Relay and Singular Segments of Optimal Trajectories in a Problem with Parabolic Equation

The optimal control for a linear object described by a parabolic partial differential equation with a bounded control in the boundary condition is investigated. The integral quadratic quality criterion does not explicitly depend on control, and adjustment time is infinite. The optimal control for this problem consists of relay and singular segments, and the sum of lengths of relay segments (if any) is finite. Singular optimal trajectories passing through the coordinate origin are determined.     

Linear Problems of Optimal Control of Multiple-Valued Trajectories

This paper deals with rapidity and rendezvous problems and with problems with multi-valued and vector quality criteria for objects whose behavior is described by linear differential inclusions that contain controls.     

FromDaDy: Spreading Aircraft Trajectories Across Views to Support Iterative Queries

When displaying thousands of aircraft trajectories on a screen, the visualization is spoiled by a tangle of trails. The visual analysis is therefore difficult, especially if a specific class of trajectories in an erroneous dataset has to be studied. We designed FromDaDy, a trajectory visualization tool that tackles the difficulties of exploring the visualization of multiple trails. This multidimensional data exploration is based on scatterplots, brushing, pick and drop, juxtaposed views and rapid visual design. Users can organize the workspace composed of multiple juxtaposed views. They can define the visual configuration of the views by connecting data dimensions from the dataset to Bertin's visual variables. They can then brush trajectories, and with a pick and drop operation they can spread the brushed information across views. They can then repeat these interactions, until they extract a set of relevant data, thus formulating complex queries. Through two real-world scenarios, we show how FromDaDy supports iterative queries and the extraction of trajectories in a dataset that contains up to 5 million data.     

Optimal control of 2-D systems

Two-dimensional (2-D) optimal control theory that parallels one-dimensional (1-D) optimal control is developed. A generalized performance measure suited to 2-D systems is introduced. The canonical equations associated with this performance measure and a general nonlinear model are obtained. The 2-D linear quadratic regulator problem is formulated, and its canonical equations are derived for the Roesser model. An earlier result by T. Kaczorek and J. Klamka (1986) for the solution of the minimum-energy problem with fixed-final local state is rederived using this approach. A new problem, minimum-energy with fixed-final-pass local states is formulated and solved, and a numerical example is given     

移动环境下基于用户轨迹的社交亲近度研究

提出了一种基于时空轨迹的社交亲近度模型,目的是为了解决新一代广播电视服务系统中移动手机电视用户之间控制内容分享问题。该模型首先将用户轨迹空间离散化,并将用户轨迹映射到该离散空间。然后根据相同时刻,用户之间的空间距离,计算用户之间的社交亲近度。根据亲近度,将其朋友分组,以控制分享内容。实验结果表明,该方法能够有效反映用户地理位置轨迹与用户之间的社交关系,平均分组正确率达89%。     

Real-Time Optimal Reach-Posture Prediction in a New Interactive Virtual Environment

Human posture prediction is a key factor for the design and evaluation of workspaces, in a virtual environment using virtual humans. This work presents a new interface and virtual environment for the direct human optimized posture prediction （D-HOPP） approach to predicting realistic reach postures of digital humans, where reach postures entail the use of the torso, arms, and neck. D-HOPP is based on the contention where depending on what type of task is being completed, and human posture is governed by different human performance measures. A human performance measure is a physics-based metric, such as energy or discomfort, and serves as an objective function in an optimization formulation. The problem is formulated as a single-objective optimization （SO0） problem with a single performance measure and as multiobjective-optimization （MOO） problem with multiple combined performance measures. We use joint displacement, change in potential energy, and musculoskeletal discomfort as performance measures. D-HOPP is equipped with an extensive yet intuitive user-interface, and the results are presented in an interactive virtual environment.     

基于文化蚁群算法的三维飞行器航路规划

研究飞行器航路规划问题时,由于目标函数复杂,计算量大,采用蚁群算法,存在航路搜索速度慢,容易陷入局部最优从而得不到最优航路的问题,把蚁群算法嵌入到文化算法中,提出了一种文化蚁群算法来解决航路规划问题.计算模型包括蚁群算法的群体空间和利用群体空间最优解的信仰空间.群体空间的群体演化采用蚁群系统,并加入了奖惩机制.信仰空间由群体空间中的最好个体组成,并利用遗传算法的思想进行更新,以指导群体空间的进化.仿真结果表明,提出的算法拥有更快的搜索速度,得到的航路也更好.     

Optimal Orthogonal Tiling of 2-D Iterations

Iteration space tiling is a common strategy used by parallelizing compilers and in performance tuning of parallel codes. We address the problem of determining the tile size that minimizes the total execution time. We restrict our attention to uniform dependency computations with two-dimensional, parallelogram-shaped iteration domain which can be tiled with lines parallel to the domain boundaries. The target architecture is a linear array (or a ring). Our model is developed in two steps. We first abstract each tile by two simple parameters, namely tile periodP_tand intertile latencyL_t. We formulate and partially resolve the corresponding optimization problem independent of the machine and program. Next, we refine the model with realistic machine and program parameters, yielding a discrete nonlinear optimization problem. We solve this analytically, yielding a closed form solution, which can be used by a compiler before code generation.     

飞机驾驶舱噪声环境下的飞行员语音端点检测

为在飞行驾驶舱噪声环境下准确判定飞行员语音端点,提出一种鲁棒语音端点检测方法。使用最优改进对数谱幅度估计语音增强算法进行初步语音降噪,通过Teager能量算子进一步滤除残余噪声,并将降噪后语音短时能量与子带谱熵的比值作为双门限判决参数,检测飞行员语音起止点。实验结果表明,与基于能量参数或频谱熵参数的语音端点检测方法相比,该方法能有效提高检测正确率。     

一种基于最优轨迹的假查询隐私保护机制

随着移动通信技术和无线传感器的发展, 基于位置服务的应用给我们的生活带来极大的便利。在实际使用中, 用户需要向不可信的LBS服务提供商发送自己的实时位置和相关的查询信息, 这可能会导致用户的个人隐私信息遭到泄露, 特别是在使用连续位置查询服务时, 服务提供商可以利用位置的时空相关性来构建用户的轨迹信息, 进而推断出用户的居住地址、公司位置等敏感信息。传统的位置隐私保护方法通常只考虑到当前位置, 在解决连续位置查询时存在挑战, 因此, 为了解决连续位置查询中难以权衡轨迹可用性与隐私性的问题, 提出一种基于最优位置轨迹的假查询隐私保护机制。首先, 通过真实轨迹和假轨迹间的互信息来度量轨迹的隐私, 解决轨迹隐私难以量化的问题。在此基础上, 提出一种基于马尔科夫链的轨迹互信息计算方法, 简化了轨迹互信息的计算过程,并使用两条轨迹上对应位置点间的欧几里距离来量化位置轨迹的可用性。其次, 考虑到生成的假轨迹可能并不符合用户的通行习惯, 容易被识别出来, 我们选择历史轨迹作为假轨迹。为了减少轨迹上位置点的数量, 使用四叉树法对路网区域进行划分, 将轨迹划分为不同的片段, 在相关约束条件下寻找最优的历史轨迹作为假轨迹, 从而保证使用的假轨迹更加真实、合理。最后, 实验结果表明,本文的方案可以最大程度的实现位置数据隐私性和可用性平衡, 与其他方案相比, 安全性更高、系统计算开销更少。     

Lipschitzian Regularity of the Minimizing Trajectories for Nonlinear Optimal Control Problems

We consider the Lagrange problem of optimal control with unrestricted controls and address the question: under what conditions can we assure optimal controls are bounded? This question is related to one of Lipschitzian regularity of optimal trajectories, and the answer to it is crucial in closing the gap between the conditions arising in existence theory and necessary optimality conditions. Rewriting the Lagrange problem in a parametric form, we obtain a relation between the applicability conditions of the Pontryagin maximum principle to the latter problem and the Lipschitzian regularity conditions for the original problem. Under the standard hypotheses of coercivity of the existence theory, the conditions imply that the optimal controls are essentially bounded, assuring the applicability of the classical necessary optimality conditions like the Pontryagin maximum principle. The result extends previous Lipschitzian regularity results to cover optimal control problems with general nonlinear dynamics.     

多提供商网络环境中移动代理路径寻优

在多提供商网络环境中,端用户在访问内容提供商提供的内容时,在一定的QoS约束下,服务提供商需要对多个网络提供商的网络性能和价格进行比较,为端用户确定一个最优路径.基于移动代理进行网络信息的采集,将网络延迟和成本均设为随机变量,在随机网络中建立了一个费用成本和延迟时间双重期望值目标的最小化模型,应用遗传算法对移动代理从服务提供商到内容提供商的路径进行了最优化求解.仿真结果表明了算法的有效性.     

点融合进近模式下的多机协同优化排序方法

为了提高终端区的飞行效率和安全,研究了基于点融合进近模式的多机协同进场4D航迹计算方法及排序算法.首先,介绍了点融合进近模式的基本结构和运行方法,分析了终端区点融合进近多机4D航迹的计算方法;其次,建立了以提高多机飞行效率和降低管制员工作负荷为目标,满足安全尾流间隔约束,以多机进近的先后顺序为决策变量的考虑间隔约束的点...     

Optimal Trajectories for a Quadruped Robot with Trot,Amble and Curvet Gaits for Two Energetic Criteria

In this paper, optimal cyclic reference trajectories aredesigned for three gaits of a quadruped robot, the curvet, theamble, and the trot, taking into account the actuatorscharacteristics. The gaits are composed of stance phases andinstantaneous double supports. The principle of virtual leg isused to obtain simpler dynamic model describing the motion ofthe quadruped. The impact phases are modeled by passive impactequations. For the curvet the step is composed of twodifferent half steps. For the amble and trot gaits twofollowing half steps are symmetrical.The optimization problem is solved with an algebraicoptimization technique. The actuated joint evolution is chosenas a polynomial function of time. The coefficients of thepolynomial functions are optimization parameters. Thequadruped studied has non-actuated ankles. The kineticmomentum theorem permits to define the evolution of this non-actuated variable in function of the actuated variables. Twoenergetic criteria are defined: a torque cost and an energetic cost. The first is represented by the integral of the torquenorm and the second by the absolute value integral of theexternal forces work. The two criteria are calculated for adisplacement of one meter. During the optimization process,the constraints on the ground reactions, on the validity ofimpact, on the torques, on the joints velocities and on themotion velocity of the robot prototype are taken into account.Simulation results are presented for the three gaits. Allmotions are realistic. Curvet is the less efficient gait withrespect to the criteria studied. For slow motion, trot is themore efficient gait. But amble permits the fastest motion withthe same actuators.     

多路口环境下RRT的最优路径规划

针对于多路口环境下RRT的搜索时间长,搜索范围广和路径不平整的问题。提出一种基于路标引导和增长采样区域的混合策略来引导RRT算法向目标搜索。将对地图做预处理,处理掉较小的障碍物,尽可能保存大障碍物,得到预处理地图;在新地图上路口区域设置路标点,路标点的可视区域的组合要覆盖整个地图,根据其在新地图上的连通区域,通过寻找出一组从起点到终点的最优路标点组合,以相邻两路标之间构建移动增长采样区域来引导RRT算法快速向目标搜索;用树枝修剪和二次贝塞尔曲线拟合生成光滑路径。通过仿真实验验证了算法的有效性、合理性和正确性。     

移动计算中用户最优路径的选择

该文主要对移动计算中,移动用户必须同时考虑移动路径的长度和通信质量两个方面影响的问题,提出了一种基于路径长度和可变通信质量的加权综合系数的方法,选择用户移动时的最优路径,并给出了算法。     

飞行器故障预测与健康管理(PHM)集成工程环境研究

故障预测与健康管理(PHM)技术能够实现故障监测、诊断、预测、状态评估及综合决策的功能,能够降低飞行器维修、使用和保障费用,提高飞行器战备完好率、任务成功率以及安全性和可用性;在分析了国内外研究现状的基础上,提出了构建飞行器故障预测与综合健康管理的通用化支撵平台和验证环境的设计思路,并展开描述了PHM开发环境、运行环境、验证环境的具体功能组成,研究成果能够为检验飞行器PHM系统工作效能提供有效验证,为降低飞行器PHM验证费用提供借鉴.     

飞机环境控制系统分布式实时仿真

该文以整个环境控制系统为研究对象,根据其仿真的实际情况,根据传热学,热力学管理,建立了系统的数学模型,在此基础上,对系统进行分布式实时仿真。     

Optimal Channel Adaptation of Scalable Video Over a Multicarrier-Based Multicell Environment

To achieve seamless multimedia streaming services over wireless networks, it is important to overcome inter-cell interference (ICI), particularly in cell border regions. In this regard scalable video coding (SVC) has been actively studied due to its advantage of channel adaptation. We explore an optimal solution for maximizing the expected visual entropy over an orthogonal frequency division multiplexing (OFDM)-based broadband network from the perspective of cross-layer optimization. An optimization problem is parameterized by a set of source and channel parameters that are acquired along the user location over a multicell environment. A suboptimal solution is suggested using a greedy algorithm that allocates the radio resources to the scalable bitstreams as a function of their visual importance. The simulation results show that the greedy algorithm effectively resists ICI in the cell border region, while conventional nonscalable coding suffers severely because of ICI.     

Aircraft Trajectory Optimization for Collision Avoidance Using Stochastic Optimal Control

Optimizing aircraft collision avoidance and performing trajectory optimization are the key problems in an air transportation system. This paper is focused on solving these problems by using a stochastic optimal control approach. The major contribution of this paper is a proposed stochastic optimal control algorithm to dynamically adjust and optimize aircraft trajectory. In addition, this algorithm accounts for random wind dynamics and convective weather areas with changing size. Although the system is modeled by a stochastic differential equation, the optimal feedback control for this equation can be computed as a solution of a partial differential equation, namely, an elliptic Hamilton‐Jacobi‐Bellman equation. In this paper, we solve this equation numerically using a Markov Chain approximation approach, where a comparison of three different iterative methods and two different optimization search methods are presented. Simulations show that the proposed method provides better performance in reducing conflict probability in the system and that it is feasible for real applications.