Study of Load Modeling Technology on Hardware-in-the-Loop Simulator of Gun Servo System

A hardware-in-the-loop (HWIL) simulator for gun servo system is described in this paper, and its load modeling technologies,such as road spectrum model,sea wave model are studied. The simulation results show that the models can be used in HWIL and satisfy the requirements of hardware-in-the-loop simulator of gun servo system.     

Real-time Extraction of Target Position Information Based on Bi-orthogonal Wavelets

Extraction of flying target position information is the prerequisite for passive infrared guided missiles to track the target. The existing missile detection system senses the target＇ s infrared radiation, and then the generated signal is sent to signal processing circuits for extracting the target position information. In order to improve anti-interference capacity of the detection system, an algorithm of module maximum edge detection based on the bi-orthogonal wavelets is proposed to replace its hardware. The signal can be decomposed in one layer, only its high frequency detail is reconstructed. After some calculations, the average target position can be obtained. The algorithm＇s real-time implementation with DSP is also discussed. To reduce the execution time, the program structure can be optimized with double buffers in memory. This im- plementation is verified by simulations. The results show that the method has only a small amount of calculations, can meet the requirements for finding out the target position in real-time and needs not the traditional processing circuit.     

Automatic Detection of Steel Bali＇s Surface Flaws Based on Image Processing

A new method to detect steel bali＇s surface flaws is presented based on computer techniques of image processing and pattern recognition. The steel bali＇s surface flaws is the primary factor causing bearing failure. The high efficient and precision detections for the surface flaws of steel ball can be conducted by the presented method, including spot, abrasion, burn, scratch and crack, etc. The design of main components of the detecting system is described in detail including auto-matic feeding mechanism, automatic spreading mechanism of steel ball＇ s surface, optical system of microscope, image acquisition system, image processing system. The whole automatic system is controlled by an industrial control computer, which can carry out the recognition of flaws of steel bali＇s surface effectively.     

Torpedo＇s Search Trajectory Design Based on Acquisition and Hit Probability Calculation

Taking aim at light torpedo search trajectory characteristic of warship, by analyzing common used torpedo search trajectory, a better torpedo search trajectory is designed, a mathematic model is built up, and the simulation calculation taking MK46 torpedo for example is carried out. The calculation results testify that this method can increase acquisition probability and hit probability by about 10 % - 30 % at some situations and becomes feasible for the torpedo trajectory design. The research is of great reference value for the acoustic homing torpedo trajectory design and the torpedo combat efficiency research.     

Numerical Simulation of Airflow Field and Structure Improvement in Engine Compartment of Armored Vehicles with Electric Transmission

When the mechanical drive is changed into the electric transmission,the cooling system of the engine compartment should be altered to meet the new requirement for the increasing in equipment such as electric apparatus.In order to predict and analyze the rationality of cooling system in the virtual engine compartment,the numerical simulation of airflow fields in the engine compartment by using computational fluid dynamics（CFD） technique is necessary.An armored vehicle with electric transmission in the research is taken as the research object.The physical model and mathematical model for the computation of 3D air flow and heat transfer in the engine compartment of an armored vehicle with electric transmission is established.Turbulent flow in the compartment is described by using the standard k-ε two-equation turbulence model.The temperature and velocity fields of 3D air flow in the engine compartment are numerically simulated and analyzed based on different fan＇s flux.A theoretical basis for determination of the fan＇s flux is given by the simulation results.The positions of the air-vent shutter are analyzed.The simulation results show that the different positions of the air-vent shutter can lead to different cooling efficiencies.     

Statistics Modeling of Shallow Sea Ambient Noise and Its Applications in Low-frequency Line Spectrum Detection

The noise’s statistical characteristics are very important for signal detection.In this paper,the ambient noise statistical characteristics are investigated by using the recorded noise data in sea trials first,and the results show that the generalized Gaussian distribution is a suitable model for the ambient noise modeling.Thereafter,the optimal detector based on maximum likelihood ratio can be deduced,and the asymptotic detector is also derived under weak signal assumption.The detector’s performance is verified by using numerical simulation,and the results showthat the optimal and asymptotic detectors outperform the conventional correlation-integration system due to accuracy modeling of ambient noise.     

Research on Instantaneous Thrust Measurement for Attitude-control Solid Rocket Motor

In order to measure the instantaneous thrust of a certain attitude-control solid rocket motor, based on the analysis of the measurement principles, the difference between the instantaneous thrust and steady thrust measurements is pointed out. According to the measurement characteristics, a dynamic digital filter compensation method is presented. Combined the identification-modeling, dynamic compensation and simulation, the system＇s dynamic mathematic model is established. And then, a compensation digital filter is also designed. Thus, the dynamic response of the system is improved and the instantaneous thrust measurement can be implemented. The measurement results for the rocket motor show that the digital filter compensation is effective in the instantaneous thrust measurement.     

Modeling of Testability Requirement Based on Generalized Stochastic Petri Nets

Testability design is an effective way to realize the fault detection and isolation. Its important step is to determine testability figures of merits （TFOM）. Firstly, some influence factors for TFOMs are analyzed, such as the processes of system operation, maintenance and support, fault detection and isolation and so on. Secondly, a testability requirement analysis model is built based on generalized stochastic Petri net （GSPN）. Then, the system＇s reachable states are analyzed based on the model, a Markov chain isomorphic with Petri net is constructed, a state transition matrix is created and the system＇ s steady state probability is obtained. The relationship between the steady state availability and testability parameters can be revealed and reasoned. Finally, an example shows that the proposed method can determine TFOM, such as fault detection rate and fault isolation rate, effectively and reasonably.     

Research on Influence of Damping Material on Structure Performance of Torpedo

Reducing the self-noise and radiated noise of torpedo is an effective way to enhance its detection and concealment capabilities.After discussing the basic principle on noise and vibration control and main noise sources in torpedo,the application of damping treatment for noise and vibration absorption was proposed in this paper.Compared composite materials(damping and metal materials)used as segment joint,their different contributions to the damping performance of base structure were investigated.The results show that the damping material can be used as segment joint effectively in vibration control.Taking cantilever beam as an example,four different damping treatments were compared in natural frequency and damping loss factor,the results show the influences of different damping layer layouts on the structure damping performance,and offer a reference for the torpedo shell design.     

Study on System Failure Probability Model Based on Dynamic Fault Tree

Aiming at the characteristics of complex logic relation and multiple dynamic gates in system, its failure probabil- ity model is established based on dynamic fault tree. For the multi-state dynamic fault tree, it can be transferred into Markov chain with continuous parameters. The state transfer diagram can be decomposed into several state transfer chains, and the failure probability models can be derived according to the lengths of the chains. Then, the failure probability of the dynamic fault tree analysis （DFTA） can be obtained by adding each chain＇ s probability. The failure probability calculation of DFTA based on the continuous parameter Markov chain is proposed and proved. Given an example, the analytic method is compared with the conventional methods which have to solve the differential equation. It is known from the results that the analytic method can be applied to engineering easily.     

Dynamic Study on Rigid and Flexible Coupling System for Terminally Sensitive Submunition

A kinetic model of the rigid and flexible coupling system for terminally sensitive submunition is set up with Kane＇s method. The parachute is considered as a flexible body, the flexible displacement is expressed with modal spread method, the position of the parachute is expressed with a hybrid coordinate method, and the kinematics of the terminally sensitive submunition is analyzed. Ten generalized coordinates relative to the attitude of the terminally sensitive submunition are chosen, and the correlative generalized active forces, the generalized inertial forces, the generalized internal forces are calculated in turn. On the base of the Kane＇s method, the ten degrees of freedom dynamic equations for the coupled terminally sensitive submunition are finally set up. This model can be used to expediently simulate and analyze accurately the exterior ballistic trajectory of terminally sensitive submunition, and provide the overall design of the terminally sensitive submunition with some helpful references.     

Numerical simulation of the natural fragmentation of explosively loaded thick walled cylinders

The ability to predict the natural fragmentation of an explosively loaded metal casing would represent a significant achievement. Physically- based material models permit the use of small scale laboratory tests to characterise and validate their parameters. The model can then be directly employed to understand and design the system of interest and identify the experiments required for validation of the predictions across a wide area of the performance space. This is fundamentally different to the use of phenomenologically based material algorithms which require a much wider range of characterisation and validation tests to be able to predict a reduced area of the performance space. Eulerians numerical simulation methods are used to describe the fragmentation of thick walled EN24 steel cylinders filled with PBXN-109 explosive. The methodology to characterise the constitutive response of the material using the physically based Armstrong-Zerilli constitutive model and the Goldthorpe path dependent fracture model is described, and the results are presented. The ability of an Eulerian hydrocode to describe the fragmentation process and reproduce the experimentally observed fragment mass and velocity distributions is presented and discussed. Finally the suitability of the current experimental analysis methodology for simulation validation is addressed.     

Spectral Match Optimization Based on Grey Relational Analysis

A spectral match optimization based on grey incidence matrix was put forward to evaluate camouflage painting design.A synthetic degree of incidence (SDI) was defined to comprehensively reflect the spectrum similarity based on theory of grey incidence analysis.A grey optimization model for camouflage painting sheme was constructed on the basis of SDI and grey incidence matrix.Its weight values were determined according to area percentages of all components in the camouflage scene,and a quantitative ordering for various schemes could be obtained according to the evaluation coefficients.Experiment results show that the method mentioned in this paper can provide a quantitative basis for the camouflage decision-making,and it can also be used in other camouflage scheme selection.     

Effects of Adhesive Characteristic on the Test Results of Damping Material＇s DMP

In the measurement of damping material＇s dynamic mechanical performance （DMP） using flexural resonating cantilever beam method, the specimen＇s adhesive characteristic influences the test precision and accuracy. Taking its effect into account, the improved measurement equations based on the resonance method are presented. The simulated resuits show that, for the sake of weakening the adhesive＇s influence on the measured results, the adhesive should be spreaded as thin as possible when specimen is prepared, the adhesive＇s density and loss factor should be selected as small as possible also, and its Young＇s modulus should be selected according to the damping material being measured; the same adhesion condition effects differently on the test results of different damping materials, i.e. the error due to the adhesive is more inconspicuous if the damping layer has bigger thickness, modulus, loss factor and a certain density according to the damping material being measured. These conclusions provide theoretical basis for selecting adhesive, improving adhesion technology, and designing specimen.     

Joint Maintenance Policies for a Stored System with Two Units

Failure of a stored system can only be detected after inspection and its reliability can be resumed by replacement of failed components. A maintenance policy of combining periodic inspection and preventive replacement is proposed to improve its availability. To coordinate component replacement and spare provision, an ordering policy of （0, 1） is consid- ered jointly. Thus, the joint maintenance policy contains inspection, replacement and spare provision. A programming model based on the joint maintenance policy is established, whose objective function is average expected cost, containing maintenance cost and inventory cost, and the constraint is system availability. Applying renewal theorem, the perfor- mance indexes are deduced under the condition that the stored system obeys the common life distribution. Numerical examples are given for a stored system with two different units, where unit 1 probability degrades with time and unit 2 probability degrades at each test. The effect of reliability parameters on the policies is discussed. The results indicate that the joint policy is very close to the independent policy.     

Analysis and Design of a New Shaped Spherical Reflector Antenna with a Horn Feed

A design method of a new shaped spherical reflector antenna with a horn feed for wide-angle scanning is presented, in which the horn＇s phase center need not be found out and its optimal position can be determined. It is found from numerical calculation that the shaped spherical reflector antenna has better electrical performance than that of the spherical reflector antenna, at the maximum gain value under the conditions of the same feed and reflector aperture, and can be used as a wide angle searching antenna.     

Reflectivity Model of Low Grazing Angle Radar Sea Clutter

The commonly used reflectivity models of radar sea clutter are summarized. Among these models, the adjusted Barton model and the adjusted Morchin model are compared. From the analysis result, the γ-p reflectivity model is presented for low grazing angle radar sea clutter by the adjustment of the original Barton reflectivity model. The model takes into account radar frequency, grazing angle, sea condition, and polarization property. The influences of these factors on the proposed model are analyzed. The model absorbs the merits from commonly used reflectivity models for sea clutter. It introduces several researchers‘ opinions, and extends them. And it accounts for the reflectivity at arbitrary radar frequency from VHF to X-band, arbitrary low grazing angle, arbitrary sea condition and different polarization property. One of the main results is the proposed γ-p reflectivity model can reflect the influence of polarization on sea clutter reflectivity to some extent. The proposed γ-p reflectivity model of low-angle radar-sea clutter is validated by comparing the simulated and statistically experimental data.     

Study on Outboard Inductive Damping Valve in Hydro-pneumatic Suspension

A new outboard inductive damping valve without any electronic control system is developed. Its working principle,structure and external characteristic are studied. Its mathematical model is presented and its damping characteristic is investigated on the basis of fluid continuity equation,differential equations of motion and Bernoulli equation. The influence of the valve parameters on the damping characteristic is studied numerically. The effects of outboard inductive damping valve and common damping valve on ride and tire load are compared also. The external characteristic of the valve is verified in bench test. The results show that the valve’s mathematical model is quite accurate and the developed valve can be adjust in two stages,which can also meet the requirements of the dynamic characteristic of the vehicle suspension system.     

A Study of New Method for Weapon System Effectiveness Evaluation Based on Bayesian Network

As weapon system effectiveness is affected by many factors,its evaluation is essentially a multi-criterion decision making problem for its complexity.The evaluation model of the effectiveness is established on the basis of metrics architecture of the effectiveness.The Bayesian network,which is used to evaluate the effectiveness,is established based on the metrics architecture and the evaluation models.For getting the weights of the metrics by Bayesian network,subjective initial values of the weights are given,gradient ascent algorithm is adopted,and the reasonable values of the weights are achieved.And then the effectiveness of every weapon system project is gained.The weapon system,whose effectiveness is relative maximum,is the optimization system.The research result shows that this method can solve the problem of AHP method which evaluation results are not compatible to the practice results and overcome the shortcoming of neural network in multilayer and multi-criterion decision.The method offers a new approach for evaluating the effectiveness.