Control allocation considers the problem of controlling instruction distribution for control systems with multiple and redundant actuators. This paper focuses on the direct allocation method, making the time requireme...Control allocation considers the problem of controlling instruction distribution for control systems with multiple and redundant actuators. This paper focuses on the direct allocation method, making the time requirement of the algorithm analogous compared with modified pseudoinverse redistribution methods, linear programming methods solved by simplex method, and sub-gradient optimization method. To reduce off-line computations of constructing the attainable moment set of actuators, a new approach based on the null space of the control effectiveness matrix is proposed, which is superior when the number of actuators is less than 10 compared with traditional method. To decrease on-line computations, an improvement method of searching the facet that is aligned with the desired moment is presented, shortening the search time by checking only the facets that lie around the desired moment. To find such facets, the vertices of the attainable moment set are normalized and saved during off-line computations. Simulation results show that at least 32.22% of off-line computation time would be saved using null space-based construction when the number of actuators is less than 10. In on-line computations, the modified method performs superiorly compared with the three aforementioned methods. Furthermore, it may solve the problem of control allocation efficiently when a remarkable large number of redundant actuators are configured.展开更多
针对无线多跳网络承载多媒体服务所面临的可扩展性、能量有效性和服务质量保证的挑战,研究了多个可伸缩编码(scalable video coding,SVC)视频流在无线多跳网络中传输的分布式跨层优化问题.在分析网络资源分配约束和SVC视频内容自适应模...针对无线多跳网络承载多媒体服务所面临的可扩展性、能量有效性和服务质量保证的挑战,研究了多个可伸缩编码(scalable video coding,SVC)视频流在无线多跳网络中传输的分布式跨层优化问题.在分析网络资源分配约束和SVC视频内容自适应模型的基础上,把SVC视频的传输问题表达为一个视频质量和网络功率消耗的跨层权衡优化问题.基于对偶问题的可分解性和次梯度求解方法,提出了一个可分布式实现的SVC视频优化传输算法.该分布式算法避免了控制开销的全网传播,通过节点的局部信息交换和独立解决相应子问题,达到底层资源分配和上层SVC视频传输内容选择的最优匹配.仿真结果表明该算法可以快速收敛到最优解,并能实现SVC视频的平均传输质量和网络总功率消耗的最优权衡.展开更多
考虑了卫星Internet拓扑变化的可预测性和组播应用的服务质量QoS(quality of service)需求,设计了一种QoS组播路由机制.给出了卫星Internet中QoS组播路由问题模型及其数学描述,引入拉格朗日松弛,设定适应度函数,使用PRIM算法,基于次梯...考虑了卫星Internet拓扑变化的可预测性和组播应用的服务质量QoS(quality of service)需求,设计了一种QoS组播路由机制.给出了卫星Internet中QoS组播路由问题模型及其数学描述,引入拉格朗日松弛,设定适应度函数,使用PRIM算法,基于次梯度优化,寻找生存周期最大化的QoS组播路由树.基于NS2进行了仿真实现和性能评价.仿真结果表明,同传统的组播路由机制相比,该机制是可行和有效的,提高了QoS组播路由树生存周期,具有良好的性能.展开更多
基金National Natural Science Foundation of China （NSFC60704020） Changjiang Scholars and Innovative Research Team of China （PCSIRT0520） Research Fund for the Doctoral Program of Higher Education of China （20070213068）
文摘Control allocation considers the problem of controlling instruction distribution for control systems with multiple and redundant actuators. This paper focuses on the direct allocation method, making the time requirement of the algorithm analogous compared with modified pseudoinverse redistribution methods, linear programming methods solved by simplex method, and sub-gradient optimization method. To reduce off-line computations of constructing the attainable moment set of actuators, a new approach based on the null space of the control effectiveness matrix is proposed, which is superior when the number of actuators is less than 10 compared with traditional method. To decrease on-line computations, an improvement method of searching the facet that is aligned with the desired moment is presented, shortening the search time by checking only the facets that lie around the desired moment. To find such facets, the vertices of the attainable moment set are normalized and saved during off-line computations. Simulation results show that at least 32.22% of off-line computation time would be saved using null space-based construction when the number of actuators is less than 10. In on-line computations, the modified method performs superiorly compared with the three aforementioned methods. Furthermore, it may solve the problem of control allocation efficiently when a remarkable large number of redundant actuators are configured.
文摘针对无线多跳网络承载多媒体服务所面临的可扩展性、能量有效性和服务质量保证的挑战,研究了多个可伸缩编码(scalable video coding,SVC)视频流在无线多跳网络中传输的分布式跨层优化问题.在分析网络资源分配约束和SVC视频内容自适应模型的基础上,把SVC视频的传输问题表达为一个视频质量和网络功率消耗的跨层权衡优化问题.基于对偶问题的可分解性和次梯度求解方法,提出了一个可分布式实现的SVC视频优化传输算法.该分布式算法避免了控制开销的全网传播,通过节点的局部信息交换和独立解决相应子问题,达到底层资源分配和上层SVC视频传输内容选择的最优匹配.仿真结果表明该算法可以快速收敛到最优解,并能实现SVC视频的平均传输质量和网络总功率消耗的最优权衡.
文摘考虑了卫星Internet拓扑变化的可预测性和组播应用的服务质量QoS(quality of service)需求,设计了一种QoS组播路由机制.给出了卫星Internet中QoS组播路由问题模型及其数学描述,引入拉格朗日松弛,设定适应度函数,使用PRIM算法,基于次梯度优化,寻找生存周期最大化的QoS组播路由树.基于NS2进行了仿真实现和性能评价.仿真结果表明,同传统的组播路由机制相比,该机制是可行和有效的,提高了QoS组播路由树生存周期,具有良好的性能.
