准分子激光原位角膜磨镶术（Laser in situ keratomileusis,LASIK）,因其效果稳定、视力恢复快、并发症少、复发率低已成为治疗近视最常用的方法之一.文献报道多认为术后欠矫和同退与患者的屈光度数高低有关.笔者对800例（1 586只眼）LA...准分子激光原位角膜磨镶术（Laser in situ keratomileusis,LASIK）,因其效果稳定、视力恢复快、并发症少、复发率低已成为治疗近视最常用的方法之一.文献报道多认为术后欠矫和同退与患者的屈光度数高低有关.笔者对800例（1 586只眼）LASIK近视患者术后屈光度数进行分析,现将其发生原因分析报告如下.展开更多
This paper presents a constructive design of new controllers that force underactuated ships under constant or slow time-varying sea loads to asymptotically track a parameterized reference path, that guarantees the dis...This paper presents a constructive design of new controllers that force underactuated ships under constant or slow time-varying sea loads to asymptotically track a parameterized reference path, that guarantees the distance from the ship to the reference path always be within a specified value. The control design is based on a global exponential disturbance observer, a transformation of the ship dynamics to an almost spherical form, an interpretation of the tracking errors in an earth-fixed frame, an introduction of dynamic variables to compensate for relaxation of the reference path generation, p-times differentiable step functions, and backstepping and Lyapunov＇s direct methods. The effectiveness of the proposed results is illustrated through simulations.展开更多
A path following controller is proposed to force an underactuated surface ship which is suffering from disturbance to follow a predefined path.The controller is based on analytic model predictive control and unscented...A path following controller is proposed to force an underactuated surface ship which is suffering from disturbance to follow a predefined path.The controller is based on analytic model predictive control and unscented Kalman filter(UKF) techniques.The analytic model predictive control provides a systematic method to get appropriate controller parameters to guarantee the stability of the closed-loop system,and the well-defined relative degree is guaranteed by introducing output-redefinition.The UKF is used to estimate the states and uncertain parameters due to time-varying added mass matrices.With help of the proposed UKF-based controller,the underactuated ship with time-varying parameters can follow a desired straight path.Simulation results are presented to demonstrate the effectiveness of the proposed controller.展开更多
文摘准分子激光原位角膜磨镶术（Laser in situ keratomileusis,LASIK）,因其效果稳定、视力恢复快、并发症少、复发率低已成为治疗近视最常用的方法之一.文献报道多认为术后欠矫和同退与患者的屈光度数高低有关.笔者对800例（1 586只眼）LASIK近视患者术后屈光度数进行分析,现将其发生原因分析报告如下.
基金Supported in Part by the Australian Research Council Under Grant No.DP0988424
文摘This paper presents a constructive design of new controllers that force underactuated ships under constant or slow time-varying sea loads to asymptotically track a parameterized reference path, that guarantees the distance from the ship to the reference path always be within a specified value. The control design is based on a global exponential disturbance observer, a transformation of the ship dynamics to an almost spherical form, an interpretation of the tracking errors in an earth-fixed frame, an introduction of dynamic variables to compensate for relaxation of the reference path generation, p-times differentiable step functions, and backstepping and Lyapunov＇s direct methods. The effectiveness of the proposed results is illustrated through simulations.
基金the National Natural Science Foundation of China (No. 50779033)the National High Technology Research and Development Program (863) of China (No. 2007AA11Z250)
文摘A path following controller is proposed to force an underactuated surface ship which is suffering from disturbance to follow a predefined path.The controller is based on analytic model predictive control and unscented Kalman filter(UKF) techniques.The analytic model predictive control provides a systematic method to get appropriate controller parameters to guarantee the stability of the closed-loop system,and the well-defined relative degree is guaranteed by introducing output-redefinition.The UKF is used to estimate the states and uncertain parameters due to time-varying added mass matrices.With help of the proposed UKF-based controller,the underactuated ship with time-varying parameters can follow a desired straight path.Simulation results are presented to demonstrate the effectiveness of the proposed controller.
