HISTORICAL PROCEDURES AND G-DSG METHOD BASED MANUFACTURING PLANNING

Oriented to CAD/CAM seamless integration, this paper presents an idea for synthetically considering the qualitative history model, which represents the whole course of modeling, and the quantitative geometry model, which contains the extended Brep model, CSG and feature pedigree. History model building captures in background the dynamic interactive definition of engineering requirement and then explicitly conveys the original intention to successive application layers, which isc onductive to the decision support of manufacturing planning in not only automatic geometry re-constructing but also machining set-up. G-DSG theory as an earlier achievement is applied to generate the topology-independent generalized mid-model as an input to manufacturing planning, which istherefore simplified and its accuracy is simultaneously improved. Manufacturing planning lays emphasis on optimizing the mapping in both geometry and function from part itself to detail machining scheme. Comparatively, process planning pays more attention to the mapping to those items like tool, fixture, etc. Theoretically, such an idea is also beneficial to realizing the parametric NC machining trajectory generation and maintaining its dynamic consistency with the update of the design model.     

动态扩展裂纹的热-弹塑性耦合分析

以弹塑性扩展裂纹的裂尖参数为研究对象,对快速扩展的裂纹问题进行了细致的分析。首先建立了经验的应变率以及热 -弹塑性耦合的材料本构关系,完善了增量路径无关积分参数 T*的数值计算。通过与 J积分的比较,给出了两种积分参数在不同扩展速度、是否考虑热和应变率影响等情况下的变化规律,说明了T*积分用于快速扩展裂纹的合理性和优越性。在裂尖场的讨论中,重点分析了裂尖应力、应变、应力三轴度和塑性区的演化发展过程,发现了快速扩展裂纹塑性区发展非单调的有趣现象,并且获得了应力三轴度可以作为裂纹扩展过程控制参数的基本结论。     

基于工艺失效知识的工艺改进方法及实现

工艺设计是一个不断改进与优化的过程,而反面工艺知识即工艺失效知识,对工艺改进与优化往往十分有效.提出了一种基于工艺失效知识的改进方法,包括8个步骤:确定潜在失效模式,分析潜在失效原因,计算风险优先数N,提出改进措施,计算改进后的风险优先数N’,权衡改进措施,采纳改进措施和存储工艺改进数据.在基于Web的工艺失效知识库管理系统——工艺FMEA(Failure Mode and Effect Analysis)的基础上,通过建立工艺失效知识与产品和工艺信息的关联,实现工艺FMEA系统与CAPP(Computer Aided Process Planning)系统的信息集成和过程集成,从而达到工艺改进的目的.给出某飞机结构件(主梁)利用工艺失效知识进行工艺改进的验证实例,为在工艺设计阶段主动预防地改进工艺方案提供了一种有效手段.      

降维法计算扩展网络的最短路径

以在军事等领域具有重要应用的扩展网络为研究对象,研究并提出了基于最短路树的网络降维方法。当子网络之间有边互连的节点数远小于原网络节点数时,利用降维网络计算扩展网络的最短路径具有很好的效果。     

多无人机协同搜索区域划分与路径规划

针对多无人机广域协同搜索问题，研究无人机工作区间划分和全区域覆盖搜索路径规划2个子问题。采用按无人机来向均衡划分的方法和凹点凸分解的方法，开展了凸多边形和非凸多边形的区域划分研究，将多机协同搜索问题转化为子区域上的单机搜索问题；在此基础上采用"Z"型路径覆盖方法以及Dubins转弯路径，对各个无人机开展覆盖其子区域的搜索路径规划，从而建立了一个区域划分和路径规划的整体调用框架，能够对目标区域快速进行划分并生成飞行路线。最后，对凸多边形和非凸多边形区域搜索开展仿真计算，验证了该方法的有效性。     

Dual Drive Curve Tool Path Planning Method for 5-axis NC Machining of Sculptured Surfaces

The problem of finished surface being not first-order continuous commonly exists in machining sculptured surfaces with a torus cutter and some other types of cutters. To solve this problem, a dual drive curve tool path planning method is proposed in this article. First, the maximum machining strip width of a whole tool path can be obtained through optimizing each tool position with multi-point machining (MPM) method. Second, two drive curves are then determined according to the obtained maximum machining strip width. Finally, the tool is positioned once more along the dual drive curve under the condition of tool path smoothness. A computer simulation and cutting experiments are carried out to testify the performance of the new method. The machined surface is measured with a coordinate measuring machine (CMM) to examine the machining quality. The results obtained show that this method can effectively eliminate sharp scallops between adjacent tool paths, keep tool paths smooth, and improve the surface machining quality as well as machining efficiency.     

基于动态变迁图的卫星总装规划建模技术研究

不同于一般机械产品装配的流程,卫星总装的过程是"拆""装"操作相结合的,为了解决这一类特殊的非线性装配顺序规划问题,提出了一种基于动态变迁图的装配规划模型。该模型在静态有向连接图的基础上,通过逐层分析和验证可能的状态以动态变迁图为核心构建装配任务过程树,从而支持卫星所有几何可行的流程序列表达和装配场景再现。最后通过某型卫星舱段总装验证了该建模方法的有效性。     

集群无人机队形重构及虚拟仿真验证

队形重构是集群无人机（UAV）控制的重要问题，指无人机按照要求安全、无碰撞地从一个队形变换到另一个队形，其难点在于快速规划最优安全轨迹并控制无人机进行轨迹姿态的高精度跟踪。针对集群无人机队形重构的上述问题，首先，基于CAPT（Concurrent Assignment and Planning of Trajectories）算法，解决了多无人机的目标分配和轨迹生成的实时性问题，实现了集群无人机的最优安全路径规划；其次，提出一种有限时间多变量积分滑模连续控制算法，解决了无人机轨迹姿态的高精度跟踪问题，并通过MATLAB仿真验证了该控制算法的有效性；最后，为了更加真实直观地演示无人机三维仿真效果，建立了基于Gazebo-ROS的无人机仿真平台，实现了12架四旋翼无人机队形重构"建模-仿真-可视化"的一体化仿真演示，验证了上述路径规划算法和轨迹姿态控制算法的有效性。     

具有时间约束的无人机遗传算法航迹规划

为无人机进行航迹规划不仅要满足路径的有效性,还需要考虑无人机的到达时间约束.将遗传算法应用于动态环境中无人机的航迹规划,通过编码生成初始航迹,确定合理的适应度函数和进化操作,同时根据要求到达时间约束为每个航迹加入过点速度和到达时间信息,最终搜索规划出可飞且满足时间约束的航迹.在仿真实验中实现了针对移动目标的规划和突然出现威胁的局部重规划.     

舰载机着舰任务下的飞行员建模研究

为研究舰载机在下滑着舰时飞行员的操纵策略,建立了着舰任务下的双通道飞行员模型.以人工着舰时飞行员控制飞机进行轨迹跟踪为背景,以着舰时惯用的“反区”操纵技术为依据,确立了舰载机飞行员控制律,并对控制增益参数进行了自适应设计.最后结合F-18A舰载机,运用SIMILINK软件进行了仿真.结果表明,该模型能很好地反映着舰任务下的飞行员操纵特性,可为飞行员着舰操纵提供参考.