An enhanced anti-disturbance attitude control law for flexible spacecrafts subject to multiple disturbances

As well-known disturbance rejection methods, active disturbance rejection control and disturbance observer-based control can effectively improve the control performances of complex systems in the presence of disturbances. However, the accurate rejection of multiple disturbances for control systems of practical engineering, for example, the attitude control system of flexible spacecraft, is still a bottleneck problem. In order to further improve the anti-disturbance capability and reduce the conservativeness, this paper proposes a novel enhanced anti-disturbance control law for the attitude control system of flexible spacecraft by combining active disturbance rejection control and disturbance observer-based control in a unified framework. More specifically, the disturbance from flexible vibration is described by an uncertain exogenous system based on the partially known information including elastic damping ratios and modal frequencies. The disturbance observer-based control is utilized to estimate and thereby reject this disturbance. On the other hand, the other disturbances such as external environmental disturbance and complex model nonlinearity are merged into a equivalent disturbance with bounded derivative, which is compensated by using the active disturbance rejection control law. Stability and robustness analysis are carried out for the disturbance observer and extended state observer. Finally, simulation results of low-earth-orbit flexible satellite are presented to verify the effectiveness of proposed methods.     

不确定广义系统的降阶H-infinity控制器设计

研究基于函数观测器的不确定广义系统的降阶H-infinity控制器设计问题. 首先提出了基于严格线性矩阵不等式的不确定广义系统H-infinity控制的充分条件, 并用于状态反馈H-infinity控制设计. 然后对所得控制增益进行降阶观测, 基于广义Sylvester矩阵方程的显式通解, 考虑系统的H-infinity性能约束, 提出了降阶输出反馈控制器的参数化设计方法.     

基于观测器的广义线性系统降阶H∞控制器设计

本文研究基于Luenberger观洲器的广义系统降阶H∞控制器的设计问题,并且该观测器是关于干扰解耦的。首先是提出了广义系统H∞状态反馈控制问题的一个充要条件,并利用线性矩阵不等式方法求解出广义系统的H∞状态反馈增益。然后对该H∞状态反馈增益进行渐进降阶观测,基于广义Sylvester矩阵方程的显式通解的参数化设计方法,实现了广义系统的降阶H∞控制。本文最主要的工作是给出了相应的广义线性系统降阶H∞控制器的设计算法。在文章的最后给出了一个例子,用来说明降阶算法的有效性。     

Observer-based approximate optimal tracking control for time-delay systems with external disturbances

This paper proposes a successive approximation design approach of observer-based optimal tracking controllers for time-delay systems with external disturbances. To solve a two-point boundary value problem with time-delay and time-advance terms and obtain the optimal tracking control law, two sequences of vector differential equations are constructed first. Second, the convergence of the sequences of the vector differential equations is proved to guarantee the existence and uniqueness of the control law. Third, a design algorithm of the optimal tracking control law is presented and the physically realisable problem is addressed by designing a disturbance state observer and a reference input state observer. An example of an industrial electric heater is given to demonstrate the efficiency of the proposed approach.     

基于观测器的不确定广义时滞系统保成本控制

讨论了基于观测器的一类不确定广义时滞系统的保成本控制问题,给出了系统保成本控制器的设计方法.控制器的构造使得闭环系统是鲁棒稳定的.利用线性矩阵不等式以及Lyapunov函数方法,给出了鲁棒保成本控制器存在的充分条件以及相应的可保成本指标,并证明了这个条件等价于一组线性矩阵不等式(LM Is)的可解性问题,同时推广了已知的相关结果.最后以算例验证了设计方法的有效性.     

Fault-tolerant Control for Linear System Under Sensor Saturation Constraint

An observer-based fault-tolerant control method is proposed for a linear system with sensor saturation constraint. Considering the linear system with simultaneous actuator faults and sensor faults, the sensor saturation would bring the output measurement error of the system, which would result in the estimation performance degradation. Firstly, the intermediate estimator is modified to estimate the system states and fault signals at the simultaneous time, and the fault-tolerant controller is designed based on the estimation to compensate the effect of actuator faults effectively. Through Lyapunov stability analysis, the sufficient conditions are obtained to ensure the states of closed-loop system to be uniformly ultimately bounded. The effect of sensor saturation error can be suppressed by adjusting some specified parameters directly without introducing any performance index. Finally, the effectiveness and superiority of the proposed method are verified by a simulation example.

     

Composite nonlinear feedback control for linear singular systems with input saturation

This paper investigates the composite nonlinear feedback (CNF) control technique for linear singular systems with input saturation. First, a linear feedback control law is designed for the step tracking control problem of linear singular systems subject to input saturation. Then, based on this linear feedback gain, a CNF control law is constructed to improve the transient performance of the closed-loop system. By introducing a generalized Lyapunov equation, this paper develops a design procedure for constructing the CNF control law for linear singular systems with input saturation. After decomposing the closed-loop system into fast subsystem and slow subsystem, it can be shown that the nonlinear part of the CNF control law only relies on slow subsystem. The improvement of transient performance by the proposed design method is demonstrated by an illustrative example.     

A fault tolerant tracking control for a quadrotor UAV subject to simultaneous actuator faults and exogenous disturbances

ABSTRACT

An observer-based robust adaptive Fault Tolerant Control approach is proposed in this paper to tackle the problem of trajectory tracking for a quadrotor unmanned aerial vehicle (UAV) suffering simultaneous actuator faults, exogenous disturbances and actuator saturation limits. An adaptive fuzzy state observer is proposed to estimate the immeasurable states by using fuzzy logic systems to approximate the unknown nonlinear functions of the uncertain system model. Based on the estimates of the fuzzy observer, an Integral Terminal Sliding Mode Controller that guarantees finite time convergence of the states to a small neighbourhood of zero, even under impaired conditions, is developed. Stability analysis was carried over using the Lyapunov method. The proposed approach was implemented to a quadrotor UAV and its performance was assessed under nominal conditions, and by subjecting the quadrotor to disturbances, simultaneously occurring actuator faults and input saturation limits. Excellent tracking performance and robustness even under worst-case scenarios are among the positive features of the proposed approach.     

一类随机系统基于干扰观测器的抗干扰控制

针对一类带有多源干扰的随机系统,研究其抗干扰控制问题.针对可以由未知参数的外源系统产生,代表频率、振幅和初相都未知的干扰,构建随机自适应干扰观测器对其进行估计.基于此,结合自适应控制和随机控制的方法,提出基于干扰观测器的抗干扰控制策略,保证复合系统的所有信号均为均方渐近有界.仿真结果验证了所提出方法的正确性和有效性.     

Stability analysis and controller design for a class of delay systems via observer based on network

This paper focuses on the problem of stability analysis and controller design for a class of delay systems based on networked control systems. By introducing some free matrix variables, some criteria for stability analysis and observer-based control law design can be obtained by the solving of linear matrix inequalities. A numerical example is also offered to prove the effectiveness of the proposed method.     

一类Lipschitz 非线性切换系统基于观测器的 H∞ 输出跟踪控制

针对一类Lipschitz非线性切换系统,研究基于观测器的H∞输出跟踪控制问题.借助微分中值定理,将Lipschitz非线性切换系统转化为线性参数切换系统.当状态变量不可测或不易测时,利用多Lyapunov函数方法,同时设计观测器、基于观测器的跟踪控制器和滞后切换信号,使得系统满足H∞输出跟踪性能.最后通过仿真例子表明了设计方法的有效性.     

带乘性噪声和延时观测广义系统的多步最优预测器

本文研究了状态空间描述的离散广义系统最优预测器的设计问题,该系统带有即时和延时观测,所有观测中带有乘性噪声.论文在两个基本假设条件下采用标准的奇异值分解方法给出了受限等价时滞系统,对于此类系统没有采用状态增广方法,而是采用新息重组分析理论给出了多步预测器.因为延时观测的存在,所给出的多步预测器包含了两套递推的广义系统黎卡提方程.本文给出了一个数学算例验证了所提方法的正确性和有效性,并给出了四幅图片,根据算例可以看出一般情况下预测的步数越少,预测的结果越好.本文方法可以进一步来研究更复杂的一些问题,如延时广义系统的H_∞滤波和控制问题.     

Fixed-time sliding mode observer-based controller for a class of uncertain nonlinear double integrator systems

This paper investigates a fixed-time convergence issue using the sliding mode observer-based controller for a class of uncertain nonlinear double integrator systems. This observer-based controller is designed assuming that only the first state measurement is available and there is no information about external disturbances and modeling uncertainties. A new form of sliding mode observer in combination with a sliding mode controller is designed to estimate unmeasured state and unknown disturbances and uncertainties as well as provide the estimated data in the control law. A novel form of sliding surfaces for the robust observer-based controller is proposed for which fixed-time convergence is guaranteed to achieve trajectory tracking. In the proposed fixed-time scheme, the bound on the settling time is user-defined using design parameters regardless of the system's initial conditions. The control law and observer law are designed such that the chattering issue is alleviated in the control signal. The stability analysis of the closed-loop system using the observer-based controller is established via the Lyapunov theory. The validity of the controller design is tested by applying and simulating an example of a robot manipulator in Simulink/MATLAB. The superiority of the proposed method is demonstrated by comparing it with two other methods from the relevant literature.     

带有观测器的广义多智能体系统二分一致性

本文研究了带有观测器的广义多智能体系统的二分一致性问题.根据符号图的特性,提出了一种基于广义观测器的分布式二分一致性控制协议.以广义系统稳定性理论和代数图论为主要研究工具,分析并得到了广义多智能体系统实现二分一致性的充分条件.利用广义观测器的相对和绝对信息设计了两种新的二分一致性控制协议.数值仿真验证了理论结果的准确性和有效性.