This work proposes a new strategy to improve the rotor position estimation of a permanent magnet synchronous motor(PMSM) over wide speed range. Rotor position estimation of a PMSM is performed by using sliding mode ob...This work proposes a new strategy to improve the rotor position estimation of a permanent magnet synchronous motor(PMSM) over wide speed range. Rotor position estimation of a PMSM is performed by using sliding mode observer(SMO). An adaptive observer gain was designed based on Lyapunov function and applied to solve the chattering problem caused by the discontinuous function of the SMO in the wide speed range. The cascade low-pass filter(LPF) with variable cut-off frequency was proposed to reduce the chattering problem and to attenuate the filtering capability of the SMO. In addition, the phase shift caused by the filter was counterbalanced by applying the variable phase delay compensation for the whole speed area. High accuracy estimation result of the rotor position was obtained in the experiment by applying the proposed estimation strategy.展开更多
In ultralong distance soliton transmission, the main limit to the single-channel bit rateis set by jitter in pulse arrival time from Gordon-Haus limit. Soliton controls in timesand in frequency domains are used to red...In ultralong distance soliton transmission, the main limit to the single-channel bit rateis set by jitter in pulse arrival time from Gordon-Haus limit. Soliton controls in timesand in frequency domains are used to reduce this jitter. Soliton control in time makesthe wavelength-division-multiplexing systems difficult to realize, while filtering in frequency do-mains does not have this problem. The latter reduces the jitter through the use of nar-展开更多
This work presents a control approach based on sliding-mode-control(SMC)to design robust H∞state feedback controllers for load frequency regulation of delayed interconnected power system(IPS)with parametric uncertain...This work presents a control approach based on sliding-mode-control(SMC)to design robust H∞state feedback controllers for load frequency regulation of delayed interconnected power system(IPS)with parametric uncertainties.Considering both state feedback control strategy and delayed feedback control strategy,two SMC laws are proposed.The proposed control laws are designed to improve the stability and disturbance rejection performance of delayed IPS,while stabilization criteria in the form of linear matrix inequality are derived by choosing a Lyapunov–Krasovskii functional.An artificial time-delay is incorporated in the control law design of the delayed feedback control struc-ture to enhance the controller performance.A numerical example is considered to study the control performance of the proposed controllers and simulation results are provided to observe the dynamic response of the IPS.展开更多
This paper presents two one-pass algorithms for dynamically computing frequency counts in sliding window over a data stream-computing frequency counts exceeding user-specified threshold ε. The first algorithm constru...This paper presents two one-pass algorithms for dynamically computing frequency counts in sliding window over a data stream-computing frequency counts exceeding user-specified threshold ε. The first algorithm constructs subwindows and deletes expired sub-windows periodically in sliding window, and each sub-window maintains a summary data structure. The first algorithm outputs at most 1/ε ＋ 1 elements for frequency queries over the most recent N elements. The second algorithm adapts multiple levels method to deal with data stream. Once the sketch of the most recent N elements has been constructed, the second algorithm can provides the answers to the frequency queries over the most recent n （ n≤N） elements. The second algorithm outputs at most 1/ε ＋ 2 elements. The analytical and experimental results show that our algorithms are accurate and effective.展开更多
基金Project(2012(PS-2012-090))supported by the Pukyong National University Research Abroad Fund,Korea
文摘This work proposes a new strategy to improve the rotor position estimation of a permanent magnet synchronous motor(PMSM) over wide speed range. Rotor position estimation of a PMSM is performed by using sliding mode observer(SMO). An adaptive observer gain was designed based on Lyapunov function and applied to solve the chattering problem caused by the discontinuous function of the SMO in the wide speed range. The cascade low-pass filter(LPF) with variable cut-off frequency was proposed to reduce the chattering problem and to attenuate the filtering capability of the SMO. In addition, the phase shift caused by the filter was counterbalanced by applying the variable phase delay compensation for the whole speed area. High accuracy estimation result of the rotor position was obtained in the experiment by applying the proposed estimation strategy.
基金Project supported by the National Natural Science Foundation of China and the Communication High Technology Program.
文摘In ultralong distance soliton transmission, the main limit to the single-channel bit rateis set by jitter in pulse arrival time from Gordon-Haus limit. Soliton controls in timesand in frequency domains are used to reduce this jitter. Soliton control in time makesthe wavelength-division-multiplexing systems difficult to realize, while filtering in frequency do-mains does not have this problem. The latter reduces the jitter through the use of nar-
文摘This work presents a control approach based on sliding-mode-control(SMC)to design robust H∞state feedback controllers for load frequency regulation of delayed interconnected power system(IPS)with parametric uncertainties.Considering both state feedback control strategy and delayed feedback control strategy,two SMC laws are proposed.The proposed control laws are designed to improve the stability and disturbance rejection performance of delayed IPS,while stabilization criteria in the form of linear matrix inequality are derived by choosing a Lyapunov–Krasovskii functional.An artificial time-delay is incorporated in the control law design of the delayed feedback control struc-ture to enhance the controller performance.A numerical example is considered to study the control performance of the proposed controllers and simulation results are provided to observe the dynamic response of the IPS.
基金Supported by the National Natural Science Foun-dation of China (60403027)
文摘This paper presents two one-pass algorithms for dynamically computing frequency counts in sliding window over a data stream-computing frequency counts exceeding user-specified threshold ε. The first algorithm constructs subwindows and deletes expired sub-windows periodically in sliding window, and each sub-window maintains a summary data structure. The first algorithm outputs at most 1/ε ＋ 1 elements for frequency queries over the most recent N elements. The second algorithm adapts multiple levels method to deal with data stream. Once the sketch of the most recent N elements has been constructed, the second algorithm can provides the answers to the frequency queries over the most recent n （ n≤N） elements. The second algorithm outputs at most 1/ε ＋ 2 elements. The analytical and experimental results show that our algorithms are accurate and effective.
