Research on localization algorithm of naval vessel for submarine based on bearing-range measurements

Combined with naval vessel practical antisubmarine equipment of towed linear array sonar,a mathematical model of naval vessel localization for submarine based on bearing measurement was built,and localization algorithm was given to solve submarine movement parameters.Localizaiton errors were analyzed.Based on localization model and algorithm,simulations were done to study the effect of factors such as initial distance between submarine and the naval vessel,submarine initial bearing angle measured by the naval vessel and submarine course on localization performance,and then simulation results were given and analyzed.The results have practical value to instruct real antisubmarine.Simulation results show that different target movement situations have great influence on sonar detection and localization performance,so the reasonable choice of sonar position and detection bearing according to the target movement situation can improve sonar detection and localization performance to some degree.

OSCILLATION CRITERIA FOR SECOND ORDER NONLINEAR DIFFERENTIAL EQUATIONS OF NEUTRAL TYPE

In this paper,the oscillation criteria for the solutions of the nonlinear differential equations of neutral type of the forms:[x(t)+p(t)x(σ(t))]″+q(t)f(x(τ(t)))g(x′(t))=0and[x(t)+p(t)x(σ(t))]″+q(t)f(x(t),x(τ(t)))g(x′(t))=0are obtained.

Composite Control of Linear/Adaptive Variable Structure Control

This paper first researches the system's response-feature due to the sliding regime related to the slope of a switching line, and then makes an investigation on the existence condition and hitting condition. Based on these conditions, the paper proposes a switching function that can realize an error adaptive variable structure control (AVSC) successfully. For eliminating the chattering of the sliding regime, this VSS introduces a dead zone, in which the PID control is applied. The composition of the PID control and the AVSC is called composite control of linear / AVSC. When the control signal is a large one, the AVSC is applied in the majority, and when the signal is a low one, the PID control is applied. Finally, an example of overload control of an anti-ship aerodynamic missile is illustrated to show the application of the composite control.

Analysis and innovation of key technologies for autonomous underwater vehicles

As the mission needs of the autonomous underwater vehicles(AUV) have become increasingly varied and complex,the AUVs are developing in the direction of systematism, multifunction, and clustering technology, which promotes the progress of key technologies and proposes a series of technical problems. Therefore, it is necessary to make systemic analysis and in-depth study for the progress of AUV's key technologies and innovative applications. The multi-functional mission needs and its key technologies involved in complex sea conditions are pointed out through analyzing the domestic and foreign technical programs, functional characteristics and future development plans. Furthermore, the overall design of a multi-moving state AUV is proposed. Then, technical innovations of the key technologies, such as thrust vector, propeller design, kinematics and dynamics, navigation control, and ambient flow field characteristics, are made, combining with the structural characteristics and motion characteristics of the new multi-moving state AUV. The results verify the good performance of the multi-moving state AUV and provide a theoretical guidance and technical support for the design of new AUV in real complex sea conditions.

Accelerated corrosion test and corrosion failure distribution model of aircraft structural aluminum alloy

Based on corrosion damage data of 10 years for a type of aircraft aluminum alloy, the statistical analysis was conducted by Gumbel, Normal and two parameters Weibull distribution function. The results show that aluminum alloy structural member has the corrosion history of pitting corrosion—intergranular corrosion—exfoliation corrosion, and the maximum corrosion depth is in conformity to normal distribution. The accelerated corrosion test was carried out with the complied equivalent airport accelerated environment spectrum. The corrosion damage failure modes of aluminum alloy structural member indicate that the period of validity of the former protective coating is about 2.5 to 3 years, and that of the novel protective coating is about 4.0 to 4.5 years. The corrosion kinetics law of aluminum spar flange was established by fitting corrosion damage test data. The law indicates two apparent corrosion stages of high strength aluminum alloy section material: pitting corrosion and intergranular corrosion/exfoliation corrosion. The test results agree with the statistical fit result of corrosion data collected from corrosion member in service. The fractional error is 5.8% at the same calendar year. The accelerated corrosion test validates the corrosion kinetics law of aircraft aluminum alloy in service.

Innovative design and motion mechanism analysis for a multi-moving state autonomous underwater vehicles

In order to achieve the functional requirements of multi-moving state, a new autonomous underwater vehicle(AUV) provided with the functions such as the submarine vectorial thrust, landing on the sea bottom, wheel driving on the ground and crawling on the ground was designed. Then five new theories and methods were proposed about the motion mechanism of the AUV such as vectorial thruster technology, design of a new wheel propeller, kinematics and dynamics, navigation control and the ambient flow field in complex sea conditions, which can all conquer conventional technique shortages and predict the multi-moving state performance under wave disturbance. The theoretical research can realize the results such as a vectorial transmission shaft with the characteristics of spatial deflexion and continual circumgyratetion, parameterized design of the new wheel propeller with preferable open-water performance and intensity characteristics satisfying multi-moving state requirements, motion computation and kinetic analysis of AUV's arbitrary postures under wave disturbance, a second-order sliding mode controller with double-loop structure based on dynamic boundary layer that ensures AUV's trajectory high-precision tracking performance under wave disturbance, fast and exact prediction of the ambient flow field characteristics and the interaction mechanism between AUV hull and wheel propellers. The elaborate data obtained from the theoretical research can provide an important theoretical guidance and technical support for the manufacture of experimental prototype.

Evolution of Interface Soliton over Topography

Several ray-type 1D and 2D KdV equations for two-layer stratified ocean with topographic effect are derived in detail in the present study. A simplified version of these equations, ray type 1D KdV equation, is used to calculate numerically the disintegration of initial interface soliton from the deep sea to the continental shelf. At the same time, a laboratory experiment is carried out in a 2D stratified flow and internal wave tank to examine the numerical results. A comparison of the numerical results with the experimental results shows that they are in good agreement. The numerical results also show that the ray-type KdV equation has high accuracy in describing the evolution of initial interface waves in shelf/slope regions. Form these results, it can be concluded that the fission process is a dominant generating mechanism of interface soliton packets on the continental shelf.

Effects of pitting corrosion on fatigue life of aluminum alloy Y12CZ based on initial discontinuity state

Based on initial discontinuity state (IDS) of material, a preliminary analytical model was presented to evaluate the effect of interaction of pitting corrosion and fatigue loading on the residual fatigue life of aluminum alloy LY12CZ. A life prediction was carried out using constant and variable amplitude loading for various pitting corrosion levels, and the prediction agreed reasonably with the available test data. The results suggest that the combination of a pit and IDS can be treated as the initial crack size. Pitting corrosion causes a significant decrease in fatigue lives with small corrosion depths. But the effect of pit on fatigue life is gradually reduced with increasing pit size. A pit with a constant depth can be applied to the model for long exposure structure. A preliminary recommendation for the pit depth is about 1 mm for LY12CZ. At last the effect of multiple-site corrosion damage (MSCD) on fatigue life was also studied, and the result shows that MSCD can decrease substantially fatigue life compared with that of a single crack.

Corrosion fatigue behavior of fastening hole structure and virtual crack propagation tests

The fatigue crack propagation behavior of the LY12CZ aluminum alloy fastener involving a central hole in air or in 3.5wt% NaCl solution was investigated. The experimental results indicated that the corrosion fatigue crack growth rate decreased with the increasing loading frequency,and in a corrosive environment,the crack growth rate was slightly larger than that in air. Based on the experimental results,the virtual corrosion fatigue crack propagation tests were investigated and the stochastic process method and the AFGROW simulation method were presented. The normal process and lognormal process were considered for the stochastic process method based on the numerically fitted Paris equation. The distribution of crack size and the corresponding probabilistic model of crack length distribution for a given number of cycles can be found by integrating the stochastic process over time. Using the AFGROW software,the virtual simulation was carried out to analyze the corrosion fatigue crack growth behavior and the predicted crack growth curve was in good agreement with the experimental results.

Corrosion damage evolution and residual strength of corroded aluminum alloys

The LY12CZ aluminum alloy specimens were corroded under the conditions of different test temperatures and exposure durations. After corrosion exposure, fatigue tests were performed. Scanning electron microscopy and optical microscope analyses on corrosion damage were carried out. The definition of surface corrosion damage ratio was provided to describe the extent of surface corrosion damage. On the basis of the measured data sets of the corrosion damage ratio, the probabilistic model of corrosion damage evolution was built. The corrosion damage decreased the fatigue life by a factor of about 1.25 to 2.38 and the prediction method of residual strength of the corroded structure was presented.

Image Compression Based on LSS Algorithm

Lifting scheme is a second-generation wavelet transform which is easier to understand than the first-generation wavelet transform. Fourier analysis is not necessary for the construction, and inverse transform can naturally be realized. Furthermore, it is faster than the first-generation wavelet transform. In terms of compression ratio and compression efficiency, SPIHT is the best algorithm based on EZW, but its theory is difficult to understand and come true. We carry out the SPIHT algorithm, and propose a reformed algorithm based on SPIHT, making the realization more easier. In the end, LSS algorithm composed of lifting scheme and SPIHT algorithm is presented, whose compression efficiency is the same as SPIHT, but running is 10% faster than SPIHT.

Register Allocation Algorithm for High-Level Circuit Synthesis for Improved Testability

Register allocation in high-level circuit synthesis is important not only for reducing area, delay, and power overheads, but also for improving the testability of the synthesized circuits. This paper presents an improved register allocation algorithm that improves the testability called weighted graph-based balanced register allocation for high-level circuit synthesis. The controllability and observability of the registers and the self-loop elimination are analyzed to form a weighted conflict graph, where the weight of the edge between two nodes denotes the tendency of the two variables to share the same register. Then the modified desaturation algorithm is used to dynamically modify the weights to obtain a final balanced register allocation which improves the testability of the synthesized circuits a higher fault coverage than other algorithms with Tests on some benchmarks show that the algorithm gives less area overhead and even less time delay.

Packet Queueing Delay in Resilient Packet Ring Network Nodes

The packet queueing delay is one of the most important performance measures of a data net-work and is also a significant factor to be considered in the scheduling buffer design for a network node. This paper presents a traffic queueing model for resilient packet ring (RPR) networks and a method for quantitatively analyzing queueing delays in RPR nodes. The method was used to calculate the average queueing delays of different priority traffic for different transit queue modes. The simulations show that, in the transmit direction, lower priority traffic is delayed more than higher priority traffic, and that Class-A traffic is delayed more in a single-queue ring than in a dual-queue ring. In the transit direction, the secondary tran-sit buffer in the dual-queue ring contributes more to the traffic delay than the primary transit buffer in the sin-gle-queue ring, which in turn causes more delay than the primary transit buffer in the dual-queue ring.

ON A PERIODIC VOLTERRA EQUATION WITH SEVERAL FINITE DELAYS AND AN INFINITE DELAY

The existence of positive periodic solutions for a periodic Volterra equation with several finite delays and an infinite delay is established. Sufficient conditions for the periodic solutions having global attractivity are obtained.