6):  814-821.  doi:10.3969/j.issn.1000-1093.2014.06.010

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The decay function for the free-surface effect is constructed by treating a target as an incompressible Mohr-Coulomb material and assuming that the cavity expansion produces a plastic-crack-elastic response region. The semi-empirical forcing function of brittle targets for oblique penetration is obtained by multiplying the semi-empirical forcing function of brittle targets with the decay function. Then the projectile is modeled with an explicit transient dynamic finite element code and the target is represented by the forcing function as the pressure boundary condition. This methodology eliminates the need for discretizing the target as well as the need for the contact and erosion algorithms, which reduces the computer time and memory requirements. The oblique penetration of 4340（RC44.5）steel into limestone target is simulated. The comparisons of the final forms of projectile and the final positions of tip in simulation and experiment demonstrate the effectiveness and advantage of the proposed method.

Preparation and Thermal Properties of NC/RDX Nano-composite Energetic Materials

JIN Miao-miao, LUO Yun-jun

2014, 35(6):  822-827.  doi:10.3969/j.issn.1000-1093.2014.06.011

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NC/RDX nano-composite energetic material with nitro-cellulose(NC) as gel matrix is prepared using sol-gel method, and the material is characterized by FTIR, XRD, SEM and TG/DSC methods. The results show that RDX is successfully composited with NC. The minimum RDX average crystallite size calculated by Scherrer equation is 50.16 nm, and although the crystallite size increases with the increase in RDX content, the maximum crystallite size is less than 100 nm. Both the temperature of maximum decomposition rate and DSC exothermic peak temperature of RDX in composite material are lower than that of RDX raw material.

Effect of RDX Content on Mechanical Properties of BAMO-AMMO Base Propellants

SONG Xiu-duo, ZHENG Wei, PEI Jiang-feng, ZHANG Jun, WANG Jiang-ning, ZHAO Feng-qi

2014, 35(6):  828-833.  doi:10.3969/j.issn.1000-1093.2014.06.012

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The mechanical properties of BAMO-AMMO base propellants with various amounts of RDX are characterized by using monaxial tensile test. The results show that the tensile stress of BAMO-AMMO base propellants increases and the tensile elongation decreases when the RDX content increases from 70% to 90%, but the change from 75% to 85% is inconspicuous. The effect of the RDX content on mechanical properties of BAMO-AMMO base propellants is analyzed by dynamic mechanical analyzer(DMA).The analysis result of DMA shows that the change rule of glass-transition temperature with RDX content is the same as that of tensile elongation. The elongation increases, the glass-transition temperature rises and the loss tangent (tan δ) enlarges with the increase in RDX content.

A Novel Spectral-spatial Sparse Method for Hyperspectral Target Detection

SONG Yi-gang, WU Ze-bin , SUN Le, LIU Jian-jun, WEI Zhi-hui

2014, 35(6):  834-841.  doi:10.3969/j.issn.1000-1093.2014.06.013

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Target detection is one of the most important applications of hyperspectral imagery (HSI). The traditional target detection techniques usually discard the spatial information of the target, resulting in a lower accuracy of detection. A novel simultaneous sparse representation model is proposed for HSI target detection. The proposed approach applies the theory and algorithm of mixed-norm to the hyperspectral target detection. By considering the combination of spectral information and spatial context of HSI, a model with a mixed-norm regularizaton based on the simultaneous sparse representation is proposed. And this model is finally solved via alternating direction mehtod of multipliers (ADMM) efficiently. The effectiveness and accuracy of the proposed simultaneous sparse representation model and algorithm are demonstrated by experimental results on a real hyperspectral images.

Disturbance Torque Compensation of Gyro-stabilized Seeker Based on Disturbance Observer

LIU Jun-hui, SHAN Jia-yuan, ZHAO Xin

2014, 35(6):  842-849.  doi:10.3969/j.issn.1000-1093.2014.06.014

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Disturbance torque directly affects the tracking and measuring accuracies of seeker and the guidance precision. To analyze the degradation of gyro-stabilized seeker tracking accuracy due to disturbance torque, the dynamics models of seeker, seeker gimbal friction and seeker cable disturbance torques are established. To reduce the influence of disturbance torque on seeker tracking accuracy, a practical disturbance observer (DOB) is designed to compensate the disturbance torques. Multi-rate sampling problem due to the difference between sampling and hold times of seeker system and DOB is considered. A discrete DOB design method is proposed based on Nyquist stability theory, so the conservation of small gain design method can be removed. Sampling, hold and filter time constants of DOB are specified by balancing system stability, disturbance torque compensation and sensor noise reduction. An extracting method of information which is required by DOB is proposed by integrating the measurement information of missile and seeker. The mathematical simulation results show that the designed DOB can improve the seeker tracking accuracy efficiently.

Observerbility Analysis of Rocket MEMS-INS/GNSS Integrated Navigation System Attitude in Classic Trajectories

DONG Jin-long, MO Bo

2014, 35(6):  850-856.  doi:10.3969/j.issn.1000-1093.2014.06.015

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MEMS-INS/GNSS integrated navigation system for artillery launched rockets is taken as the research object. Based on the singular value decomposition of system observability matrix, a new concept, “equivalent singular value”, is proposed to test the observability of a system state. The method is used to analyze the observability of Euler angle errors in three kinds of trajectories without maneuver and with pitch and yaw maneuvers. The curves of “equivalent singular value” (observability) of three Euler angles errors are plotted, which illustrate that the roll error observability becomes better when projectile body maneuvers, the pitch angle error observability is mainly related to the acceleration in the axis of the body symmetry, and the azimuth error observability is proportional to horizontal acceleration. The simulation results are consistent with the analysis results.

Development of an Equivalent Equipment on Underwater Explosion Impulsive Loading

XIANG Da-lin， RONG Ji-li， HE Xuan, HU Chang-hua， LI Jian , ZHANG Wei， REN Peng

2014, 35(6):  857-863.  doi:10.3969/j.issn.1000-1093.2014.06.016

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In order to obtain an equivalent underwater explosion impulsive loading, the theoretical analysis is carried out for the impact of a flyer plate on a piston, which seals a conical target chamber filled with water, based on one-dimensional elastic wave propagation and a linear equation of state for water. The impact process is simulated by using AUTODYN software, and the decay times of shock waves for two pistons with different thicknesses are analyzed and compared. According to the theory and numerical simulation research, an equivalent equipment is designed, and the pressure-time curve is measured at the central point of chamber medial wall. The results show that it is feasible to obtain an equivalent underwater explosion shock waves in the laboratory through high speed impact, and the flyer speed and the piston thickness determine the peak pressure and decay time in the conical target chamber, respectively. The equivalent equipment can be used to investigate the shock response of typical structures and materials subjected to underwater explosion impulse loading.

Calculation of the Static Corrosion-related-magnetic Field Produced by a Submarine in Shallow Sea

CHEN Cong， YAO Lu-feng， LI Ding-guo， GONG Shen-guang

2014, 35(6):  864-871.  doi:10.3969/j.issn.1000-1093.2014.06.017

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In order to forecast the distribution characteristics of the static corrosion-related-magnetic field produced by a submarine in shallow sea, a static horizontal electric dipole is adopted to simulate the static magnetic field source, and a three-layered conductive media mode is adopted to simulate the shallow sea environment. At first, the expressions for the magnetic field distribution in all the spaces produced by a static horizontal electric dipole located in the middle layer are derived, and then the numerical simulation method is used to analyze the distribution characteristics and the attenuation law of far field, as well as the influences of the ocean environmental factors, such as conductivity, seawater depth, and air-water interface, on it. The research results show that the static corrosion-related-magnetic field of a submarine in shallow sea has measureable magnitude and obvious distribution characteristic in seawater, and its far field degenerates with the inverse square of distance, so it can become an important signal source for detection or striking. In addition, because of the influence of the space current in conductive medium, the seabed of which conductivity is less than seawater enhances the magnetic field in seawater, and the air-seawater interface weakens the field. The research results lay a foundation for the further actual application.

Finite Element Simulation of Dynamic Crack Propagation in Brittle PMMA Plates

ZHANG Zhen-ya, MA Yuan-yuan， ZHOU Feng-hua

2014, 35(6):  872-878.  doi:10.3969/j.issn.1000-1093.2014.06.018

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A user-defined material mechanical behavior subroutine (VUMAT) is developed to incorporate it into ABAQUS for numerically simulating the propagation of dynamic cracks in the preloaded brittle PMMA plates. The initial-rigid, linear decay, and irreversible cohesive rule, rate-independence or rate-dependence, are adopted in the subroutine. The simulation results are compared with the experimental observations. It is shown that, in most cases, the crack propagation velocities simulated using a rate-independent cohesive law are greater than the experimental values under the prescribed preloading, except in the high crack velocity regime, when the numerical results are similar to the experimental data. A rate-dependent cohesive law is proposed. The numerical simulation results obtained by the rate-dependent cohesive law agree well with the experimental data in all test velocity range. It also confirmed that the utilization of a rate-dependent cohesive law is necessary for the simulations of brittle crack propagation, because it better describes the complex fracture process occurring in the tip zone of the fast propagating cracks.

Development of Virtual Test System for Real-time Control and Performance of Amphibious Vehicle

JU Dong-mei, XIANG Chang-le, LI Jun, SUN Xu-guang, LIU Jing

2014, 35(6):  879-884.  doi:10.3969/j.issn.1000-1093.2014.06.019

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Amphibious vehicles have three operating conditions: on-water, on-land and water-land transition. At present, two main simulation methods have been used for amphibious vehicle. One is to use the multi-body dynamics software for simulation of on-land operating condition, and the other is to use CFD software for simulation of on-water operating condition. The methods are used to simulate a single operating condition. In order to solve the computing problem of dynamics under various operating conditions, a real-time control dynamic simulation system for all operating conditions of amphibious vehicle is established by using the coupling theory of particle flow field and collision and the calculating methods of multibody dynamics. Based on this, many virtual tests were completed. The test results were verified by taking a high-speed tracked amphibious vehicle for example. The results show that the proposed method has a certain degree of accuracy, and the calculation error is less than 15% compared to the experimental data.

Position and Pose Measurement of Cylinder-like Object Based on Virtual Pole Mechanism

LUO Lei, CHEN Ken, MA Zhen-shu, MU Xi-hui

2014, 35(6):  885-890.  doi:10.3969/j.issn.1000-1093.2014.06.020

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A mechanism, which uses a digital pan-tilt and a beam from laser rangefinding sensor as virtual pole to measure the position and pose of cylinder-like object, is presented. The structure, constitution and measuring principle of the mechanism are described in detail. Calculation method and formulas are also given. The position and pose of an ammunition can be synchronously measured using the given mechanism and algorithm if the positions of two points in space are known. The mechanism can be used for explosive ordnance disposal robot for the position and pose measurement of ammunition. The measured data can be used to guide the route planning and autonomous movement of robot arm.

Research on Material Removal Rate of SiC/Al Particulate Metal Matrix Composite by Micro-wire ElectricalDischarge Machining

GENG Xue-song， CHI Guan-xin， WANG Yu-kui， WANG Zhen-long

2014, 35(6):  891-899.  doi:10.3969/j.issn.1000-1093.2014.06.021

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The material removal of SiC/Al particulate (SiCp/Al) metal matrix composite by micro-wire electrical discharge machining (micro-WEDM) is influenced by many factors, which makes it difficult to obtain the mathematical model of material removal rate (MRR) effectively. To solve this problem, an experimental study method is conducted under the constraint conditions. A central composite design (CCD) testing with 3-factor and 5-level is carried out, SiCp/Al metal matrix composite machining test scheme is designed, and then a second-order relational model is established between MRR and main power parameters (open-circuit voltage, discharge capacitance, and pulse duration) by using response surface methodology. Through multiple quadratic fitting, a quadratic regression mathematical model of MRR is obtained. Constrains of actual machining condition upon the parameters are analyzed further. With the goal of improving MRR of SiCp/Al metal matrix composite by micro-WEDM, a parameters optimization model is established. Particle swarm optimization algorithm and its procedure are designed to solve the model.

Research on Friction and Wear Properties of CaF₂/TiC/ Ni-Base Alloy Composite Coatings at Different Temperatures

CAI Bin， TAN Ye-fa， TANG Jian， TAN Hua， WANG Wei-gang

2014, 35(6):  900-907.  doi:10.3969/j.issn.1000-1093.2014.06.022

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In order to improve the friction and wear properties of Ni-base alloy composite coatings in the condition of rigor friction , especially in the condition of high temperature dry friction, Ni-base alloy composite coating modified by CaF₂ and TiC particles is prepared on the surface of 45 carbon steel. The microstructure of composite coating is analyzed. The tribological behaviors and mechanisms of the composite coating are researched. The results show that CaF₂/TiC/Ni-base alloy composite coating presents the lamellar microstructure, which is composed of the phases of γ-Ni, CrB, Cr₇C₃, TiC and CaF₂. The CaF₂/TiC/Ni-base alloy composite coating has excellent anti-friction and anti-wear properties at various temperatures. The friction coefficient of the composite coating decreases from 0.42 to 0.29 as the temperature increase from room temperature to 500 ℃, which is 16.2%～33.9% less than that of Ni-base alloy coating. The wear losses of the composite coating gradually decrease as the temperature increases, which is sharply reduced compared with that of Ni-base alloy coating. The transferred layer is prepared on the worn surface of the composite coating at 500 ℃. The transferred layer contains CaF₂ which has the anti-friction effect at high temperature, so the friction coefficient of the composite coating is reduced. The wear mechanism of the composite coating is mainly the fatigue delamination of the transferred layer. The coverage area of the transferred layer, which may protect the composite coating, increases with temperature. So the wear loss of the composite coating decreases with the increasing temperature.

Experimental Investigation on Propulsion Performance of Laser Chemical Micro-propulsion

LI Long， HU Xiao-jun， TANG Zhi-ping

2014, 35(6):  908-914.  doi:10.3969/j.issn.1000-1093.2014.06.023

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The parameters of laser and propellants are the main factors affecting the propulsion performance of laser chemical micro-propulsion. The thickness of propellant is an important experimental parameter under T-mode. Hence, the propulsion performances of complex double-base propellants with different thickness are studied experimentally. The experimental results show that the momentum coupling coefficient increases with the incease in thickness of propellant while the specific impulse reduces on the contrary. The effect of laser power density on the release of chemical energy is studied. When a semiconductor laser with the power of 1.80 W and the double-base propellant are used, the momentum coupling coefficient and specific impulse are 130.8 dyne/W and 493.0 s, respectively, while the laser energy coefficient is 316.4%, which is 6.46 times better than that of PVC propellant without the release of chemical energy.

Function Partitioning Algorithm of Maintenance Equipment Based on Occasion Failure Rate

SHI Xian-ming， CHEN Chun-liang， ZHAO Mei， SHI Quan

2014, 35(6):  915-920.  doi:10.3969/j.issn.1000-1093.2014.06.024

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Function partitioning of maintenance equipment is studied based on the fact that failure rates are different in different usage conditions. With the consideration of the types, usage occasion and volume of maintenance equipment, an assigning model from maintenance device to maintenance equipment is built for the failure rate in main occasion of maintenance equipment. The maintenance devices can be initially assigned to maintenance equipment by its main usage occasion without consideration of volume limitation, and the assigning correction of maintenance devices is conducted based on the difference between occasion failure rates with the consideration of volume limitation. An assigning algorithm of two maintenance equipment is proposed, and an example is given, which proved the model and solution algorithm are scientific.

Study of on-line Diagnosis Strategy for Multiple faults

ZHENG Zhi-gang， HU Yun-an， WU Liang

2014, 35(6):  921-926.  doi:10.3969/j.issn.1000-1093.2014.06.025

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The present system multiple fault diagnosis is generally realized by generating a test sequence with minimal average test cost under fixed initial fault ambiguous groups, and then the faults are isolated through the fault diagnosis tree constructed according to the generated test sequence, so the test sequence and fault diagnosis tree are relatively fixed. When the initial faults ambiguous groups change, the test strategy still keep unchanging. To resolve the problem, an on-line strategy for multiple fault diagnosis is proposed, the iterative formulas to calculate the possibility of ambiguity groups are deduced, and the optimal test is selected by evaluation function based on fault isolation degree and information entropy of unit cost. The faulty unit with highest posterior possibility to be repaired is searched by set covering algorithm. Test case shows that the on-line strategy can isolate multiple faults by flexibly utilizing known information. It has the advantages of simple calculation and small storage space, and is feasible for multiple fault diagnosis of complex system.

Research Notes

Design and Response Characteristics Analysis of a Fast-response Sensor for Temperature and Heat Flux Measurement

YANG Qing-tao, BAI Han-chen, ZHANG Tao, YANG Juan, WANG Hui

2014, 35(6):  927-934.  doi:10.3969/j.issn.1000-1093.2014.06.026

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A fast-response thermal resistance type heat flux sensor is designed to measure wall surface temperature and heat flux simultaneously in hypersonic vehicle long-time ground test. The thermocouple junctions are formed at the interfaces among different metal layers, and the heat flux and surface temperature could be achieved using the measured temperatures at the interfaces. A FEA model is built to simulate the internal heat transfer and response characteristics of the sensor. The numerical results show that theoretical assumptions could be met after a short-time response. The surface temperature and heat flux could be achieved simultaneously by considering temperature difference term and energy storing term during data reduction, and the effect of surface temperature on heat flux could be more closely reflected compared to the steady data reduction method.

Study of the Equivalence between Gelatin and Muscle Target Based on Temporary Cavity Effect

JIN Yong-xi, MAI Rui-min, ZHANG Jing-min, ZHOU Ke-dong, ZENG Xin , CUI Hai-lin, YUAN Rui

2014, 35(6):  935-939.  doi:10.3969/j.issn.1000-1093.2014.06.027

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Gelatin target is used as a muscle target minic in theory or experiment study for temporary cavity effect. The equivalent relationship between gelatin and muscle targets is established. The physical process of temporary cavity formation is analyzed to get the physical parameters which affect the cavity size. A mathematics equivalent model for gelatin and muscle targets is established by using an similarity theory to deduce the similarity law about temporary cavity and a lot of different targets to calculate the coefficient of the similarity law.The experimental data prove the correctness of the model. The study shows that the diameter of temporary cavity in gelatin target is similar to that in muscle target with the relative error of less than 4.0%.

An Approximated Calculation Method for Lateral Trajectory Correction

WANG Zhong-yuan, CHANG Si-jiang

2014, 35(6):  940-944.  doi:10.3969/j.issn.1000-1093.2014.06.028

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For the technical scheme of the two-dimensional trajectory correction projectiles (TDTCPs) with drag brake and despining blade, the mathematical model of two dimensional trajectory corrections is discussed based on the theory of exterior ballistics. An approximate formula for predicting the ballistic drift and trajectory correction quantity is deduced with respect to the process of lateral trajectory correction. The capability of lateral trajectory correction and the flight stability of TDTCP are also analyzed. By comparing with the results of flight test, the accuracy and effectiveness of this approximate calculation method are verified. The result of the approximate method is in accordance with those of 6DOF trajectory model and firing test, and the maximum error is no more than 40 m. All the work is valuable for further research.