An adaptive iterative learning control scheme is presented for a class of strict-feedback nonlinear time-delay systems, with unknown nonlinearly parameterised and time-varying disturbed functions of known periods. Rad...An adaptive iterative learning control scheme is presented for a class of strict-feedback nonlinear time-delay systems, with unknown nonlinearly parameterised and time-varying disturbed functions of known periods. Radial basis function neural network and Fourier series expansion （FSE） are combined into a new function approximator to model each suitable disturbed function in systems. The requirement of the traditional iterative learning control algorithm on the nonlinear functions （such as global Lipschitz condition） is relaxed. Furthermore, by using appropriate Lyapunov-Krasovskii functionals, all signs in the closed loop system are guaranteed to be semiglobally uniformly ultimately bounded, and the output of the system is proved to converge to the desired trajectory. A simulation example is provided to illustrate the effectiveness of the control scheme.展开更多
Winding and web transport systems are subjected to quasi-periodic disturbances of the web tension due to the eccentricity and the non-circularity of the reel and rolls. The disturbances induced by the non-circularity ...Winding and web transport systems are subjected to quasi-periodic disturbances of the web tension due to the eccentricity and the non-circularity of the reel and rolls. The disturbances induced by the non-circularity and eccentricity of the rolls are quasi-periodic with a frequency that varies with their rotation speed. An adaptive method of rejection of these disturbances is proposed in this paper. It is based on a phase-locked loop structure that estimates simutaneously the phase and magnitude of the perturbation and then cancels it. This algorithm can be plugged in an existing industrial controller. The stability and robustness of the algorithm are also discussed. The ability of the algorithm to reject quasi-periodic disturbances with slowly varying frequencies is shown through simulation results.展开更多
For an underactuated spacecraft using only one thruster, the attitude controllability with respect to the or- bit frame is studied in the presence of periodical oscillation disturbance, which provides a preconditional...For an underactuated spacecraft using only one thruster, the attitude controllability with respect to the or- bit frame is studied in the presence of periodical oscillation disturbance, which provides a preconditional guide on de- signing control law for underactuated attitude control sys- tem. Firstly, attitude dynamic model was established for an underactuated spacecraft, and attitude motion was described using the special orthogonal group （SO （3））. Secondly, Liou- ville theorem was used to confirm that the flow generated by the drift vector of the underactuated attitude control system is volume-preserving. Furthermore, according to Poincar6＇s re- currence theorem, we draw conclusions that this drift field is weakly positively poisson stable （WPPS）. Thirdly, the suffi- cient and necessary condition of controllability was obtained on the basis of lie algebra rank condition （LARC）. Finally, the controllable conditions were analyzed and simulated in different cases of inertia matrix with the installed position of thruster.展开更多
Surface wave dynamics of falling film on the surface of periodic rectangular wall under monochromatic-frequency flowrate forcing disturbances is studied via numerical simulation. Waveforms formed on the periodic recta...Surface wave dynamics of falling film on the surface of periodic rectangular wall under monochromatic-frequency flowrate forcing disturbances is studied via numerical simulation. Waveforms formed on the periodic rectangular wall are different from those on the flat plate. At low frequency, the perturbation introduced at the inlet first undergoes a steady flow region and then develops into solitary waves. When the frequency becomes higher, solitary waves disappear. Film deformations in the steady flow region and characteristics of solitary waves are studied as the film travels down. There are circulations at the depression of periodic wall which are dependent on the local film characteristics and geometry of the corrugation. Moreover, the flow rate and geometry of the corrugations can also affect the evolvement of the monochromatic perturbation.展开更多
In this paper, We investigate the almost periodic systems (1)and(2) where g(t,x) ∈H(f). By using the inherited property of Liapunov function, under the suitable conditions, we prove that the bounded solution of (1 ) ...In this paper, We investigate the almost periodic systems (1)and(2) where g(t,x) ∈H(f). By using the inherited property of Liapunov function, under the suitable conditions, we prove that the bounded solution of (1 ) and (2) are stable under disturbances from H(f) with respect to the compact set. From this, we obtain some theorems of the existence of the almost periodic solutions for systems (1) and (2).展开更多
继1997年5月采用LacosteET-21重力仪在中国南极中山站观测发现South of Kermadec Islands7．1级地震前的“重力扰动”现象之后，2008年5月又在武汉大地测量国家野外科学观测站LacosteET-20重力仪的观测资料中发现了汶川大地震的“重力...继1997年5月采用LacosteET-21重力仪在中国南极中山站观测发现South of Kermadec Islands7．1级地震前的“重力扰动”现象之后，2008年5月又在武汉大地测量国家野外科学观测站LacosteET-20重力仪的观测资料中发现了汶川大地震的“重力扰动”现象：从大震前两天开始，“重力扰动”逐渐增大、最大振幅约为±0．8×10^-8ms^-2，直到大震发生。由于这两次监测的时间不同、地点不同、仪器不同（ET-21与ET-20），这就使得监测结果的可靠性得到了加强。初步认识是：在某些强震发生前两天左右，往往会出现较明显的“重力扰动”，其振幅在±（1～2）×10^-8ms^-2左右、信号周期4～8s。展开更多
基金supported by National Natural Science Foundation of China (No. 72103676)partially supported by the Fundamental Research Funds for the Central Universities
文摘An adaptive iterative learning control scheme is presented for a class of strict-feedback nonlinear time-delay systems, with unknown nonlinearly parameterised and time-varying disturbed functions of known periods. Radial basis function neural network and Fourier series expansion （FSE） are combined into a new function approximator to model each suitable disturbed function in systems. The requirement of the traditional iterative learning control algorithm on the nonlinear functions （such as global Lipschitz condition） is relaxed. Furthermore, by using appropriate Lyapunov-Krasovskii functionals, all signs in the closed loop system are guaranteed to be semiglobally uniformly ultimately bounded, and the output of the system is proved to converge to the desired trajectory. A simulation example is provided to illustrate the effectiveness of the control scheme.
文摘Winding and web transport systems are subjected to quasi-periodic disturbances of the web tension due to the eccentricity and the non-circularity of the reel and rolls. The disturbances induced by the non-circularity and eccentricity of the rolls are quasi-periodic with a frequency that varies with their rotation speed. An adaptive method of rejection of these disturbances is proposed in this paper. It is based on a phase-locked loop structure that estimates simutaneously the phase and magnitude of the perturbation and then cancels it. This algorithm can be plugged in an existing industrial controller. The stability and robustness of the algorithm are also discussed. The ability of the algorithm to reject quasi-periodic disturbances with slowly varying frequencies is shown through simulation results.
基金supported by National Natural Science Foundation of China (10902003)
文摘For an underactuated spacecraft using only one thruster, the attitude controllability with respect to the or- bit frame is studied in the presence of periodical oscillation disturbance, which provides a preconditional guide on de- signing control law for underactuated attitude control sys- tem. Firstly, attitude dynamic model was established for an underactuated spacecraft, and attitude motion was described using the special orthogonal group （SO （3））. Secondly, Liou- ville theorem was used to confirm that the flow generated by the drift vector of the underactuated attitude control system is volume-preserving. Furthermore, according to Poincar6＇s re- currence theorem, we draw conclusions that this drift field is weakly positively poisson stable （WPPS）. Thirdly, the suffi- cient and necessary condition of controllability was obtained on the basis of lie algebra rank condition （LARC）. Finally, the controllable conditions were analyzed and simulated in different cases of inertia matrix with the installed position of thruster.
基金Supported by National Natural Science Foundation of China (No. 20976118)
文摘Surface wave dynamics of falling film on the surface of periodic rectangular wall under monochromatic-frequency flowrate forcing disturbances is studied via numerical simulation. Waveforms formed on the periodic rectangular wall are different from those on the flat plate. At low frequency, the perturbation introduced at the inlet first undergoes a steady flow region and then develops into solitary waves. When the frequency becomes higher, solitary waves disappear. Film deformations in the steady flow region and characteristics of solitary waves are studied as the film travels down. There are circulations at the depression of periodic wall which are dependent on the local film characteristics and geometry of the corrugation. Moreover, the flow rate and geometry of the corrugations can also affect the evolvement of the monochromatic perturbation.
文摘In this paper, We investigate the almost periodic systems (1)and(2) where g(t,x) ∈H(f). By using the inherited property of Liapunov function, under the suitable conditions, we prove that the bounded solution of (1 ) and (2) are stable under disturbances from H(f) with respect to the compact set. From this, we obtain some theorems of the existence of the almost periodic solutions for systems (1) and (2).
文摘继1997年5月采用LacosteET-21重力仪在中国南极中山站观测发现South of Kermadec Islands7．1级地震前的“重力扰动”现象之后，2008年5月又在武汉大地测量国家野外科学观测站LacosteET-20重力仪的观测资料中发现了汶川大地震的“重力扰动”现象：从大震前两天开始，“重力扰动”逐渐增大、最大振幅约为±0．8×10^-8ms^-2，直到大震发生。由于这两次监测的时间不同、地点不同、仪器不同（ET-21与ET-20），这就使得监测结果的可靠性得到了加强。初步认识是：在某些强震发生前两天左右，往往会出现较明显的“重力扰动”，其振幅在±（1～2）×10^-8ms^-2左右、信号周期4～8s。
