Active vibration control is needed for future space telescopes, space laser communication and other precision sensitive payloads which require ultra-quiet environments. A Stewart platform based hybrid isolator with 6 ...Active vibration control is needed for future space telescopes, space laser communication and other precision sensitive payloads which require ultra-quiet environments. A Stewart platform based hybrid isolator with 6 hybrid struts is the effective system for active/passive vibration isolation over 5-250 Hz band. Using an identification transfer matrix of the Stewart platform, the coupling analysis of six channels is provided. A dynamics model is derived, and the rigid mode is removed to keep the signal of pointing control. Multi objective robust H∞ and μ synthesis strategies, based on singular values and structured singular values respectively, are presented, which simultaneously satisfy the low frequency pointing and high frequency disturbance rejection requirements and take account of the model uncertainty, parametric uncertainty and sensor noise. Then, by performing robust stability test, it is shown that the two controllers are robust to the uncertainties, the robust stability margin of H, controller is less than that of μ controller, but the order of μ controller is higher than that of H, controller, so the balanced controller reduction is provided. Additionally, the μ controller is compared with a PI controller. The time domain simulation of the μ controller indicates that the two robust control strategies are effective for keeping the pointing command and isolating the harmonic and stochastic disturbances.展开更多
The alternating wedge strut,serving as both an injector and a vortex generator,has great potential for application in the scramjet combustor.The expansive trailing edge structure can further enhance the mixing perform...The alternating wedge strut,serving as both an injector and a vortex generator,has great potential for application in the scramjet combustor.The expansive trailing edge structure can further enhance the mixing performance of the alternating wedge strut.To enhance the performance of scramjet engines,it is essential to investigate the fuel/air mixing characteristics and mechanism downstream of alternating wedge struts with expansive trailing edges.The research focused on the impact of two different fuel injection schemes on the air/fuel mixing process and plume morphology.The optical diagnostic technique,particle laser-induced fluorescence,was employed to measure fuel plume morphology at various downstream locations under ambient temperature conditions.The results show that the expansive trailing edge significantly enhances the vertical diffusion of the fuel,leading to distinct plume characteristics.Compared to the strut injecting fuel into the edge of the streamwise vortex,the strut injecting fuel into the core of the streamwise vortex results in a larger fuel plume area with a more uniform distribution.Additionally,a streamwise vortex model was established to investigate the vortex dynamics and mixing mechanisms behind the strut from a mechanistic perspective.The simulation results indicate that the model demonstrates good performance in forecasting the dynamics of streamwise vortices and the evolution of fuel plume morphology.展开更多
研究采用Struts2+Hibernate3+Spring2组合架构搭建物流数据交换平台的方法与技术。该组合架构综合应用了Struts2的模型-视图-控制器MVC(Model-View-Controller)设计模式,Hibernate3的对象-关系映射O-R映射(Object-Relation Mapping)工具...研究采用Struts2+Hibernate3+Spring2组合架构搭建物流数据交换平台的方法与技术。该组合架构综合应用了Struts2的模型-视图-控制器MVC(Model-View-Controller)设计模式,Hibernate3的对象-关系映射O-R映射(Object-Relation Mapping)工具,Sprng2的控制反转IoC(Inversion of Control)管理功能,提出了集成的策略,并在现代物流实验室进行了集成应用。展开更多
文摘Active vibration control is needed for future space telescopes, space laser communication and other precision sensitive payloads which require ultra-quiet environments. A Stewart platform based hybrid isolator with 6 hybrid struts is the effective system for active/passive vibration isolation over 5-250 Hz band. Using an identification transfer matrix of the Stewart platform, the coupling analysis of six channels is provided. A dynamics model is derived, and the rigid mode is removed to keep the signal of pointing control. Multi objective robust H∞ and μ synthesis strategies, based on singular values and structured singular values respectively, are presented, which simultaneously satisfy the low frequency pointing and high frequency disturbance rejection requirements and take account of the model uncertainty, parametric uncertainty and sensor noise. Then, by performing robust stability test, it is shown that the two controllers are robust to the uncertainties, the robust stability margin of H, controller is less than that of μ controller, but the order of μ controller is higher than that of H, controller, so the balanced controller reduction is provided. Additionally, the μ controller is compared with a PI controller. The time domain simulation of the μ controller indicates that the two robust control strategies are effective for keeping the pointing command and isolating the harmonic and stochastic disturbances.
文摘The alternating wedge strut,serving as both an injector and a vortex generator,has great potential for application in the scramjet combustor.The expansive trailing edge structure can further enhance the mixing performance of the alternating wedge strut.To enhance the performance of scramjet engines,it is essential to investigate the fuel/air mixing characteristics and mechanism downstream of alternating wedge struts with expansive trailing edges.The research focused on the impact of two different fuel injection schemes on the air/fuel mixing process and plume morphology.The optical diagnostic technique,particle laser-induced fluorescence,was employed to measure fuel plume morphology at various downstream locations under ambient temperature conditions.The results show that the expansive trailing edge significantly enhances the vertical diffusion of the fuel,leading to distinct plume characteristics.Compared to the strut injecting fuel into the edge of the streamwise vortex,the strut injecting fuel into the core of the streamwise vortex results in a larger fuel plume area with a more uniform distribution.Additionally,a streamwise vortex model was established to investigate the vortex dynamics and mixing mechanisms behind the strut from a mechanistic perspective.The simulation results indicate that the model demonstrates good performance in forecasting the dynamics of streamwise vortices and the evolution of fuel plume morphology.
文摘研究采用Struts2+Hibernate3+Spring2组合架构搭建物流数据交换平台的方法与技术。该组合架构综合应用了Struts2的模型-视图-控制器MVC(Model-View-Controller)设计模式,Hibernate3的对象-关系映射O-R映射(Object-Relation Mapping)工具,Sprng2的控制反转IoC(Inversion of Control)管理功能,提出了集成的策略,并在现代物流实验室进行了集成应用。
