The unintentional islanding of micro-grid may cause negative impacts on distribution loads and distributed generations,so it must be detected within the acceptable duration.In this paper a new islanding detection algo...The unintentional islanding of micro-grid may cause negative impacts on distribution loads and distributed generations,so it must be detected within the acceptable duration.In this paper a new islanding detection algorithm is proposed.This algorithm introduces the frequency feedback method by the reactive power compensation to derive the frequency continuous shift. Accordingly,the islanding can be detected by monitoring the frequency within 0.1 s.The simulation results prove that this algorithm has extremely small non-detection zone,and meanwhile it presents an excellent islanding detection speed as well.展开更多
In a secure group communication system, messages must be encrypted before being transmitted to group members to prevent unauthorized access. In many secure group communication schemes, whenever a member leaves or join...In a secure group communication system, messages must be encrypted before being transmitted to group members to prevent unauthorized access. In many secure group communication schemes, whenever a member leaves or joins the group, group center (GC) immediately changes the common encryption key and sends the new key to all valid members for forward and backward secrecy. If valid members are not on-line, they will miss the re-keying messages and will not be able to decrypt any ciphertext. Therefore, group members must be able to store the state of the system. In some applications, like global positioning systems (GPS) or pay-per-view systems, it is not reasonable to ask group members to stay on-line all the time and save the changes to the system. A hierarchical binary tree-based key management scheme are proposed for a secure group communication. This scheme reduces the key storage requirement of GC to a constant size and the group members are not required to be on-line constantly (stateless).展开更多
A motion control structure used for autonomous walking on uneven terrain with a hexapod biomimetic robot is proposed based on function-behavior-integration. In the gait planning level, a set of local rules operating b...A motion control structure used for autonomous walking on uneven terrain with a hexapod biomimetic robot is proposed based on function-behavior-integration. In the gait planning level, a set of local rules operating between adjacent legs were put forward and the theory of finite state machine was employed to model them; further, a distributed network of local rules was constructed to adaptively adjust the fluctuation of inter-leg phase sequence. While in the leg-end trajectory planning level, combined polynomial curve was adopted to generate foot trajectory, which could realize real-time control of robot posture and accommodation to terrain conditions. In the simulation experiments, adaptive regulation of inter-leg phase sequence, omnidirectional locomotion and ground accommodation were realized, moreover, statically stable free gait was obtained simultaneously, which provided hexapod robot with the capability of walking on slightly irregular terrain reliably and expeditiously.展开更多
基金National High-Tech R&D Program of China(No.2007AA05Z241).
文摘The unintentional islanding of micro-grid may cause negative impacts on distribution loads and distributed generations,so it must be detected within the acceptable duration.In this paper a new islanding detection algorithm is proposed.This algorithm introduces the frequency feedback method by the reactive power compensation to derive the frequency continuous shift. Accordingly,the islanding can be detected by monitoring the frequency within 0.1 s.The simulation results prove that this algorithm has extremely small non-detection zone,and meanwhile it presents an excellent islanding detection speed as well.
文摘In a secure group communication system, messages must be encrypted before being transmitted to group members to prevent unauthorized access. In many secure group communication schemes, whenever a member leaves or joins the group, group center (GC) immediately changes the common encryption key and sends the new key to all valid members for forward and backward secrecy. If valid members are not on-line, they will miss the re-keying messages and will not be able to decrypt any ciphertext. Therefore, group members must be able to store the state of the system. In some applications, like global positioning systems (GPS) or pay-per-view systems, it is not reasonable to ask group members to stay on-line all the time and save the changes to the system. A hierarchical binary tree-based key management scheme are proposed for a secure group communication. This scheme reduces the key storage requirement of GC to a constant size and the group members are not required to be on-line constantly (stateless).
文摘A motion control structure used for autonomous walking on uneven terrain with a hexapod biomimetic robot is proposed based on function-behavior-integration. In the gait planning level, a set of local rules operating between adjacent legs were put forward and the theory of finite state machine was employed to model them; further, a distributed network of local rules was constructed to adaptively adjust the fluctuation of inter-leg phase sequence. While in the leg-end trajectory planning level, combined polynomial curve was adopted to generate foot trajectory, which could realize real-time control of robot posture and accommodation to terrain conditions. In the simulation experiments, adaptive regulation of inter-leg phase sequence, omnidirectional locomotion and ground accommodation were realized, moreover, statically stable free gait was obtained simultaneously, which provided hexapod robot with the capability of walking on slightly irregular terrain reliably and expeditiously.
