为快速、准确地观测系统中的未知扰动及状态,提出一种有限时间线性扩张状态观测器(Finite-time linear extended state observer,FT-LESO),它具有期望的收敛性能且结构简单、易于设计.假设系统的状态无法量测,观测器设计问题转化为扰动下的输出反馈控制问题.针对该问题,提出一种扰动下的有限时间线性输出反馈控制方法,得到控制器参数与闭环系统状态向量2-范数间的解析关系.在此基础上,提出有限时间线性扩张状态观测器,得到观测器参数与观测误差收敛速度及稳态观测误差间的解析关系,给出一充分条件保证观测误差有限时间有界、且能以不低于指数收敛的速度收敛到给定范围内,为观测器参数设计提供理论依据.通过数值仿真验证提出的观测器,仿真结果与理论分析相符,提出的观测器是有效的.
This paper proposes a state estimation method for a class of norm bounded non linear sampled data descriptor systems using the Kalman filtering method. The descriptor model is firstly discretized to obtain a discrete time non singular one. Then a model of robust extended Kalman filter is proposed for the state estimation based on the discretized non linear non singular system. As parameters are introduced in for transforming descriptor systems into non singular ones there exist uncertainties in the state of the systems. To solve this problem an optimized upper bound is proposed so that the convergence of the estimation error co variance matrix is guaranteed in the paper. A simulating example is proposed to verify the validity of this method at last.
This paper investigates a fractional terminal sliding mode control for flexible spacecraft attitude tracking in the presence of inertia uncertainties and external disturbances. The controller is based on the fractional calculus and nonsingular terminal sliding mode control technique,and it guarantees the convergence of attitude tracking error in finite time rather than in the asymptotic sense. With respect to the controller,a fractional order sliding surface is given,the corresponding control scheme is proposed based on Lyapunov stability theory to guarantee the sliding condition,and the finite time stability of the whole close loop system is also proven. Finally,numerical simulations are presented to illustrate the performance of the proposed scheme.
