传统有限控制集的模型预测控制(finite control set model predictive control,FCS-MPC)在一个控制周期内输出单一的开关状态,当采样频率较低时,控制精度较差,且开关频率不固定导致交流侧滤波器难以设计。针对上述问题,在传统FCS-MPC的...传统有限控制集的模型预测控制(finite control set model predictive control,FCS-MPC)在一个控制周期内输出单一的开关状态,当采样频率较低时,控制精度较差,且开关频率不固定导致交流侧滤波器难以设计。针对上述问题,在传统FCS-MPC的基础上,为三相脉冲宽度调制(pulsewidth modulation,PWM)整流器提出一种基于功率跟踪目标函数的定频模型预测控制。首先基于FCS-MPC的功率跟踪目标函数最小值求解,精确计算变换器输出电压矢量的扇区,接着根据扇区确定控制周期作用的两个有效矢量和零矢量,最后利用3个矢量的功率跟踪差值计算各电压矢量的作用时间。通过仿真验证,与传统FCS-MPC相比,所提方法能实现开关频率的固定,减小功率脉动,提高整流器的输出性能。展开更多
In order to improve tracking accuracy when initial estimate is inaccurate or outliers exist,a bearings-only tracking approach called the robust range-parameterized cubature Kalman filter(RRPCKF)was proposed.Firstly,th...In order to improve tracking accuracy when initial estimate is inaccurate or outliers exist,a bearings-only tracking approach called the robust range-parameterized cubature Kalman filter(RRPCKF)was proposed.Firstly,the robust extremal rule based on the pollution distribution was introduced to the cubature Kalman filter(CKF)framework.The improved Turkey weight function was subsequently constructed to identify the outliers whose weights were reduced by establishing equivalent innovation covariance matrix in the CKF.Furthermore,the improved range-parameterize(RP)strategy which divides the filter into some weighted robust CKFs each with a different initial estimate was utilized to solve the fuzzy initial estimation problem efficiently.Simulations show that the result of the RRPCKF is more accurate and more robust whether outliers exist or not,whereas that of the conventional algorithms becomes distorted seriously when outliers appear.展开更多
Quintessence field is a widely-studied candidate of dark energy. There is ＂tracker solution＂ in quintessence models, in which evolution of the field φ at present times is not sensitive to its initial conditions. Wh...Quintessence field is a widely-studied candidate of dark energy. There is ＂tracker solution＂ in quintessence models, in which evolution of the field φ at present times is not sensitive to its initial conditions. When the energy density of dark energy is negleetable （Ωφ 〈〈 1）, evolution of the tracker solution can be well analysed from ＂tracker equation＂. In this paper, we try to study evolution of the quintessence field from ＂full tracker equation＂, which is valid for all spans of Ωφ. We get stable fixed points of we and wφ （noted as wφ and Ωφ） from the ＂full tracker equation＂, i.e., we and ωφ will always approach ωφ and Ωφ respectively. Since wφ and Ωφ are analytic functions of φ, analytic relation of φ can be obtained, which is a good approximation for the we φ relation and can be obtained for the most type of quintessence potentials. By using this approximation, we find that inequalities ωφ 〈 we and 〈ωφ are statisfied if the we （or ωφ） decreases with time. In this way, the potentiai U（φ） can be constrained directly from observations, by no need of solving the equations of motion numerically.展开更多
In considering the characteristic of a rudder,the maneuvers of a ship were described by an unmatched uncertain nonlinear mathematic model with unknown virtual control coefficient and parameter uncertainties.In order t...In considering the characteristic of a rudder,the maneuvers of a ship were described by an unmatched uncertain nonlinear mathematic model with unknown virtual control coefficient and parameter uncertainties.In order to solve the uncertainties in the ship heading control,specifically the controller singular and paramount re-estimation problem,a new multiple sliding-mode adaptive fuzzy control algorithm was proposed by combining Nussbaum gain technology,the approximation property of fuzzy logic systems,and a multiple sliding-mode control algorithm.Based on the Lyapunov function,it was proven in theory that the controller made all signals in the nonlinear system of unmatched uncertain ship motion uniformly bounded,with tracking errors converging to zero.Simulation results show that the demonstrated controller design can track a desired course fast and accurately.It also exhibits strong robustness peculiarity in relation to system uncertainties and disturbances.展开更多
Wheeled mobile robot is one of the well-known nonholonomic systems. A two-wheeled sell-balance robot is taken as the research objective. This paper carried out a detailed force analysis of the robot and established a ...Wheeled mobile robot is one of the well-known nonholonomic systems. A two-wheeled sell-balance robot is taken as the research objective. This paper carried out a detailed force analysis of the robot and established a non-linear dynamics model. An adaptive tracking controller for the kinematic model of a nonhotonomic mobile robot with unknown parameters is also proposed. Using control Lyapunov function （CLF）, the controller＇s global asymptotic stability has been proven. The adaptive trajectory tracking controller decreases the disturbance in the course of tracking control and enhances the real-time control characteristics. The simulation result indicated that the wheeled mobile robot tracking can be effectively controlled.展开更多
This paper discusses an implementation based on CMEX S-functions to model and to check implementation feasibility of two most commonly used Maximum Power Point Tracking （MPPT） algorithms, namely Hill Climbing/Pertu...This paper discusses an implementation based on CMEX S-functions to model and to check implementation feasibility of two most commonly used Maximum Power Point Tracking （MPPT） algorithms, namely Hill Climbing/Perturb ＆ Observe （P＆O） and Incremental Conductance. This study can also be generalized to encompass the whole digital techniques family, including artificial intelligence like Neural Network and Fuzzy Logic Control.展开更多
Linear recurring sequences over finite fields play an important role in coding theory and cryptography. It is known that subfield subcodes of linear codes yield some good codes. In this paper, we study linear recurrin...Linear recurring sequences over finite fields play an important role in coding theory and cryptography. It is known that subfield subcodes of linear codes yield some good codes. In this paper, we study linear recurring sequences and subfield subcodes. Let Mqm(f(x)) denote the set of all linear recurring sequences over Fqm with characteristic polynomial f(x) over Fqm . Denote the restriction of Mqm(f(x)) to sequences over Fq and the set after applying trace function to each sequence in Mqm(f(x)) by Mqm(f(x)) | Fq and Tr( Mqm(f(x))), respectively. It is shown that these two sets are both complete sets of linear recurring sequences over Fq with some characteristic polynomials over Fq. In this paper, we firstly determine the characteristic polynomials for these two sets. Then, using these results, we determine the generator polynomials of subfield subcodes and trace codes of cyclic codes over Fqm .展开更多
Reliable connection of turbine generators in complex main wiring structures to the power grid through a plurality of switches is a new key problem,referred to as multipoint automatic synchronization(MPAS),in automatic...Reliable connection of turbine generators in complex main wiring structures to the power grid through a plurality of switches is a new key problem,referred to as multipoint automatic synchronization(MPAS),in automatic control systems(ACS).In this paper,different methods of voltage-frequency and phase-difference control are analyzed,and a control methodology based on active frequency tracking(AFT)is presented.Through the establishment of the multi-point automatic synchronization model and the analysis of the governor transfer function with this control method,the important control parameters and automatic process control sequence are summarized.The correctness and effectiveness of the designed methodology are inspected through on-site testing,and the importance of the function and selection of parameters are also explored.展开更多
文摘传统有限控制集的模型预测控制(finite control set model predictive control,FCS-MPC)在一个控制周期内输出单一的开关状态,当采样频率较低时,控制精度较差,且开关频率不固定导致交流侧滤波器难以设计。针对上述问题,在传统FCS-MPC的基础上,为三相脉冲宽度调制(pulsewidth modulation,PWM)整流器提出一种基于功率跟踪目标函数的定频模型预测控制。首先基于FCS-MPC的功率跟踪目标函数最小值求解,精确计算变换器输出电压矢量的扇区,接着根据扇区确定控制周期作用的两个有效矢量和零矢量,最后利用3个矢量的功率跟踪差值计算各电压矢量的作用时间。通过仿真验证,与传统FCS-MPC相比,所提方法能实现开关频率的固定,减小功率脉动,提高整流器的输出性能。
基金Projects(51377172,51577191) supported by the National Natural Science Foundation of China
文摘In order to improve tracking accuracy when initial estimate is inaccurate or outliers exist,a bearings-only tracking approach called the robust range-parameterized cubature Kalman filter(RRPCKF)was proposed.Firstly,the robust extremal rule based on the pollution distribution was introduced to the cubature Kalman filter(CKF)framework.The improved Turkey weight function was subsequently constructed to identify the outliers whose weights were reduced by establishing equivalent innovation covariance matrix in the CKF.Furthermore,the improved range-parameterize(RP)strategy which divides the filter into some weighted robust CKFs each with a different initial estimate was utilized to solve the fuzzy initial estimation problem efficiently.Simulations show that the result of the RRPCKF is more accurate and more robust whether outliers exist or not,whereas that of the conventional algorithms becomes distorted seriously when outliers appear.
基金Supported in part by the National Science Foundation of China under Grant No.10425525
文摘Quintessence field is a widely-studied candidate of dark energy. There is ＂tracker solution＂ in quintessence models, in which evolution of the field φ at present times is not sensitive to its initial conditions. When the energy density of dark energy is negleetable （Ωφ 〈〈 1）, evolution of the tracker solution can be well analysed from ＂tracker equation＂. In this paper, we try to study evolution of the quintessence field from ＂full tracker equation＂, which is valid for all spans of Ωφ. We get stable fixed points of we and wφ （noted as wφ and Ωφ） from the ＂full tracker equation＂, i.e., we and ωφ will always approach ωφ and Ωφ respectively. Since wφ and Ωφ are analytic functions of φ, analytic relation of φ can be obtained, which is a good approximation for the we φ relation and can be obtained for the most type of quintessence potentials. By using this approximation, we find that inequalities ωφ 〈 we and 〈ωφ are statisfied if the we （or ωφ） decreases with time. In this way, the potentiai U（φ） can be constrained directly from observations, by no need of solving the equations of motion numerically.
基金Supported by the National Natural Science Foundation of China under Grant No.60974136
文摘In considering the characteristic of a rudder,the maneuvers of a ship were described by an unmatched uncertain nonlinear mathematic model with unknown virtual control coefficient and parameter uncertainties.In order to solve the uncertainties in the ship heading control,specifically the controller singular and paramount re-estimation problem,a new multiple sliding-mode adaptive fuzzy control algorithm was proposed by combining Nussbaum gain technology,the approximation property of fuzzy logic systems,and a multiple sliding-mode control algorithm.Based on the Lyapunov function,it was proven in theory that the controller made all signals in the nonlinear system of unmatched uncertain ship motion uniformly bounded,with tracking errors converging to zero.Simulation results show that the demonstrated controller design can track a desired course fast and accurately.It also exhibits strong robustness peculiarity in relation to system uncertainties and disturbances.
基金Supported by the National High Technology Research and Development Programme of China (No. 2006AA04Z245)the Program for Changjiang Scholars and Innovative Research Team in University ( No. IRT0423)the Fund for Foreign Scholars in University Research and Teaching Programs (No. B07018)
文摘Wheeled mobile robot is one of the well-known nonholonomic systems. A two-wheeled sell-balance robot is taken as the research objective. This paper carried out a detailed force analysis of the robot and established a non-linear dynamics model. An adaptive tracking controller for the kinematic model of a nonhotonomic mobile robot with unknown parameters is also proposed. Using control Lyapunov function （CLF）, the controller＇s global asymptotic stability has been proven. The adaptive trajectory tracking controller decreases the disturbance in the course of tracking control and enhances the real-time control characteristics. The simulation result indicated that the wheeled mobile robot tracking can be effectively controlled.
文摘This paper discusses an implementation based on CMEX S-functions to model and to check implementation feasibility of two most commonly used Maximum Power Point Tracking （MPPT） algorithms, namely Hill Climbing/Perturb ＆ Observe （P＆O） and Incremental Conductance. This study can also be generalized to encompass the whole digital techniques family, including artificial intelligence like Neural Network and Fuzzy Logic Control.
基金supported by National Key Basic Research Program of China(973 Program)(Grant No.2013CB834204)National Natural Science Foundation of China(Grant Nos.61171082 and 10990011)
文摘Linear recurring sequences over finite fields play an important role in coding theory and cryptography. It is known that subfield subcodes of linear codes yield some good codes. In this paper, we study linear recurring sequences and subfield subcodes. Let Mqm(f(x)) denote the set of all linear recurring sequences over Fqm with characteristic polynomial f(x) over Fqm . Denote the restriction of Mqm(f(x)) to sequences over Fq and the set after applying trace function to each sequence in Mqm(f(x)) by Mqm(f(x)) | Fq and Tr( Mqm(f(x))), respectively. It is shown that these two sets are both complete sets of linear recurring sequences over Fq with some characteristic polynomials over Fq. In this paper, we firstly determine the characteristic polynomials for these two sets. Then, using these results, we determine the generator polynomials of subfield subcodes and trace codes of cyclic codes over Fqm .
文摘Reliable connection of turbine generators in complex main wiring structures to the power grid through a plurality of switches is a new key problem,referred to as multipoint automatic synchronization(MPAS),in automatic control systems(ACS).In this paper,different methods of voltage-frequency and phase-difference control are analyzed,and a control methodology based on active frequency tracking(AFT)is presented.Through the establishment of the multi-point automatic synchronization model and the analysis of the governor transfer function with this control method,the important control parameters and automatic process control sequence are summarized.The correctness and effectiveness of the designed methodology are inspected through on-site testing,and the importance of the function and selection of parameters are also explored.
