Advanced exergy analysis of an absorption cooling machine: Effects of the difference between the condensation and absorption temperatures

The water–LiBr absorption machine was analyzed with the purpose of identifying the endogenous, exogenous, avoidable and unavoidable fractions of the exergy destruction. The latter was observed to be largely of endogenous nature, with the desorber and absorber being the major contributors. When the difference between the absorption and condensation temperatures was raised, both the first and second law efficiencies degraded. Furthermore, the absorber endogenous avoidable irreversibility was much larger than that at the desorber when the absorption temperature was lower than the condensation temperature, and the situation reversed when the absorption temperature became higher than the condensation temperature. The same trends were observed in terms of the exogenous avoidable exergy destruction. However, the endogenous unavoidable exergy destruction at the absorber was initially smaller than that at the desorber, and the two components equally contributed to the total endogenous unavoidable irreversibility when the absorption temperature became higher than the condensation temperature.     

基于几何解析的双雷达地面目标定位算法

传统的双雷达地面目标定位算法因测量数据本身固有的误差和量测噪声,使得基于非线性估计定位算法的定位精度不高。本文研究了一种新的双雷达地面目标定位算法,该算法将已知雷达探测数据以几何方式加以表示,通过几何解析对地面目标进行定位。此外,还详细分析了各种因素在不同情况下对定位精度的影响。所研究的算法具有计算量小、远距离定位精度高等优点。最后,通过仿真验证了该算法能够提高远距离定位的定位精度。     

Accurate positioning of a drilling and riveting cell for aircraft assembly

Modern aircraft assembly demands assembly cells or machines with higher machining efficiency and accuracy. Thus, a dual-machine drilling and riveting cell is developed in this paper. We firstly discuss its physical design, as well as the automatic drilling and riveting process. With the automatic drilling and riveting cell, drilling and riveting production line of aircraft panels can be expected. The frame chain of the drilling and riveting cell is constructed to link the assembly cell to its task space, which is the kinematics base. System calibrations, including task space calibration, the sensor calibration of an orientation alignment unit, the floating calibration of the implicit hand-eye relationship, are explored. For high positioning accuracy, a multi-sensor servoing method is proposed for cell positioning. An orientation-based laser servoing strategy, which uses the feedback of the orientation errors measured by laser displacement sensors, is used to align drilling direction and camera shooting direction. Besides, A single-camera-based visual servoing is applied to align the tool center point (TCP) to reference holes, to obtain their coordinates for drilling position modification. Experiments of multi-sensor servoing for cell positioning are performed on an automatic drilling and riveting machine developed for the panel assembly of an aircraft in China. With the cell positioning method, the automatic drilling and riveting cell can approximately achieve an accuracy of 0.05 mm, which can adequately fulfill the requirement for the assembly of the aircraft.     

变邻域分解多目标自适应差分进化算法

分解方法是处理复杂问题常用的一种手段,而差分进化算法被广泛地应用于多目标优化问题(multiobjective optimization problems,MOP),为了克服经典差分进化算法和分解方法的缺陷,本文提出了一种自适应差分进化算法和变邻域分解方法相结合的新颖算法一ADEMO/D-ENS,该算法采用Tchebycheff方法将多目标优化问题分解成多维标量优化子问题,并利用邻域子问题的信息进行优化,基于邻域种群集依概率自适应选择邻域种群规模;同时采用概率匹配(]probability match,PM)自适应方法从差分策略池中选择差分进化策略;同时分析了算法的复杂度;最后,通过和经典的非支配排序遗传算法(non-dominated sorting genetic algorithmsⅡ,NSGA-Ⅱ)和多目标差分进化算法(multi-objective differential evolution algorithm,MODE)仿真对比,说明ADEMO/D-ENS方法可以更有效的处理多目标优化问题.     

基于数字高程模型数据的机载认知雷达地杂波建模方法研究

针对机载认知雷达信号处理的特点,设计了一种基于数字高程模型数据的地杂波建模方法。该方法首先从数字高程模型数据中提取对杂波功率谱有影响的地形因子,然后结合地理地貌学理论和地形因子对数字高程模型提供的真实地貌类型进行量化分类;设计动态数据库来存储量化后的地貌信息,以提高杂波建模过程的实时性;最后基于地貌信息和后向散射系数模型构建地杂波。仿真结果表明,采用该方法构建的地杂波模型符合机载雷达所处的地貌实际情形,用作机载认知雷达的先验信息时具有真实、稳定和可靠的优势,可有效地辅助机载认知雷达提高工作性能和生存力。     

基于Gist特征与PHOG特征融合的多类场景分类

Gist特征是根据稀疏网格划分提取图像全局特征,它可以很好地描述单一场景,但是对于同一图像可能包含的多个场景,该特征的区分性能有所下降;而PHOG特征,提取的是图像局部轮廓特征,对Gist特征有一定的补充.本文以此提出基于Gist特征与PHOG特征融合的场景分类技术,首先分别提取图像的Gist特征和PHOG特征,然后将两种特征串接起来形成融合特征,最后使用SVM分类器进行场景训练和分类.在OT数据集上,考察了单一特征的分类精度和融合特征的分类精度,以及训练样本数对分类性能的影响,通过实验对比发现特征融合能够有效地提高场景分类的正确率.     

基于UML集成测试用例的算法研究

对基于状态图生成集成测试用例的方法进行了研究,通过构造集成测试模型,重点描述了两个对象或组件的状态图进行合并的方法,并给出了状态图的形式化描述,以及如何对组合状态图进行展开用于集成测试用例的生成.为了验证该方法的实用性,又以实际项目研究为例,实现了基于状态图集成测试用例的生成工具,对该方法进行了验证,并给出了算法的部分实现代码.该方法将系统设计和测试用例的设计统一起采,是软件测试自动化的一个探索.     

一种改进的组间互补码及其性能分析

在分析组间互补码、零相关区正交互补码的基础上,构造一种适合于多进制正交码扩频系统或准同步CDMA系统的正交码集――改进的组间互补码。通过理论分析与性能仿真表明,改进的组间互补码的集合数量多于组间互补码;零相关区长度大于组内组间互补码,但比组间的组间互补码小;在相同码长条件下,改进的组间互补码的自相关特性优于组间互补码,互相关特性与组间互补码相当。     

翼伞系统在较大风场中的归航控制

翼伞系统是一类特殊的柔翼飞行器,由于其飞行速度较低,容易受到风场的影响.针对翼伞系统在较大风场中难以准确跟踪归航轨迹、实现精确着陆,因此将风场中平均风的影响在轨迹规划中予以考虑,采用一种改进的粒子群算法(particle swarm optimization,PSO)优化分段归航轨迹;将紊流的影响作为外界的干扰,由线性自抗扰控制器(linear active disturbance rejection controller,LADRC)进行修正.仿真结果表明,该归航控制方法对提高翼伞系统在较大风场环境下的抗风性能和归航精度有重要意义.