A novel non-smooth controller of the second order double integrator system with a bounded disturbance is proposed,which stability is proved and which disturbance rejection capability is analyzed by MATLAB simulation e...A novel non-smooth controller of the second order double integrator system with a bounded disturbance is proposed,which stability is proved and which disturbance rejection capability is analyzed by MATLAB simulation experiments. The novel non-smooth output feedback controller and tracking differentiator are applied to control the azimuth servo systemof the small floating satellite antenna. The MATLAB simulation and hardware in the loop simulation experiments are conducted. The experiment results validate that the non-smooth output feedback controller with stronger surge and sudden disturbance rejection capability can realize the stable azimuth servo control of the small floating antenna to ensure the communication between the target satellite and the antenna with high quality.展开更多
The performance of three wireless local-area network(WLAN) media access control(MAC) protocols is investigated and compared in the context of simulcast radioover-fiber-based distributed antenna systems(RoF-DASs) where...The performance of three wireless local-area network(WLAN) media access control(MAC) protocols is investigated and compared in the context of simulcast radioover-fiber-based distributed antenna systems(RoF-DASs) where multiple remote antenna units(RAUs) are connected to one access point(AP) with different-length fiber links.The three WLAN MAC protocols under investigation are distributed coordination function(DCF) in basic access mode,DCF in request/clear to send(RTS/CTS) exchange mode,and point coordination function(PCF).In the analysis,the inter-RAU hidden nodes problems and fiber-length difference effect are both taken into account.Results show that adaptive PCF mechanism has better throughput performances than the other two DCF modes,especially when the inserted fiber length is short.展开更多
In this article,room temperature gallium-based fluids(RTGFs)with unique thermal and conductive properties are proposed as a transmission fluid for the force carrying medium of hydraulics,which rectify the lack of the ...In this article,room temperature gallium-based fluids(RTGFs)with unique thermal and conductive properties are proposed as a transmission fluid for the force carrying medium of hydraulics,which rectify the lack of the multi-functional hydraulic roles of liquid metal(LM).The typical physical properties of RTGFs and comparative conventional hydraulic fluids(commercial hydraulic oil and deionized water),such as thermal stability and rheological characteristics,are evaluated.Experimental and numerical methods,then,were adopted to clarify the force transmission performance of RTGFs and commercial hydraulic oils,as well as the influence of temperature fields on the viscosity of fluids.The results disclosed that the advantages of inherent flame resistance,wide liquid temperature range,and the viscosity changing slightly with temperature made RTGFs potential in finding efficient application in the hydraulics as new working fluids.Finally,for illustration,the rigid and flexible actuators driven by RTGFs were designed as hydraulic fluid and demonstrated their capabilities in grasping objects with various shapes and weights,respectively.And the tunable stiffness of such a flexible actuator was enabled via the solid-liquid phase change of LM.Additionally,a frequency-adjustable antenna was manufactured and showcased owing to the introduced transformable electromagnetic behaviors of LM.Overall,the gallium-based LM fluids with thermoelectrical and mechanical multimodal signal medium would serve as a potential candidate for future complex multifunctional signal transmission systems.展开更多
基金Supported by Academic Innovation Project of Beijing(201106149)
文摘A novel non-smooth controller of the second order double integrator system with a bounded disturbance is proposed,which stability is proved and which disturbance rejection capability is analyzed by MATLAB simulation experiments. The novel non-smooth output feedback controller and tracking differentiator are applied to control the azimuth servo systemof the small floating satellite antenna. The MATLAB simulation and hardware in the loop simulation experiments are conducted. The experiment results validate that the non-smooth output feedback controller with stronger surge and sudden disturbance rejection capability can realize the stable azimuth servo control of the small floating antenna to ensure the communication between the target satellite and the antenna with high quality.
基金supported in part by National 973 Program(2012CB315705)NSFC Program(61302086,61271042,61107058, 61302016,and 61335002)+2 种基金Specialized Research Fund for the Doctoral Program of Higher Education(20130005120007)Program for New Century Excellent Talents in University(NCET-13-0682)Fundamental Research Funds for the Central Universities
文摘The performance of three wireless local-area network(WLAN) media access control(MAC) protocols is investigated and compared in the context of simulcast radioover-fiber-based distributed antenna systems(RoF-DASs) where multiple remote antenna units(RAUs) are connected to one access point(AP) with different-length fiber links.The three WLAN MAC protocols under investigation are distributed coordination function(DCF) in basic access mode,DCF in request/clear to send(RTS/CTS) exchange mode,and point coordination function(PCF).In the analysis,the inter-RAU hidden nodes problems and fiber-length difference effect are both taken into account.Results show that adaptive PCF mechanism has better throughput performances than the other two DCF modes,especially when the inserted fiber length is short.
基金supported by the National Natural Science Foundation of China(Grant No.91748206)Dean’s Research Funding and the Frontier Project of the Chinese Academy of SciencesBeijing Municipal Science(Grant No.Z151100003715002)。
文摘In this article,room temperature gallium-based fluids(RTGFs)with unique thermal and conductive properties are proposed as a transmission fluid for the force carrying medium of hydraulics,which rectify the lack of the multi-functional hydraulic roles of liquid metal(LM).The typical physical properties of RTGFs and comparative conventional hydraulic fluids(commercial hydraulic oil and deionized water),such as thermal stability and rheological characteristics,are evaluated.Experimental and numerical methods,then,were adopted to clarify the force transmission performance of RTGFs and commercial hydraulic oils,as well as the influence of temperature fields on the viscosity of fluids.The results disclosed that the advantages of inherent flame resistance,wide liquid temperature range,and the viscosity changing slightly with temperature made RTGFs potential in finding efficient application in the hydraulics as new working fluids.Finally,for illustration,the rigid and flexible actuators driven by RTGFs were designed as hydraulic fluid and demonstrated their capabilities in grasping objects with various shapes and weights,respectively.And the tunable stiffness of such a flexible actuator was enabled via the solid-liquid phase change of LM.Additionally,a frequency-adjustable antenna was manufactured and showcased owing to the introduced transformable electromagnetic behaviors of LM.Overall,the gallium-based LM fluids with thermoelectrical and mechanical multimodal signal medium would serve as a potential candidate for future complex multifunctional signal transmission systems.
