水面舰船对声自导鱼雷防御机动方法研究

根据水面舰船机动对其辐射噪声和反射强度的影响,首先建立了水面舰船与声自导鱼雷规避机动对抗的数学模型,然后采用Monte-Carlo法,计算水面舰船不同规避机动方法的生存概率,并分析了水面舰船转向、加速对其生存概率的影响,最后,得出水面舰船对声自导鱼雷防御的最优规避机动方法。提出的规避机动方法对水面舰船水下防御系统研究,具有十分重要的指导意义。

三级边坡稳定性分析的机动方法

三级边坡与普通边坡相比,可以在保证坡度的条件下提高边坡的稳定性,可以减少工程占地面积,具有广泛的环境效益和经济效益,在实际工程中有着广泛的应用。基于极限分析上限法建立了三级边坡的破坏机构,推导了三级边坡的外部做功功率及内部耗损率平衡方程,求出三级边坡临界高度的表达式。采用序列二次规划算法对其临界高度进行优化,求出三级边坡的一个上限解。将本文的计算结果与前人研究成果进行对比,验证了该方法的有效性。

用于机动目标跟踪的分段机动识别方法

分段轨迹识别方法是一种将目标轨迹分成若干段曲线,对每一段曲线进行参数估计进而估计目标状态的跟踪方法.基于分段轨迹识别方法提出了一种分段机动识别方法,使之能够适用于更多的目标机动类型.针对速度变化的目标,提出了新的曲线参数描述的模型以及新的优化跟踪性能的代价函数,改进了判断分段结束的条件以及起始新分段的方法.仿真结果表明:分段机动识别方法在稳态性能不变的情况下,能够更好地跟踪加减速目标;同时,分段机动识别方法对于高度机动目标的跟踪性能和准确构造的交互多模型算法相似,且远优于匀速直线运动模型下的卡尔曼滤波器.

基于三支决策的飞机空战机动决策方法

为了提高战斗机在信息不充足条件下的机动决策能力,提出一种基于三支决策的飞机空战机动决策方法。首先,使用三支决策意图识别模型对目标意图进行识别;其次,将目标的作战意图因素引入到威胁评估中后,结合目标的威胁程度,提出基于三支决策的机动决策权重因子动态调整法;最后,使用模糊逻辑构建机动决策因子评价函数,并利用权值动态调整策略和机动决策评价函数求出每一阶段飞机最佳的机动方式,从而形成可行有效的飞行路线。仿真实验结果表明,所设计的基于三支决策的飞机空战机动决策方法具有可行性和有效性。

Support design method for deep soft-rock tunnels in non-hydrostatic high in-situ stress field

Due to the long-term plate tectonic movements in southwestern China,the in-situ stress field in deep formations is complex.When passing through deep soft-rock mass under non-hydrostatic high in-situ stress field,tunnels will suffer serious asymmetric deformation.There is no available support design method for tunnels under such a situation in existing studies to clarify the support time and support stiffness.This study first analyzed the mechanical behavior of tunnels in non-hydrostatic in-situ stress field and derived the theoretical equations of the ground squeezing curve(GSC)and ground loosening curve(GLC).Then,based on the convergence confinement theory,the support design method of deep soft-rock tunnels under non-hydrostatic high in-situ stress field was established considering both squeezing and loosening pressures.In addition,this method can provide the clear support time and support stiffness of the second layer of initial support.The proposed design method was applied to the Wanhe tunnel of the China-Laos railway in China.Monitoring data indicated that the optimal support scheme had a good effect on controlling the tunnel deformation in non-hydrostatic high in-situ stress field.Field applications showed that the secondary lining could be constructed properly.

考虑剪胀系数影响的土质边坡强度反分析

普通边坡土体强度参数的反演一般只需考虑粘聚力c与内摩擦角φ的影响,但当边坡土体不满足相关联流动法则时,则需考虑剪胀系数η的影响。文中在明确滑动面方程与边坡强度参数之间关系的基础上,基于塑性力学的机动方法,在对数螺旋线的破坏机构下,建立了安全系数Fs的隐函数表达式,并由此建立了η与边坡滑动面深度D的关系;通过选取滑坡体的不同断面进行分析,建立了关于c、φ及η的三组方程表达式,采用序列二次规划方法进行优化后,对边坡的粘聚力、内摩擦角及剪胀系数进行求解。

潜艇利用“迪卡斯”盲区规避反潜飞机跟踪

"迪卡斯"声纳阵存在探潜盲区,潜艇可利用其进行规避。通过对盲区的分析和计算机可视化,并建模、仿真计算了"迪卡斯"声纳浮标阵对潜跟踪概率,得出了通常情况下、特殊情况下潜艇机动规避方法和规避过程中的速度优化方法。尽管利用盲区规避可造成反潜飞机探测或定位中断,但利用盲区并非任何情况下的最优方法。

小推力最优轨道转移问题的UKF估计算法

为了快速精确地求解小推力最优轨道转移问题,提出了一种基于无损卡尔曼滤波(UKF)参数估计算法的轨道机动优化方法。针对小推力情况下的燃料最优轨道转移问题,应用极大值原理将其转化为对应的最优控制两点边值问题,然后以协态变量初值为待估计参数,以端点条件为期望观测值,将该两点边值问题转化为参数估计问题,并应用UKF滤波算法求解。该算法收敛原理是基于概率估计理论的,避免了传统间接法所需的相关梯度矩阵的推导,同时又克服了协态变量初值猜测的困难。由于问题构造形式相似,该算法同样适用于求解时间最短轨道转移问题。数值仿真表明,该算法结构简洁,求解效率较高,所得结果精确且具有良好的鲁棒性。

An approach to improving maneuver performance of coning algorithm

Aiming to improve the maneuver performance of the strapdown inertial navigation attitude coning algorithm a new coning correction structure is constructed by adding a sample to the traditional compressed coning correction structure. According to the given definition of classical coning motion the residual coning correction error based on the new coning correction structure is derived. On the basis of the new structure the frequency Taylor series method is used for designing a coning correction structure coefficient and then a new coning algorithm is obtained.Two types of error models are defined for the coning algorithm performance evaluation under coning environments and maneuver environments respectively.Simulation results indicate that the maneuver accuracy of the new 4-sample coning algorithm is almost double that of the traditional compressed 4-sample coning algorithm. The new coning algorithm has an improved maneuver performance while maintaining coning performance compared to the traditional compressed coning algorithm.

Modelling of ultrasonic motor with dead-zone based on Hammerstein model structure

The ultrasonic motor (USM) possesses heavy nonlinearities which vary with driving conditions and load-dependent characteristics such as the dead-zone. In this paper, an identification method for the rotary travelling-wave type ultrasonic motor (RTWUSM) with dead-zone is proposed based on a modified Hammerstein model structure. The driving voltage contributing effect on the nonlinearities of the RTWUSM was transformed to the change of dynamic parameters against the driving voltage. The dead-zone of the RTWUSM is identified based upon the above transformation. Experiment results showed good agreement be- tween the output of the proposed model and actual measured output.

Approximate Solution for Mechanism of Thermally and Wind-driven Ocean Circulation

The thermally and wind-driven ocean circulation is a complicated natural phenomenon in the atmospheric physics. Hence we need to reduce it using basic models and solve the models using approximate methods. A non-linear model of the thermally and wind-driven ocean circulation is used in this paper. The results show that the zero solution of the linear equation is a stable focus point, which is the path curve trend origin point as time (t) trend to infinity. By using the homotopic mapping perturbation method, the exact solution of the model is obtained. The homotopic mapping perturbation method is an analytic solving method, so the obtained solution can be used for analytic operating sequentially. And then we can also obtain the diversified qualitative and quantitative behaviors for corresponding physical quantities.

Response of train-bridge system under intensive seismic excitation by random vibration method

Earthquake is a kind of sudden and destructive random excitation in nature.It is significant to determine the probability distribution characteristics of the corresponding dynamic indicators to ensure the safety and the stability of structures when the intensive seismic excitation,the intensity of which is larger than 7,acts in train-bridge system.Firstly,the motion equations of a two-dimensional train-bridge system under the vertical random excitation of track irregularity and the vertical seismic acceleration are established,where the train subsystem is composed of 8 mutually independent vehicle elements with 48 degrees of freedom,while the single-span simple supported bridge subsystem is composed of 102D beam elements with 20 degrees of freedom on beam and 2 large mass degrees of freedom at the support.Secondly,Monte Carlo method and pseudo excitation method are adopted to analyze the statistical parameters of the system.The power spectrum density of random excitation is used to define a series of non-stationary pseudo excitation in pseudo excitation method and the trigonometric series of random vibration history samples in Monte Carlo method,respectively solved by precise integral method and Newmark-βmethod through the inter-system iterative procedure.Finally,the results are compared with the case under the weak seismic excitation,and show that the samples of vertical acceleration response of bridge and the offload factor of train obeys the normal distribution.In a high probability,the intensive earthquakes pose a greater threat to the safety and stability of bridges and trains than the weak ones.

Research on methods of designing and building digital seabed database

With a review of the recent development in digitalization and application of seabed data, this paper systematically proposed methods for integrating seabed data by analyzing its feature based on ORACLE database management system and advanced techniques of spatial data management. We did research on storage structure of seabed data, distributed-integrated database system, standardized spatial database and seabed metadata management system in order to effectively manage and use these seabed information in practical application. Finally, we applied the methods researched and proposed in this paper to build the Bohai Sea engineering geology database that stores engineering geology data and other seabed information from the Bohai Sea area. As a result, the Bohai Sea engineering geology database can effectively integrate huge amount of distributed and complicated seabed data to meet the practical requisition of Bohai Sea en-gineering geology environment exploration and exploitation.

Reachability analysis of web service compositions via NWA

In order to improve the design and implementation quality of web service compositions,formal methods are used to model them and certain properties are verified.WCFA （web service interface control flow automata）is used to model web services,especially the control flow and possible interactions with other web services.A web service composition consists of a set of interacting WCFA.The global behavior of web service compositions is captured by NWA（nested word automata）.A variation of the depth-first search algorithm is used to transform a set of WCFA into an NWA.State formulae and call stacks at each node of NWA are computed by a path-sensitive reachability analysis.Safety properties,call stack inspection properties and pre/post-conditions of service invocations are described by assertions.Then verification of these assertions is carried out by an automated SAT tool.

Kinematic Characteristics Analysis of 3-PRS Parallel Manipulator

The 3-PRS parallel mechanisms,whose kinematic chain is connected by prismatic joint P,revolute joint R and spherical joint S,have two rotational and one translational DOF.But the DOF of 3-PRS parallel mechanism cannot be explained by the Grubler-Kutzbach method or Herve method.To illuminate the special kinematic characteristics of 3-PRS parallel mechanism,a novel analytical approach is proposed in this paper.All the feasible instantaneous motions of 3-PRS mechanism are studied by using this method.The analysis of kinematic characteristics of 3-PRS mechanism help to understand the mechanism and estimate the motion capacity of mechanism.Finally,it is also helpful to optimize the topology of the mechanism and the trajectory for desired performance.

A gait generation and transition method for quadruped walking machine

In nature, quadrupeds as horses or cats change their gait to be suited to their motion speed. This fact is very important to realize smooth motion with different gaits. In this article a method of the gait transition for the quadruped walking machine is proposed. With analyzing the accustomed gaits of quadruped, some standard gaits and the relationships between duty factor and the phasic differences of the legs corresponding to the first leg could be concluded. With this, the gaits transferring could be continuous. Besides, celerity and on line method for generation and modifying gaits is studied, which can make the robot have a smooth motion to adapt the uncharted rough terrain.

Dynamic modelling of 2-DOF luffing mechanism with serial closed kinematic chains

Luffing mechanism is a key component of the construction machinery.This paper proposes a two degree of freedom(2-DOF)luffing mechanism,which has one more pair of driving cylinders than the single DOF luffing mechanism,to improve the performance of the machinery.To establish the dynamic model of the 2-DOF luffing mechanism,firstly,we develop a hierarchical method to deduce the Jacobian matrix and Hessian matrix for obtaining the kinematics equations.Subsequently,we divide the luffing mechanism into six bodies considering actuators,and deduce the kinetic equations of each body by the Newton-Euler method.Based on the dynamic model,we simulate the luffing process.Finally,a prototype is built on a pile driver to validate the model.Simulations and experiments show that the dynamic model can reflect the dynamic properties of the proposed luffing mechanism.And the control strategy that the front cylinders retract first shows better mechanical behavior than the other two control strategies.This research provides a reference for the design and application of 2-DOF luffing mechanism on construction machinery.The modeling approach can also be applied to similar mechanism with serial closed kinematic chains,which allows to calculate the dynamic parameters easily and exactly.

Fusing PLSA model and Markov random fields for automatic image annotation

A novel image auto-annotation method is presented based on probabilistic latent semantic analysis(PLSA) model and multiple Markov random fields(MRF).A PLSA model with asymmetric modalities is first constructed to estimate the joint probability between images and semantic concepts,then a subgraph is extracted served as the corresponding structure of Markov random fields and inference over it is performed by the iterative conditional modes so as to capture the final annotation for the image.The novelty of our method mainly lies in two aspects:exploiting PLSA to estimate the joint probability between images and semantic concepts as well as multiple MRF to further explore the semantic context among keywords for accurate image annotation.To demonstrate the effectiveness of this approach,an experiment on the Corel5 k dataset is conducted and its results are compared favorably with the current state-of-the-art approaches.